Plunge cuts- help

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Re: Plunge cuts- help

Postby cncdrive » Sun May 28, 2017 4:11 pm

Hi Brendon,

OK, thank you. An email was sent back, because I have some problems understanding how to view the g-code file.
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Re: Plunge cuts- help

Postby cncdrive » Mon May 29, 2017 7:36 pm

We've managed to measure your g-code step/dir signals out using a logic analyser.
Because on your photo it can be clearly seen that there is a movement to the cross (X) direction at the end of the cut we've eximaned the X-axis signals,
especially if any X axis movement happens between the Z pluge in start and plunge out finish.
The test results clearly shows that there is no movement at all on the X-axis between these.

So, my conclusion is that the issue is not with the UCCNC. I guess that the problem is that the cut is really deep (18mm) made from about a single pass.
What I think is happening is that when the cut ends it is at a so deep level that it cannot drop the wood chips out quick enough, so when the tool starts plunging out it probably vibrates the tool or even the axis when the servos try to compensate creating that deformation on the toolpath.

In the following I will copy the measurement printscreens.
I will do that in a few separate posts, because there is a picture number limit per post.
But first I'm posting the g-code which we cut down to see only the code of interest.
Attachments
Flutedowncush_short.txt
(700 Bytes) Downloaded 30 times
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Re: Plunge cuts- help

Postby cncdrive » Mon May 29, 2017 7:37 pm

The following image shows the full g-code run with the X step, X dir, Y step, Y dir, Z step, Z dir signals in order from the top to bottom:
Attachments
IMG_29052017_203033_0.png
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Re: Plunge cuts- help

Postby cncdrive » Mon May 29, 2017 7:38 pm

The Z-axis plunge in movement:
Attachments
IMG_29052017_203309_1.png
IMG_29052017_203309_1.png (3.3 KiB) Viewed 1037 times
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Re: Plunge cuts- help

Postby cncdrive » Mon May 29, 2017 7:39 pm

The end of the Z plunge out:
Attachments
IMG_29052017_203405_2.png
IMG_29052017_203405_2.png (3.67 KiB) Viewed 1037 times
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Re: Plunge cuts- help

Postby cncdrive » Mon May 29, 2017 7:39 pm

The full Z plunge out movement:
Attachments
IMG_29052017_203516_3.png
IMG_29052017_203516_3.png (3.99 KiB) Viewed 1037 times
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Re: Plunge cuts- help

Postby Battwell » Mon May 29, 2017 8:24 pm

Thanks
At least I know I'm looking for something my end :-(
And you don't have to do anything to the software :-)

Strange how this has just started.

I ran a test file last night and could just see it - with only a 1mm depth of cut. But not as bad
Now the headache begins for me - to find the cause . Il let you know.


Thanks again for checking
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Re: Plunge cuts- help

Postby Derek » Tue May 30, 2017 12:33 am

If you run he code twice in the same spot does it remove more material?
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Re: Plunge cuts- help

Postby cncdrive » Tue May 30, 2017 12:48 am

I also have an idea that your Z axis may be not aligned perfectly.
I think this as another possiblity for this problem, because if your Z is for example bent to the side in the X direction, that could perfectly explain the issue on the picture with your g-code, because you plunge in and out at that same spot only, so the bottom of the tool only contacts with the workpiece surface on that spot only. With a missaligned Z axis your tool will make the widest mark on the spot where you plunged in and out, because that spot will contact with the whole length of the tool while the other parts of the path only contact with the upper side of the tool which is then more to the left or to the right.
So, in my opinion this could explain the result on the photo.

I would try to plunge in a relatively deep drill and check the shape and size of the hole.
If the size of the hole is different than the tool diameter then this will be the issue.
And if the hole is oval then the missalignment differs in X and Y, maybe it is only around one axis.
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Re: Plunge cuts- help

Postby Battwell » Thu Jun 08, 2017 11:18 am

my spindle is trammed perfectly- i skim the spoil board with 100mm cutter- with no witness lines :-)
i can re run code fine- in same place.

too busy to investigate until after my holidays now
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