Another PM940-CNC-VS Thread...

I missed one thing that I needed to get done... I need some kind of containment. Since we had the kiddo, we decided that my wife should park inside, so she doesn't have to walk out on our steep(ish) driveway when it snows. Also, she doesn't have to scrap windows, which saves her some time in the AM and you need every second you can get trying to get this fat baby out the door. Anyway, can't be shooting chips all over her car, and need to try to keep them from getting into the house.

So, I summoned my inner Martha Stewart and made it happen...
IMG_20190113_150342 by Phazer Two, on Flickr

I have been thinking about doing this for a while, but couldn't decided if it was going to be too hodge podge. Turned out to be fantastic! It contained chips so they are only on the floor below the mill, so no more mess all over the garage. Another big plus is that it makes cleaning up much faster. The curtain rings are snap on things that I can get on and off pretty quick, so I can move it all out of the way pretty fast if I need too. When it's closed the two shower curtains meet right in the middle in front. Super happy with it. If you're looking for budget containment, I think this cost me $45-$50 all said and done.

I also got Centroid CNC12 updated, and tuned in for 2k steps/rev. I was able to tune it pretty well, I think it's actually better than last time, however it makes me want to go to 4000 steps/rev. I feel like that would make it even better/smoother.

After the curtain was up and the machine was tuned, it was time to make a simple test part. I just grabbed some scrap I had laying around and modeled up some features to measure.
IMG_20190113_171937 by Phazer Two, on Flickr

Everything came out great. I was taking it very easy because of the wood motor mount and all, so I ran it at about 50% speed to start. However halfway though it was doing so well I bumped it back to 100% and it just sang. Everything is really working well together, which feels really good. Now I just need to get my dang mist coolant running more consistently.... that should be next! Soon I will be cutting my new motor mount!

Parts used:
PZ
 
Why is this unit or any other unit for CNC not offered anymore by PM?
 
I don't think they ever offered any CNC units on their new site, and their old site didn't offer the 940CNC. You have to call or email them (I emailed).

If you have not contacted PM, I highly suggest you do. Matt is fantastic to deal with, and responds very fast. If I hadn't emailed him I would have ordered the wrong machine for sure.

PZ
 
I actually just ordered and received one of the last two 940 CNC's they have. Also got a good deal on it as well. If you are still looking I would suggest calling them. I think the problems with Mach3 and the nmotion card pushed the cnc version out. Based on what he said it sounds like they may be looking at bringing it back later with a different control.
 
makes sense...I sent an email inquiring.....
 
Well, I got what feels like a fair bit done in the last two weeks... In an effort to make things faster I didn't take many pics and just trucked though what I could. Turns out the wooden motor mount was just fine, never once ran into a problem. It cut the new motor mount with zero issues, and being able to run at 6k RPM is VERY NICE!

My friend made this tensioner shaft for me on his lathe. He's an excellent hobby machinist and he turned it out in no time, and it's dead nuts.
IMG_20190213_192209 by Phazer Two, on Flickr

The motor plate took me two nights to run. I used some slotting, which I normally try to avoid, and it didn't go very well. Slotting is defiantly on my list of things to work on. I also had some serious chatter on with the Superfly, I think I need to pony up and get some of the Al specific inserts as the general use inserts seem to cause problems. All and all it came out okay, even with all the stoopid mistakes I made.
IMG_20190213_192119 by Phazer Two, on Flickr

Yes, that is a massive air cylinder in the background... no idea what it could be for...

Here is what it looks like all assembled.
IMG_20190213_200210 by Phazer Two, on Flickr

And a quick vid of how the tensioner works (click to see vid).
VID_20190213_200523 by Phazer Two, on Flickr

Should make tensioning the belt a breeze. Finally, it installed on the machine.
IMG_20190213_201543 by Phazer Two, on Flickr

I've been working on wiring ever since. I got the servo drive mounted in the cabinet, and the cables run though cable glands out of the cabinet. I stated mounting some cable chain, and that's where it sits. Hoping to get the cable chain finished up this weekend, and start testing out this servo!

PZ
 
Well it has been a long time since I updated this... but here we go! Keep in mind that all of these updates happened in the last year, not yesterday... so I may be forgetting somethings.

The spindle servo has been on for a year... and the jury is still out. Not sure if I like it. I had problems stalling it using a 1/2" EM in steel. I ended up running the EM way to fast (to much surface speed for HSS) to get the job done. With the pulleys I have, it just doesn't have any low end grunt. The larger issue is that it vibrates for some reason. I have pulled the motor out and ran JUST the motor and tuned JUST the motor twice now, and it just vibrates above 5k RPM. I also had my friend build a roller to go over the tensioner bearings to slow them down a bit, they were getting pretty hot. At this rate, I really think one of the Marathon 1000:1 torque ratio motors is a better bet.

Next it was time to tear the mill apart and make sure everything was tight and had the proper bearings. My X axis backlash was creeping up and I wanted to make sure everything was as it should be... Cut2Cut pulled his X axis apart and found regular deep groove ball bearings holding the ball screw in place and that is what I expected to find... I was in for a very pleasant surprise.

IMG_20200201_165641 by Phazer Two, on Flickr

IMG_20200201_165710 by Phazer Two, on Flickr

That's right, matched, serialized AC bearings. Notice the serial number is the same except for the -1 and -2? These even have the "V" on the OD to show which way they go, and the run out is marked (that's the -2 in the face). Very nice bearings... never heard of the manufacture, but they seem very nice. The only issues was that the bearing retainer bolts were loose, on all three axis.

The rest of the ball screw mount left a little to be desired...
IMG_20200201_165741 by Phazer Two, on Flickr

That is the surface that the head of the bolts that hold the mount to the table sit... not so good. These screws were also quite loose. A quick trip to a friends house and it was all fixed up.
IMG_20200222_192001 by Phazer Two, on Flickr

I also pulled the table and saddle off, the bolts that hold the ball nuts to the ball nut mounts were also lose. I tightened the X and Y, Z will have to wait a bit. In case anyone was wondering, or can read Chinese, these are the markings on the ball nut:
IMG_20200217_202334 by Phazer Two, on Flickr

Note that the ball screws don't look rolled, but does have a grease groove in the base of the ball track... Again, didn't expect that kind of quality.

Re-assembly was not bad, except there was a lot of paint on mounting surfaces, so I did lots of scraping and stoning to get them clean again. I was very careful when pressing the bearings back into the mounts, making sure the "V"s were aligned, and lining up the run out (not pictured).
IMG_20200222_213553 by Phazer Two, on Flickr

Next I got after the Y axis. The mount didn't have the same issues with the bolt head surface as the X, but there was plenty of other bad news in the ball screw mount.
IMG_20200222_210426 by Phazer Two, on Flickr

You can see that they didn't get full clean up on the bearing bore for those beautiful bearings... shame. Also, you can see that the bore is WAY off center, so much so that the bearing retainer is actually missing a screw, and was ground to clear.
IMG_20200222_213039 by Phazer Two, on Flickr

Not much to do besides put it together...
LOTS of scraping on the Y axis re-assembly... The mount bolts to the nice clean machined surface... that was painted. They also had to grind a bunch out of the column to get the mount in there. Again not the best.
IMG_20200222_214142 by Phazer Two, on Flickr

I must have forgot to snap a picture of the mounting surface all cleaned up...

Up next, new motors for X, Y and Z. I bought a 1700oz-in leadshine motor off ebay. The motor is the same series as the motors that came with the machine, just bigger. No need for new drives. I will use this to replace the Z motor, and use the 1200oz-in off the Z on the Y. Cut2Cut was nice enough to sell me his old motors, so I will use his 1200oz-in on my X.

PZ
 
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What better time to work on the mill than when we are "social distancing"?

From the factory the axis motors are wired in series, which gives you similar HOLDING torque as wiring them in parallel. The difference between series and parallel is in the torque the motor can supply while it's actually moving. If you look at the graph below right from Leadshine (1200oz-in motors), wiring in parallel will net me more torque after 150 RPM's which is about 30IPM for me. I choose to wire the motors in parallel for now.
1584897540168.png


I had to bore out one coupler from 14mm to 16mm for the 1700 oz-in, but on my friends lathe that was no big deal. The motors look good in place, the X cover almost looks like it was made to cover the longer 1200oz-in motor!
IMG_20200229_200353 by Phazer Two, on Flickr

IMG_20200321_151624 by Phazer Two, on Flickr

Z axis wires were long enough, but the flex conduit is a bit tight. I might try to find a different conduit to cover these better, but for now they are covered.
IMG_20200229_200343 by Phazer Two, on Flickr

With all the motors fired up and tuned, I was able to get 250IPM out of the X and Y, and 175IPM out of the Z! This is SCREAMING fast compared to the old motors where which were 100IPM in X and Y and 65IPM in the Z. However after lots of testing, I decided to set everything at 150IPM. Things seem smoother limiting the machine to this speed, and I think that is because of the accelerations of the motors not being fast enough to get to 250IPM fast enough. Anyway, I really like everything moving 150IPM, it's much faster than it was and is running great.

My thoughts on the motor upgrade... don't waste your time/money. While this did work great, and I'm happy with it, I wish I would have just put the money towards servos. Considering the machine ran reliably before I upgraded, the only thing I gained was speed.

You may notice in some of the pics above that the cable/hose management to the head is poor at best. In reality its embarrassing. I set the thing up to test the new spindle motor, added some mist coolant, and just ran with it. Well, I couldn't take it any more! I took a few nights and cleaned everything up. I used some Amazon cable chain, and had work laser me out some stainless panels and brackets. I added bulk head fittings for everything, which really made things look nice. I am also trying out a new logo (no idea why I have, or need a logo).
IMG_20200321_151608 by Phazer Two, on Flickr

IMG_20200321_151614 by Phazer Two, on Flickr

It's still not perfect, but I'm not embarrassed by it anymore. The button on the front cover will be for a power draw bar when I get there, the extra holes were for things that I decided went better on the side cover.

Last, you might have noticed a probe in the spindle... I bought a DrewTronics S5000LED with TTS, it was about $260 to get it to my door and let me tell you... WORTH EVERY PENNY! I am repeatedly getting better results than they have listed, so I can't complain at all. I still have some figuring out to do with the Acorn. I have some issues stemming from the probe being a normally closed probe and Acorn is really designed to work with a normally open probe. Hopefully I can get some resolution on it soon, as I am not the only one with this issue.

Until next time,
PZ


Parts used:
Cable Chain:

Cable Drag Chain, URBEST 18mm x 50mm Wire Carrier 1 M/ 3.3Ft Plastic Black Towline Machine Tool: Amazon.com: Industrial & Scientific

Cable Drag Chain, URBEST 18mm x 50mm Wire Carrier 1 M/ 3.3Ft Plastic Black Towline Machine Tool: Amazon.com: Industrial & Scientific
www.amazon.com
DrewTronics S5000LED TTS:
 
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