DIY heavy duty PM-833 CNC conversion

[buzzfab]

One thing that I’ve already come across - the AZvideo kit (and, I suspect most other conversion kits) are sized for NEMA 34 motors, but I am leaning towards using a less expensive Chinese servo, and those have a different frame size (80 or 90 mm).

Dave will make the plate for whatever motor mount you need I'm pretty sure.

Before you decide on motors, you need to decide what your controller will be. A windows pc with Mach3/4, an Arduino with GRBL, Linuxcnc with a Mesa card, maybe a EtherCat Master or even something like one of those sweet Masso G3 touch things. Some types of controller might not work with all motors.

I have a shelf with some controller cards on it, a Ethernet Smoothstepper, a Pokey57cnc card because I was originally goign to use mach3 because i have been running if for like 25 years. Then i decided it was dated and switched to linux for this build. Bought 2 Mesa 7i76e cards and then decided on different motors so now I've switched to a OrangePi as a open source LinuxCNC EtherCat master and computer all in one SBC. I want the ProbeBasic GUI and touch screen so really I wont need any of those other cards anymore.

Cheap Chinese servos might not tune very well anyway, if you are going with a Chinese company going at least go with a reputable one like Leadshine. Personally I would stay away from away the crap like those ali-express JMC motors.

Eric

 

[3Dogs]

I have already bought a Mesa 7I76e card. I also bought a couple of those LED driver cards to play with (ColorCNC).
I’m going to use a Rpi 4 as the computer.
The motors I’m looking at are from Lichuan. Tuning is a big issue. Their drivers have a “self learn” setting, but who knows how good that will be.
I’ve been learning about servo tuning, and I think I can do it without the fancy manufacturer’s software. There is a video by “Vhospher” on youtube: How to Tune Cheap Chinese Servos Drives
where he shows some software he has written to plot the commanded vs actual velocity. I am trying to track him down, and see if I can get him to send me a copy of the software, but that would just be a time saver - I think I can write it myself if necessary. He uses an oscilloscope to capture the samples, but I have a logic analyzer, which is probably better.
If worse comes to worse, the motors are cheap enough that I can just replace them if I have to, but I don’t think it will come to that.

 

[buzzfab]

@3Dogs, So it looks like you are going with LinuxCNC on a RPi4b with AC Servos connected through a Mesa card. A suggestion I have would be to swap the RPi4 with a OrangePi 5b or OPi5 Plus, The RPi4 is a little underpowered for LinuxCNC I see a lot of people in the forum try to start with one of those but end up switching to something else. Currently on the Forum there is a small group of people who have managed to get the OPi5 working with very little jitter, the OPi5 Plus was just released last week, I bought one the first day. I got the tracking number this morning so it finally shipped out. The OPi5 Plus has a more powerful chip with dual ethernet ports which would be handy for the 7i76e card and wired network access. The support for this card is very limited but a few people smarter than myself have already started making images for linuxCNC, by the time you are ready to build it should be fully implemented.

More info here.... can-the-opi5-be-configured-to-run-lcnc

if you are using AC Servos you will need to get a few other electrical components, you will have to read the manual specific to the drives you are getting but here is a example setup for 3 axis setup from DMM-Tech, it shows a, mini Circuit Breaker, Magnetic Contactor, Line Reactor, multiple Noise Filters, fuses and terminals. These parts were a few hundred $$$ alone and only for the AC side then you will need logic level power for the 7i76e and Sensors. I decided to mount everything on DIN rails even the stuff that has no DIN clips. I 3D printed custom mounts for all the components so everything is neatly on rails.



I don't know how it is in your area but where I am in Vancouver Canada there are always cheap steppers and servos showing up on FB Marketplace, last month there were 11 sets of 750watt DMM dyn4 drives and motors, $300 per set. considering I paid $2000 for 3 of them to do a upgrade at work. 300 is a steal.. The dude was selling then with all of the other electrical components also. That is Canadian dollars as well. before you buy those motor I would wait and be sure you can get them to work properly and stable. find someone who had previously got them to work on the linuxCNC forum and talk to them. My Leadshine motors/drives are their flagship line, very expensive for me but I saved up and got what I wanted. One thing is they are so new no one else has got them running on LinuxCNC yet. I'm sure i will figure it out with time but i would have been so much easier if i just got something that other people had already got up and running. EtherCat is very new and not officially supported on linuxCNC but its what i wanted so i will have to struggle though figuring it out.

Today I am going to start a basic mock-up layout on plywood of electrical components so hopefully I can start bench testing when the OPi5+ shows up and start to figure out what size electrical box i need. a few days wired a 30amp 240v plug in the living room of my rental house with no electrician and no permission from landlord so I can bench test. I know what i am doing though I'm sure they wont like what I have done but I can remove it when I am finished and putty over the hole.



Eric

 

[buzzfab]

I made this adapter plate for the Z ballscrew on the router at the place I work. All of the rest of the aluminum pieces will be made on the converted mill using 3d printed parts. I would have made this part on the mill as well but to install it would require removing the head again and I don't want to do that.






My OrangePi 5 Plus showed up so I'm going to start messing around with the software side of the build. I need LinuxCNC running to bench test the servo motors and drives. I think I have all of the electrical components I need so the only thing holding me back is lack of free time.

Eric

 

[buzzfab]

I have been so busy with side work that I didn't even get to touch this project since I made the aluminum Z adapter. I even had to pack it all away in boxes because I needed the work space. Today I got to pull all the electrical components out, assemble the 3d printed parts, attach them all to DIN rails and do and initial layout for a enclosure. I am going to TIG weld my own aluminum cabinet because I can and the prices of buying 24x24x12" off the shelf is at least a few hundred $$$. The blue tape represents wire ducting I ordered from digi-key, it comes in 6ft lengths and I was hoping to only need 1 but it seems I will need 2.



I want to be clear about something because I have had a few people on here and youtube message me with questions. The mechanical side of this build is fully designed, printed, assembled and moves as smooth as the ****ty import ballscrews allow. The design is sound and functional. The hold up in not the machine parts, its the controller side of the build. I have assembled and wired cnc controllers before of retrofitting old routers at a place I used to work. These drives were either DC or AC Servos that used analog STEP/DIR signals from MACH3 with a parallel port BOB or ethernet smooth stepper. This time I am going with LINUXCNC and ETHERCAT on a experimental rk3588 SBC that has an ARM64 processor. Linuxcnc does not support any of these things so there is not guide to follow, no simple youtube tutorial. Every step of the way has required me to learn something new and since this stuff is all really new in the hobbyist world it seams i have the first to try this setup. its not going to be easy and a lot of times i think "this would be done if i bought cheap steppers" but I like to challenge myself even to the point of detriment sometimes.

I guess next step is to so some wiring, I have 8/3 SOOW for the main power line but I need to pick up some hook up cable and a heat shrink label maker because i want this to be as neat as I can get it.

Eric

 

[3Dogs]

It’s too bad you are so far away - I’d love to see this system in person.

I am going to try installing LinuxCNC on an older Mac Mini, and use a Mesa card. I’d like to see if I can get that working before I do much else.
I haven’t even bought the PM-833TV yet.

 

[buzzfab]

It’s too bad you are so far away - I’d love to see this system in person.

I am going to try installing LinuxCNC on an older Mac Mini, and use a Mesa card. I’d like to see if I can get that working before I do much else.
I haven’t even bought the PM-833TV yet.

This is a good idea, the mechanical side is the easy part as its just nuts and bolts. The rest can slow you down so get it out of the way or you will have a machine sitting around while you figure it out.

 

[buzzfab]

So, didn't touch the project for a while. Went on vacation, did some other stuff which pays and then tackled the wiring for bench testing.


I posted a little video here.

I decided to order a Pilz PNOZ S2 safety relay but it hasn't arrived yet. Still a long way to go but I will get there.

Eric

 

[7milesup]

I am going to TIG weld my own aluminum cabinet because I can and the prices of buying 24x24x12" off the shelf is at least a few hundred $$$.

You might want to consider Vevor electrical boxes. I bought one for my mill and am very happy with it. Here is a link to their 24x24x12 box.

 

[RonnieW]

I am going to TIG weld my own aluminum cabinet because I can and the prices of buying 24x24x12" off the shelf is at least a few hundred $$$.

A man after my own heart! I’ve got more time than money so this is exactly the path I’m going as well. Plus get to practice my tig welding!!