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Author Topic: Loosing steps or backlash  (Read 6202 times)

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Re: Loosing steps or backlash
« Reply #10 on: September 20, 2010, 04:37:27 PM »
I just ran a few test programs, on the last program I noticed that when the machine came back to 0,0 it was off by .0008 in the y axis. I am running another test under the same settings to see if this happens again.

Offline Hood

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Re: Loosing steps or backlash
« Reply #11 on: September 20, 2010, 05:25:36 PM »
But did you start and finish going the same direction? 0.0008 is not very much on 30yr old ballscrews if it has been used.
Hood
Re: Loosing steps or backlash
« Reply #12 on: September 20, 2010, 06:37:08 PM »
I don't know what you mean by start and finish in the same direction. Well I haven't been able to get my machine to act up again. I know that .0008 isn't much, but that was in a 5 minute program, I thought in a longer program it might compound. I am now trying to run a pocketing program and see if I can get any errors. At this time I haven't made any progress, I think I will slow down my feeds and try running another part and see what happens. I don't have a whole lot to loose at the moment.

Is this forum running slow today?

Offline Hood

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Re: Loosing steps or backlash
« Reply #13 on: September 20, 2010, 08:01:04 PM »
Well what I mean is if you moved in a positive direction and stopped then zeroed the DROs and  then ran the code and the your last move back to the Y zero was in a negative direction then it is likely your 0.0008" was backlash. If it is backlash then it wont increase, if its losing steps it likely will.
Yes forum is getting bogged down, Scotts been working on it, hopefully he will get it fixed soon.
Hood

Offline RICH

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Re: Loosing steps or backlash
« Reply #14 on: September 20, 2010, 09:43:04 PM »
Hmm....
A program with a prep move to take out backlash along with the dro's referenced to zero moving in one direction and then backtracking exactly  in reverse you should end up at 0,0,0. For testing over time just make it a subroutine. So you could test linear or circlular movements.
Add the poor mans pulse counter using a disc to rotate along with the motor shaft gives you a phyisical reading if a step is lost. The bigger the disc the more accurate or even a 75 cent protractor ie; approx 2 deg=a step.

The smaller the number the harder it is to isolate what is contributing to it. Heck it could be the indicator, a little backlash, etc and gets difficult to isolate each part. Even timing belt tension can account for lost movement which you may think is an electronic pulse missed.

FWIW,
RICH
Re: Loosing steps or backlash
« Reply #15 on: September 20, 2010, 10:57:40 PM »
Well I ran a few different programs to see if I can replicate a lost move, but I failed. I Well I ran a few different programs to see if I can replicate a lost move, but I failed. I am cutting a part at a much slower IPM to see if that will show anything. One thing I am doing is I am keeping track of the temperature of my motors. So far the x and y motors have gotten up to 135 degrees each. The y motor retains heat longer, I had to run an errand and when I came back the toolpath had finished, the x moltor was 109 degrees and the y was 123 degrees. I don't know if maybe there is a breakdown in the one motor when it gets hot? Right now I'm running at 3 IPM, the x motor is 106 degrees and the y is 124 degrees.
Re: Loosing steps or backlash
« Reply #16 on: September 22, 2010, 12:26:46 AM »
Well another scrapped part, just like the others, off in the Y axis. I don't know if it will make a difference but I picked up to new steppers today. Tomorrow I will see if this solves the problem, if it doesn't then I'll start to look elsewhere. One thing that I discovered by accident is last night I accidently left my machine on, this morning I checked the temperature of the stepper motors, the x motor was 96 degrees, the y was 126 degrees. I didn't even think of checking the z motor. It only reaches 96 degrees when running.


Hood, what IPM do you cut with on your BP?

Offline Hood

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Re: Loosing steps or backlash
« Reply #17 on: September 22, 2010, 02:29:24 AM »
Hood, what IPM do you cut with on your BP?

All depends on the material and size/flutes of cutter but anywhere from 40mm/min (1.6 IPM) to about 1,000mm/min(40 IPM)
Hood

Offline RICH

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Re: Loosing steps or backlash
« Reply #18 on: September 22, 2010, 07:05:45 AM »
Should be interesting to see what the new motors will do. A motor that dosen't get warm is not doing any work, the more work the motor does the hotter it will get. As long as the motor is operating in a temp range below the rated insulation you should be ok and with age it would be prudent to operate it taking age into consideration. Greater than 140F  you can't hold your hand on it very long and can get burnt. The motor case temp you see is influenced by the how well heat is being removed from it so dirty fins or evan different paint thickness and location can influence it. So relatively small temp changes of say 10 deg diff is subjective for any conclusion.  I have motors on my mill that are  are older than me and work great. don't be suprised if you see a difference in microstepping position as i found different motors required small change in the steps per unit and would attribute that more to the quality of the motor. Let me remark that it's within a roatation or very small moves.
Just some comments on the motor end they are  generalizations.
RICH
Re: Loosing steps or backlash
« Reply #19 on: September 22, 2010, 05:44:37 PM »
Motors are installed and we are making chips. Hopefully my next report will be of a completed part.