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Author Topic: loosing steps in one direction  (Read 9054 times)

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Offline Graham Waterworth

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Re: loosing steps in one direction
« Reply #10 on: August 07, 2007, 04:24:53 PM »
Hi Mick,

from the test you have done I would say that it is NOT a machine error more a driving error, try a different cable and/or breakout board.

Graham.
Without engineers the world stops

Offline jimpinder

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Re: loosing steps in one direction
« Reply #11 on: August 08, 2007, 04:31:09 AM »
I do not like spending money until I find out where the problem lies.

I run 220CNm motors on my Warco Lathe. I have Stepmaster drivers. I do not have a breakout board, but run the drivers direct from an old printer cable about 18" long. I got the motors from ArcEuroTrade.
The motors were eight wire that I connected in series to make bi-polar motors. I run them from a 24 volt supply - from large batteries which ensures a steady voltage over a wide current range.

My only difference to your set-up is that the motors are geared down 3 to 1 to drive my axis and therefore I need 6400 steps per rev.
I have tested my set-up quite rigourously for accuracy - I am fortunate because I kept the old 1thou dials on when I converted it, so you can see that the lathe returns to where it started - or you can have a second check on distance travelled. The geared down drive was because I tried using smaller motors - which kept missing steps. With the 220 performance is fine and I upped the gearing to 3 to 1 from 5 to one.

With these settings I have found it impossible to move my axis faster than 4 inches per minute - but I am happy to trade accuracy for speed.

Without getting your ****** in a twist, I think you must be patient and keep trying to find where the loss is. Yes - from what you have said, it would seem that you are loosing steps, but in one direction only.

I cannot think that this will be in the middle of travel, but is probably at the start or finish.

Make up a table with different settings on it. Try a different set of motor speeds and do short - say 1 to 6 inches movement, and check them with digital calipers - in both directions.  Start with slow movement and slow acceleration, and see if you were ever accurate.

Gradually increase the speed of travel, and finally the acceleration.

I left my pulse length at 5  - I tried putting in 10 but it didn't seem to take it.

This may sound a bit complicated - but with a little thought you can do it all in an evening.

I have to be careful with my set up - which works perfectly in the  mid area of my lathe (which, or course, I used to use a lot) but at the extreme ends, I can loose steps, where the lathe (not the steppers) sticks a fraction.

There must be an answer.

Jim





 
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Re: loosing steps in one direction
« Reply #12 on: August 08, 2007, 09:07:11 PM »
Try changing the step active low state ... It is worth a try :)
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Offline mick

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Re: loosing steps in one direction
« Reply #13 on: August 09, 2007, 04:37:46 AM »
GRAHAM,BRIAN ,
                          thanks for the suggestions ,will have a go.
         
                                                                          regards mick.

Offline mick

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Re: loosing steps in one direction
« Reply #14 on: August 28, 2007, 10:37:35 AM »
thank you gents,
                       my problem is solved thanks to Ians suggested bob change.

after fitting the new board this morning, i ran x & y axies through 50 cycles each , after which the d.t.i  read .0005 error.

  happiness !                      thanks mick.
Re: loosing steps in one direction
« Reply #15 on: August 30, 2007, 05:19:29 PM »
Mick,

Pleased to hear you got it sorted.

Ian
Re: loosing steps in one direction
« Reply #16 on: October 04, 2011, 06:47:23 PM »
I am having a problem loosing steps on one axis.  When I run a 35000 line project I loose aprox.  .025 inches on my Y axis, the  X axis comes back exactly to 0.  I switched the X with the Y and the problem switched axes too.  I am using a gecko  G540,  xylotex 270 oz. in. motors, running  20 in per min. with the acceleration of 20 percent.  I can run it at well over twice that speed and acceleration without stalling.  The kernel speed is  25000  the step and direction pulse width is  2.   This board has a charge pump that I believe is working.  I noticed a post saying he changed the pulse width and fixed his problem so I changed mine to 5 on both and am running the project now;  it takes 2.5 hours.  If that does not work does any one have any ideas.  It is 28000 pulses per inch.  This project covers an area of  .75 inch by 4 inches.
Thanks  silveron.

Offline RICH

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Re: loosing steps in one direction
« Reply #17 on: October 04, 2011, 07:24:35 PM »
Silveron,
Don't know how manny moves your making with the y axis, how good all the mechanical stuff is, etc.
How much backlash do you have and where is it coming from?
How linear are the screws?
Mechanical errors can add up over manny moves and result in what your seeing.
Just some thoughts,
RICH


 
Re: loosing steps in one direction
« Reply #18 on: October 05, 2011, 12:02:07 PM »
Thanks Rich
I am only loosing position on one axis.
When I switch the axis X with Y the problem switches axes also.  If it were a mechanical problem the error should stay with that axis.
I believe this would rule out noise between the driver and the motors being the problem also.  I should mention that  I had a TB6560
driver a few weeks ago the problem was similar but worse, much worse, it lost a little position on one axis and a lot in the other.
That is why I bought the Gecko  G540.
I have not been counting the moves because after running this program multiple times which would amount to well over a hundred thousand lines and ten hours of running the good axis looses nothing but the other one looses aproximately .025 per 35000 line run.  When I then switch the motor plugs X for Y the problem switches axes and the axis that was loosing steps now works perfectly even over multiple runs.
Thanks: silveron


Re: loosing steps in one direction
« Reply #19 on: October 05, 2011, 12:32:41 PM »
That is a lot of moves! Is the error accumulative? or does it vary up and down. If accumulative, then it could be a rounding up (or down) error in the maths associated with the G code, but finding it would be time consuming. You would have to look for square roots and trig functions or something similar.

Ian