Need 3D help

[Craig Thompson]

I was doing a 3d carving of a badge. I used a 1/8 bull nose for the carving. After it got about half way through the bit dropped and finished the carving about 1/16 of an inch lower. I did not change bits it was used through out the carving. Can anyone tell me why it did not carve the same depth across the model. I have attached pictures of the problem. If you look at the Aspire drawing it does not show where the bit started cutting deeper. In the photo you can see to the left of the center there is a line from top to bottom, this is where the bit lowered and finished the carving. Any help would be appreciated. I just destroyed an expensive piece of Cherry wood.

[Rcnewcomb]

Can anyone tell me why it did not carve the same depth across the model

The direct cause was that your Z lost position.

There are various possible root causes:
- Z axis missed steps: perhaps due to mechanical binding, perhaps static discharge from the dust collector - do you have a ground wire running through the dust collection hose?
- Bit slipped in the collet
- Spindle/Router may have slipped in its holder
- The material may have slipped - what is your holddown mechanism?


If you see something like that while it is still on the machine it is sometimes possible to salvage the material by resetting the zero somewhat lower and recarving the design.

I just destroyed an expensive piece of Cherry wood.

It may also be possible to smooth out the discontinuity in that piece with careful use of chisels and/or a Dremel.

[Craig Thompson]

I had the panel screwed to the table, so I know it didn't move. The bit was tight in the collet so I'm sure it didn't move. I didn't have my dust collection turned on. Only thing I can think is that I ran the cut directly from a flash drive instead of uploading it to the CNC. I was also wondering if I needed a zero plane. If you notice around the cut out it is rough. Not sure how to do the zero plane but searching the forum to see if that helps anything. I had the model made, but I don't think its a problem there.

[Rcnewcomb]

When the results don't match the preview 99% of the time it is due to a machine, material movement, mechanical, or electrical issue.

Running from a thumb drive may have introduced some latency that your control software didn't appreciate. Your machine vendor may have more insight on that topic.

I was also wondering if I needed a zero plane. If you notice around the cut out it is rough.

I always use a zero plane. A zero plane would help with the edges but would not explain the discontinuity while carving.

In Aspire you add a zero plane by selecting:
Model/Create Component/Add Zero Plane

[TSM2018]

>>The direct cause was that your Z lost position.

Thanks Rcnewcomb, for responding to this post; it is very helpful. I had a similar experience recently, so I will try all these potential solutions for troubleshooting my issues. In my case my x position when I went back to zero, zero, zero, was off by about 1".

[adze_cnc]

When the results don't match the preview 99% of the time it is due to a machine...

And 99% of the time people will insist that it must be the preview that is wrong...

[Craig Thompson]

OK, I think I figured out what the problem was. I'm re-cutting the same model on another panel. It seems to be doing what it is suppose to. I uploaded the tool paths to the machine and its working so far. I think is was a glitch in the flash drive. I reformatted it and started over. So far so good. One question I do have is, on the photo I sent earlier, it left a bad edge where the model ended. It dropped the bit down approximately 1/8 inch all the way around. Is this where the zero plane would help? I've been watching the tutorials about this, but not sure that is the reason it's dropping down on the edges. I'm new at modeling and trying to learn the ins and outs. All the classes are far away so I'm having to learn on my own. I appreciate all the help. Thank you very much.

Craig

[dealguy11]

A zero plane will probably help. You must be using a boundary offset, otherwise the bit shouldn't be falling off the edge like that. Not using a boundary offset would probably address it, but might leave an artifact around the edge, as the bit may not round the edge nicely. If the level of the zero plane is at the same level as the edge of the badge then it will help. If the badge has a base height, such that it has vertical sides, then you'll need to give the zero plane the same base height and set its combine mode to merge.

[Rcnewcomb]

it left a bad edge where the model ended. It dropped the bit down approximately 1/8 inch all the way around. Is this where the zero plane would help?

Here is an post I wrote 9 years ago that explains the cause of "software chatter" on the edge of a model and how to solve it. Subsequent releases of Aspire added the option of creating a Zero plane to deal with the issue.
Identifying and eliminating software generated chatter marks

[Craig Thompson]

It was a glitch in the flash drive, the second time around it carved perfectly. Thanks for all your help. I really appreciate it.

Craig