Need Help: Acorn, DMM DYN4 New Build

[n2xd]

I do not use the db25 connector for any thing. My red and brown wires from the drives are connected to in24v next to IN8. The 24 volt supply is connected to in24v next to in4. Hope that helps.

John

[ShawnM]

I do not use the db25 connector for any thing. My red and brown wires from the drives are connected to in24v next to IN8. The 24 volt supply is connected to in24v next to in4. Hope that helps.

John

John,
Many users posted they were losing steps on the DYN4 drives wired to the headers. There were some fixes, resistors and workarounds but the latest Centroid schematic has the DYN4 drives wired to the DB25 and now users seem to be no longer reporting lost steps. Keep this in mind if you start to have issues in the future.

[ShawnM]

Conducted a retune. During the retune, it was flawless -- no jittering. As soon as I updated the gains and went back to pulse and direction mode, the jitter came back on all three servos.......

What do you mean you "updated the gains"? After you tune does it not save the parameters to the drive automatically? I've used the DYN5 software and it saves parameters to the drive automatically. Are you saying you adjusted the parameters after the autotune?

Have you tried the manual tuning procedure outline in the manual? Some report better luck with a manual tune.

[Richards]

I've been looking at the photo of your layout. My eyes are really bad, but it looks to me like you have Step, Direction, Enable, and Common connected via the DYN4's DB25 connector. I can't see clearly enough to see how you've connected +24VDC to the DYN4's Step, Direction and Enable signals. The "H" connectors are open-collector. That means that the "H" pins will SINK current. They do not SOURCE current. A +24VDC source has to be supplied.

[lavrgs]

you can check to see if you are losing steps with the DMMDRV utility; monitoring the (a) drive after cycling with CNC12. For info on using the DMMDRV Utility go to the first link; on Page 7 - 1/26/21 there is a basic set of instructions.
There are several threads about losing steps with DYN4 drives.
https://centroidcncforum.com/viewtopic.php?f=60&t=6472
https://centroidcncforum.com/viewtopic.php?f=60&t=4123

[farrcustomfab]

Thanks everyone for providing your thoughts and insight.

Update and answers to questions:
(1) @ShawnM: I tried auto-tuning (again...never touching the gains, just turning it back to Pulse/Dir mode and saving) and manual tuning based on the guidance from the DMM DYN4 manual (DYN4MS-ZM7-A10A) pg 45. Ended up leaving it with all gains set to 4 (couldn't get the slider to stop on 5) and torque filter at 99 (couldn't get to 100). While adjusting the torque filter softened some of the harshness of the popping/jitter, it didn't come anywhere near eliminating it.
(2) @Mike Richards: the 24VDC supply for the brown and red coming off the DYN4 DB25 cables are tied to 24VDC, but in two different places because six wires into one ferrule into one terminal doesn't fit (or at least I couldn't get it to fit). So all 3x brown wires are going to a distribution block and the 3x red wires are going to the 24VDC terminal on H1 next to IN8.
(3) @lavrgs: That looks promising. I'll try switching from the headers to the Acorn's DB25, but will have to wait until a DB25 can be delivered (don't have any in the shop). It's not *just* losing steps though, it's actively drifting/jittering/wandering when uncommanded by the Acorn (i.e. Acorn DRO remains a home position, but the servos are visibly moving and jerking around making a popping or rattling noise). It runs the pre-loaded g-code that came with the Acorn installation fine, but while turning the servos present the same symptoms as when uncommanded. So they're surely losing steps.
(4) I thought I may have made some grounding/shielding mistakes, so chased a couple of items I thought may be contributing but no success.
(5) Also dropped step rate down to 100k steps/sec. No change in symptoms.

I'll post an updated report and DMM DRV settings shortly (editing this post).

[farrcustomfab]

I disassembled the entire cabinet. Went back to bench testing starting with just the Acorn. Worked up to all three axes working perfectly in bench testing with 120VAC main supply (no filters, no contactors, no breakers, no line reactor). Ran it through several of the canned gcode programs that come with CNC12 and it's perfect. Tells me I probably have a grounding or shielding issue somewhere, so I'll go back and add one variable at a time until I find the culprit...it'll take a while. Appreciate the support this weekend. More to questions to follow as I fumble my way through this first build.

The dining room table is my go-to alternative work-bench when all horizontal surfaces in the garage are otherwise occupied.

[cncsnw]

In your new layout, make sure you have a DIN rail and some terminal blocks adjacent to the inputs or axis-interface side of the Acorn, so you can have +24V and 0V distribution handy there. That way there is no need to put six, or even three, wires into one terminal; and no need to use the input commons as a feed-through distribution point for unrelated 24V loads.

[n2xd]

I do not use the db25 connector for any thing. My red and brown wires from the drives are connected to in24v next to IN8. The 24 volt supply is connected to in24v next to in4. Hope that helps.

John

John,
Many users posted they were losing steps on the DYN4 drives wired to the headers. There were some fixes, resistors and workarounds but the latest Centroid schematic has the DYN4 drives wired to the DB25 and now users seem to be no longer reporting lost steps. Keep this in mind if you start to have issues in the future.

I have not encountered any problems in this area. But i will remember this if I do. Thanks for the information.

John

[farrcustomfab]

Rebuilt the enclosure. Focused on grounding and shielding and tested at every step along the way: bench tested with one drive, two drives, three drives; then mounted everything to the backplane and re-tested; then mounted it into the enclosure and tested with and without the bulkhead connectors.

Testing was with a 120VAC power source, because I don't have 240VAC in my dining room (the table I was using as a workstation). Each test consisted of running it through some of the provided g-code programs that came with the CNC12 download and everything worked perfectly on 120VAC. Took the entire assembly out to the garage and plugged it into 240VAC and the jitter/drift when uncommanded came right back (same as before). All the same symptoms and conditions as previously described.

I have half a mind to just run a 30A 120VAC circuit to where I have the mill and be done with it, but I can't find a reasonable explanation as to why it doesn't work properly on 240VAC. Measured input voltage is 244VAC and output of the 24VDC power supply is 24.2VDC. Any help would be greatly appreciated.