Deep V-Carving w/ Multiple Passes

[mattster]

Hi guys,
I've been around here a while, more of a lurker than a poster, but I think I will start contributing more from now on.

So, to begin with, I have a question about VCP v-carving in multiple passes.

I am using VCP since it came out, and am currently using v3. This job I cut last night was using a 3/4" diameter 90 deg cutter. The deepest cuts were approaching .7 deep. I set my doc per pass at .25 inches.

As you can see, something did not line up between the first pass and the final (deepest) pass. These are not as sharp as when they were first cut, because I took a little sand paper to them.

Any ideas?

Thanks,

Matt

[James E]

Hi Mattster.
Are you saying the ovals in the bottom pic should run into the thin lines?
Is it definitly your final pass that is out?

Do the shallower angles on your work, ie the wider side of your leaf, produce a cut that is longer than the cutting edge on your tool?

Jim

[mattster]

Hi Jim,

Hi Mattster.
Are you saying the ovals in the bottom pic should run into the thin lines?
Is it definitly your final pass that is out?

Do the shallower angles on your work, ie the wider side of your leaf, produce a cut that is longer than the cutting edge on your tool?

Jim

1. As to the bottom picture, the ovals are supposed to run into the thin lines. That was probably not the best picture for showing the detail I wanted, but you can see it in the leaf pictures.

2. By shallower angles, do you mean shallower depths of cut? I'm not sure I understand your question. But here is a little more info. The 'leaf' features in question, are cut in 3 passes, .25 inch per pass. I'm not sure if it is the first pass that is not consistent with the last, or vice versa. What is odd, is that the opposite side of the leaf is perfect.


Thanks for the reply.

-Matt

[James E]

Hi Mattster,
I'm not sure what I meant either now, could you post the .crv file so I ( and poss some experts) can eyeball it?
Also, did you try it again, and did it do the same?

Jim

[bryson]

mattster, It looks like you need to change your tool geometry. You probably have it set for 90 degrees and it appears to be closer to 88 degrees. You may have to play with that until you get good results. The reason the short side looks alright is because the the bit is cutting it completely and since the tangent line is longer on the top you are cutting beyond the bit.
Bryson

[Paco]

I see three issues from the above pictures:

-bit geometry has something wrong; the include angle of the V bit is not the one entered in the tool database... that happen. You need to either spend some time with a machinist protractor or make a few tests with different angles. Change the include angle up then down one increment at a time.

-The V carving is going through the material... maybe that was intended?

-The oval thing with the line going on; it look like the oval is carved as a distinct entity from the line crossing it...

Maybe that'll help sort out things... keep us post.

[James E]

The reason the short side looks alright is because the the bit is cutting it completely and since the tangent line is longer on the top you are cutting beyond the bit.

That's what I meant, yeah, thanks Bryson.
If you look at the shapes of your outlines, they're sweet, no bulges or bumps, so you're not losing steps or anything.

If you look at the shape of the final pass, the shape of the side which appears to be cut right is copied on the side where the error is. The maximum distance they are apart is probably the width of your tool.
I think the wizards have it.
Vcarve thinks your bit is wider than it is.

Match up the bit angle in vcarve with the actual bit angle and you will get what you see on the vcarve visual

Keep us posted

Jim