Help with a plaque

[redwood]

I have a decent size plaque 17" x21". It consists of a oval frame with modeled text and items in the recessed oval. I've done a much smaller version of this and used a 1/16" ball nose bit and it came out great. Using a 1/16" bit with this size will take a long time, so I thought I would do the whole plaque with a 1/4" ball nose and then come back and using vectors around the items, do another 3D pass using a smaller 1/16" ball nose bit on just the items in the bowl. The problem is that these tooling paths don't seem to want to play well together. All items are set to merge and everything looks great in the 3D image. But when I run the toolpath preview, it's not so clean. I've used various boundary offsets on the second 3D finish pass, but nothing looks good. Any suggestions?

I tried loading the drawing file, but I guess it was too big.

[Pete Cyr]

1/4" ball - stepover 6%
3/16" ball stepover 7%
1/8 Ball - Stepover 7%

Try one of the sizes above to determine how it will carve - use the biggest bit that carves and maintains the desired detail

[mtylerfl]

Unfortunately, it's likely you'll be faced with "witness marks" where the two different bits were used if you are attempting a Rest Machining type of operation.

You may have to spend some "quality-time" with trying to sand/blend the marks out.

Perhaps you could do a smaller-area test on some scrap of the same material to get an idea of the end result before doing the whole thing.

Personally, I would probably just use one bit as normal for the Finish pass. Takes longer, of course, but in the scheme of time the item will be enjoyed, is trivial (hours of Carve time vs years of enjoyment).


How much larger is this version compared to the one you did with your 1/16" ballnose? If it's double the size (or very near double), then you'll have comparable detail with a 1/8" ballnose and won't need to use the 1/16" at all

[redwood]

So, I tried offsetting the boundary vectors of the individual items 1/16" and went with a 1/8" ball nose with the first path and a 1/16" ball nose for the offset boundary vectors for the 2nd finish pass. On paper at least, this came out a lot better. Time will tell if theory delivers on a actual cut.

[Phil]

I haven't tried this but I have read that a finishing toolpath at a 45 degree angle will give good results. Does anyone have experience with this?

Phil

[jarm2]

I have had good luck with the 45 degree finishing pass also. Better than 0 or 90 anyway.