Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: damien.walker on October 21, 2024, 03:35:12 PM
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Dear All,
My home constructed plasma table works quite well until I ask it to cut small holes....e.g.8mm dia
The table appears to jump between data points cutting these small holes and the net effect is that they aren't circular! My code has 63 (I think) individual g-code steps (these are simple x-y G1 movement coordinates) for each hole and so the number of data points is surely adequate to get a smooth cut. (MACH3 displays perfectly round holes too). The problem therefore appears to be that the table isn't following the code accurately.
I have tinkered with speed, acceleration and micro stepping settings but have yet to hit upon the cause of this problem. Larger curves and other movements appear to be being cut smoothly and accurately. The axis are calibrated and the current speed and acceleration on both cutting axis are set to 1420mm/min and 1420mm/s/s respectively in the MACH3 motor tuning setup.
My G-Code is calling for 1000 mm/min, so not particularly fast, but I can't go much slower or the plasma cutter gets bored and switches off (because it thinks there's no metal present to cut - well there isn't, because it has already cut it! ie a minimum movement speed is vital to maintain the arc!).
The X axis has a 16mm pitch lead screw essentially directly driven by the stepper (actually a 1:1 belt drive) and the Y axis is directly belt driven and the belts are tensioned. Measurements show that the X axis moves 16mm per rev (not over surprising!) and the Y axis 177mm per rev. Clearly the Y resolution is much bigger than that of the X axis and I wonder if this could be associated with my problem?
Is there anyone out there who is still reading this ramble and who can suggest what my problem might be and what I can do to fix it please?
Many thanks in advance!
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If it’s any help my first thoughts would be to look at your CAD/CAM post processor and select one that supports arcs. This would then create your Gcode using (circular interpolation) G2 or G3 moves for the holes rather than (linear interpolation) G1 moves for the holes.
Tweakie.
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Thanks Tweakie, I'll have a look to see what the programme can do.
I need to get to the bottom of why my table doesn't apear to move as addressed though. It could be that it is also doing this with larger movements but it is much less noticeable, manifesting itself only with small objects. If it's a general problem of missing steps, then I clearly need to solve it.