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December 17, 2018, 04:53:44 am


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Author Topic: Can’t get the correct depth  (Read 837 times)
jwalter007
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« on: August 07, 2018, 23:52:07 pm »

I’m just getting started with Cnc milling and cambam.
I’m trying to cut a pocket square in quarter inch plywood.
I’ve tried different combinations of settings for target depth and stock surface but I can’t get it to cut thru. Each time it gets most of the way but not all the way deep.
I’ve tried making stock surface 0 and -.25. Ive also tried making stock surface 0 and target depth more than -.25, such as -.40.
What is the correct settings.
Thnx
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Garyhlucas
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« Reply #1 on: August 08, 2018, 00:17:27 am »

Does the Z return to the proper height after the cut because it sounds like you may be simply losing steps?  Did you you zero the Z with the tool touching the top of the part?  Check CamBam's G-code output.  Look at the Z depth it is sending.  If you asked for -.25" and you see -.25" then the only possibilities are a wrong Z zero value or losing position, and neither is a CamBam problem.  CamBam is extremely reliable and we use it without reservation.
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Gary H. Lucas

Have you read my blog?
 http://a-little-business.blogspot.com/
kvom
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« Reply #2 on: August 08, 2018, 12:33:12 pm »

What does the mill's DRO show when at the bottom?
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Dragonfly
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« Reply #3 on: August 08, 2018, 14:26:03 pm »

Despite my already considerable experience I had recently a case where I did not guess that the tool is fixed too short and would not reach the required depth which resulted in a broken mill at the end. 
I don't have a lower limit switch (will mount one) on the Z slide and it is a stepper driven machine. So with all the noise and slow down movement I didn't hear the motor noise blocked at the end of travel.

Check that your tool tip can physically go to the required depth.
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lloydsp
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« Reply #4 on: August 08, 2018, 19:53:51 pm »

I'm perplexed by how a bit can be broken by not going deep enough!  I would think that all that could happen is that the cut wouldn't be as deep as the design called-for.

Huh
Lloyd
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EddyCurrent
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« Reply #5 on: August 08, 2018, 20:04:45 pm »

The tool can also come loose in the collet
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jwalter007
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« Reply #6 on: August 08, 2018, 23:27:42 pm »

I looked at the Gcode step by step in Mach 3 and it gets to the plunge which does say -.25. So I assume it should be going deep enough.
Its the first time I've used the mill since I built it.
Maybe I need to calibrate something.
thanks
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Bubba
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« Reply #7 on: August 09, 2018, 00:59:11 am »

Maybe I need to calibrate something.
******************************
Hmm, you think?  How you know your ZYZ axis travel commanded units? Measure exact travel of each axis and go from there.
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RonC
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« Reply #8 on: August 09, 2018, 11:34:00 am »

I hesitate to ask the obvious question,
but you are setting Z zero when the tool is touching the top of the work aren't you?
RonC
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EddyCurrent
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« Reply #9 on: August 09, 2018, 11:46:29 am »

And the vital piece of missing information is . . .;

Its the first time I've used the mill since I built it.
Maybe I need to calibrate something.
thanks

Watch these videos;

https://www.youtube.com/watch?v=2HbeyggcwU4
https://www.youtube.com/watch?v=XkO5tc-jSxw
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kvom
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« Reply #10 on: August 09, 2018, 11:53:06 am »

If you set it to cut air and stop at the target depth (as per the DRO), then measure the actual depth, you'll know if it's a calibration error vs. lost steps.
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Dragonfly
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« Reply #11 on: August 09, 2018, 17:17:13 pm »

I'm perplexed by how a bit can be broken by not going deep enough!  I would think that all that could happen is that the cut wouldn't be as deep as the design called-for.

Huh
Lloyd
Didn't want to go into details. When at end of travel and the stepper was still trying to push down the whole drive got blocked, so the stepper lost even more steps when trying to lift up before the horizontal move to the next drill hole. That's the moment I heard the stepper (trying to lift at G0 speed) but it was too late even though I hit the 'pause' key.  Wink
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lloydsp
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« Reply #12 on: August 09, 2018, 19:07:19 pm »

Ah! OK, I now understand how that could create a calamity!  You had me 'guessing'! <grin>

Lloyd
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