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PM932 CNC Build

jbolt

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#1
I had not planned on posting a build thread but since I have received a lot of information from other builds I figured I would give back.

My original build was going to be servo based but I ran across a great deal on stepper build parts similar to what jumps4 did on his zx45 conversion.

I have very limited space so the x & y steppers will be mounted off to the side with timing belts to the ball screws.

Here is a CAD screen capture of the layout done in Solidworks.

CADcapture1.jpg CADcapture2.jpg

Jay

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jbolt

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#2
Here are some pictures of the mill shoehorned into my garage.

I setup a temporary coolant tray and enclosure to make as many conversion parts before dismantling the mill.

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jumps4

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#3
that looks good
I still haven't got into 3d drawing and cam software, Ill have to try something pretty soon
the coupling for z should be a bellows or disc type, my first try was a spiral cut and the torque made it spin up and flex too much under load. I also lost about .5 of an inch at the top of the Z travel by putting the bearing inside the column to lower the motor.
steve
 

jbolt

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#4
Here are the parts I have milled so far. I got to the point I needed to tear down the mill to get the final measurements for the ball nut mounts for the x and y axis. Yesterday I removed the table and cross slide, measured and made drawings for the ball nut mounts. Photos at the end are turning and milling some of the parts on my Smithy Granite 1324.

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Anyone know how to keep the photos from rotating when uploading?

Jay

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jbolt

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#5
that looks good
I still haven't got into 3d drawing and cam software, Ill have to try something pretty soon
the coupling for z should be a bellows or disc type, my first try was a spiral cut and the torque made it spin up and flex too much under load. I also lost about .5 of an inch at the top of the Z travel by putting the bearing inside the column to lower the motor.
steve
Thanks Steve, I got a disc type coupling based on your build thread. I'm spacing the z-axis motor just high enough to allow full travel. I cant go higher due to the garage door clearance.

I help mentor a high school robotics team so I get a student copy of Solidworks every year. I'm still slow at it.


Jay
 

jbolt

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#8
I made a little more progress this week. The X & Y ball nut blocks are done. I cut the grooves and ports in the center base for the one-shot oiler, made the oiler distribution manifold, modified the center base for the Y axis ball nut block and finished up the Z axis upper mount.

Next up is enlarging the Y axis slot in the machine base to keep full travel with the larger ball nut and fitting the ballscrew.

Jay

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jbolt

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#9
Got the machine base modified for the x axis travel and finished the x axis ball screw assembly.

The ball screw shaft where the angular contact bearings fit were a light press fit which is too tight to get on and off by hand for fitting and assembly so I chucked it in the lathe and lightly sanded with 320 paper until it I could slide the bearings on with slight resistance.

After checking the fit of the x axis ball screw assembly in the base it looks like I need to relieve the ball nut block a little for clearance.

Jay

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jbolt

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#10
Ran into my first hiccup last weekend when I discovered the x axis ball screw was bent. Fortunately the supplier is replacing it but it will be a few weeks before I get the replacement.

This week I started on fitting the one-shot oiler supply lines. The ball nuts came with zert fittings but I plan on running oil lines to them so I modified the zert fittings to accept the tube fittings.

I need to start thinking about the coolant tray. I would like to use sheet metal but don't have access to a shear or break large enough.

Jay

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bvd1940

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Active Member
#11
Ran into my first hiccup last weekend when I discovered the x axis ball screw was bent. Fortunately the supplier is replacing it but it will be a few weeks before I get the replacement.

This week I started on fitting the one-shot oiler supply lines. The ball nuts came with zert fittings but I plan on running oil lines to them so I modified the zert fittings to accept the tube fittings.

I need to start thinking about the coolant tray. I would like to use sheet metal but don't have access to a shear or break large enough.

Jay

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I been lurking watching you do this build, keep up the good work looking nice.
 

jbolt

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#13
While I am waiting for the replacement ball screw I took a closer look at the BK bearing blocks that came with the ball screws. These hold the angular contact bearings that support the fixed end of the ball screw. I have no idea as to the quality of rating of the AC bearings but I do know they are not matched sets meaning they have no pre-load.

On top of that, with the bearing cap on the block there is extra space to let the bearings move back and forth. This turned out to be okay as it allowed space for shims to take up the slack in the bearings. Also note that the bearings were not orientated in any particular direction which is incorrect for the AC bearings.

To measure the slop in the bearings and bearing block I installed the ball screw on the machine and locked down the center base. The bearings are oriented in the DB configuration. This is so shims can be installed in-between the outer races and keep the correct loading.

AC-DB Mounting.png

A dial indicator placed at the end of the screw is zero'd and by turning the screw until tight by hand it shows the combined bearing / block slop. (I used pliers on this shaft to crank on it since it is being replaced it doesn't t matter if it gets marred). With the bearing block cap removed I measured the setback of the bearings at the outer race and then the depth of the cap. This difference difference is subtracted from the overall slop measurement which gives the bearing slop. For example overall measurement = 0.014", Bearing block / cap setback slop = 0.008". 0.014" - 0/008" = 0.006" bearing slop.

In this instance I installed 0.008" of shims. This tales up the slop and adds some pre-load. I have not taken the time to setup a jig to measure how much pre-load is really needed. I plan waiting until the machine is operational to see what the backlash is under machine load.

For the 2005 BK blocks they have 32mm OD bearings. I used 0.002" round shims. http://www.amazon.com/gp/product/B006U1JMZ2/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1 The shim OD had to be turned down to 32mm.

Another issue with the BK blocks is the cap is secured to the block with (4) 4mm 0.7 x 6mm cap screws. The BK cap under the screw head is 3mm which leaves only 3mm of thread engagement. Subtract the bevel at the threaded hole and you only get 2 threads engaged in the block. Not cool. Fortunately the holes are 15mm deep so the threads can the extended with a tap. I replaced the 6mm long screws with 12mm.

The AC bearing in the photo below is actually from VXB bearings. I managed to blowup one of the BK bearings while fitting them to the ball screw shafts and lost half the balls to my not so tidy and crowded garage floor. The VXB AC bearings are not expensive bearings so I'll see how the hold up compared the the BK bearings. The VXB do have less slop than the BK's.

Jay

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jbolt

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#14
A little more progress.

The head is now separated from the column. The z-axis ball screw and motor are assembled and temporarily installed. The top of the column only had a 3" hole and the motor coupler tube is 3.5" so I enlarged the hole to 4" with a 4" hole saw. The ball screw support and thrust bearing block are fabricated and fitted. Next step is to fabricate the ball nut to dovetail plate block.

Jay

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bvd1940

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#15
Thanks Bill.

It's hard to appreciate how much work is involved until you are actually doing it.

Jay
I just ordered up some ball screws for my 45 to convert it over but am going to do it in steps.
Did a lot of reading on the different conversions here and on the cnc site and am getting educated best I can.:thinking:
 

jumps4

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#16
Hi jay looking good
I like how you raised the z to pick up the extra z travel. I lost that on mine by flush mounting the motor.
when you put the shims in the bearing housing, you put them in between the 2 bearings right?
if you measure the inner and outer race heights of the bearings you will see they are the same. so you cannot get any preload unless your shims are in between the bearings. I could not tell from the picture. the shims have to be tall enough that when in between the 2 bearings the outer races press against each other before the cap contacts the housing. then the bearing can be adjusted to have preload and zero backlash by the nut on the ball-screw.
Every one of these bearing I purchased I had to do this, but its easy since the shim height is not critical as long as it is tall enough to keep the 2 inner races from contacting each other during preload adjustment.

steve
 

jbolt

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#17
Hi Steve,

By your description I believe we have done the same thing other than I'm adding just enough shims between the outer races to add preload and keep the inner races tight to each other. Final preload adjustment will be done by adding additional shims between the outer races. I prefer the shaft nut the be tightened against a solid assembly.

I'm still not thrilled by the small screws they use to hold the bearing caps on, especially the FK support which only has 3mm screws.

Jay

- - - Updated - - -

I just ordered up some ball screws for my 45 to convert it over but am going to do it in steps.
Did a lot of reading on the different conversions here and on the cnc site and am getting educated best I can.:thinking:
Which machine do you have?
 

bvd1940

Active User
Active Member
#18
Hi Steve,

By your description I believe we have done the same thing other than I'm adding just enough shims between the outer races to add preload and keep the inner races tight to each other. Final preload adjustment will be done by adding additional shims between the outer races. I prefer the shaft nut the be tightened against a solid assembly.

I'm still not thrilled by the small screws they use to hold the bearing caps on, especially the FK support which only has 3mm screws.

Jay

- - - Updated - - -
Which machine do you have?

Enco zx45 I think that is the model, but just about all the 45s are related some what LOL:roflmao:
I bought mine two years ago and have not been happy with my choice so finally tore the X/Y apart and cutting groves for oil passage and one shot lube. Also going to ball screws for future conversion to CNC.
I am accustom to using Bridgeport's, Grazinos, American, Monarchs, & Leblond.
So I was a fool to buy this Enco model and not buy a used Bridgeport I found in AZ prior to purchase of the Enco 45.
Well just and old fools grumbling, I will make it into a usable piece of equipment.:thinking:
 

jbolt

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#20
Got the z-axis ball nut to dovetail connector finished. Fun part to make. I was a bit nervous because the z-axis assembly is difficult to measure properly to get everything to align properly. I did a test fit tonight and it all works as planned. Tomorrow I will get the z axis completed and power up the stepper. Earlier this week I added oiler grooves and ports to the z-dovetail. A friend has access to a cnc laser cutter and large press brake so he is making me the parts for a chip / coolant pan. I'm hoping to pick that up this weekend.

Jay

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jbolt

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#22
Woo Hoo!!! got the z-axis powered up today and reattached the head. Feels good to finally be putting things back together.

The 4200 oz stepper moves the head likes it not even there. Parts for the chip tray wont be here until Tuesday so this weekend I will work on finishing the controller wiring.

Jay
 

jbolt

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#24
While waiting for the chip pan parts I worked on installing a sub frame to support the chip pan. I'm using the cast iron stand drip tray as part of the drainage system because it already had a drain hole and it allows a little more depth.. The hole from the factory is only 5/8" so I used a hole saw with a pilot bushing to open up the drain hole and used a 1-1/2" pipe tap to use 1-1/2" abs pipe for the drain pipe to the coolant bucket.

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jbolt

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#25
Also spent some time on the machine wiring. I was able to reuse all of the machine electronics except 2 momentary switches used for the z up/down. I installed a new enclosure which is a little larger and mounted it to the column. By getting it off the gear head and setting it back I can get the head lower to the table when turned 90 deg. All of the machine controls are in one place. Only power and switch legs go the the stepper control box. In the enclosure the upper contactor runs the power for the spindle motor and also switches the latching circuit for the 2 other contactors. This way when the e-stop is triggered all power is cut. The 2 lower contactors split power to the stepper drives. Coming into the enclosure is a 40amp 220v circiut. This goes into a breaker tray which splits the power to a 220v 15A circuit for the spindle motor and 2 110v 15A circuits for the steppers, coolant pump machine lights and stepper enclosure fans.

Jay

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jbolt

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#26
I picked up the chip pan parts on Friday and took it over the the robotics lab to assemble. The pan is 3 pieces, 2 sides and the lower tray. The lower tray has edge flanges all around. These are turned down to keep the inside of the pan clear of fasteners. The sides are sized so the tray locks inside the edge flanges. The tray was assembled with pop rivets and a Permatex gasketing sealant which is oil and water resistant. The assembled pan was then attached to the machine base using 10-32 flanged button head screws and the same gasketing sealant to the subframe I installed earlier.

Jay

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bvd1940

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#27
I picked up the chip pan parts on Friday and took it over the the robotics lab to assemble. The pan is 3 pieces, 2 sides and the lower tray. The lower tray has edge flanges all around. These are turned down to keep the inside of the pan clear of fasteners. The sides are sized so the tray locks inside the edge flanges. The tray was assembled with pop rivets and a Permatex gasketing sealant which is oil and water resistant. The assembled pan was then attached to the machine base using 10-32 flanged button head screws and the same gasketing sealant to the subframe I installed earlier.

Jay

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That is to pretty to mess up with chips and coolant:allgood:
 

09kevin

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#29
Looks like you are doing a fantastic job! Do you plan on having any type of enclosure to keep the chips and coolant inside?

Kevin
 

jbolt

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#30
Looks like you are doing a fantastic job! Do you plan on having any type of enclosure to keep the chips and coolant inside?

Kevin
Thanks Kevin.

I plan on doing a simple curtain enclosure out of pvc pipe and clear shower curtain liners. I don't want to do anything substantial so as to keep the machine accessible for oversized parts.

Jay