Part II: Converting Chinese CNC Router from Open Loop Steppers to DMM DYN4 Servos

[slodat]

As the subject says, this is round two with my 5' x 8' x 12" Chinese manufactured CNC router. As Gary Campbell has suggested, I am replacing (nearly) everything with a wire touching it. In all reality, I'm keeping a few panel mount switches and the spindle/vfd for now. Part III will be a new spindle. What I have is working plenty well until the new spindle.

Almost a year ago I completed Part I, converting to Centroid Acorn from XHC Mach3 controls.

I will do my best to document this process in hopes it will help others considering using the same components I chose. I work in specialized controls for a living, so that background influenced some of my choices. Several people on this forum helped me and I'm hoping to give back.

What I'm removing and replacing:

• Yako open loop steppers, drives and cabling
• What I suspect to be knockoff Omron normally open NPN inductive proximity sensors
• almost all original wiring and components

What I'm adding and installing, and a little bit about why:

• DMM DYN4 DYN4-H01A2-00 servo drives
• DMM 86N-DHT-A6MD1 0.75kW brushless ac servo motors. These should be a drop in replacement for my existing motors.
• DMM's associated power, encoder and Acorn specific cables
• Referring to DMM's user manual and Acorn supplement I decided to size everything for 7.5A/drive, using 240v single phase supply. Four drives = 30A.
  • 12-3 SO cord for drive power connections. 10ga for main supply connection.
  • 30A two pole main circuit breaker for the drives
  • 36A main noise filter. I chose 36A because it was only a couple bucks more than the smaller 30A version.
  • 30A line reactor
  • 40A 24vdc coil three pole contactor. I chose three poles in case I decide I want status of the contactor available at some point.
  • From there the 240vac gets distributed to each of the four drive power inputs and a branch for logic power.
    • 4A two pole circuit breaker for the control power
    • 1A noise filters for each drive
• NC (normally closed) NPN shielded inductive proximity sensors with M12 connectors. NPN because that's what Acorn wants. Shielded because it detects what's in front of the sensor mostly, the sides not so much. M12 connectors because it's a lot easier to replace a sensor with a connector vs a lead that has to be fished through everything.
• Associated shielded M12 cables. Shielded to help with noise immunity.
• I will be using these as close to home only. I'll add ZRI from the DYN4 for more precise homing. I currently intend to have CNC12 handle travel limits. I have physical stops in place to prevent going off the rails, though I don't ever want them to be used.
• Shielded cable for spindle vfd connection to Acorn.

What I'm starting with:







Majority of the parts arrived today:

The DMM DYN4 Acorn cables are right at 36" long:

[cnckeith]

nice thanks for sharing.. that new system is going to fly!

[slodat]

My DIN rail terminal boards didn’t make it here today because of the winter weather. Looks like Tuesday and I’ll have the rest of the parts. With any luck second Acorn and relay board will be here tomorrow. I bought a second because I plan to use all of the takeoff parts on a lighter weight cnc router build.

I’m trying to do this right the first time. Things are looking good.

Current status while I wait for parts:

[martyscncgarage]

No video clip of motors moving? Fish stories....

[cbb1962]

Your plan looks well thought out. I have the little brother to your machine, and I'm looking at a similar phase 2 upgrade.

I wish ClearPath had ZRI like the DMM Servos... imho that would be the best of both worlds.

[slodat]

No video clip of motors moving? Fish stories....

Oh! I took a video right when I powered the first motor up!

https://youtu.be/lrl3538ECFo

Second Acorn board is supposed to arrive today. I only powered up one motor thus far and moved it with the DMM software. Was waiting to fully wire the bench test until my terminal boards arrived. Tuesday now.

[slodat]

Your plan looks well thought out. I have the little brother to your machine, and I'm looking at a similar phase 2 upgrade.

I wish ClearPath had ZRI like the DMM Servos... imho that would be the best of both worlds.

I went back and forth for quite a while between the two. Both are great options. Ultimately, I obviously chose DMM. I’m building this to last, I hope I may upgrade to Oak when I do the spindle upgrade in the future.

[martyscncgarage]

Okaaay, not a fish story.
Thanks, continued luck on the build!
Marty

[slodat]

Bench test went well. Now I wait for parts to arrive next week.

https://youtu.be/UGVX93IjKZQ

[martyscncgarage]

Nice...
I like the 16" Walker Turner Bandsaw in the background.