Ghost in the machine?

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Ghost in the machine?

Postby GEdward » Tue Aug 27, 2019 8:29 pm

For some reason I am getting a shadow on one side of some of my 3D VCarves. It always on the right hand side and more prominent along the edge of steep deep profiles. If the issue is uncompensated back lash in the Z axis then I'd expect the shadow to appear throughout. I am at a loss for what kind of hardware malfunction could cause such an aberration. It does not show up in the preview so I am confident that it is not software related. I have no idea what to "fix" and detail sanding out that shadow gets old pretty quick.
BTW This particular piece of wood was given to me and I have no idea what it is. My thought was perhaps alder? It works beautifully, is very close grained, is about as dense as red oak but a little softer and I love the way it finishes. I have not applied any finish to this piece yet so it is in its natural state. The actual color is not as dark as it appears in the photo; my photography skills and equipment have room for improvement. Any ideas?
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Re: Ghost in the machine?

Postby Rcnewcomb » Tue Aug 27, 2019 8:39 pm

Try:
- checking the spindle/router for plumb/square
- resurfacing the spoilboard

YouTube videos are available on both topics.

Also check your material holding and material movement. When a lot of wood is removed the boards tend to cup, twist, or bow.
Last edited by Rcnewcomb on Tue Aug 27, 2019 8:40 pm, edited 1 time in total.
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Re: Ghost in the machine?

Postby rscrawford » Tue Aug 27, 2019 8:40 pm

Probably backlash, and only happens after a longer Z movement (where it has longer to accelerate and actually gets up to a higher speed).

Another possibility is with longer Z plunges, there is more lifting force with an upcut spiral ballnose bit, and the wood can be moving slightly upwards, giving a deeper cut at the bottom of the plunge.
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Re: Ghost in the machine?

Postby GEdward » Tue Aug 27, 2019 9:09 pm

rscrawford wrote:Probably backlash, and only happens after a longer Z movement (where it has longer to accelerate and actually gets up to a higher speed).

Another possibility is with longer Z plunges, there is more lifting force with an upcut spiral ballnose bit, and the wood can be moving slightly upwards, giving a deeper cut at the bottom of the plunge.


The shadow is actually about 0.01 - 0.015 higher than the model specifies. The shadow is also smooth which indicates that the tool is lifting up before it get to the "cliff" as well as not fully dropping off coming off the "cliff'. And again, why only on the right hand side?
Rcnewcomb wrote:Try:
- checking the spindle/router for plumb/square
- resurfacing the spoilboard

YouTube videos are available on both topics.

Also check your material holding and material movement. When a lot of wood is removed the boards tend to cup, twist, or bow.


The stock is being clamped down on all four corners to a Blanchard ground aluminum tooling plate. The spindle trams to within .006 TIR on a 8 inch sweep last time I checked it. If the wood is moving after it is relieved then again, I'd expect the issue to seen throughout.
This occurs quite often on a number of my projects and it is always the same; just on the right hand side.
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Re: Ghost in the machine?

Postby Ken Rychlik » Wed Aug 28, 2019 3:11 am

You could try to raster the other direction to see if any kind of problem follows that. It's to even for loosing steps so that seems out. Those files run back and forth like a typewriter, so it almost seems like software. Other wise it would be every other direction. I guess you have tried the preview? It might have something to do with cutting 3d stuff with vcarve instead of Aspire? I'm just thinking out loud here.
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Re: Ghost in the machine?

Postby GEdward » Wed Aug 28, 2019 2:56 pm

I will be trying the raster in a couple of other directions to see if the problem follows. I have the tool paths calculated, I just need to load and run. I really do like to raster along x though as the x axis is easy to service and there is less mass that has to accelerate/decelerate which theoretically allows me to carve greater detail at higher speeds. That of course is a moot point if I have to spend an hour or so cleaning up the shadow.
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