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Author Topic: Tool change problem with full-depth finish  (Read 519 times)
lloydsp
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« on: January 14, 2012, 00:39:25 am »

I've _almost_ had an accident with a workpiece, but caught the bit traversing the wrong way, and hit the E-stop before it ploughed across the piece.

Attached are two files, identical except for the depth increment for the finish pass.

I spiral drill a hole, then ask for a toolchange (in this case, it's the same bit, it's just an opportunity for me to clean up the workspace, and check the work).  I then (presumably) rapid to the same spot and do a full-depth finish pass.

If I set the depth increment on the finish pass to the full target depth, then after a tool change, the bit slowly ploughs across the whole workpiece, moving on a G1 from the toolchange position (say, -3,-3,3) all the way to the target depth.  Of course, the G1 moves in all three axes, as it should.

If I set the depth increment only a ten-thousanth shallower (say -.7499 instead of -.75, as in the example), then it properly does a G0 to the target location.  The G0, of course, moves to the target position first, before plunging to depth.  This is what is desired after a tool change.

CutViewer doesn't show the error, because it doesn't show a toolchange as altering the position, but in reality, many machines move to a "safe change" position off the workpiece for a toolchange.

These results are duplicated if I change to all three available optimization methods.

I think this is a bug, Andy, unless I misunderstand how the G1 and G0 commands should work.

BTW... I tried this with the Mach 3 post instead of my own, and the symptoms somewhat change, but it still issues only a G1 after the toolchange, which traverses at the cut speed, instead of rapid.


LLoyd

* ToolChangeBug-shown.cb (19.59 KB - downloaded 40 times.)
* ToolChangeBug-fixed.cb (19.59 KB - downloaded 42 times.)
« Last Edit: January 14, 2012, 01:59:27 am by lloydsp » Logged

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lloydsp
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« Reply #1 on: January 14, 2012, 02:07:18 am »

I think I have it figured out, but not solved.

If the commands are set up as modal, and IF one issues a goto clearance as the finish to the last MOp, then CamBam only issues the portion of the G1 necessary to get back to the correct spot.

If they are not modal, and the goto clearance is not issued, then CB issues the G1 with the new target Z, which is fatal.

I think this is a mix of post issues and maybe a bug in how CB interprets a command which has a full-depth plunge as the first command in a new MOp after a toolchange (after a previous MOp).

(whew!  Complex relationships!)

LLoyd
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Bubba
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« Reply #2 on: January 15, 2012, 01:51:41 am »

Lloyd, last year I had the same problem after tool change(furloughing thru). Solved this by setting safe Z in Mach3 to .125". Not sure your post allow for you to do this.. Hope this helps.
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lloydsp
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« Reply #3 on: January 15, 2012, 02:06:30 am »

thanks... not familiar with "safe Z".  I know what "clearance plane" is...
But this particular 'error' is different.  The code honors the clearance plane, it simply does a G1 where I'd expect a G0 to have been done.

I'll explore your suggestion.

Thanks again,
Lloyd
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lloydsp
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« Reply #4 on: January 15, 2012, 02:29:07 am »

Ahh... it took a bit of searching, but I see "SafeZ" is a custom post macro.

I think I shall try that.

LLoyd
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lloydsp
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« Reply #5 on: January 19, 2012, 01:27:20 am »

I believe this also may be solved by the "safe toolchange" I implemented in the "Fixture Crashes" thread in the general usage section.

Lloyd
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