Acorn Trials and Tribulations - PROBLEM SOLVED

All things related to the Centroid Acorn CNC Controller

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cncman172
Posts: 94
Joined: Thu Nov 02, 2017 4:07 pm
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System Serial Number: 985DAD429EE9-0926170118
Location: Westerville, Ohio

Re: Acorn Trials and Tribulations

Post by cncman172 » Fri Dec 01, 2017 9:24 am

diycncscott,

The cable from the acorn to the Pansonic Amp is 2 feet long. swapping the Cable at the amplifers is exactly the same as unscrewing the wires on the Acorn and swapping them. I will be glad to unscrew the step and direction between X and Y at the Acorn but please help me understand how that is different than unplugging the cable at the other end and swapping?

The symmetrical pulse rate at 2.5 micro seconds should not be too fast, the amplifier can handle 2 microsecond width in differential mode, so that part should be ok. I will also build a new cable for CN1, since I will need one for the A axis in the future. And report both results.

Russ

martyscncgarage
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Re: Acorn Trials and Tribulations

Post by martyscncgarage » Fri Dec 01, 2017 9:35 am

Russ,
By switching the connection AT Acorn (NOT at the Amplifiers) and observing the axis movement tells a lot.
You should circle back to Scott's first post giving you specific instructions and follow them, and report back your findings point by point and wait for further instructions.(Very first page, about 8-9 posts down)

Sometimes we dig a big hole trying to find the problem, and then reallize its the simple things that bite us. Help is being given, but you have to follow the instructions explicitly.
Scott is a very sharp guy. You've got one of Centroid's best trying to help you. FOLLOW his instructions to the T....

This problem is an interesting one. We are all here to learn as well as have a good experience with Acorn. Persevere my friend. We look forward to hearing back from you once you reread Scotts first post with explicit instructions.

Marty
"Jack of all trades, master of none!"
Mesa, AZ

cncman172
Posts: 94
Joined: Thu Nov 02, 2017 4:07 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
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 » Fri Dec 01, 2017 10:34 am

Marty,

I will go back to the beginning as you suggest and run all those tests again, swapping at the Acorn. I've been doing electronics and design for 35 years with a MSEE, maybe I missed something in some of my classes. LOL

I agree this is likely something easy, perhaps even a bad differential driver which sits between the Acorn and Panasonic Amps. It has to be a cable, configuration, or noise. The mechanical aspect was verified good, the Amplifiers and Servos verified good, their power and encoder cables verified good. At least this confines this issue to a pretty small area.

Ok, back to the beginning to test it all again. Thanks Marty for the encouragement.

Russ

martyscncgarage
Posts: 728
Joined: Tue Mar 28, 2017 12:01 pm
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Location: Mesa, AZ

Re: Acorn Trials and Tribulations

Post by martyscncgarage » Fri Dec 01, 2017 11:12 am

cncman172 wrote:
Fri Dec 01, 2017 10:34 am
Marty,

I will go back to the beginning as you suggest and run all those tests again, swapping at the Acorn. I've been doing electronics and design for 35 years with a MSEE, maybe I missed something in some of my classes. LOL

I agree this is likely something easy, perhaps even a bad differential driver which sits between the Acorn and Panasonic Amps. It has to be a cable, configuration, or noise. The mechanical aspect was verified good, the Amplifiers and Servos verified good, their power and encoder cables verified good. At least this confines this issue to a pretty small area.

Ok, back to the beginning to test it all again. Thanks Marty for the encouragement.

Russ
It's great you have the background and a scope. That may come in handy. But put the machine back into the configuration it was in when you started (issues with Y axis movement) and just swap the X & Y step/dir/enable wires at Acorn terminal blocks and report back. I think Scott wants to see if the issue moves to X or stays with Y.

You are welcome for the encouragement. We all need it. I think you are going to like working with Centroid Acorn hardware and the CNC12 software. It will all be worth it once the kinks are sorted out. Believe you me, Centroid stands behind their software and hardware. That in of itself is huge! They supply both hardware and software.

Good luck!
Marty
"Jack of all trades, master of none!"
Mesa, AZ

cncman172
Posts: 94
Joined: Thu Nov 02, 2017 4:07 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
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 » Fri Dec 01, 2017 12:32 pm

Here are the results of the requested test. I first trammed in the 24" linear scale to ensure it was aligned with Y axis. Then on each move I would jog slightly to take any backlash out of the question. Then zero the Y axis in Centroid software, then execute the follow Gcode commands on the MDI screen. Keep in mind there is no mechanical connection from the spindle and the linear scale, I am just pushing the scale so small errors could result.
IMG_1904.JPG
This test was done five times, bring Y back to zero position jogging slightly zero linear scale and Y DRO.
G1 Y10 F10
10.008
10.005
10.006
10.008
10.005

Now I swapped the Step/Dir leads for X axis and Y axis

Now the following command had to be issued to get the axis to move in the correct direction due to swapping

G1 X-10 F10
10.006
10.009
10.002
10.005
10.004

The results seem pretty consistent using the X axis outputs or the Y axis outputs. But I leave that analysis to the experts.

Let me know what you want me to do next.

Russ

diycncscott
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Joined: Thu Mar 04, 2010 4:03 pm

Re: Acorn Trials and Tribulations

Post by diycncscott » Fri Dec 01, 2017 3:13 pm

I need to see X and Y measurements before swapping at the Acorn and after.
I also provided specific g code to be used. I've provided it again for your reference. Please use it.
Use this approach and command for all measurements I'll use X axis in the example (all units imperial):
Do not jog the machine or reverse direction at any point in the commands listed below. If a reversal is needed, start over at step one. You can write a program or use MDI to command the moves. HINT - You can use the up/down arrow keys to access the MDI history to greatly reduce typing.

1. Move to -.05 on the axis. G0 x-.05

2. Move to X0 at a VERY slow rate: G1 X0 F.25

3. Set axis dro to 0 G92 X0

4. Command move to X9.9 G1 X9.9 F10

5. Command move to X10 at a VERY slow rate. G1 X10 F.25

6. Record DRO and scale readout

7. Lather, rinse and repeat with different feed rates.

cncman172
Posts: 94
Joined: Thu Nov 02, 2017 4:07 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
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 » Fri Dec 01, 2017 7:29 pm

OK, this took a while to complete but I am finally done doing exactly what your requested.

Traming each axis to make sure they are clearly parallel to the axis being tested takes some time as well.
IMG_1905.JPG
Here are the results, all axis wired up normally

X axis results

F10
10.003
10.002
10.003

F50
10.003
10.003
10.003

F100
10.003
10.003
10.003

Y axis results

F10
10.017
10.016
10.022

F50
10.020
10.017
10/016

F100
10/018
10.012
10.027

NOW REVERSING the Step/Direction on the X and Y axis at the Acorn

X axis results

F10
10.019
10.017
10.021

F50
10.003
10.003
10.003

F100
10.003
10.005
10.004

Now at this point I decided to retest the F10 results as they seemed way off

F10
10.004
10.004
10.004

Y axis results

F10
10.004
10.011
10.015

F50
10.014
10.011
10.011

F100
10.013
10.011
10.013

I should probably build all these results in a table to make them easier to view at one time. Anyway let me know what you think.

The F10 results I tried twice make them think somehow there is noise somehow getting into the system. But let me know you thoughts.

Russ

diycncscott
Posts: 634
Joined: Thu Mar 04, 2010 4:03 pm

Re: Acorn Trials and Tribulations

Post by diycncscott » Fri Dec 01, 2017 8:51 pm

Awesome. Thanks Russ.

I assume these results are in metric units since you only took them out to 3 places?

If so, you're absolute worst result was about .001" long. .027/25.4 = .0010... 1 measurement. Out of 38 others almost all easily less than a half thous.

I don't see any problem here. I would expect most of the variance can be attributed to limitations in measurement with your setup. Can you please post your G code program with the arc that is giving you grief?

cncman172
Posts: 94
Joined: Thu Nov 02, 2017 4:07 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
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 » Fri Dec 01, 2017 9:58 pm

Scott
The scale does both metric and us unit. I had it in us but think the gauge is only good to .oo1”

Will check the scale

Russ

diycncscott
Posts: 634
Joined: Thu Mar 04, 2010 4:03 pm

Re: Acorn Trials and Tribulations

Post by diycncscott » Fri Dec 01, 2017 10:14 pm

Hard to say Russ,

Sometimes you take data out to 3 places, sometimes 4. My bad. I should not assume 3 places = metric units .

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