Acorn Trials and Tribulations - PROBLEM SOLVED

All things related to the Centroid Acorn CNC Controller

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cncman172
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Re: Acorn Trials and Tribulations

Post by cncman172 » Wed Nov 29, 2017 10:41 pm

Hey Dickeybird,

Yeah the part is really simple but the gcode was not my problem. I posted the gcode at work with Mastercam but posted it to a generic mill bet they have a post output for Centroid. We have some Fadal’s, but will repost code that will probably fix the drill cycle, My accuracy is is something in Acorn configuration, will dig deeper tomorrow

Russ

martyscncgarage
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Re: Acorn Trials and Tribulations

Post by martyscncgarage » Wed Nov 29, 2017 11:06 pm

You were asked to swap X and Y axis to see if the problem followed or stayed. This is typical machine troubleshooting procedure. Centroid seems very willing to help if you follow Scott's requested procedure.

I am interested to understand from a learning perspective should I happen across it in the future. It is solvable. The information shared is useful to everyone.
Marty
"Jack of all trades, master of none!"
Mesa, AZ

cncman172
Posts: 94
Joined: Thu Nov 02, 2017 4:07 pm
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Re: Acorn Trials and Tribulations

Post by cncman172 » Thu Nov 30, 2017 9:19 am

Marty,

I did the tests that Scott requested and posted the results. He has been helpful no question. At this point I know the hardware is good, using my old computer and the parallel card and Mach3 it cut out the plastic part within .001" of the drawing so right on the money.

What I think might be going on in my situation is I posted this job at work and the default output was set to GE FANUC three axis mill. I did not even think about this when I did my test cut. Mach3 works because it emulates the GE FANUC standard which has been around a long time. I am going to check and see if they have a POST output for Centroid that will fix the drill cycle issue for sure. It also might fix the other aspects of the entire job being off since each post process does things differently. I would not think standard gcode for example G0 X5.2354 Y6.456 could change between posts and even drill holes were not in their correct locations with the Acorn.

The second thing I am going to check is the pulse width that the Panasonic servos can accept and then compare that to the specs of the Acorn. It is possible that the Panasonic is not seeing all the pulses or it is right on the edge which would explain it not doing things correctly.

At this point I have verified the hardware is good and accurate. Meaning the motors, amplifiers, ballscrews, couplings, etc are all working correctly. I am also pretty sure the encoder count and ratio are also correct, they match my settings in Mach3 exactly.

More to follow as I am certain other people will run into this issue sooner or later. I am excited to get this all working correctly.

Russ

martyscncgarage
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Re: Acorn Trials and Tribulations

Post by martyscncgarage » Thu Nov 30, 2017 10:03 am

You were commanding linear moves with your Y axis from MDI. You were not getting consistent results. That does not seem to have anything to do with the G code. Rather a signal issue from Acorn to your motor driver. I think you were asked to swap the step and direction signal wires for X & Y axis at the Acorn terminal blocks to see if the problem followed the axis or stayed the same.

Unless you did this and didn't post, we have no idea where you are. Seems to me that you need to square away this issue first before even worrying about G code.

I am very interested to understand what's going on. What you described is not a G code issue or a Post issue. Its a signal issue that needs to be pin pointed.

Good luck, 4 Acorn boards and CNC12 running well over here are various machines/setups! :D
Marty
"Jack of all trades, master of none!"
Mesa, AZ

cncman172
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Re: Acorn Trials and Tribulations

Post by cncman172 » Thu Nov 30, 2017 10:43 am

Marty,

Post by cncman172 » Tue Nov 28, 2017 10:14 am

Please see the post on the first page back on Nov 28th, the control cables were swapped between axis and the results logged. Clearly this is not a servo or driver or control cable issues, as I clearly used the same exact machine and all gear except for the brain Acorn and Centroid software and it all works.

As I said a couple of times now, I am suspect of the pulse width coming out of the Acorn, it might be either too short or too wide for the Panasonic drivers to reliably follow. At work now but this will get investigated during my lunch break.

Russ

cncman172
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Re: Acorn Trials and Tribulations

Post by cncman172 » Thu Nov 30, 2017 1:23 pm

DickeyBird,

Well I checked out machine at work and they do not have a post processor for Centroid. I used GE FANUC which according to the CNC house at the link below is what the Centroid control is based on as far as gcode implementation.


http://www.cncsnw.com/PostProcessorsMill.htm

This afternoon I search the spec sheets for pulse width for Acorn and Panasonic drivers. Ugh

Russ

diycncscott
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Re: Acorn Trials and Tribulations

Post by diycncscott » Thu Nov 30, 2017 1:29 pm

Russ,

To reiterate. When you swapped the cable, the problem stayed with the cables, motor and drive on the Y axis.

Regarding the program. If you would simply post the g code program here you would save yourself you could eliminate all the guessing.

cncman172
Posts: 94
Joined: Thu Nov 02, 2017 4:07 pm
Acorn CNC Controller: Yes
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MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: 985DAD429EE9-0926170118
Location: Westerville, Ohio

Re: Acorn Trials and Tribulations

Post by cncman172 » Thu Nov 30, 2017 2:13 pm

diycncscott,

All I did was switch two control cables CN1 between the two amplifiers. All the encoder cables, power cables all remained the same. When I tested the entire system using a different older XP computer and Mach3 the only cable different was the control cable. The new control cable has been carefully constructed and tested with an ohm meter. I will run all these tests again now that I have my job completed.

What I think is more suspect is the pulse width of the signals that leave the Acorn. My Panasonic drivers which I posted the manual in an earlier post will accept an input frequency when using the differential inputs pins 5,6,7,8 of up to 500kpps. The Acorn can only send out pulses at a maximum of 400kpps. My driver can only process a pulse with a minimum pulse width of 2us in differential model or 5us in single ended mode. This is detailed in the manual on page 48, under parameter 29, which for this application is set to 3.

On the gcode I only had the option to post it with generic GE FANUC, which is what Centroid is based on with the exception they implemented the drill cycles slightly differently, this was highlighted on a cnc site in a previous post, which explains the drill cycle not doing the first hole.

I could not find the specs of the pulse width created by Acorn in the spec sheet, but I will set it up on my scope later tonight or tomorrow. This more likely a noise issue or pulse width issue. I do not think this has to do with the configuration of the encoder which is 2000 and the ration which is 2.54. Those are the same in the old Mach3 software which move this hardware correctly.

I can post the gcode to just drill the holes, and make that a standalone program. Right now I am more interested in understanding what is causing my root issue. Setting up my scope might help highlight any obvious issues. I have been doing this stuff a long time and have put together many machines. Normally I can figure out most of this stuff pretty quickly.

Russ

cnckeith
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Re: Acorn Trials and Tribulations

Post by cnckeith » Thu Nov 30, 2017 8:33 pm

russ,

the cable swap test is a great tool to home in on the root of the issue.

if you swap axis drive cables at the Acorn between a working axis and an axis with problems (and do nothing else!) much information can be gained by this simple test.

after the axis cable swap if the problem moves to the axis that didn't have an issue before the swap (follows the cable swap), then the issue is with the cabling and drive.

also...if it was a pulse width problem then why would one axis be working and another axis would not be working?

another separate test would be to remove the diff board that you have in between the Acorn and the Panasonic drives and run the problem axis directly from the Acorn and see what happens. (process of elimination)

diycncscott
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Re: Acorn Trials and Tribulations

Post by diycncscott » Fri Dec 01, 2017 9:01 am

Russ,

I very specifically requested that you swap the cable ONLY at the Acorn. Instead, you chose to do something else and didn't even inform me? I've been wasting my time. You seem to insist on doing something other than what I've asked you to do. I can't help you

FWIW The Acorn pulse width is always symmetrical at max pulse rate. Hence, at the default of 200Khz the pulse width is 2.5 micro seconds (on for 2.5, off for 2.5 = 200khz).

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