Verify, Zank VIP does not work on non-flat surfaces

[Doug98105]

It seems the Zank procedure for inlays does not work on curved surfaces like a domed box top if there are inside corners.

The reason is cutting the female pocket using the Vcarve toolpath the inside corners do not have sharp edges. By using a profile toolpath instead and using the optional internal/external sharp corner option does work.

[martin54]

I don't do a lot of inlays & certainly never tried on a curved surface but can't see why Pauls method wouldn't give you sharp corners, the whole point of it was to be able to cut sharp corners which was somethine the inlay toolpath could not do.
I can see how you might have a problem cutting the 2 parts to match properly but not how it won't give you a sharp internal corner.

[Adrian]

Depends on the amount of curvature/height of component. On a steeply curved surface a projected V-Carve toolpath can appear to round off some corners as the tool has to drop so far onto the surface.

[scottp55]

May be of interest;
http://forum.vectric.com/viewtopic.php?f=27&t=15920

viewtopic.php?f=28&t=22207
scott

[Doug98105]

Here's what I'm talking about.

Line drawing from CAD shows outline of pocket. Size is .8" across.

Screen capture from is from Vcarve Desktop using the Vcarve pocket function .2" deep. Notice the inside corners are round a they approach the bottom depth. If I use a profile tool path the inside corners are sharp.

The problem comes when I put the inlay on the domed top of a turned box. The doming cuts down into the inlay around perimeter exposing gaps from the rounding of corners.

If i'm missing something in this please let me know. Otherwise I'll continue making female pockets with the profile tool path (and clear bottom with an end mill). I should mention I don't think the problem exists if there are no inside corners.

[adze_cnc]

Notice the inside corners are round a they approach the bottom depth. If I use a profile tool path the inside corners are sharp.

As long as the plug and the pocket (male and female) are both rounded to mate together it doesn't matter that the corners (I'd argue they are not "inside corners") are not sharp. While I haven't cut them out I have little doubt, if any, that the pocket and plug in the attached images would nestle together perfectly.

The problem comes when I put the inlay on the domed top of a turned box. The doming cuts down into the inlay around perimeter exposing gaps from the rounding of corners.

These two sentences seem to contradict each other:

a. Are you applying the male part to the female pocket in an existing convex turned box?

b. Or are you joining male and female parts "flat" and then turning the resulting union to a convex form?

If you are doing the former (a) are you cutting the pocket "flat" or are you projecting to a convex 3D model? If projecting to 3D model you would also need to project the plug to a concave model (the negative of the turned box).

If the latter (b) perhaps the gaps you see are inevitable if the curve crosses the edge of the usual gap left in the v-inlay process? (See fixitmike's explanatory image below.)

fixitmike's v-inlay explanatory image

[Doug98105]

What I'm doing would be your "b." I have a flat top, I inlay, say .2" deep, into the flat. Then it's turned to the dome shape. After turning the inlay is slightly distorted by the angle of the v-bit as the outer portion of the male inlay is reduced in thickness. For example if the inlay was a plain square after turning the corners would be brought in a little giving a bulged look to the square. But, it'd still be recognizable as a distorted square.

Looking at your attachments, let's say they're glued together and they're a good fit (male/female good match). At the base surface chances are it'll look good after the male inlay is sanded smooth with the base. But, what if for some reason the base surface needed to be milled down half the depth of the inlay. You'd have a different shape, the sharp inside corners would have a fillet instead as shown in my attachment below. My method will always have the sharp corners intact through the thickness of the inlay.

I'm satisfied with the method I'm using, my concern was maybe I was missing an easier method. At this point I don't think so though.

[rscrawford]

Yes, the v-carve inlay is meant to show the correct shape ONLY on the surface, and if you carve down into the inlay you can get a distorted look due to the way the v-carve tool path is calculated.

One way around this is to project the tool paths onto a model surface (you need a 'negative' of that model to project the male inlay onto). This works very well, but is a little more complex.

This is a close up of an inlay cut into a dish, by projecting the cuts onto the surface of a model. This preserves the exact look of your inlay (will not work on too steep of an angle on your model).

[martin54]

One way around this is to project the tool paths onto a model surface (you need a 'negative' of that model to project the male inlay onto). This works very well, but is a little more complex.

That's what I thought the OP was doing, didn't realise they were cutting the dome after the inlay was done which is why I couldn't see how they weren't getting square corners & why I thought there could be potential problems getting the 2 to match up properly especially with a complex inlay

[adze_cnc]

You'd have a different shape, the sharp inside corners would have a fillet instead as shown in my attachment below.

That's sort of the point I was trying to make is that if you start with something the looks good flat it won't do so when "domed". You could get around this by pre-distorting the shape so that it looks odd "flat" in 2D but when turned "domed" in 3D it regains its shape.

[Doug98105]

Here's a summary of how I do inlays.

First pic is a picture of a couple inlays. On the left is a .75" radius star with 40% inner on a 7/8" radius round stock (1-3/4" diameter). The star was inlaid onto the flat workpiece, after that the top was radiused 3.25". The radius cut shortened the points of the star. The original star point would have been 1/8" from edge of the 7/8" radius blank, but it's closer to .2" now. The inlay to the right shows a 1" square that was reduced in size by the radius and it has a bulged look. None of the distortions are a problem, I expected them.

The second pic shows a cross section of the inlay and how the radiusing affects the size of the inlay.

The third pic shows the vector design, .75" radius star with .1155" inner offset (that offset is calculated from a 60 degree bit .2" deep).

Next pic is the female pocket cut with a profile tool path (outer star vectors) using the sharp interior/exterior corner option and clearing with an 1/8" end mill. Note the small areas in the pocket that the end mill couldn't reach, a hand held Dremel cutter cleared those.

Final pic is the the male inlay again using the profile too path (inner offset star vectors) with sharp corner option. And a pocketing operation to clear the surrounding area. The inlay was cut by offsetting its size .01" so there'd be a glue space under it.