Possible Z-Axis skipping in 3d milling?

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benjamd
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Joined: Wed Sep 18, 2013 5:03 pm

Possible Z-Axis skipping in 3d milling?

Post by benjamd » Tue Sep 09, 2014 6:16 pm

So I milled a lithophane last night, came out pretty good but I got one raised corner. Its clearly delineated and everything in that corner is raised. Any ideas what could be causing this?

The piece was milled first with a roughing pass using a 1/8th ball nose, then the finishing pass with a 1/16th ball nose. The finishing pass was made at a 45 degree angle so its clear this artifact came from this pass. I'm guessing the z-axis must have skipped coming back down at some point resulting in this offset? I have a fan blowing on my TinyG drivers, though I'm not sure how well thats working, my Z-axis motor does seem to get a little hot (I can touch it but its uncomfortable to hold my finger on it for too long) so perhaps this is the problem?

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cvoinescu
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Re: Possible Z-Axis skipping in 3d milling?

Post by cvoinescu » Tue Sep 09, 2014 6:48 pm

You are almost certainly right, it looks like a few lost steps on the Z axis. The temperature of the motor should not cause it, and if the driver entered thermal shutdown, it's weird that it did that only once, and not all the time as I would have expected. In other words, I have no clue what could have caused you to lose steps.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

dataway
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Re: Possible Z-Axis skipping in 3d milling?

Post by dataway » Tue Sep 09, 2014 8:27 pm

I experienced a similar issue with my tinyG setup and loaded the latest EDGE build and it seemed to fix my issue with 3D Milling. I would recommend you try the latest edge build found here: http://synthetos.github.io if that does not resolve you issue I would post your inquiry to the tinyG forum : https://www.synthetos.com/forums/tinyg/tinyg-support/ The team on there is very good at resolving issues.
Shapeoko 2, Dewalt DW660 1/4" shaft/ 1/8" shaft, 3D printed Dust Shoe,Dual Y Axis.

benjamd
Posts: 27
Joined: Wed Sep 18, 2013 5:03 pm

Re: Possible Z-Axis skipping in 3d milling?

Post by benjamd » Tue Sep 09, 2014 8:51 pm

Huh, I had not considered it being the TinyG firmware. I had an edge build from a month or so ago but I'll update again and see if its any better I know they were fiddling around with a lot of things over the last couple of months so its quite possible. I'll try that tomorrow, hopefully it will fix this last niggling issue. I was having z-axis problems before where the shaft had some play between the bearings so I took part my old Shapeoko V1 z-axis and modified it into something like the v2 axis (replaced the axis carriage plates with the new style, cut down the old motor mount plate to mount the spindle onto, flipped the rail around and rounded off the bottom plate on the rail for clearance). I then ground down a large washer to fit between the bearing plates and I think this has eliminated any movement on the shaft now. Hopefully I a firmware upgrade will fix this latest issue then I'll finally be able to reliably cut :-)

secretspy711
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Re: Possible Z-Axis skipping in 3d milling?

Post by secretspy711 » Thu Sep 11, 2014 3:07 pm

had the same issue recently. dropping the Z acceleration from 25 to 20 mm/s/s did the trick for me.
Shapeoko 2 #5510: 1200 x 500 mm, Makita RT0701

Gadgetman!
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Re: Possible Z-Axis skipping in 3d milling?

Post by Gadgetman! » Thu Sep 11, 2014 3:28 pm

I had a similar mess on my ShapeOko recently.
But on mine it was the collet not gripping the bit properly, so on some passes it wouldn't plunge properly, but instead push the bit more and more up into the collet.
Weird guy...
Shapeoko 2014F: 1000mm X/Y, 300W Quiet Cut spindle, Arduino Uno/G-shield and GRBL 0.9i
15x30 drag chains, custom spindle mount, 9mm belts, 8mm endplates, 6mm motor plates.

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