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Topics - Radguy

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General Mach Discussion / Formula axis correction limitation
« on: June 08, 2013, 01:55:24 PM »
Hi, I have been trying to set my z axis to shift about 17º relative to the x axis.  I use the formula z + x/3.4 (also found that 100x/310 doesn't work) which works unless the z axis is given a g0 z0 command; such is used for a go to zero command or within a gcode, in which case the z stepper squeals briefly while mach3 thinks it is moving, causing the reported z location to be wrong.

I have played around a bit (after hardwiring motors, lubing the rails and trying two different computers) before realising it was the axis correction formula applied that is the cause of this problem.  I have tried slowing the axis acceleration down which does shorten the squeal time, but it doesn't stop the squeal and position loss.  I also tried setting a shallower angle to z + x/100 which seems to be about the point which the squealing disappears.

I have tried a workaround by turning off the formulas before I go to zero, then turning them back on when home.  However this is the point where I found that any g0 z0 command may cause the motor squeal evidenced by a hefty gouge in my workpiece.

I have observed that the acceleration is way above my settings with no audible wind up in the motor squeal.  It seems that the axis correction is occurring without due acceleration and it is only by chance that the axis occasionally elevates at all prior to the next move.  This would explain why small axis corrections work while larger ones don't.

Putting an angled hole through a flat workpiece is very useful to me.  The particular workpiece is set at the 17º angle, meaning that without the axis correction, the toolpath cuts a lot of air.  The cutting depth is also limited to the highest depth the spindle can encounter around the hole, rather than allowing the z axis to follow the angle of the workpiece thereby enabling the maximum cutting depth around the entirety of the hole.

It was a bit disappointing seeing the lovely toolpath make little waves as the z axis lowers, yet being prevented from using this strategy successfully due to a small detail in the software.

Is there a setting that can be manipulated to enable large axis corrections?  Otherwise, is there a possibility that this feature can be implemented properly into mach3?  I have a g540 controller which works perfectly otherwise and I am reluctant to try the tb6540 or whatever those cringeworthy toshiba boards are called (I have received two out of three duds from China).

Thanks

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