Messages

21

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 27, 2008, 09:25:03 PM »

Hood,

Thanks for the clarification.  I'm new to all this so it's easy to overlook something obvious.

Well, I just finished a test using Exact Stop Motion Mode under General Logic Configuration.  I believe this is what Jimpinder recommended.  Anyway, I still have the progressive error but do like the fact that it no longer rounds the corners!

I just ordered a refurbished PC to make sure this isn't the problem.  I'll give it to my daughter if it doesn't work so no loose here to try this variable.  Sometime this week I will have the breakout box made for the parallel cable but will need to wait for my father to return from vacation to get the scope.

The comment about the 201s vs the 203Vs is cerrtainly an interesting one.  Has anyone other than Cobus encountered this problem?  If nothing else works, I may need to drop the coin and get the 203Vs.

This reminds me of a Wang VS65 I was supporting for the Navy which was acting up.  The vendor replaced every board and driver in the computer over a course of a month before realizing the power supply was a couple of volts off and causing all of the other devices to be erratic.  Hopefully I will figure this out before replacing everything.

Best Regards.

Carl

22

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 27, 2008, 07:52:43 PM »

Gentlemen,

I just got back from touring the Rockies on my new motorcycle so am just getting caught up with the replies.  I can't thank everyone enough for thier replies and suggestions so I will be picking this up and working the recommendations.

I am in the process off building a breakout box for the parallel cable so I can hook a scope to it before the breakout board.  The test cables I made did not help nor did the movements of the lines in the box to try and eliminate coupling if that's even a factor?!

I am going to try some tests as Jimpinder recommends with Abosolute Stop mode.

I don't see how this can be backlash as the error is progressive.  Each cycle it gets further off.  I may not understand Hood's point but backlash should be a fixed error in each direction but never more than the total backlash amount I would have thought.

Back to the shop for some test.

Best Regards.

Carl

23

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 14, 2008, 08:42:19 PM »

RICH,

I started with the easiest test which was to eliminate the possiblity of inductive coupling.  I noticed that the X and Y were gaining steps when run together but were right on when run alone.  Seemed like there must be some coupling but I'm no EE.   When I brought the cables directly out of the top of the box, I did the original test which was a simple x1y1 and then an x0y0 and it worked amazingly even if I did if 50 times.  I then did the test in my last post and was happy when the 10 cycles worked.  But when I added that 1 line things went south.  I'm trying to do one step at a time and test enough before I declare victory.

I just received the new parallel cable and will try to setup a breakout box so I can put a scope on it easily and also connect directly to the drivers.  I wanted to rule out coupling before moving to the parallel cable.  Now I'm just trying to undersand the results of the test.

I have the drivers set for 6A for the X and Y axis using a 270K ohm resistor for each.  The Z axis driver is set for 2A with an 18K ohm resistor.

In any event, here are some pictures of my setup.  Let me know if you need more details.

Best Regards.

Carl

24

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 14, 2008, 06:52:42 PM »

Hood,

I have Nema34 Steppers (720 oz/in) on the x and y axis and a Nema23 Stepper (370 oz/in) on the Z axis.

I made test cables so I can bring them directly out of the top of my box to the drives.  My first test was promising.  I ran the following code where lines 3 through 6 reapted 10 times:

G01
F20
X-3Y-1.5
X3
Y2
X0Y0

After cycling 10 times, there was no deviation when returning to the final X0Y0.  I was very pleased and thought I had finally cracked this nut.  So I decided to do some more testing.  This time I only added 1 additional line so on the second test lines 3 through 7 repeated:

G01
F20
X-3Y-1.5
X3
Y2
X-1Y-2
X0Y0

After cycling 10 times, there was a deviation of 0.060 when returning to the final X0Y0.  Why would this one line cause things to fail?  What am I missing that makes this error?

Any suggestions would be greatly appreciated.

Best Regards.

Carl

25

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 09, 2008, 09:20:13 PM »

Brett,

The screws are belt driven using 1 to 1 pulleys.  They are the XL series pulleys and belts.  The error is always cummulative in the same direction so I think I can rule out slipage.  In addition, I pulled the covers and twisted and pulled on the pulleys and there was no movement.

I just ran another test at 40IPM acceleration at 1 that repeated the following lines about 100 times and it was right on the money with dial indicators on both axis.

X1
X0
Y1
Y0

I'm also checking the wiring to see if I have any inductive coupling.  I may wire some test cables to bring the cables out of the top of the box from the gecko's and go direct to the drives to see if anything is going on there too.

I'll keep you posted and thanks again for the great support.

Best Regards.

Carl

26

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 09, 2008, 07:53:22 PM »

RICH,

Thanks for the ideas.  I installed the older R2.61 version but got the same results.  I may try something like R2.58 tomorrow just for kicks.  Took the covers off the pulleys and checked each pulley to ensure they were not slipping and everything seems nice and tight so I believe there's no problem there.

I also ran a test setting the motors to 10IPM and 0.2 acceleration and got the same results.  My first test I repeated 15 times runing the simple program
G1F10
X1Y1
X0Y0

and the results, where the x and y column are thousands off, were:

Cycle   x   y
-----  --  --
 1      0   0
 2      3   3
 3      6   6
 4      8   7
 5     11   9
 6     13  11
 7     15  14
 8     18  14
 9     19  15
10     24  18
11     24  18
12     26  20
13     29  21
14     31  22
15     34  24

So I have some type of cummulative error.  I then did the following test on just the x axis:

G1F10
X1
X0

I ran that 12 times and the dial indicator was exactly on each time.  No variation at all.

I then did:

G1F10
Y1
Y0

I ran that 12 times and the dial indicator was exactly on each time also.

Very puzzling for me.  My next steps include:

1. Bypass breakout board.  I have a new parrallel cable on order so will do that when it arrives.
2. Borrow PC and try a desktop PC instead of the laptop.  Still looking for a loaner.
3. Gear down.  I ordered a 20 tooth and 60 tooth MXL pulley and will try to gear this down as recommended.  Not sure if this will work due to my current configuration but the advice made sense so it's worth trying.
4. Try recommendations that come in from the form.

Thanks again everyone.  It's greatly appreciated.

Best Regards.

Carl

27

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 08, 2008, 04:43:36 PM »

Chip,

OK, so it sounds like this is not a recommended configuration since the drivers and the breakout board are both opto-isolated correct?  If that's the case, I will need to bypass the breakout board to eliminate this variable.

Best Regards.

Carl

28

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 08, 2008, 04:19:40 PM »

Jimpinder,

Thanks for the confirmation on the setting and driver output.  You mentioned that twin opto-isolation might be a problem.  I'm not sure what that means.  My breakout board is opto-isolated but how would I deterimne if it is twin opto-isolated?

Best Regards.

Carl

29

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 07, 2008, 09:05:01 PM »

Brett,

Thanks again for the help.  I have attached the dirver test screen shot and the xml configuration files.  In addition, you can see the box I made at this link:  http://www.cnczone.com/forums/showthread.php?t=28973&page=3

If you need more details on the box let me know and I will get some more pictures.  I'm going to try and locate another PC and see how that works.  If that fails, I may wire the gecko drives direct as you recommended bypassing the breakout board.

Best Regards.

Carl

30

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: July 07, 2008, 05:58:08 PM »

Jimpinder,

My apologies as I was under the assumption that if my 6" dial indictor registers 3" when I coded G1X3 then I assumed the steps were properly set correctly.  I was able to move back and forth and only off by 0.004 thousands comparing the dial indicator to theentered command and DRO for both the X and Y axis.  My equipment doesn't measure below ½ thousands unfortunately so if I entered that in one of my post, I fat fingered it by accident.  Sorry.

Let me go over the setup and calculations as I do agree that being a newbie it's probably human error on my part.

1.   Nema 34 Steppers on X and Y Axis.
2.   Nema 24 Stepper on Z Axis.
3.   Gecko 201s Driving Each Stepper
4.   5 TIP Ballscrews on the X and Y Axis.
5.   Using the Micro Feed on the Enco Table Top Mill for the Z Axis.
6.   CNC4PC C11G Breakout Board.
7.   48V Unregulated Power Supply.

I calculated the X and Y steps the same as follows:

Turns per Inch = 5
Motor Steps per Revolution = 200
Micro Steps = 10

5 * 200 * 10 = 10,000 Steps Per Inch

The Z axis required 10 turns per inch so the calculation was:

10 * 200 * 10 = 20,000 Steps Per Inch

These were the values I entered in Motor Tuning and Setup.

I am unable to get the Step Pulse and Dir Pulse to persist.  Each time I enter Motor Tuning and Setup and press OK, it decrements the values of each by 1 until they return to zero.  This I believe is also causing me problems as things change as I test and I'm starting to see a correlation. 

Not sure if the Sherlin ½ Pulse Mode uses these values but it did not work the same after I reinstalled the software and tried this option.  This was very puzzling as the first time I set it in Sherline ½ Pulse Mode, it appeared to be correct when doing combined xy moves.  But after the fresh installation, it was back to the original behavior no matter what mode I used.

The machine has always worked correctly doing single axis moves.  Once again, my assumption may be wrong but when I test with the dial indicator doing single axis moves, it matches the command entered and DRO.

I have Step Low Active for the X, Y, and Z axis.  I have Dir Low Active for the X and Z axis.  I do not have Dir Low Active for the Y axis.  I can't remember why but I believe it was due to the direction it was moving?

As you can see I have a steep learning curve and appreciate the time that your team has put into this.  Thanks again for all the help.

Best Regards.

Carl