Centroid Community CNC Support Forum

So, today I finally had a finally had a full day to spend on the machine. I had a whole day of nothing going wrong and only crossed jobs off my todo list! In fact, I am down to only two items on my list now. I have a big list of things I wish I could fix, but most of them are just the way they and will have to stay that way (e.g. due to the way Centroid, DMM and Delta do things).

I spent the morning making my tool library in Fusion 360 and setting up and measuring all the tools on the machine. Then I got to spend some time playing to see how hard I can push the machine. Previously I had thought the machine was not very rigid but with some new tooling and the right speeds and feeds I was surprised. I didn't beat the shit out of it but was not disappointed. I got as far as a using a 10mm (~3/8) 3 flute carbide end mill in 6061, 10mm (~3/8) DOC, 2mm width of cut at 6000 RPM, 2500mm/min (100 inch/min). The machine seemed to not struggle at all with that.

I added a ferrite to the spindle motor cable, HDMI cable and power cable going to the front panel and it has completely cured the noisy HDMI. It is rock solid now.

The only thing I am not happy about and have been battling with all along is the DMM motor drives motion control. The machine still clunks and bangs sometimes. I know the DMM drives are underdamped and slightly oscillate at small movements. They guaranteed me they have never failed a CNC application before so I changed my motors to their (underperforming) motors including all the necessary mods to the machine. They eventually ran out of ideas to resolve the issue and offered my money back. A bit late given how invested I was at that point! I have tried all sorts of combinations of tuning settings. Its a real shame they didn't allow you to fully tune the drive like other drives. If I slow the acceleration rates down it seems better but then the machine takes all day to do anything. Smoothing helps during cutting.

I did however see evidence of this oscillation in the cutting finish today. Notice the oscillation in the chamfer.
the cutting direction is to the left in the picture. On entry it oscillates, this is accompanied by a thunk sound, you can see that the chamfer finish is good on the way back around. .

I am not sure how I am going to resolve this!

Time for another installment...

I have battled and cannot seem to get rid of the oscillation while machining parts. So, I made a snap decision to replace the motor drives, and by extension the motors. Like I always do, I underestimated how long it would take but the job is almost done now.

Fitting the motors mechanically was trivial as I had already done the modifications to the machine. I was lucky that the motor supplier offered to make me some custom motor couplings. They found the right size and cut keyways for me. A perfect fit first go. And only charged $8.50 USD each for them!!!
Running motor and encoder cables was easy too, just time consuming due to them all being inside these black zipper things. Shortening the encoder cables without much spare length to work with was a bit tricky but worked out OK.
I have seen many posts where people comment not to make your own Oak to servo drive cables and just buy the pre-made ones. That wasn't really an option for me, well without wasting money. I already had cabled and the Delta connectors. It turned out that making cables was not bad after all, I actually kind of enjoyed it. But, probably did take an hour per cable.
I'm not going to lie, fitting the servo drives was a shite of a job! I had built the control panel for the DMM drives with screws from behind. Unfortunately now that it is fully assembled you cannot access those screws from behind and removing the panel off the door would have been a huge job. I made an assumption that those drives were there for life! Luckily I was able to find a workaround and got them all fitted nicely!

Anyways, here is a before and after:
I got as far as powering the drives, configuring them and checking I could jog them from CNC12 and that estop and rest worked etc. So far so good. Now for tuning and sorting out index pulse to limit switch positions and all that stuff...

Sorry you went through all of that. You will know that machine inside and out now.
DMM AC Servos/drives are definitely on the bottom entry level. Give the high speed nature of your machine, I don't think I would have chosen them for it. I DO hope DMM does follow through and refund your money for the motors and drives.

Thanks for keeping us posted on your build!
Marty

martyscncgarage wrote: ↑Sun May 22, 2022 9:38 am Sorry you went through all of that. You will know that machine inside and out now.
DMM AC Servos/drives are definitely on the bottom entry level. Give the high speed nature of your machine, I don't think I would have chosen them for it. I DO hope DMM does follow through and refund your money for the motors and drives.

Thanks for keeping us posted on your build!
Marty

DMM have been excellent to deal with. I give them top marks for support.

ashesman wrote: ↑Sun May 22, 2022 6:21 pm

martyscncgarage wrote: ↑Sun May 22, 2022 9:38 am Sorry you went through all of that. You will know that machine inside and out now.
DMM AC Servos/drives are definitely on the bottom entry level. Give the high speed nature of your machine, I don't think I would have chosen them for it. I DO hope DMM does follow through and refund your money for the motors and drives.

Thanks for keeping us posted on your build!
Marty

DMM have been excellent to deal with. I give them top marks for support.

That has been my experience. I have also heard that if it didn't work out, they refunded the customer AS long as the customer was reasonable and fair to work with.

ashesman wrote: ↑Sun May 22, 2022 6:21 pm
DMM have been excellent to deal with. I give them top marks for support.

I was considering going with them but feel I'm going to go with Delta at this time. I found a good deal for a pair of ASDA-A2-1521-M paired with ECMA-E11315RS motors for my Mazak Quick Turn 20N Universal.

Contact this company for Delta drives. Good prices and excellent service. Will make you couplings and all sorts.

https://zstoppower.en.alibaba.com/?spm= ... st_company

Contact them and talk to Max Liang

ashesman wrote: ↑Sun Jun 12, 2022 2:50 am Contact this company for Delta drives. Good prices and excellent service. Will make you couplings and all sorts.

https://zstoppower.en.alibaba.com/?spm= ... st_company

Contact them and talk to Max Liang

I reached out and they said they do not sell them. Strange.

I ordered these on Ebay instead.
Now to start piecing together my Oak system.

Oh, interesting. I had no trouble with them. They are still sending me messages trying to sell me stuff! Maybe out of stock of that model. We cant really buy from ebay here so is probably a good choice if you can.