# Need Help to Improve Surface Finish



## TomS

At the suggestion of another forum member I'm starting this thread here for more exposure.   A few week ago I opened up this discussion on my PM-932 build there here - http://www.hobby-machinist.com/threads/taking-the-cnc-plunge.24858/.  It starts on page 12, post #344.  

Now to the issue at hand.  A few months back I installed a 3ph motor and VFD to my CNC converted PM-932.  This also included upgrading the stock tapered roller spindle bearings to angular contact bearings (ABEC 5 for the top bearing and ABEC 7 for the lower bearing).  Then I followed up with new electronics: a PMDX-126 breakout board, a PMDX-107 spindle control board, and a ethernet smoothstepper.  All these "improvements" are working well except that since then the surface finish on angular and circular cuts is terrible.

I've tried a multitude of Mach3 CV settings such as CV Distance Tolerance, bumped Look Ahead to 200 lines, made sure G100 Adaptive Nurbs CV was turned off, Shuttle Acceleration, changed speeds, feeds, cutter size, number of flutes, DOC, WOC, feed direction and spindle drive belt.  Also made some changes to my CAM program but still no change in surface finish. Even went back and checked gib adjustment, twice. No improvement in surface finish. I'm at a loss as to what's causing this.

Any help is appreciated.

Here are a couple of pictures for reference.

X and Y straight cuts give me a very smooth surface finish. 



This is the surface finish I get with angular and circular cuts.


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## countryguy

There are a few ideas in this post: 
https://www.machsupport.com/forum/index.php?topic=19101.0
_.If you are cutting the circle with GCode created from a CAD program then there is a good chance that the circumference consists of many straight lines and depending on the resolution it could be quite rough and lead to the problem you describe._
_Try cutting a circle using the Mach wizard which uses circular interpolation, which is as near to a curve as you are going to get, and see if that improves the situation_

Some detail in this post maybe could help?
http://www.cnczone.com/forums/mach-mill/213832-cnc-software-posts.html

I was wondering what design CAD tool and which CAM is being used?


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## gradient

Why not mill the hole almost to size and finish up with a boring tool to get to final size? The boring tool will leave a very smooth and uniform finish since it is not interpolating circular motion.


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## TomS

countryguy said:


> There are a few ideas in this post:
> https://www.machsupport.com/forum/index.php?topic=19101.0
> _.If you are cutting the circle with GCode created from a CAD program then there is a good chance that the circumference consists of many straight lines and depending on the resolution it could be quite rough and lead to the problem you describe._
> _Try cutting a circle using the Mach wizard which uses circular interpolation, which is as near to a curve as you are going to get, and see if that improves the situation_
> 
> Some detail in this post maybe could help?
> http://www.cnczone.com/forums/mach-mill/213832-cnc-software-posts.html
> 
> I was wondering what design CAD tool and which CAM is being used?



I'm using CamBam for CAD and CAM but have used Fusion 360 for both as well with the same results.  I'll try the Mach wizard and see what happens.

That CNCZone thread was quite interesting.  I need to study it further to find out how it compares to my gcode.

Thanks

Edit:  I did zoom in on the arcs and did not see any straight line segments.  CamBam has an "arc fit" setting.  I set this to .002".


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## TomS

gradient said:


> Why not mill the hole almost to size and finish up with a boring tool to get to final size? The boring tool will leave a very smooth and uniform finish since it is not interpolating circular motion.



The rough/faceted surface is on all internal and external angle and arc cuts.  There is an underlying problem that I'm trying to nail down so I can correct it.  I didn't have this problem before the VFD/electronics upgrade.


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## spumco

Ditto above from countryguy.

A very quick way to see if it's hardware or software is to look at the code section with the hole that has unacceptable surface finish.  Is the code posted as arc moves or is it G1 X/Y moves?  If it's arc moves and it looks like that, you'll be chasing backlash, vibration, chattering, or some other mechanical gremlin.  Something to consider is your steps per rev or steps per inch - a coarser setting (no micro steps) will not be able to move in a curve as smoothly as if you're at 5x or 10x microsteps.  Linear moves along the x or y will be fine unless you're at extremely low feed rates where the stepper poles are cogging along: thump thump thump. 

If you still suspect hardware, either use the Mach wizard or your CAM program to generate a very simple boring operation.

If the moves are posted as G1 linear moves, the the threads above should be helpful.  If you don't get it right away, do a little math and see how long each linear segment is.  Like this:

001 G1 Fxx X1.002345 Y1.00566 (or whatever)
002 X1.003456 Y1.00666 (again, whatever the values are)

In this case, you can estimate the length of each segment between each code line, given the angle of movement.  If the segments are more than .002 (ish) long they'll show up visually in a fresh cut.

With a small diameter cutter longer segment lengths will show up as faceting.  [I know, it shouldn't matter about the cutter, but cutter deflection can make it look worse).

So... what CAM are you using?  I'm using Fusion 360, and while it's great so far there are a few settings that can output some funky code.


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## spumco

You beat me to it on the CAM.


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## spumco

So, assuming you're not getting a series of coarse resolution linear moves from your CAM, and Mach is displaying the code as arc segments...  the next check is the hardware I mentioned above.  How many steps per inch is your machine set to?


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## TomS

spumco said:


> Ditto above from countryguy.
> 
> A very quick way to see if it's hardware or software is to look at the code section with the hole that has unacceptable surface finish.  Is the code posted as arc moves or is it G1 X/Y moves?  If it's arc moves and it looks like that, you'll be chasing backlash, vibration, chattering, or some other mechanical gremlin.  Something to consider is your steps per rev or steps per inch - a coarser setting (no micro steps) will not be able to move in a curve as smoothly as if you're at 5x or 10x microsteps.  Linear moves along the x or y will be fine unless you're at extremely low feed rates where the stepper poles are cogging along: thump thump thump.
> 
> If you still suspect hardware, either use the Mach wizard or your CAM program to generate a very simple boring operation.
> 
> If the moves are posted as G1 linear moves, the the threads above should be helpful.  If you don't get it right away, do a little math and see how long each linear segment is.  Like this:
> 
> 001 G1 Fxx X1.002345 Y1.00566 (or whatever)
> 002 X1.003456 Y1.00666 (again, whatever the values are)
> 
> In this case, you can estimate the length of each segment between each code line, given the angle of movement.  If the segments are more than .002 (ish) long they'll show up visually in a fresh cut.
> 
> With a small diameter cutter longer segment lengths will show up as faceting.  [I know, it shouldn't matter about the cutter, but cutter deflection can make it look worse).
> 
> So... what CAM are you using?  I'm using Fusion 360, and while it's great so far there are a few settings that can output some funky code.



Heading to the shop this morning to test out the wizards.  

I have microstepping set at 1000.  My machine has been cutting good surfaces for the past couple of years at this setting.  I did try 2000 and 5000 but no change in the finish quality.

CamBam is generating arc moves as you can see in the attached gcode file.  Here's a picture of the finish.  It's rougher than it looks.  The picture I posted above is more representative of the finish.


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## TomS

As countryguy suggested I read through the cnczone thread and changed my configuration as follows.  Turned off CV Distance and Feedrate on the Settings screen.  Went into General Config and made sure all of the CV selections were not checked.  I also upped my acceleration from 15 to 25 on the X and Y axis.  I then ran the Mach3 circular pocketing wizard.  The finish was only marginally better.  Tried it again in absolute mode and again with Exact Stop enabled.  No noticeable difference in the surface finish.  What is interesting is I was expecting a herky jerky motion using Exact Stop but it was very smooth. 

If it was mechanical I would expect to see surface roughness on straight line cuts also.  But I'm not.  Even if I had excessive backlash I would think that it would be taken up on 90 deg. arc cuts.  Arc cuts are very rough.  Still at a loss.


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## spumco

Ok, code looks good in simulation mode using UCCNC (seeing if Mach was lying to you).  As you said it's a series of arc moves so surface finish isn't in the code.

Not the spindle, even though you recently replaced the bearings and might have possibly gotten that wrong.  If that were the case you'd be breaking tools or seeing the same problem on straight axis cuts too.

As you say, it's probably not backlash, as I think that causes out of round at the direction changes and not just a general surface finish problem on arcs.  On the other hand, backlash-induced surface problems may not show up in a straight axis cut if the axis with slop is snug due to cutter pressure.

So...  If not mechanical, and not the code, then what's left is Mach and your motion control hardware.  If you want to rule out the VFD making noise and causing the stepper drivers to freak out, stick a fine point pen in the spindle and have it trace on paper with the spindle off.  Just do a series of big arc moves and some direction changes.  You might be able to see if there's any jittering in the lines.

The pen might be too coarse to see problems, but a scribe on a flat piece of aluminum going down 0.001" might be fine enough if you put a thin layer of dyekem on it first.  Another thing to consider would be to see if your Z is oscillating up and down when the VFD is on.  Using another flat piece of aluminum or MDF (or something else really flat), run back and forth with the spindle off and a DTI attached to the head and indicating the surface.  Then do it again with the spindle on (no tool needed) and see if the needle is bouncing more.  I would think that VFD noise would show up on that axis as well as the X/Y.

I'm also running a 126 and 107 board, so I don't think there's an issue there with steps making it through your BOB to the drivers.  If the 107 board were freaking out, you'd hear the spindle throbbing as the RPM changed.  Besides the VFD, motor, 126 & 107, what else have you changed?  My guess is most of the wiring is new or different, but you'd obviously know better than I.  Have you followed best practices and isolated all of your signal wires from the VFD?  Is the VFD in a separate enclosure from the BOB & ESS?

I guess another thing to try would be to make a fairly deep cut in two (or three) depths.  Then check the surface with a magnifying glass - if the surface lines line up everywhere, the machine is being commanded (by something) to generate that surface you can completely rule out lost motion or mechanical issues. There's no way noise or mechanical problems would duplicate a surface like that in the exact same location over two or three passes.

Seriously not an expert here, but maybe something will help.

-S


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## TomS

spumco said:


> Ok, code looks good in simulation mode using UCCNC (seeing if Mach was lying to you).  As you said it's a series of arc moves so surface finish isn't in the code.
> 
> Not the spindle, even though you recently replaced the bearings and might have possibly gotten that wrong.  If that were the case you'd be breaking tools or seeing the same problem on straight axis cuts too.
> 
> As you say, it's probably not backlash, as I think that causes out of round at the direction changes and not just a general surface finish problem on arcs.  On the other hand, backlash-induced surface problems may not show up in a straight axis cut if the axis with slop is snug due to cutter pressure.
> 
> So...  If not mechanical, and not the code, then what's left is Mach and your motion control hardware.  If you want to rule out the VFD making noise and causing the stepper drivers to freak out, stick a fine point pen in the spindle and have it trace on paper with the spindle off.  Just do a series of big arc moves and some direction changes.  You might be able to see if there's any jittering in the lines.
> 
> The pen might be too coarse to see problems, but a scribe on a flat piece of aluminum going down 0.001" might be fine enough if you put a thin layer of dyekem on it first.  Another thing to consider would be to see if your Z is oscillating up and down when the VFD is on.  Using another flat piece of aluminum or MDF (or something else really flat), run back and forth with the spindle off and a DTI attached to the head and indicating the surface.  Then do it again with the spindle on (no tool needed) and see if the needle is bouncing more.  I would think that VFD noise would show up on that axis as well as the X/Y.
> 
> I'm also running a 126 and 107 board, so I don't think there's an issue there with steps making it through your BOB to the drivers.  If the 107 board were freaking out, you'd hear the spindle throbbing as the RPM changed.  Besides the VFD, motor, 126 & 107, what else have you changed?  My guess is most of the wiring is new or different, but you'd obviously know better than I.  Have you followed best practices and isolated all of your signal wires from the VFD?  Is the VFD in a separate enclosure from the BOB & ESS?
> 
> I guess another thing to try would be to make a fairly deep cut in two (or three) depths.  Then check the surface with a magnifying glass - if the surface lines line up everywhere, the machine is being commanded (by something) to generate that surface you can completely rule out lost motion or mechanical issues. There's no way noise or mechanical problems would duplicate a surface like that in the exact same location over two or three passes.
> 
> Seriously not an expert here, but maybe something will help.
> 
> -S



Thanks for your input.  Yes, my wiring is new with the electronics installation.  All of the spindle control wiring has the drain wire grounded in the VFD enclosure.  Limit switch drain wire is grounded in the BoB enclosure.  Driver drain wires are grounded in the Driver enclosure.  I make it a habit not to bundle power cables with control wiring and do my best to separate them as much as possible.  Hope I did this right.

I don't think it's bearings either.  The preload is in the ball park because I can run the spindle at 8600 on long runs (more than an hour) I get less than 30 deg. F temperature rise.  

Tomorrow I'll run the tests you suggest and see what I get.

For everyone's reference I've attached a few pictures of my control cabinet.

Here's a shot of my BoB/ESS enclosure.                        115vac enters at the top.  Limit switch and 107 control wiring, ethernet cable, and driver to BoB wiring at the                                                                                                              bottom.




My VFD enclosure.  107 board wiring enters at the top.  230vac comes in on lower left back (black and white wires) and exits to the motor lower left front.  PT cable enters above the high voltage wiring. 



View of my control cabinet. Power panel and e-stop on the upper left.  Power supplies and driver are in the lower rollaway drawer.  VFD enclosure is lower left and BoB/ESS enclosure is lower right.


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## TomS

I created a 4-1/2" diameter circle and generated gcode so I could monitor Z axis movement as Spumco suggested.   The DTI is contacting the top of the moveable jaw on my 5" Kurt clone vise that is held down to the table with four strap clamps.  The attached video shows the DTI needle bouncing around quite a bit.  Looks like I have some harmonics being fed back into the table.  Source of my poor surface finish?  Steppers maybe?  BTW - this test is with the VFD off.


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## spumco

Now we're getting somewhere.  Great video, BTW.

Next thing I would check is to see if the PMDX-126 is outputting signals to the Z-driver while you run that test.  Open the cabinet and see if the Z pin LED is flickering while the X/Y are doing the circle thing.  If it is, then open the Mach diagnostics page to see if Mach is outputting on those pins even though your code isn't commanding any motion.

Or try it with the Z-driver unplugged and see if the Z is being commanded (again, by noise or by Mach or something else) to move or if you're getting mechanical resonance.  You can also try it at a different feed rate - I find my steppers hum quite a bit at about 12-15IPM, and I've read that the typical 2-pole steppers are prone to this at about this speed.  Can't remember where I read that, but there you go.  Maybe it was one of Tormach's white papers, which are excellent by the way.

Run the test(s) again and then we'll start speculating on root cause.  And pray it isn't a combination of mechanical AND electrical gremlins...

-S


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## TomS

spumco said:


> Now we're getting somewhere.  Great video, BTW.
> 
> Next thing I would check is to see if the PMDX-126 is outputting signals to the Z-driver while you run that test.  Open the cabinet and see if the Z pin LED is flickering while the X/Y are doing the circle thing.  If it is, then open the Mach diagnostics page to see if Mach is outputting on those pins even though your code isn't commanding any motion.
> 
> Or try it with the Z-driver unplugged and see if the Z is being commanded (again, by noise or by Mach or something else) to move or if you're getting mechanical resonance.  You can also try it at a different feed rate - I find my steppers hum quite a bit at about 12-15IPM, and I've read that the typical 2-pole steppers are prone to this at about this speed.  Can't remember where I read that, but there you go.  Maybe it was one of Tormach's white papers, which are excellent by the way.
> 
> Run the test(s) again and then we'll start speculating on root cause.  And pray it isn't a combination of mechanical AND electrical gremlins...
> 
> -S



Yeah, I think we've hit on something.  I'm going to run the test again with the VFD on and spindle turning and see happens.  Yes, I'll mount the DTI on the head before turning on the spindle.  Then I'll run it and check the BoB Z axis lights.

I ran the DTI test at 5, 10 and 20 IPM.  Didn't notice any significant difference in needle bounce.

And I'll take a look at the Tormach white papers.


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## countryguy

Awesome stuff Tom and SpumCo... Nice collaboration there for sure.  I am not into the smooth-stepper sides much as we moved to Centroid and a server based system for our upgrade.   Sounds like you have the source about nailed down.  I hope this fix is an easy one!


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## spumco

As much as I'd like to claim victory, I don't think anything is about nailed down at this point.  We know it isn't X/Y backlash, and it isn't spindle bearings.  And we know the code is good-to-go.

Depending on what he finds in the next round of testing we may find it's noise (from what?), mechanical vibration (from what?), the ESS flipping out, or Mach causing the issue.

Or some combination of the above, which would suck.

Tom may get lucky and find something silly like a loose drain wire, but if I'm involved my typical luck will rub off and he'll be chasing his tail for a while.

-S


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## jbolt

*updated for clarity*

Add to when you are troubleshooting and you get into the ground wires try disconnecting all the drain wires except the control wires from the 107 to the VFD. Ground issues can be tricky to figure out. We went through ground issues with the router/mill we built for the school. Our issue was different but we found that even though we thought we had done the grounds correctly we created a condition that was worse than not having a ground at all.


Sent from my SM-G955U using Tapatalk


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## jbolt

TomS said:


> I created a 4-1/2" diameter circle and generated gcode so I could monitor Z axis movement as Spumco suggested.   The DTI is contacting the top of the moveable jaw on my 5" Kurt clone vise that is held down to the table with four strap clamps.  The attached video shows the DTI needle bouncing around quite a bit.  Looks like I have some harmonics being fed back into the table.  Source of my poor surface finish?  Steppers maybe?  BTW - this test is with the VFD off.



I'm not sure I would read too much into the needle movement running across the top surface of your vice. I would be more inclined to mount the TDI on the head or dovetail plate and measure against a fixed point on the column and take away any variables of the saddle, table and vice.


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## jbolt

I see in your photos that the enable wires are not connected to the BOB, are they still hooked up to the drives? If so disconnect them at the drives. Also make sure the bare ends are not touching the metal back panel. On the BOB enclosure is the 110vac earth ground attached to anything else besides the back plate?

What we learned from the school ground issues was that terminated wires or improperly terminated wires acted like antennas, the grounding system was undersized and it was easy to create ground loops. 

Where the motor drain entered the metal enclosure we had not terminated them at the enclosure wall but had instead ganged the drains inside the enclosure to a single ground lug. By not terminating the drains at the enclosure wall the drain wires inside the enclosure acted as antennas picking up interference from the inside. 

Another issue was all the components of the system were grounded but the ground was not robust enough and we had daisy chained the grounds. The best strategy is to do a star ground system where each enclosure or device like the VDF and the machine are grounded to a single point separately and to not daisy chain the grounds. We moved to a 3/8" wide braided ground strap that was grounded to the machine structure, electronic enclosure case and VFD base as separate runs being careful not to inadvertently create loops. The VFD on this machine is mounted outside of the electronics enclosure. The electronics enclosure also contained the main power disconnect so it was also terminated to earth ground. The electronics enclosure was divided inside by full depth metal baffles to separate the high voltage from the low voltage and again for the signal wiring. Basically separate Faraday cages in one enclosure. In the course of troubleshooting the original build we tried separating out the the encoder termination boards in a separate metal enclosure but in the process mistakenly created a ground loop which made things worse.

On my PM-932 CNC conversion I removed any unnecessary wires (stepper enable) and any unused wires from the system. All the motor wires, limit switch wire, and spindle control wire drains terminate at the metal enclosure wall. There are no shielded wires or drain wires inside the electronics enclosure(s).


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## TomS

I ran the circle test again with the VFD on and spindle running at 2200 rpm.  DTI needle bounce was the same as the previous test.  Looks like the vfd has no effect, which is good.  While running the test I monitored the Z axis step and dir pin lights on the BoB.  The step pin light (pin 5) stays on throughout the run.  The Dir pin light (pin 4) turns on only at the end during Z retract.

Looking over my driver and BoB wiring, again, and had a "Doh" moment.  I have the drain wire connected to ground on both ends.  Easy enough to fix but still can't believe I did it.  I'll disconnect one end and run the test again and see how the DTI needle responds.  If no change then reconnect and disconnect the other end.  Going to run the test as jbolt suggested too.


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## TomS

jbolt said:


> I see in your photos that the enable wires are not connected to the BOB, are they still hooked up to the drives? If so disconnect them at the drives. Also make sure the bare ends are not touching the metal back panel. On the BOB enclosure is the 110vac earth ground attached to anything else besides the back plate?
> 
> What we learned from the school ground issues was that terminated wires or improperly terminated wires acted like antennas, the grounding system was undersized and it was easy to create ground loops.
> 
> Where the motor drain entered the metal enclosure we had not terminated them at the enclosure wall but had instead ganged the drains inside the enclosure to a single ground lug. By not terminating the drains at the enclosure wall the drain wires inside the enclosure acted as antennas picking up interference from the inside.
> 
> Another issue was all the components of the system were grounded but the ground was not robust enough and we had daisy chained the grounds. The best strategy is to do a star ground system where each enclosure or device like the VDF and the machine are grounded to a single point separately and to not daisy chain the grounds. We moved to a 3/8" wide braided ground strap that was grounded to the machine structure, electronic enclosure case and VFD base as separate runs being careful not to inadvertently create loops. The VFD on this machine is mounted outside of the electronics enclosure. The electronics enclosure also contained the main power disconnect so it was also terminated to earth ground. The electronics enclosure was divided inside by full depth metal baffles to separate the high voltage from the low voltage and again for the signal wiring. Basically separate Faraday cages in one enclosure. In the course of troubleshooting the original build we tried separating out the the encoder termination boards in a separate metal enclosure but in the process mistakenly created a ground loop which made things worse.
> 
> On my PM-932 CNC conversion I removed any unnecessary wires (stepper enable) and any unused wires from the system. All the motor wires, limit switch wire, and spindle control wire drains terminate at the metal enclosure wall. There are no shielded wires or drain wires inside the electronics enclosure(s).



All very good points.  Thanks.

If I understand correctly you are saying to run a ground from each enclosure to the machine.  Then terminate/star ground all incoming cable grounds at the enclosure wall.  And yes, the 110vac ground is connected to the back plate only.  Probably should ground the back plate too.


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## spumco

Tom,

Yes - star ground, not daisy chain.  Also, PMDX advised me to run a drain from the 126 mounting holes to the star ground point inside the enclosure and not rely on the board to backplane mount screws.  This may not be an issue for you, but if you're in there fiddling around and doing some wiring it's easy enough to do.

Good to hear there's no difference in with the VFD on or off.  And I'm interested to hear how the DTI responds when you're indicating the head to column.


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## TomS

spumco said:


> Tom,
> 
> Yes - star ground, not daisy chain.  Also, PMDX advised me to run a drain from the 126 mounting holes to the star ground point inside the enclosure and not rely on the board to backplane mount screws.  This may not be an issue for you, but if you're in there fiddling around and doing some wiring it's easy enough to do.
> 
> Good to hear there's no difference in with the VFD on or off.  And I'm interested to hear how the DTI responds when you're indicating the head to column.



Jbolt's post got me thinking about my wiring.  I've gone through 3 upgrades since the initial installation and the wiring is beginning to be a bit untidy.  Before doing any more testing I'm going to clean things up.  Finding the driver/BoB ground loop may be significant.  We'll see.  And I will run a drain wire from the BoB to the star ground lug.


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## spumco

Tom,

Here's a thread on the PMDX forum (those guys are way helpful, by the way) relating to my build last year.  There may be a few tidbits of use to you regarding shielding and grounding.

https://www.pmdx.com/PMDX-Forums/index.php?topic=353.msg1482#msg1482

-S


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## jbolt

TomS said:


> All very good points.  Thanks.
> 
> If I understand correctly you are saying to run a ground from each enclosure to the machine.  Then terminate/star ground all incoming cable grounds at the enclosure wall.  And yes, the 110vac ground is connected to the back plate only.  Probably should ground the back plate too.



For the grounding system I use the location of where earth ground enters the system as the starting location for each arm of the ground runs.

On the VFD you have earth ground from the 220vac so nothing else needs to be done there other than the drain wire from the spindle control board to the VFD base ground. 

For the BOB enclosure, if you ground the BOB to the ground system, don't run a separate ground to the back plate. I would keep the BOB isolated from the back plate to reduce the chance of the back plate picking up interference.

With your VFD and BOB enclosures being plastic you don't get the added protection of the Faraday cage affect of a full metal enclosure. Even with a full metal enclosure the openings in the enclosure need to be kept as small as possible for it to work properly.


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## homebrewed

TomS said:


> Jbolt's post got me thinking about my wiring.  I've gone through 3 upgrades since the initial installation and the wiring is beginning to be a bit untidy.  Before doing any more testing I'm going to clean things up.  Finding the driver/BoB ground loop may be significant.  We'll see.  And I will run a drain wire from the BoB to the star ground lug.



Your comment about untidy wiring got my attention.

Cable dress can be important when it comes to reducing magnetic interference.  You have a situation where you have conductors carrying high current to your steppers, and conductors that are relatively high impedance signal lines.  Magnetic coupling between them can cause problems (ask me how I know).  Shielding in the form of copper braid really doesn't address this kind of interference.  Good cable dressing, and keeping high current lines separated as far as practically possible from signal lines, is the way to do it.  The cable dresing should minimize the area between your drain lines and signal lines.  See my illustrations below

Example 1, bad lead dress (lines far apart)
                             signal line ---------------------------------------------------------------------------



                             Drain line ---------------------------------------------------------------------------

Example 2, better lead dress
                              Signal -----------------------------------------------------------------------------
                             Drain-----------------------------------------------------------------------------

Example 3, Even better lead dress (this is hard to draw so I won't):  make a twisted pair using the signal and drain lines. Induced voltages tend to cancel.  I've even seen this approach used in high frequency integrated circuits.

Reason:  the larger the spacing between the signal and drain lines, the more magnetic flux can pass through the loop that is formed, producing more induced voltage.

Ideally you'd also route your cables so the high current lines are at right angles to the signal lines but that could be difficult to do.


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## TomS

jbolt said:


> For the grounding system I use the location of where earth ground enters the system as the starting location for each arm of the ground runs.
> 
> On the VFD you have earth ground from the 220vac so nothing else needs to be done there other than the drain wire from the spindle control board to the VFD base ground.
> 
> For the BOB enclosure, if you ground the BOB to the ground system, don't run a separate ground to the back plate. I would keep the BOB isolated from the back plate to reduce the chance of the back plate picking up interference.
> 
> With your VFD and BOB enclosures being plastic you don't get the added protection of the Faraday cage affect of a full metal enclosure. Even with a full metal enclosure the openings in the enclosure need to be kept as small as possible for it to work properly.



Thanks for the clarifications.  We're on the same page.


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## TomS

My plan for today was to have test data to share.  Unfortunately not.  I stripped out the unused X and Y Enable - wire and rerouted all of the drain wires.  Also added a ground wire from the BoB to the star ground.  Ran individual ground wires from the BoB/ESS enclosure and the motor driver enclosure then terminated them at the VFD ground lug.  Powered up the system and the Y axis driver fault light is on.  Checked all the wiring making sure the termination points were tight then double checked again.  Made sure I hadn't crossed a wire and all is good there.  Gave up for the day out of utter frustration.  Tomorrow I'll swap out the Y driver with the X driver.  If the green light comes on then it's the driver.  If no green light then it's back to figuring out what changed.  Sure would like to be making parts.


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## spumco

Sorry, I knew my luck would rub off.

You'll get 'er.


----------



## TomS

homebrewed said:


> Your comment about untidy wiring got my attention.
> 
> Cable dress can be important when it comes to reducing magnetic interference.  You have a situation where you have conductors carrying high current to your steppers, and conductors that are relatively high impedance signal lines.  Magnetic coupling between them can cause problems (ask me how I know).  Shielding in the form of copper braid really doesn't address this kind of interference.  Good cable dressing, and keeping high current lines separated as far as practically possible from signal lines, is the way to do it.  The cable dresing should minimize the area between your drain lines and signal lines.  See my illustrations below
> 
> Example 1, bad lead dress (lines far apart)
> signal line ---------------------------------------------------------------------------
> 
> 
> 
> Drain line ---------------------------------------------------------------------------
> 
> Example 2, better lead dress
> Signal -----------------------------------------------------------------------------
> Drain-----------------------------------------------------------------------------
> 
> Example 3, Even better lead dress (this is hard to draw so I won't):  make a twisted pair using the signal and drain lines. Induced voltages tend to cancel.  I've even seen this approach used in high frequency integrated circuits.
> 
> Reason:  the larger the spacing between the signal and drain lines, the more magnetic flux can pass through the loop that is formed, producing more induced voltage.
> 
> Ideally you'd also route your cables so the high current lines are at right angles to the signal lines but that could be difficult to do.





spumco said:


> Sorry, I knew my luck would rub off.
> 
> You'll get 'er.





spumco said:


> Sorry, I knew my luck would rub off.
> 
> You'll get 'er.



This is wierd.  I clicked Reply on your post and it brought me to Homebrewed's post.  Yeah, I'll get it done just frustrating.

Homebrewed - I like your idea about twisting the drain wire and signal wire.  Being that I've got some additional wiring ahead of me tomorrow I'll give it a try.


----------



## TomS

TomS said:


> My plan for today was to have test data to share.  Unfortunately not.  I stripped out the unused X and Y Enable - wire and rerouted all of the drain wires.  Also added a ground wire from the BoB to the star ground.  Ran individual ground wires from the BoB/ESS enclosure and the motor driver enclosure then terminated them at the VFD ground lug.  Powered up the system and the Y axis driver fault light is on.  Checked all the wiring making sure the termination points were tight then double checked again.  Made sure I hadn't crossed a wire and all is good there.  Gave up for the day out of utter frustration.  Tomorrow I'll swap out the Y driver with the X driver.  If the green light comes on then it's the driver.  If no green light then it's back to figuring out what changed.  Sure would like to be making parts.



I swapped the X and Y driver wires at the BoB.  If it was a wiring issue I would have expected the X axis driver fault light to come on.  It didn't.  The Y axis driver fault light is on so it looks like a bad driver.  Looks like I'll be ordering a new driver.  The price isn't too bad, about $40 to $45, but it's coming from China.  Probably going to take 2 to three weeks to get here.


----------



## jbolt

If I recall you used the DQ860MA drivers for the X & Y? Both of mine eventually went bad. There are rectifier diodes on the back of the PBC that kept failing. I went to the KL-11080 from Automation Technologies. It is similar to the DQ2272 I have on the Z axis.


----------



## homebrewed

TomS said:


> This is wierd.  I clicked Reply on your post and it brought me to Homebrewed's post.  Yeah, I'll get it done just frustrating.
> 
> Homebrewed - I like your idea about twisting the drain wire and signal wire.  Being that I've got some additional wiring ahead of me tomorrow I'll give it a try.



I've never heard of it causing a problem like you're describing but it's possible for the different steppers to talk to each other as well.  If your wiring configuration for the steppers has changed since your initial build, you might want to take a look at it with this in mind.  You wouldn't want to bundle all the stepper cables together because that would be worst-case as far as coupling is concerned.  Bundling each stepper's wires together should be OK because the currents should -- more or less -- cancel out (i.e., you've got the same current flowing IN as OUT so the mag fields should cancel).  You actually end up with a dipole type of magnetic field, which drops off in intensity much more rapidly than the field from a single wire.

I recall a story one of my electrical engineering professors told long ago. He was contacted by a mining company that was having problems with a new 3-phase electric motor they had gotten.  The motor was running as though it had insufficient voltage.  The company was testing it before they hauled it into the mine, and he noticed they had coiled and stacked the (very long) wire bundles on top of each other.  On a hunch he told them to separate the coils:  and the motor began to operate correctly.  The problem was the mutual inductance between the phases, exacerbated by their close proximity.


----------



## spumco

_The problem was the mutual inductance between the phases, exacerbated by their close proximity._

Interesting, and is a parallel to what I was taught in the Navy about extension cords.  We were told not to use extension cords or welding cable coiled up but to spread them out to reduce heating.  Of course, we didn't want to do that on some big old 00 welding leads when we only needed a couple feet for the job, but you pretty much say Yes, Chief and get on with it.  I get my NDE inspectors to do the same thing now when we're doing mag particle inspections running 600 amps through giant cables.  You can measure the voltage drop in a 50' cable when it's coiled vs. spread out.

I also was advised by someone here or on CNCZone to twist my VFD conductors inside the conduit to help cancel out noise.  Twist the three leads, but do not twist the motor ground with the bundle.  Each conductor is looped through an individual ferrite ring right at the VFD end, and then the twist starts.  Everything is run inside metallic conduit with ferrite and so far I've had zero VFD noise issues.

Not that that's an issue with Tom's current woes, but I figured I'd mention it anyway since we're swapping electrical pixie stories.


----------



## TomS

Received my new driver today and got the mill up and running.  I ran a quick test with the mag base mounted to the column and the DTI on the vise jaw as in the previous test.  Needle movement was the same as the first test.  Tomorrow I'll run the test as jbolt suggested.

I've been doing a lot of reading while waiting for the replacement driver.  There are a few settings in CamBam (my CAM software) and the Mach3 post processor that may need to be tweaked.  In CamBam there is a arc fit tolerance and auto arc fitting setting.  In the Mach3 post processor I found arc center mode which can be absolute or incremental.  There is one absolute setting and four different incremental settings.  Default is incremental (C-P1).  One CamBam user has been using absolute for years without issue so I'm going to give that a try.  Then there is arc to line tolerance.  The default is .01.  I did find a reference that .01 is the default for working in metric.  Couldn't find a reference to the default for inch mode but .01 of an inch is much greater than .01 of a millimeter.  Looks like I need to make a change.

For info my X and Y power supplies are set at 60 volts output.  I've read that higher is better but how high is too high?

I'll post more test results tomorrow.


----------



## spumco

Good to hear you're making progress.  I had the same problem when I switched from Mach to UCCNC; the default settings are for metric units.  My machine profile imported correctly, but all the variables not in my profile caused a few pucker moments until I went through every single thing and set it up for proper units.

As far as the driver supply voltage - it's too high when the smoke comes out   If you're still using the  DQ860MA driver, it's rated to 80 volts.  If I recall my internet stepper theory lessons, power is a function of voltage, and torque is a function of current (all else being equal).  Increase the voltage, and the power (torque x speed) goes up.  The low-speed maximum torque won't change, but the point where it starts dropping off will be at a higher RPM.

The way to increase low speed torque is to raise the max current.  The downside to this is motor heating - so just set the driver to the motor rating and be done with it.

_(Hopefully someone smarter will chime in and confirm my hillbilly stepper motor hypothesis.)_

I suggest you leave them at 60v and get your machine sorted out.  Once you have the surface finish problem fixed and you've cleaned up the copper octopus in your enclosure, then you might try bumping the voltage and seeing what feed rates you can achieve in a standard cut before you start losing steps.  Increasing the voltage will probably permit you to take more aggressive or faster cuts, assuming your spindle isn't the limiting factor.  Again, this assumes your power supplies are capable of maintaining 80v to the drivers at max current draw.

Cant wait to hear how _The Jbolt Method (TM_) works.

-S


----------



## TomS

spumco said:


> Good to hear you're making progress.  I had the same problem when I switched from Mach to UCCNC; the default settings are for metric units.  My machine profile imported correctly, but all the variables not in my profile caused a few pucker moments until I went through every single thing and set it up for proper units.
> 
> As far as the driver supply voltage - it's too high when the smoke comes out   If you're still using the  DQ860MA driver, it's rated to 80 volts.  If I recall my internet stepper theory lessons, power is a function of voltage, and torque is a function of current (all else being equal).  Increase the voltage, and the power (torque x speed) goes up.  The low-speed maximum torque won't change, but the point where it starts dropping off will be at a higher RPM.
> 
> The way to increase low speed torque is to raise the max current.  The downside to this is motor heating - so just set the driver to the motor rating and be done with it.
> 
> _(Hopefully someone smarter will chime in and confirm my hillbilly stepper motor hypothesis.)_
> 
> I suggest you leave them at 60v and get your machine sorted out.  Once you have the surface finish problem fixed and you've cleaned up the copper octopus in your enclosure, then you might try bumping the voltage and seeing what feed rates you can achieve in a standard cut before you start losing steps.  Increasing the voltage will probably permit you to take more aggressive or faster cuts, assuming your spindle isn't the limiting factor.  Again, this assumes your power supplies are capable of maintaining 80v to the drivers at max current draw.
> 
> Cant wait to hear how _The Jbolt Method (TM_) works.
> 
> -S



I'm taking it a step at a time.  I want to specifically identify the root cause so I can pass it along to others.  The "copper octopus" is gone.  I ran the test today to see if the wiring changes had an effect.  They didn't so now it's on to the next test.

Thanks


----------



## jbolt

Here is what kept failing on my DQ860MA drivers. Exploding diodes! The diodes are only a couple of bucks and easy enough to fix but after the third one I gave up.  Wantai to their credit offered to fix them under warranty but failed to understand that the shipping charges back and forth to China would exceed the replacement cost. They did give me the US spec for a replacement diode.


----------



## homebrewed

jbolt said:


> Here is what kept failing on my DQ860MA drivers. Exploding diodes! The diodes are only a couple of bucks and easy enough to fix but after the third one I gave up.  Wantai to their credit offered to fix them under warranty but failed to understand that the shipping charges back and forth to China would exceed the replacement cost. They did give me the US spec for a replacement diode.
> 
> View attachment 239887
> View attachment 239888


If the diodes are blowing themselves off the board they are severely overstressed!  The important parameters are the diode type (speed rating), breakdown voltage and current handling capability.   I found a teardown log here:  http://blog.bouni.de/blog/2015/02/03/taking-a-dq860ma-stepper-driver-apart/ that provides a link to the diode data sheet.  The diodes are "ultra-fast" type with 2 amp/50 amp average/peak, 280/400V RMS/peak ratings.  The key to finding a US replacement is the speed -- they MUST be fast-recovery for a PWM application.  Of course, you want the current and voltage ratings to be equal to or better than the OEM.

BTW from the same teardown log I note there are some indications that the driver manufacturer may be using counterfeit chips -- the sanded-off surface of the controller IC either says it's counterfeit or the manufacturer did not want their board to be reverse-engineered.  If it IS counterfeit, they also may be using diodes that were pulled from other boards.  If so, they may or may not be fast-recovery.  That could explain the early failure of the diodes.


----------



## TomS

homebrewed said:


> If the diodes are blowing themselves off the board they are severely overstressed!  The important parameters are the diode type (speed rating), breakdown voltage and current handling capability.   I found a teardown log here:  http://blog.bouni.de/blog/2015/02/03/taking-a-dq860ma-stepper-driver-apart/ that provides a link to the diode data sheet.  The diodes are "ultra-fast" type with 2 amp/50 amp average/peak, 280/400V RMS/peak ratings.  The key to finding a US replacement is the speed -- they MUST be fast-recovery for a PWM application.  Of course, you want the current and voltage ratings to be equal to or better than the OEM.
> 
> BTW from the same teardown log I note there are some indications that the driver manufacturer may be using counterfeit chips -- the sanded-off surface of the controller IC either says it's counterfeit or the manufacturer did not want their board to be reverse-engineered.  If it IS counterfeit, they also may be using diodes that were pulled from other boards.  If so, they may or may not be fast-recovery.  That could explain the early failure of the diodes.



Thanks for the info.  Not inclined to try a repair as the cost for a replacement driver is only about $40.


----------



## TomS

I ran a multitude of tests this morning.  The first test was mounting the DTI as jbolt suggested and running gcode.  The DTI needle bounced around quite a bit.  I read on another forum that you can run a Fanuc post processor with Mach3.  So I tried it.  No surface finish change using the standard PP settings.   I then set the Fanuc PP Arc Center mode to Absolte and made the same change in Mach3 General Configuration.  Again, no change.  Made the same change to the Mach3 post processor with no change in surface finish quality.  Out of desperation I changed Arc Output from Normal to Convert to Lines.  Nada!  All these tests were run with Arc Fit Tolerance set at .0004 and Spline to Polyline Tolerance set at .0001.  The last test were test cuts made at three different Z heights to see if the faceting lined up.  They didn't.  See the pictures below.

Still have to run the drain wire disconnected test as jbolt suggested.  If that doesn't show anything then I'm leaning towards  a motor tuning issue.


----------



## homebrewed

TomS said:


> Thanks for the info.  Not inclined to try a repair as the cost for a replacement driver is only about $40.



Sometimes it's the down-time that is more important than waiting for a replacement driver.  If the driver is that unreliable maybe you should get one or two backups?  Depends on whether or not the down-time delays delivery to a customer vs. delaying a personal project.  

I suppose your decision to replace or repair also depends on your ability to solder/de-solder surface mount parts without damaging the board or other components.  I've done that at work but now, lacking a good stereo-zoom microscope,  SMT would be a bit more challenging for these old eyes.  I thought I might be able to use a cheap USB microscope but the frame rate is so low it's really difficult to place small components.  This is a case of you really DO get what you pay for.


----------



## TomS

homebrewed said:


> Sometimes it's the down-time that is more important than waiting for a replacement driver.  If the driver is that unreliable maybe you should get one or two backups?  Depends on whether or not the down-time delays delivery to a customer vs. delaying a personal project.
> 
> I suppose your decision to replace or repair also depends on your ability to solder/de-solder surface mount parts without damaging the board or other components.  I've done that at work but now, lacking a good stereo-zoom microscope,  SMT would be a bit more challenging for these old eyes.  I thought I might be able to use a cheap USB microscope but the frame rate is so low it's really difficult to place small components.  This is a case of you really DO get what you pay for.



I hope I didn't come across as flippant.  My mill has been running for about three years now so if I have to replace a driver again in three years I'm OK with that.  This driver failure was a first for me.  Everything else has been running fine.  

I'm with you on soldering small electronic components.  My eyes aren't what they used to be and I don't have the proper equipment.  I'd rather spend my money on tooling for the mill and lathe.


----------



## jbolt

My drivers are the ones that kept blowing up diodes, not the OP's. I believe this is the first driver failure for Tom and I have no idea what the failure is. I was just sharing my experience and why I moved away from them.  As surface mount components go they are fairly large and easy to replace with a fine tipped variable heat soldering iron. I fixed mine a few time since it only takes a little time to do vs waiting.  I'm not suggesting he abandon them but if it is a diode that failed to be aware. 

Tom - if you exhaust all options with you current setup you might try reinstalling the old BOB and motion controller. Not fun but it might tell you if it is something in the 126, 107, ESS combo.

Grasping at straws here but I have seen issues (non CNC) with some cheap Ethernet cables. I make sure to use high quality shielded cables, keep them as short as possible and away from power cords.


----------



## TomS

jbolt said:


> My drivers are the ones that kept blowing up diodes, not the OP's. I believe this is the first driver failure for Tom and I have no idea what the failure is. I was just sharing my experience and why I moved away from them.  As surface mount components go they are fairly large and easy to replace with a fine tipped variable heat soldering iron. I fixed mine a few time since it only takes a little time to do vs waiting.  I'm not suggesting he abandon them but if it is a diode that failed to be aware.
> 
> Tom - if you exhaust all options with you current setup you might try reinstalling the old BOB and motion controller. Not fun but it might tell you if it is something in the 126, 107, ESS combo.
> 
> Grasping at straws here but I have seen issues (non CNC) with some cheap Ethernet cables. I make sure to use high quality shielded cables, keep them as short as possible and away from power cords.



I understand your logic but I really don't want to reinstall the old breakout board and the UC100.  I've changed so much that it would be nearly a complete rewire job.  I've got a couple of new things to try first.  I'm going to lower the power supply output voltage and see what happens.  Read that on Practical Machinist where the lower voltage altered motor resonance and improved the surface finish.  I read somewhere else that raising the voltage did the same thing.  Who knows?  It's an easy thing to do.

I did run the drains disconnected test you suggested.  Surface finish didn't change so my assumption is the grounding system is sound.

You bring up a good point about the ethernet cable.  It's Cat6 but that's all I know.  I'll check into it and make sure it's shielded.


----------



## jbolt

TomS said:


> I understand your logic but I really don't want to reinstall the old breakout board and the UC100.  I've changed so much that it would be nearly a complete rewire job.  I've got a couple of new things to try first.  I'm going to lower the power supply output voltage and see what happens.  Read that on Practical Machinist where the lower voltage altered motor resonance and improved the surface finish.  I read somewhere else that raising the voltage did the same thing.  Who knows?  It's an easy thing to do.
> 
> I did run the drains disconnected test you suggested.  Surface finish didn't change so my assumption is the grounding system is sound.
> 
> You bring up a good point about the ethernet cable.  It's Cat6 but that's all I know.  I'll check into it and make sure it's shielded.



I totally get not wanting reinstall but it might narrow down the cause of your issue. 

When you ran the test as I suggested how much did the Z jump around? Does it jump only when doing arcs or both arcs and straight moves?


----------



## TomS

jbolt said:


> I totally get not wanting reinstall but it might narrow down the cause of your issue.
> 
> When you ran the test as I suggested how much did the Z jump around? Does it jump only when doing arcs or both arcs and straight moves?



I'm going from memory here but as I recall the needle jumped about .007" to .010" and only during arc moves.  You can hear the motors change sound when cutting arcs.  During straight moves they are much quieter.

I tried a test run today with the power supply set at 55 vdc and 65vdc.  Didn't make a difference in surface finish.  I rerouted my ethernet cable so it was no where near a AC power cable.  Again, no change in surface finish.  Using a 2 flute 3/8" end mill I ran a 1/4" DOC by .005" WOC at 20 IPM then ran the same scenario at 5 IPM.  Something is causing the motors to jump around corners but I don't why.  It's got to be a harmonics/resonance issue.  Wish I knew what's causing it.


----------



## spumco

I'm pretty stumped, too.

Shot in the dark here... Do you have one power supply for all three axis?  I'm wondering  - you mentioned motor noise changing - if the PS is acting wonky when there's a load from both X/Y at the same time.  'Cause you also mentioned that it's a problem on straight angle cuts, not just arcs, right?  Any time you're cutting with both axis moving there's a problem?

Maybe a test doing an X/Z or Y/Z move might result in the same surface finish issue.  Do a quickie CAD/CAM of a hill-shaped object and use a bullnose cutter with a parallel 3D contour.


----------



## TomS

spumco said:


> I'm pretty stumped, too.
> 
> Shot in the dark here... Do you have one power supply for all three axis?  I'm wondering  - you mentioned motor noise changing - if the PS is acting wonky when there's a load from both X/Y at the same time.  'Cause you also mentioned that it's a problem on straight angle cuts, not just arcs, right?  Any time you're cutting with both axis moving there's a problem?
> 
> Maybe a test doing an X/Z or Y/Z move might result in the same surface finish issue.  Do a quickie CAD/CAM of a hill-shaped object and use a bullnose cutter with a parallel 3D contour.



I have a dedicated power supply for each axis drive. Straight line cuts are fine.  Surface finish is good.  So yes, problem/poor surface finish is on arc and circular cuts.

I'll try a sloped 3D cut and see what happens.


----------



## homebrewed

So the Z is jumping around and the sound of the X & Y steppers is different when cutting arcs or angles?  What happens when you remove power from, say, the X driver (Y still powered up), and then reverse the situation?  There seems to be some odd interaction going on between the axes.

Something else I would suggest would be to write up a table of each hypothesis, experiment and result.  Or, since nothing has really solved the problem, at least a list of what you've tried and why.  While you may think you've exhausted a particular avenue,  you may find some holes in your testing while you are writing up your summary.  This has been helpful for me when working on a gnarly problem.

Are you using the sense connections on your power supplies or are they unconnected?


----------



## TomS

homebrewed said:


> So the Z is jumping around and the sound of the X & Y steppers is different when cutting arcs or angles?  What happens when you remove power from, say, the X driver (Y still powered up), and then reverse the situation?  There seems to be some odd interaction going on between the axes.
> 
> Something else I would suggest would be to write up a table of each hypothesis, experiment and result.  Or, since nothing has really solved the problem, at least a list of what you've tried and why.  While you may think you've exhausted a particular avenue,  you may find some holes in your testing while you are writing up your summary.  This has been helpful for me when working on a gnarly problem.
> 
> Are you using the sense connections on your power supplies or are they unconnected?



Power supply sense connections?  Here's a picture of the terminal connections on my X and Y power supplies.


----------



## TomS

spumco said:


> I'm pretty stumped, too.
> 
> Shot in the dark here... Do you have one power supply for all three axis?  I'm wondering  - you mentioned motor noise changing - if the PS is acting wonky when there's a load from both X/Y at the same time.  'Cause you also mentioned that it's a problem on straight angle cuts, not just arcs, right?  Any time you're cutting with both axis moving there's a problem?
> 
> Maybe a test doing an X/Z or Y/Z move might result in the same surface finish issue.  Do a quickie CAD/CAM of a hill-shaped object and use a bullnose cutter with a parallel 3D contour.




Today I ran a couple of tests in the XZ plane and the YZ plane.  Below are pictures of each test done with a two flute 3/8" HSS ball end mill at 3000 rpm, .005" DOC and 010" stepover.  As you can see there is virtually no difference in surface finish.  

Grasping at straws, between the two tests, I ran a ground wire from my earth ground rod to my enclosure.  Guess what?  No change.  Geez this is frustrating.

But I didn't come away empty handed.  During the ZX test the motors emitted a monotone sound.  Not so with the ZY test.  The Y motor tone changed multiple times during each pass.  There may be something there so tomorrow I'll pull the motor and check the ball nut mount and the ball screw AC bearings.


----------



## TomS

I think I found the problem, hopefully.  I disassembled the Y axis ball screw bearing block and one of the AC bearings was in failure mode.  Spinning it by hand it was rough.  The other one was OK.  I'm going to replace all four of the bearings on the X and Y axis while I have it apart.  I'm praying this is it.


----------



## homebrewed

TomS said:


> Power supply sense connections?  Here's a picture of the terminal connections on my X and Y power supplies.
> 
> View attachment 240025


Most high current PSU's have sense terminals, to compensate for voltage drops on the lines.  I guess that's one of the things you give up with these types of inexpensive supplies.  Or perhaps in this type of application there's not much benefit to be had (PWM stepper driver supply).

Good find with the rough bearing.  Hopefully that's the source of your problem.  Seems sort of strange for a bearing to go bad in that application.  I'd double-check other components in the Y axis to make sure the bearing is not the result of some other problem.  Otherwise you could be back in there sooner than you like.


----------



## TomS

homebrewed said:


> Most high current PSU's have sense terminals, to compensate for voltage drops on the lines.  I guess that's one of the things you give up with these types of inexpensive supplies.  Or perhaps in this type of application there's not much benefit to be had (PWM stepper driver supply).
> 
> Good find with the rough bearing.  Hopefully that's the source of your problem.  Seems sort of strange for a bearing to go bad in that application.  I'd double-check other components in the Y axis to make sure the bearing is not the result of some other problem.  Otherwise you could be back in there sooner than you like.



I've looked things over and didn't see anything else of concern.  The ball nut mount is tight to the saddle and the ball screw rotated smoothly.  I believe it's the bearings as they are cheap, as in poor quality, asian imports.  They came with the bearing blocks.  I've got four on order from VXB.  Should be here on Wednesday.

Got my fingers crossed.


----------



## spumco

I'm throwing the chicken bones for you.  Keep us posted.


----------



## jbolt

I hope that solves your problem but it would be an odd coincident that it would happen at the same time you changed the controller. I'll keep my fingers crossed for you.


----------



## TomS

jbolt said:


> I hope that solves your problem but it would be an odd coincident that it would happen at the same time you changed the controller. I'll keep my fingers crossed for you.



Looking back on some jobs prior to changing out the controller there were some surface finish issues starting to appear.  They just were not bad enough at that time.  Or I wasn't paying attention.

I'm hoping too!


----------



## spumco

Bearings come in?

I don't think I'm the only one with fingers crossed...


----------



## TomS

The bearings arrived in yesterday's mail which was two days early.  Thank you VXB!  Headed to the shop first thing this morning and got them installed and preloaded.  Ran some test cuts and the surface finish is much better.  Not absolutely smooth but my mill isn't a Haas either.  It's smooth enough and the arc faceting is the same as the straight run faceting which is at an acceptable level.  Haven't done a pocket yet to check for roundness but will do so in the next couple of days.  The motors are much quieter or more likely the bearings are quieter.  Here's a few pictures of the surface finish and failed bearings.

If it wasn't for my recent VFD/belt drive conversion and electronics upgrade it might have been a bit easier to find the problem.  What a journey!!  Thank you Spumco, Jbolt and Homebrewed for helping me through this ordeal.  










And some pictures of the bad AC bearings.


----------



## spumco

SWEET!

Frankly, you figured this one out - but I'm happy to have helped by suggesting a few incorrect theories.

I love it when unrelated variables send you down the wrong rabbit hole when troubleshooting.  I spent two days researching process conditions and chemistry upsets when diagnosing a pressure vessel nozzle that corroded though.  On the third day I noticed a dirty old sledgehammer about 20 feet away from the vessel tucked in to some angle iron.  For some reason I decided to ask the area operator why a mechanic left it there.  Turns out the _operators_ frequently used it to 'massage' the connected piping to clear fouling, and one of them apparently decided to hit the ceramic-lined vessel nozzle when the pluggage was particularly stubborn.  Further inspection revealed they had hit it so enthusiastically that they rolled the edge of a 16" class 300 nozzle flange, but you couldn't see it until after the goop was cleaned off.

Turns out ceramic corrosion-barrier sleeves are not particularly impact resistant, and process conditions don't matter when a gorilla is having his way with the equipment.

Now it's my turn to figure out why a ball spline groove I'm trying to mill in a tool shank isn't coming out quite the right size.  Cam path wrong? Tool undersized? Steps/inch not quite right?  Gremlins?

We'll see.

-S


----------



## TomS

spumco said:


> SWEET!
> 
> Frankly, you figured this one out - but I'm happy to have helped by suggesting a few incorrect theories.
> 
> I love it when unrelated variables send you down the wrong rabbit hole when troubleshooting.  I spent two days researching process conditions and chemistry upsets when diagnosing a pressure vessel nozzle that corroded though.  On the third day I noticed a dirty old sledgehammer about 20 feet away from the vessel tucked in to some angle iron.  For some reason I decided to ask the area operator why a mechanic left it there.  Turns out the _operators_ frequently used it to 'massage' the connected piping to clear fouling, and one of them apparently decided to hit the ceramic-lined vessel nozzle when the pluggage was particularly stubborn.  Further inspection revealed they had hit it so enthusiastically that they rolled the edge of a 16" class 300 nozzle flange, but you couldn't see it until after the goop was cleaned off.
> 
> Turns out ceramic corrosion-barrier sleeves are not particularly impact resistant, and process conditions don't matter when a gorilla is having his way with the equipment.
> 
> Now it's my turn to figure out why a ball spline groove I'm trying to mill in a tool shank isn't coming out quite the right size.  Cam path wrong? Tool undersized? Steps/inch not quite right?  Gremlins?
> 
> We'll see.
> 
> -S



Yeah, this one had a few twists and turns in it.  That's the way it goes sometimes.  Besides curing the finish problem I did learn quite a bit about the inner workings of Mach3 and post processors.  All in all it was a frustrating road trip but the end result was worth it.

Thanks again for your help.


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## homebrewed

To quote Sherlock Holmes, "when you have eliminated the impossible, whatever remains, however improbable, must be the truth".  You went through quite an exercise but found the problem, despite my efforts to distract you .  Now you can go back to making stuff again!


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## spumco

As long as the brain trust is still paying attention to this thread, I might as well throw up my problem and see if anybody has some good ideas.

Pocketing a .1255" radius groove in a 12mm shaft along the long axis (ball spline drive).  Groove is not to full radius depth - C/L of the radius is 0.025" above the top surface.  A 0.250" ground bearing ball is supposed to drop in the groove and sit on the bottom with just enough clearance for free movement along the groove.

Groove length is good enough (I have no way of measuring accurately).  Max groove depth in the G-code is supposed to be 0.0998" but it's coming out at 0.0972" deep when measuring with a .1875" bearing ball down in the groove.  This means my .250 bearing ball doesn't sit in the bottom of the groove but is riding up on the edges of the groove by about 0.010".  It looks like the groove was cut to a smaller radius than desired.

Using Fusion 360 CAD & CAM, 3D adaptive for the first two ops (3/16" & 1/8".030"R bullnose carbide), and morphed spiral for the cleanup with a 3/16" ball.  (No, I didn't want to just plow in with a 1/4" ball mill and take my chances.)  I turned off "stock to leave" on the finishing op and did a 0.0025 step-over. 

Tool offsets set using a 1-2-3 block, and stock Z-height set using a ground pin between the tools and the stock.  Double checked axis calibration tonight and I'm within .0004" over 12" in Z, and .0003" over 9" in Y.  Pocket/groove is along the X axis, so I'm not concerned with X right now.

The finish looks superb, and I lucked out on the feeds & speeds - it sounded great with no squealing or chatter.  I'm discounting tool deflection because the finishing op tool pressure should be extremely low - it's only taking .001" to 0.002" from the adaptive clearing ops.

I could solve this pretty quickly by changing the CAD model to a .126" or .127" radius (or forcing a negative "stock to leave" in CAM), but I'd like to figure out why it's not coming out right before brute-forcing a solution.

Any ideas?  3/16" ball mill not actually to size?  I don't have a good way of measuring the ball mill radius, but the shank and flutes are spot on published diameter.

Thanks,
Spumco


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## spumco

Never mind.  CAM user fail.

Cutting strategy was inappropriate for the pocket geometry - switched to 3D scallop and the simulation is now cutting all the way to the edge.  Previous strategy was going to depth, but not cutting the full width so I wound up with a narrower than desired groove top.


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## TomS

homebrewed said:


> To quote Sherlock Holmes, "when you have eliminated the impossible, whatever remains, however improbable, must be the truth". You went through quite an exercise but found the problem, despite my efforts to distract you .  Now you can go back to making stuff again!



No distraction at all.  I asked for help and you offered up your opinion, and I appreciate that.  This kind of interaction among our members is what makes this forum so good.


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## TomS

spumco said:


> Never mind.  CAM user fail.
> 
> Cutting strategy was inappropriate for the pocket geometry - switched to 3D scallop and the simulation is now cutting all the way to the edge.  Previous strategy was going to depth, but not cutting the full width so I wound up with a narrower than desired groove top.



Glad you got it sorted out.  Usually it's a simple fix.  Ask me how I know.


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## spumco

Just cut it with the new code and there's no daylight between the ball and the pocket.    Lesson learned - scrutinize the tool path simulation.  Had I done that, I would have seen it wasn't going all the way to the outer edge of the groove with the first attempt.

Tomorrow we do it for real in the 4th axis and cut three of them around the circumference.  Making a spring-loaded engraving tool holder and Mr. Cheapo here won't spend money on a broach to cut some internal splines. 

So we'll see if my shiny balls will transmit torque without too much slop between the shaft and the bore...



TomS said:


> This kind of interaction among our members is what makes this forum so good.



No Kidding.


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## jbolt

Tom, I'm glad to hear you figured it out. Good catch on the bearing. Based on what you were seeing it didn't seem likely to be a mechanical issue. With a motor driven system it is really hard to "feel" these kinds of things. I'll bet you could write a paper on Mach3 and cutting arcs.


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## jbolt

spumco said:


> Never mind.  CAM user fail.
> 
> Cutting strategy was inappropriate for the pocket geometry - switched to 3D scallop and the simulation is now cutting all the way to the edge.  Previous strategy was going to depth, but not cutting the full width so I wound up with a narrower than desired groove top.



Simulation is an invaluable tool. About the only time I get bit is when I don't take the time to run full simulations. I have also gotten in the habit of modeling all the holding fixtures as well. Every so often I will grab a tool from the tool library that has a minimal tool retract and the sim will catch it. Virtual tools are a lot cheaper.


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## TomS

jbolt said:


> Tom, I'm glad to hear you figured it out. Good catch on the bearing. Based on what you were seeing it didn't seem likely to be a mechanical issue. With a motor driven system it is really hard to "feel" these kinds of things. I'll bet you could write a paper on Mach3 and cutting arcs.



I had me scratching my head for sure.  As you mentioned I'm a lot smarter on Mach3.

Thanks for your help along the way.


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