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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

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General Mach Discussion / Reversing slave axis going from leadscrew to R&P drive

« on: November 29, 2011, 07:54:55 PM »

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.

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General Mach Discussion / Controlling Mach with Powerpoint? Is this possible?

« on: May 16, 2011, 12:58:44 AM »

I'm in the process of making my own 3d printer. With that said, is there any was to link Powerpoint & Mach 3 so that when you display a slide in PP, it will send a gcode instruction to Mach?   In other words....If I run a slide show in PP of 3d object slices, I would need Mach to run a couple lines of Gcode to lower or raise the Z axis by a few thousanths, thus building an object layer by layer.

The crude way to do this is to set up gcode in Mach to match the timing of the slide show....So that if the slides are on the screen for 10 seconds and there is a 3 second pause between the slides, I would want to move the Z axis between each slide so I would write the Gcode to match the proper timing ( is this even possible? Can you time your moves in gcode?). Then I would start both at the same time and hope they would stay in sync.


So....Is there any way to link the two programs?  Or can Mach be set up to be triggered by an optical sensor so I can put up a trigger slide in between the regular slides to trigger the Z axis in Mach? 

Any ideas would be appreciated. Thanks