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Frank G
08-28-2003, 9:09 PM
You can laser flat material and round material but can you do oblong stuff. If you had an oval bottle and wanted to put something on it all the way around, could it be done.

Nick Silva
08-29-2003, 10:04 AM
You can laser flat material and round material but can you do oblong stuff. If you had an oval bottle and wanted to put something on it all the way around, could it be done.

I'll field this one. The quick answer is yes you can do oblong material. The true answer is YES you can do oblong material BUT you may not get what you think.

The thing to remember is that the laser has a focal point where the light converges. As you move away from that you begin to lose focus. What that translates into is that you start to get some stretching. Here are some examples:

1) If you draw a circle and engrave it on a straight vase (round) you will get a circle. Why, well the surface of the vase stays at the same distance from the focal point the whole time.

2) If you draw a circle and engrave it on a tapered vase you will get a oval. Why?, well you guessed it, the laser starts to lose focus.

Can this be overcome? Well only partially. I've had some success at breaking up the picture and doing the picture in sections - stopping to refocus the laser on each new section. This is a pain and takes a lot of more time than simply letting the laser 'print'. If the piece is round and on the rotary fixture, you can begin by tilting the fixture so the surface is perpindicular to the laser the entire time.

Hope this helps. peace.

Frank G
08-29-2003, 8:25 PM
My family tree didn't branch much but I got some of it. I can understand how an oval bottle that was turning would get out of focus and I suppose some of the cutting would be deeper than others so here is the next question. If we were talking wood, ( I can only assume different material reacts differently ) what would the variance in distance be before losing focus. Boy I hope this makes sense.

Nick Silva
08-29-2003, 9:05 PM
My family tree didn't branch much but I got some of it. I can understand how an oval bottle that was turning would get out of focus and I suppose some of the cutting would be deeper than others so here is the next question. If we were talking wood, ( I can only assume different material reacts differently ) what would the variance in distance be before losing focus. Boy I hope this makes sense.

Well, wood is indeed some of the most forgiving materials and you can get away with a little bit. But, you'd be surprised how well the human eye can detect those small variances. Now I didn't think about the material, but if this is a glass bottle, then things are different. You cannot engrave glass. You can, frost it. Glass engraving is actually a process of causing microfractures from the heat of the laser. It looks like it was sandblasted without the depth. If it is glass, you can get away with a fair amount of focus error. Other than these two materials, you'd have to play with it to get a good feel for what you need to do. I'll see if I can dig up some pictures.

I guess I forgot to mention one other thing in my previous response, it isn't just a matter of focus. As the laser comes around a curved surface, it is no longer hitting the surface at a 90 degree angle. The steeper the curve, the worse it gets. That's another reason you get a stretching effect. About all you can do is minimize the effect, either by doing it in sections or by multiple engravings or by changing the angle of the piece itself. You will not eliminate the stretching effect altogether. Don't get me wrong, you can still get good results, its just a pain resetting everything up for each pass. peace.

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P.S. I did find a pict of engraved glass. It is attached.
-Nick