Acorn DMM Servo, wrong axis moves, and other issues.

[the_Swede]

Hi.
In dire need of help...

Just completed the installation/upgrade on my DIY machine, from Ebay steppers to DMM servos.
Whilst connecting to them directly and running, for example auto tune, they work perfectly, but as soon as I run them via CNC12 and the Acorn controller, things start getting wierd.

Issue no.1
Jogging the Y axis, in either direction, makes the motor feed by itselft as soon as you release the jog botton and it will not stop. Always the same direction at the same speed. It only stops when I hit the reset button in the VCP.

Issue no.2
There´s no movement whilst jogging the Z axis. And when I run the auto home sequence, the Y axis starts to move, and the VCP is indicating that
it´s moving the Z axis. So the VCP believes it´s moving Z but in fact X is running.

I have checked all connections several times and all settings in the wizard and the servo drives, and can not for the life of me figure out what is wrong.

Any good ideas?

Best regards:
P-J Johansson

[tblough]

My guess is a wiring issue. If you will post a report and some detailed photos of the machine, control, wizard screens, and wiring we can provide more help.

[farrcustomfab]

Need a little more information: specifically wiring diagram, DYN2 or DYN4, if latter, if you're using the DMM to Acorn cable (CA-CUACRN-M4-1). Could be a wiring issue, but you could be dabbling with the header vs DB25 port issues many have encountered on this forum with DYN4 (me included).

If you're using DYN4 and the DMM Acorn cable, what worked for me was scrapping the DMM cable to make my own (huge pain) and shifting from the header connections for step and direction over to the Acorn DB25 port. It gets a little weird in the Acorn Wizard to make it work -- either the DB25 bench test config or using a slightly modified DYN2 config.

[ShawnM]

Or it it the DYN5 drive? I just installed 3 of these on a router retrofit I did and they are great.

And this certainly sounds like a wiring issue. As stated earlier, post pics of the wiring and a report along with some wizard screen shots.

[the_Swede]

Thank you all for the response.
Yes I´m using the DYM4 to Acorn cable provided by DMM. #CA-CUACRN-M4-05 and not the CA-CUACRN-M4-1 as mentioned
by farrcustomfab, but I´m guessing they´re the same.
I´ll get back to you with the pictures,reports and diagrams during tomorrow.

// P-J

[the_Swede]

Hi all.
Hope this is all the info you need to help me out.

By the way, another issues presented itself today. When entering MDI in the VCP the Y axis starts moving.

Please excuse my poor cable management in the pictures, this is not finalized by any means.

CNC12 Report

[lavrgs]

There are many discussions about DMM losing steps and how to test for that. I had a Z axis that would intermittently dive...once you get wiring straitened out
https://centroidcncforum.com/viewtopic.php?f=60&t=6472

[ShawnM]

The issue is the OEM cable provided by DMM. You need to remove the resistor in the cable and wire the drives to the DB25 header. This has been documented in another topic and can be found here.

https://centroidcncforum.com/viewtopic. ... 0&start=10

Either remove the resistor from their cable or better yet make your own cables. I made all my own DYN5 cables using only the connectors provided by DMM.

Follow diagram S14969 and ditch the diagram you are using.

FYI, wires 111 and 112 need to be a shielded pair if you want any sort of accuracy from your spindle.

[the_Swede]

Hi.
Thank you all for the quick response.
Yeah, I got kinda convinced that the DMM cables where at the heart of the problem.... because my Z axis all of a sudden started working flawlessly, and all of a sudden did not.

I guess the Youtube clip by Marty where he recommends using the DMM cable, was a bit out of date.

ShawnM, correct me if I´m wrong here, the dropping resistor is at the heart of the problem? Or are the screw terminals also contributing?
If so, how do the DB25 connection differ from the screw terminals? Why are one more precise than the other?

Reagarding wires 111 and 112, yeah I know, was suppose to be temporary but I got away with it when I had the stepper, but now I can clearly see a disturbance in the force... the values on the VFD display is, mildly put, fluctuating.

// P-J

[ShawnM]

Hi P-J

First, there are A LOT of old videos on YouTube in regards to the Acorn that should be removed as they provide outdated info that is no longer relevant and just create more problems when viewed. I've mentioned this on the forum numerous times.

Dropping the resistor is only part of the problem and the screw terminals are adding to the problem. The screw terminals and the DB25 offer up different types of signals and sinking versus sourcing. There are many users that have reported issues using the DYN4 on the headers. You still need the ENABLE terminal on the headers to enable the drives, there is no enable signal on the DB25.

I'd suggest removing the resistor from the cable and wiring up the drives to the DB25. I attached a draft of the diagram from Centroid for you to follow. Let us know how it works out for you.