V Carveing onto a curved surface;

[LTO]

Does anyone have any suggestions about how I could carve a file created in VCarve Pro onto the concave side of a 21" radius? Imagine the curved back of a wooden chair, personalized with whatever the customer desires.

For reference; I would want to machine this on a 3 axis Shopbot.

Thanks

[js11110]

At work, we use Mastercam to do this, but usually its only to serialize parts, and the engraving is about .010" deep. The problem is the deeper you cut the deeper it cuts on the "up" side of the radius. (the side towards the middle of the chair.) Also, you need to be positive that your accurate about the arc radius as a slight difference in radius will be VERY noticable.

Jason

[Paco]

Hi Louis (is that you?)!

I guess you have condidered bending after the carving... right?

As to V carve on curved surface, I believe you wouldn't like the result... still, you would be the one to say if you like it. Check with an ArtCAM PRO user, I believe the program have this feature; he may just be able to provide you with a 3D render sample...

[RoutnAbout]

LTO, welcome to the board.

I attempted this on the inside of a 16 degree radius. The peice was 4 inches wide and had a chord length of 18 inches.

I used a rule and a pencil and marked off the spacing needed between each letter.
Then built a jig to hold that radius peice (with the open side of the radius up ), I also marked a center line on the jig. Placed double faced tape on the jig to hold the peice.

I made a file for each letter needed. I then manually indexed the peice by lining up my spacing makes on the peice and the center line on the jig.

To mass produce something like this would be to use an indexer.

Hope that helps

[LTO]

Thanks for the replies;

I really like the simplicity, and the capability of VCarve Pro. I suppose hoping to conform the VCarve output to the inside of a radius was rather wishful thinking.

I didn't fully realize at first the distortion that would be caused to a V Carving by not having the tool perpendicular to the surface (when moving away from the center). I'm also not sure how an indexer would allow me to achieve my goal as this carving is on the inside rather than the outside of the 21" radius. Am I missing something? I have no experiance with an indexer.

[Peter Stenabaugh]

LTO, if you really want to do this properly, fast and efficiently, you will need to incorporate a 4th (rotary) axis.

One way to generate this sort of artwork, from what I have experimented with anyway, was to create the solid feature in Solidworks.

Once you have the basic solid created (back of the chair), you now need to start a new sketch above the surface to be carved out. This sketch should be on a plane that is perpendicular (normal) to the center line of the text (sketch).

The new sketch now will incorporate the graphic you want to carve on the chair back. It can be a graphic or text, it does not matter to solidworks.

Once the sketch is completed, you will now use the 'wrap' feature to wrap the sketch onto the surface you wish to carve out. The main limitation here is that the surface to be carved must be a cylindrical surface (single curvature) it cannot be a tapered surface or double curved. Within the 'wrap' command you can select to 'emboss' or demboss' the sketch onto or into the surface.

This feature will cut the sketch into the surface at right angles to the surface at every point, just as if you had rotated the part as you carved it out.

Now from solidworks, you would export the solid as an stl file. From here you are on your own, as this is as far as I have taken it at this point, however you will most likely need to bring this stl file into a program like other software or the like, and finally into your controller program (I use Mach 3). I am in the process of converting my mill to cnc, and I will be adding a 4th axis, but I think I have a bit of a learning curve ahead of me before I venture into things like this. I dont think you will have much success using Vcarve for this, unless you can fool it to think it is carving a flat surface while in fact you are rotating the part, but I dont think it will work that way.

Have fun experimenting, after this is what this "Bleeding Edge Technology" is all about. I hope these points help out.

Pete

[RoutnAbout]

LTO,


Is this a one or two off project? or do you need to mass produce these chair backs?

[LTO]

I forsee using this repeatedly, with different vectors of course, IF I find a way where it's not a whole lot more time consuming than if I were doing a standard V-Carving. Otherwise I'm afraid the cost may eliminate most customers.

Paco, Your idea of bending after routing is good. We've done this, I was hoping to improve on what is possible using this method. Any cross grain vectors carved to more than minimal depth are subject to collapse or wrinkle as they are subjected to compression on the ID of the bend.

Below is an embossed chair back, and a link to more. Some of these are similar to v carvings. The advantage of embossing is that it creates detail with little or no sanding afterwards. The disadvantage is you can't customize or personalize.

Gotta offer something the Chinese can't!

http://www.barevillewoodcraft.com/wood_embossing.html

Thanks for all the ideas!

[RoutnAbout]

LTO,

you mentioned it was a 21" radii, what is the chord length? what is the height of your z travel?

[LTO]

Cord lenght would usually be between 17 and 23".

I have a Shopbot with a 6"+ Z travel.

[Peter Stenabaugh]

LTO:

I took a look at the web site you sent to us. I would venture a guess that most of the wood embossing that they do is done first on flat panels and then bent using steam. This is what they specialize in, so I doubt that they are doing the embossing on material that is already curved, however it is possible, just a lot more difficult.

If you want to try it out, here is another thought on how to machine it.....

If you material is already bent, you could support it on 2 rubber rollers, spaced about 6 inches apart or so. You would need another roller or two to provide some hold down force, and some method of keeping the material moving straight. This would allow you to motorize the bottom rollers to create the rotary axis for the embossing. Doing this, your cutter would only need to move on either the X or Y axis, at right angles to the rollng movement of the curved material, or in otherwords, parallel to the axis of rotation.

This would be a kinky thing to design, and I have no idea how you would write the code to do this, but once you had it mastered you would really have a corner on the market.

Actually in thinking about it, maybe it is not too hard to do after all, as the movement about the rotary axis would actually be either the X or the Y, travel of the cutter, except the code is sent to the rotary motor and not the usual motor on the X or Y which ever it turned out to be. You would still be able to use the Z as you would normally.

To do all this you could make up a fixture that included the rotary mechanism, and merely mount it under your shopbot. Then disconnect the wire going to the Y axis, for example and connect it to the rotary motor, or it could be done with a switch or similar also.

The straightness issue could be handled by having a fixed plate for the material to run against, with a couple of spring loaded rollers to provide pressure. The surface that you are rubbing against could also be allowed to move, if you had a rubber belt, like a timing belt or such stretched between two rollers. The back and forth motion would allow the belt to move back and forth with the material, and it would not cause any rubbing againt the wood. On the back side of the belt, you would need a slippery surface such as teflon or maybe delrin, maybe uhmw might work. Anyway you probably get the idea.

Hope this helps. If you ever get this working let us know, and send pictures. If you need more ideas, you can contact me directly by email: <pstenabaugh@shaw.ca>

Later.