Any thoughts on inlay on a curved surface?

[TonyMemphis]

i have been trying all sorts of things. Nothing has worked so far (or I'd be telling you all! ). Seems like using the normal v bit inlay technique doesn't quite work on a curve. I've ben trying it on a dome from clip art. The female part is easy. I then use the same dome and "flip" it. Then use the method of specifying the start depth and flat depth. But first, I don't know how deep the female part is (too small for specifying a flat depth), and the male part seems to always be full depth. I cut a test piece in half and there is no clearance at the bottom. So, no wedging and the fit is not great.

My last thought was to make the male part, then mill a tiny amount of of that. That's why I was asking about model height in my recent post. Still a bit confused about the modeling stuff, but I'm getting there.

There is a video out there of a guitar guy doing an inlay on a curved surface, but that didn't work for me.

I may just give up and make an epoxy inlay and be done with it!

I used my lathe to turn the waste part of the male piece. That works well. I did a small box with an inlaid top, but the top was flat. That was relatively easy. But I would have preferred a dome shape, hence the current adventure.

Thanks,

Tony

[4DThinker]

First off I'll confess I've never tried this.
Before the curved surface is cut and the top is still flat, use a small end mill to cut the negative inlay shape deep enough that it would still be there in the curve when it was exposed.
Next pocket out the male shape in the white wood. Don't cut all the way through, but cut around and deep enough that the inlay shape will fit straight down into the negative recess. Check that it will fit. If a good fit glue it in. Once the glue is dry go to a band saw and cut off any of the male material still sticking above the flat surface.

Now CNC the curve with the inlay already in place, Your curve is shallow enough that this should work. Just take care that the male and female cuts fit together well. Allow for the bit diameter in corners.
4D

[garylmast]

At the bottom of the toolpath selection, check the Project toolpath onto 3D model.

Gary

[TonyMemphis]

4D - the problem with that, if I understand you correctly, is that when you then turn or mill the dome, the lines become narrower as you cut down into the inlay. Even doing it flat like I did, I had to fudge it a little to get a consistent line width. Could be a neat effect though if that was what you were looking for. Something to try and see how it looks.

Gary - that's what I did for the female part. That is working well. Its the male part that is giving me fits. I copy the dome to another sheet, reverse it, then use the typical inlay technique setting the start and flat depths, but it doesn't work well. When I cut the glued up part in half, I see that the male part is full depth. My thought was to try and mill some of the male part off to create the clearance and get a good wedge type fit. But, the male part is not a consistent height, so all the little peaks are not cut - just the highest ones. Guess I could just modify it by hand! But some of those peaks are pretty delicate. That's the other thing, some of these depths get fairly deep on a concave shape, and Vcarve cuts full depth! That gets a little scary. So, I have been trying to create a path to remove as much material as I can before the v bit is used.

Maybe this just won't work, but I'm not there yet.

Thanks for the input. Much appreciated.

Tony

[adze_cnc]

You might want to search for some posts here.

• Next to the search box above click on the “gear” button for advanced search.
• For the search term enter: barrette
• For the author enter: JoeBlow

[4DThinker]

My suggestion was to not do it as a Vcarve inlay with a V bit. Use a small end mill, 1/16" if you have one. Do it as a conventional pocket inlay, straight down. Yes, you may loose the sharp corners and tips, but the design would still be recognizable to most.
4D

[adze_cnc]

There does seem to be a prejudice against using the auto inlay toolpath. I guess you'd have to sand / plane a bit of the perimeter of the plug as there'll be a flat around the perimeter or the socket.

[TonyMemphis]

4D- Ahh. I misunderstood. Sorry. Good idea. I would have to just work around the radius in the design, but that might be ok. I'll have to experiment to see how good of a fit I can produce.

Yeah, the v tool inlay method does help to get a better fit that the the standard inlay.

I've taken one of my female test parts and filled it with colored epoxy just to play. I used craft acrylic paint and 5 minute epoxy. It dried good and hard. We'll see. Its going on the lathe in a minute.

Thanks for the help folks! Much appreciated.

Tony

[Wayne Locke]

You cannot make a v carve inlay on curved surfaces because of the geometry.

. The bit is attacking perpendicular to the table surface and distinctly not perpendicular to the arc> Because of that the the finished angle will be off. Even if this were not so the inlay has to go in perpendicular to the mating piece and since this varies around the arc it will be difficult tho assemble and not likely to fit. The greater the arc, the greater the issues.

[JoeBlow]

But first, I don't know how deep the female part is (too small for specifying a flat depth)

When doing a vcarve inlay on a dome or any other 3D model, you need to create a 2nd female vcarve (same as the first) but without projecting to the model. This will give you the numbers needed to set the male part up with. Once you know those, then it is just a matter of working the SD and FD numbers for your male part.

The inlays on this Sakura barrette that ADZE mentioned were quite small. The branch was .08 and I did a .07 SD with a .05 FD. The barrette itself is .125 and I did not want to go through the backside. This particular piece had 3 inlay operations.

This next piece was definitely more challenging and pushed the limits a little more. This pic shows the first inlay operation and is a good example of carving onto a dome.

Followed by the outer eyes…

And then the pupils and nose…

Completed Totoro…

The walnut inlays in the body did not come out “perfect”. Mostly due to my heavy handed approach to clamping and the use of CA. Wood glue would have been better to afford a little more open time. However, all the info I need to keep moving forward with inlaying on a curved surface is there. Each project will get better as I tighten up the process.

This one was done with a pocket toolpath. No vcarving, SD and FD involved.

The back of the previous barrette. This inlay was projected onto a concave surface. All worked as expected but I did lose maple on the male part during milling.

A little support from the software showing that the Zank Vinlay technique can be done…

I hope you keep at it.

[TonyMemphis]

Thanks for that tip. I'll give that a shot tomorrow. I had not thought about creating the female without projection. Good idea.

Yeah, I was using some tiger maple for my plug (sounds better than male parts!) and I did lose a few sharp corners. Doing small stuff is a different ballgame. I just finished a table with an inlay in the center. I used tiger maple for it too. I didn't realize that some of the sharp points were missing until I cleaned it up. I did the best patch job I could, but its still there.

I milled the grooves for the string inlay on this using a tiny little end mill.

Thanks again,

Tony

[TonyMemphis]

Well, I tried using the settings for the plug based on the depth of the inlay without projecting it. That still didn't work for me. I think what I am seeing is that the male plug is still being cut to full depth. If I use the same settings on a flat inlay, the male plug has flats at the top (or what will be the bottom). I guess there is something lost in translation when doing that and projecting it on a curved surface. Just for kicks, I made another set and this time, I sanded the sharp peaks off of the plug. Its in clamps tonight. I'll see what it looks like tomorrow.

I took some pics. I'll try and post them.

This is a cross section. You can see that there is no clearance, even though I specified a start depth.

A little fuzzy because I reduced it, but you can see that it is not a great fit.

For reference, the dome is 2 1/2" in diameter. The socket is 0.098 deep. I used about 2/3 of that for start depth and 0.075 for flat depth on the plug.

I'm really beginning to think it just won't work. If the sanding thing works, at least I'll know that is an option.

Tony

[TonyMemphis]

Uncle! I've tried about everything I could think of to make this work. The last shot was sanding the peaks of the plug off. That maybe helped a little. But I still didn't get a good fit. I'm going to move on to other projects. If anybody figures out a better way, please post!


The pic is a little fuzzy, but you can see some halo and spots where the glue filled in the holes.

Just for kicks, I compared a plug using the same file and same values and the plug was different. There were flat areas instead of sharp peaks.


Oh, well, I tried. Thanks again for the help. I'm going to play around with some epoxy resin in the inlays. I did a test using 5 min. epoxy with acrylic paint as the colorant. It worked well, but I ended up with lots of bubbles. So, I ordered some "real" epoxy resin and colorant to play with.


Tony

[adze_cnc]

Tony,

Are you comfortable posting your little test file pictured above for diagnostic purposes?

Steven

[Jchaplin]

I have been inlaying small parts on pool cues for years using cut 2 d and cutting flat pockets. V carve is identical on this type of thing. You just have to make sure your pockets are deep enough to not cut out on the edges but cues have much more curve than what you are doing. I use a .020" end mill that had a depth of .170" and with proper speeds they don't break and produce acceptably sharp inside corners. Using the inlay toolpath to cut the part and the pocket I like about .002 pocket allowance. Cutting out the parts I use two methods. If my material is thick enough I will just cut it to maximum depth then cover the part with masking tape on the cut end and skim off the end of the wood on my band saw to proper depth. The tape generally holds the parts while cutting from being destroyed. If your wood is thin then use double tape and CA to hold it to your spoil board and cut right through. Again at a slow feed rate the tape will generally hold the part as you cut through into the spoil.

I do it like this because I am not advanced enough yet to do anything else. My inlays have symmetry from side to side so any distortion caused by the curvature isn't noticeable. I could foresee an issue on some shapes but probably not on your mild curve.

John Chaplin
www.cooscues.com