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Messages - watsonstudios

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11
General Mach Discussion / Re: Missing steps! Upgraded my screw drive to R&P
« on: December 17, 2011, 11:34:27 AM »
Hey Rich, I don't think it is my steps per unit. I've already played with that and determined that the deviation is more random and not compounded over distance. I actually cut a 24" x 48" profile and the measurements were right on.  I put my vel to 100 and accel to 2 and cut 13 lines, two inches apart along Y.  Measured between them and there was a .02 variation at most. I put the ruler on the first line, the second & third were slightly off from the first but exact in relation to each other, the the next 2 or 3 were slightly off the the next was on and the next 2 were off, etc. very random in the variation of distance between all the lines. I will check with the router off but I'm keeping the router cable away from the motor cables and even have it in a separate power outlet. I may try to put it on a separate circuit just to be sure. The thing is, when I ran the exact same electronics & motors on my smaller 2" x 3" table, I didn't have any issues so everything is still the same except now I'm connected to an R&P and the axis' are triple in size. It sounds like noise to me because of the very subtle errors in accuracy (.02) I just don't know id its coming from the router. Any other thoughts?  Thanks,
Jon

12
General Mach Discussion / Missing steps! Upgraded my screw drive to R&P
« on: December 17, 2011, 12:07:16 AM »
I just upgraded my router to a 5x10' R&P drive and now I seem to be having accuracy issues. I've been playing with the settings in Mach, slowing velocity & acceleration and also bumping up step & direction pulse width but I can't seem to get my accuracy back. I think I'm missing steps but I have no idea where. I'm going to rule out the possibility of losing steps going from the computer to the breakout board to the drivers because it worked fine when I was running my smaller screw drive system.

I'm basically cutting 4 parallel lines that are 4 inches apart. I'm getting inconsistency whether I cut them in X or in Y. I've attached a quick diagram of what is happening.

In the attached diagram, The blue lines are what it's supposed to look like and the red lines are what I'm getting. You can see how it's almost random where the errors lie. 2 or 3 lines can be right on and then one may be slightly off. Any ideas about what could be going wrong? Everything worked great on my smaller, screw drive router and accuracy was fine.

Also what is happening is when I cut out a profile, the position where the bit is on the exit cut is slightly off from the position of the entry or start of the cut. This is telling me that steps are being lost in the process of cutting the profile and not ending up where it started.

Now could there be an issue of noise or interference in the cables? I did just replace my Y & Z motor [/img]cables with larger 18ga 4 conductor shielded wire but have not done so yet on my X & A motors, which still have thinner 24ga unshielded wires. Could this make a difference? Also, could it make a difference if the cable lengths are different? I'm looking for all possibilities here.

Any thoughts would be greatly appreciated. Thanks,
Jon

13
General Mach Discussion / Re: Missing steps
« on: December 15, 2011, 07:38:09 PM »
Graham, I seem to be having the same problem. I was cutting some slot car track pieces from a 4x8 sheet of MDF and was getting inaccurate spacings between the slots which should be exactly 4" - some were 4" and some were a bit off. Some of the track pieces line up better than others and it is inconsistent where the errors lie.

I have a 5' x 10' R&P table. My velocity is at 400 and my accel is at 12. For the next test I will try 200 vel. and 8 accel. Do you think this will help?

I have a feeling I'm missing steps somewhere. Is that what it sounds like to you?
Thanks,
Jon

14
Thanks! I actually did it in homing/limits and just reversed A  - Worked perfect!  Now does it matter what setting I use, or will it be the same whether using active low or reverse in homing/limits?

15
Yes, I think active low is selected for all motors. So do I just de-select active low for the A axis and that will reverse it?

16
Ok, where do you do that in Mach?  I can't find any setting or config that lets you reverse direction of axis.

17
In My original MACH setup on my smaller CNC router, My X and A were slaved for my gantry and the steppers were connected to a lead screw system. Thus they were both spinning the same direction. I'm re-building my router to a larger size and now using a Rack & pinion system to drive the gantry. Now....The X & A motors will need to turn in the opposite direction because they will be mounted perpendicular to the X axis & facing each other, meaning they will need to turn in opposite directions to move the gantry in the same direction. My question is can I just reverse one of them in Mach or do I need to re-wire one of the motors in reverse?

Any advise appreciated. Thanks.

18
The final configuration is this:

For s=1 To numSlides
  Code "G1 Z" & ZIncrement + ZIncrement 'lift Z a couple of tads
  Code "G4 P2"
  While IsMoving()
    sleep 10
  Wend
  Code "G1 Z-" & ZIncrement 'lower Z a tad
  While IsMoving()
    sleep 10
  Wend

The G4 is not really necessary, it just gives a slight delay between the moves. I will know if it needs to be there or not once I start experimenting.

19
Thanks TP, That did the trick!

20
Andrew, I have a question:  Right now, when I run the macro, the machine moves at the start of (before) the first slide. Is there a way to start the Zmovement "after" the first slide? The first slide needs to be shown when Z is still at zero(Const ZStartPoint) then I need it to do the first move before the second slide, then continue as is. How can we edit the macro to do this?  Thanks.
Jon

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