Inside cylinder blasting/engraving - Engraving Etc. Forum

From:	Larry (CELESTIALPROD)	19 Mar 2007
To:	ALL	9 of 12

6351.9
Wow, thanks for all the feedback on the INSIDE A CYLINDER engraving/blasting/etching. There are some good ideas here. I have a Universal 35 watt laser now... but no rotary engraver (yet) nor sand blasting equipment (yet). I wonder if a laser manufacturer has ever considered an accessory extension arm on the laser head that would move the optical head to the tip of that arm. Coupled with a rotary accessory capable of holding the piece (cylinder in this case) by only one end, one could then laser the inside of this cylinder. (This is more of a rhetorical question for the forum, but a real question if a laser manufacturer is monitoring the threads.) Back to the thread issue and considering only an acrylic tube for the moment. Here is what I belive would work. 1. Use one of those "pencil" size blasting heads someone referred to to create a tranlucency to the entire inside of the cylinder. 2. Use my laser to create a sandblast mask of the sundial hour lines and points. Mount the mask inside the cylinder and then deep carve (say 0.005 inch) those lines and points on the inside surface. 3. Leave the mask inside and apply the acrylic paint fill to the lines and points. One question I have is how well the mask will hold back the paint from leaking under the edges where the blasting has cut. Will I have bleed out? Again for the benefit of those of you interested in seeing a prototype (this one uses a printed mylar mask simply snugged on the inside wall of the cylinder) here is a link to some information and photos: http://www.celestialproducts.com/images/AboutSunVial.htm Larry

From:	gt350ed	19 Mar 2007
To:	Larry (CELESTIALPROD)	10 of 12

6351.10 In reply to 6351.9
quote: 2. Use my laser to create a sandblast mask of the sundial hour lines and points. Mount the mask inside the cylinder and then deep carve (say 0.005 inch) those lines and points on the inside surface. At least with any lasermask that I have used, the lasermask has an adhesive backing without a cover sheet. In order for it to be lasered and consequently turned into a mask for blasting/etching/carving, it must be applied to the substrate to be blasted, et al, AT THE TIME OF LASERING. So, your statement "use my laser" and "mount the mask inside the cylinder" is a non-starter. Ed Holley Victor Valley Trophy & Awards Co. and Coffee Mugs Online www.coffeemugsonline.com

From:	Dave Jones (DAVERJ)	19 Mar 2007
To:	Larry (CELESTIALPROD)	11 of 12

6351.11 In reply to 6351.9
Have you considered doing a slightly different scale that accounts for the diffraction of the glass cylinder and then etch the scale on the outside instead of the inside? Perhaps with some kind of overcoat for the weather? ...Dave Dave Jones Design

From:	Larry (CELESTIALPROD)	19 Mar 2007
To:	Dave Jones (DAVERJ)	12 of 12

6351.12 In reply to 6351.11

>Have you considered doing a slightly different scale that accounts for the diffraction of the glass...

Yes, that is a possibility and I have done the mathematics to handle the refraction of the beam (somewhat complicated because of the angle if incidence changes with the change in elevation of the sun). There are two reasons the outside engraving is less desirable:
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1.) As the angle of incidence gets larger, the amount of reflected beam grows larger to the point where the sun spot image becomes lost in amient light.
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2.) Exterior engraving is subject to wear and tear in operating the instrument.