Acorn Trials and Tribulations - PROBLEM SOLVED

All things related to the Centroid Acorn CNC Controller

Moderator: cnckeith

cnckeith
Posts: 520
Joined: Wed Mar 03, 2010 4:23 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: Yes
CNC11: Yes
CPU10 or CPU7: Yes
System Serial Number: none
Contact:

Re: Acorn Trials and Tribulations

Post by cnckeith » Tue Nov 28, 2017 10:35 am

Russ,
Hello.
what make model motors and drives are being used?
and what hookup schematic have you followed or created (please post if you created your own) thanks, K

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 » Tue Nov 28, 2017 11:05 am

Keith,

I am using Panasonic Servos and Amps
MSD021A1X, 100V, 200W, 2500 P/R encoders, set at 2000, with matching motors MSM021A1A

Manual on Panasonic Servo Drives
KEEP msd0_XX-Serie Manual_E 14-01-2002.pdf
(2.65 MiB) Not downloaded yet
Wiring Diagram for Acorn and Panasonic Amps
S1483X.pdf
(23.21 KiB) Downloaded 2 times
On the X, Y axis I am using 200W amps, on the X axis I am using a 100W motor, and on the Y axis a 200W motor. Photo of setup was posted on a previous post.


Russ

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 » Tue Nov 28, 2017 11:07 am

Keith,
This previous post shows photos of the machine and the motors and the new controller box.
Russ



viewtopic.php?f=60&t=1089&hilit=panasonic

cnckeith
Posts: 520
Joined: Wed Mar 03, 2010 4:23 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: Yes
CNC11: Yes
CPU10 or CPU7: Yes
System Serial Number: none
Contact:

Re: Acorn Trials and Tribulations

Post by cnckeith » Tue Nov 28, 2017 11:23 am

awesome thanks..great photos.

..and just wanna make sure we are covering the basics before we dig a big hole.this is what i would do if i was standing in front of the machine, i would go back to baseline and start from there.
1.) use an indicator to float in the linear scale so that it is perfectly parallel with the axis to be measured
2.) set the overall turns ratio of that axis according to the mechanical properties of the ballscrew and the connection between the screw and the motor (2.54 in Inch mode)
3.) set the steps per revolution of the motor to the setting being used with the particular motor and drive being used (2000?)
4.) set axis accell/decell rate to .5
5.) home the machine
6.) jog axis to end of scale
7.) jog in opposite direction a small amount .25" (this move takes up any backlash)
8.) set part zero at that position
9.) command 10" move at 10 inches per minute in same direction as the short move in step 7

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 » Tue Nov 28, 2017 11:46 am

Keith,
I made a quick movie testing the backlash on the Y axis. On the X axis it steps exactly .010 with each click and after moving then and then returning ten moves it ends up exactly on zero for that axis. This video is doing the same exact test on the Y axis. Strange it gets off slightly during the moves but ends up being on at the end, there could be something still in the ball nut not positive.
IMG_1885.zip
(2.68 MiB) Downloaded 5 times
Will do some more testing this afternoon after a few work calls.

Russ

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 » Tue Nov 28, 2017 1:22 pm

Keith,

After lunch I decided to replace the Y servo motor with a new one as one more test. I removed the old servo motor and then moved the Y axis manually and it moved very smooth I could not feel any binding. I went ahead and put in the new motor and then did the same back lash test in the video in the previous post, same exact results.

This suggests the motor is fine, I will next exchange the servo driver but pretty much already proved that when I swapped the control cables. I am going to find this issue if it kills me. Ugh

Russ

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

Re: Acorn Trials and Tribulations

Post by diycncscott » Tue Nov 28, 2017 1:33 pm

One thing at a time. Until the axes (or Axis - Y ) is moving the correct distance, I would leave backlash out of it since it has nothing to do with moving from Y0 to Y10. That is why I specified a procedure that removed backlash from the measurement entirely.

Your final position was greater than your target position. This implies that steps are being added (likely through noise). Please refer to my previous post and answer my questions.

Also, Keith mentioned that there is an intermediate board of some type between the Acorn and the Panasonic. What is this? Purpose? Is it a quadrature pulse generator of some type?

Make and Model?

Where is it located?

How far from the Acorn?

How close to the Drive?

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 » Tue Nov 28, 2017 2:37 pm

Scott,

The Acorn sends it singled ended outputs of Step/Direction into a differential line driver board, which converts these signals to differential signals for the amplifiers get Step Step/ Direction Direction/. The small board is located three inches from the Acorn with very short leads. The leads that leave the differential board are shielded and run two feet to the servo drives. I have used these little driver boards for years with no issues at all.

http://www.ti.com/lit/ds/snosbk1c/snosbk1c.pdf

I actually designed the driver board they have filter caps and run from a 5V supply, you will note the standard 24V supply that shipped with the Acorn was replaced with the same brand supply with three outputs 5, 12, 24.

I will run the tests again and see if I can take a video of these test as well.

Russ

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

Re: Acorn Trials and Tribulations

Post by diycncscott » Tue Nov 28, 2017 2:50 pm

To take advantage of any differential line driver board, it should be mounted as close as possible to the single ended source (the Acorn). The distance to the drives is immaterial since the whole point of the differential line driver is to get rid of the noise susceptible single ended signal as quickly as possible. Once noise is injected in the single ended signal, the line driver will simply propagate it.

What is the accuracy/repeatably of the scales you are using? Make Model?

Sorry, missed the 3" part... I'm getting blind in my old age.

We use the same chip on our TTL2Diff boards we make here.
Last edited by diycncscott on Tue Nov 28, 2017 2:54 pm, edited 1 time in total.

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 » Tue Nov 28, 2017 3:14 pm

Keith,

As you pointed out the entire reason to use the differential drivers was to help with noise immunity. I have tested it on the scope it looks very clean.

As far as scales for testing.

This is the 24" scale it did not have a brand printed on the documents but I have found it to be pretty darn accurate. I got this on ebay years ago, pretty sure it is a Chinese scale.
IMG_1886.JPG
The dial indicator is by CDI.
IMG_1887.JPG
The most accurate indicator I have is a Mitutoyo 12" caliper, which I will tram in and do those tests using it later this afternoon. It is very accurate, I use it to measure parts when creating the drawings.
IMG_1888.JPG
Russ

Post Reply

Who is online

Users browsing this forum: Rolquin and 4 guests