Question: convex and concave surfaces
- Thread starter ETHELBERT
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dlilazteca
~ Elite 1000 Member ~
First what method are you using to transfer your image?
silverchip
~ Elite 1000 Member ~
I have an inverted parabolic surface to engrave and I tried several ways to find a transfer method that would be precise. NO SUCH LUCK, The best is to draw directly on the metal,but you can spray that with a fixative to help preserve your design while cutting!!!
There's no way I know of except fiddling with it to get the best results you can and then drawing in the missing parts, hoping for proper alignment. Sometimes it works and sometimes is best to do a pencil layout.
mitch
~ Elite 1000 Member ~
- Joined
- Jul 23, 2007
- Messages
- 2,636
i wonder if anybody has ever tried a pad printer? as just one example, this company came on a google search for "pad printing": http://www.printexusa.com/?gclid=CMKA0NbP0bwCFWYaOgodfhUAHg
the basic concept is transferring an inked impression from a 2D plate to a 3D object with a soft spongy pad. obviously an engraver would need to adapt some sort of low-tech means of making & inking a master image, then getting it accurately registered onto the pad then the object to be engraved (maybe in a drill press?), but if you had enough parts to do it might be worth the trouble...
the basic concept is transferring an inked impression from a 2D plate to a 3D object with a soft spongy pad. obviously an engraver would need to adapt some sort of low-tech means of making & inking a master image, then getting it accurately registered onto the pad then the object to be engraved (maybe in a drill press?), but if you had enough parts to do it might be worth the trouble...
Marrinan
~ Elite 1000 Member ~
They used to be used in silverware engraving. on one of the three forums some once had one for sale. they did not know how to use it and it seems to me there was quit a bit of info about the process. was a long time ago, might have been on fine embellishment. I will see if I can find the old thread this evening. Fred
these surfaces and others as well, are reason enough to get up to speed on drawing. drawing direct on such surfaces is the only practical way to do layout on them. a dwg is 2 d. when transferring 2d to 3d, one gets what is called "warp". double plus ungood for an engraver. 2d transfers well to a single curve, like a cylinder. take the same dwg onto a double, or compound curve, and the warp will happen.
Marrinan
~ Elite 1000 Member ~
From my days teaching graphic arts: Use rubber stamp rubber, it softens with heat. cut your first one, I would suggest going slight on the detailed shading for now. Cut the rubber slightly larger (say half inch). Heat this rubber following manufacturers specs. Place hot rubber over the engraving leaving quarter inch all the way around. clamp hard and leave to cool. The clamping is important. It take pressure to fore into the cut pattern so plan this ahead of time. Another way is to use rubber mold material or silicon caulk-same registration issues apply. ink and print on piece two. could be the bottom of a bowl-just going to have a big rubber stamp. Fred
dlilazteca
~ Elite 1000 Member ~
JAT
Member
You can cover the whole part to be engraved in strips of masking tape. Lay the pieces in different directions so they all hold together. Once you do this you can lift the tape off of the object in one big piece. You would basically have a bowl made out of masking tape. You can take your tape template and cut slits toward the center until it lays perfectly flat. You would then have a flat template that matches the curve of the bowl when you bring all cut edges together. Now the flattened tape template is traced onto your flat sheet of drawing paper. This way when you put the drawing inside of the bowl, all the edges line up and you have a near perfect template, matching the contour of your bowl. I have used this method a couple of times and it is fidgety but it does a good enough job to get most of the design where it should be. Hope this helps a little! One more thing.. this works on slight curves but really tight curves are trouble no matter how you do it!
Chujybear
~ Elite 1000 Member ~
theres thinking Jat!
Mike Fennell
Elite Cafe Member
Cut the outline of the image on a practice plate. Ink it, or rub graphite and wax into the cuts; wipe the surface clean with stiff paper. Cut a strip of Scotch Magic Tape a bit longer than the plate, fold over the tips to use as handles. Lay the tape over the inked image, sticky side down, and burnish with your fingertip to pick up the ink in the cuts.
Coat the item to be engraved with thinned damar varnish and wait till it is almost dry, just tacky to the touch. (On some surfaces, this method will work even without the varnish.) Lay the inked tape in proper position, sticky side down, and burnish the ink into the varnish. The tape has just enough stretch and give to it that the image should transfer with minimal distortion
If the image is larger than the width of the tape, do the transfer in two or three strips. Or you can try to do it in one stroke by using the wider, clear packaging tape, but you will struggle to avoid wrinkles during the transfer
Coat the item to be engraved with thinned damar varnish and wait till it is almost dry, just tacky to the touch. (On some surfaces, this method will work even without the varnish.) Lay the inked tape in proper position, sticky side down, and burnish the ink into the varnish. The tape has just enough stretch and give to it that the image should transfer with minimal distortion
If the image is larger than the width of the tape, do the transfer in two or three strips. Or you can try to do it in one stroke by using the wider, clear packaging tape, but you will struggle to avoid wrinkles during the transfer
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Mike Fennell
Elite Cafe Member
Oops. Duplicate post.
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Marrinan
~ Elite 1000 Member ~
Interesting seeing different approaches to the problem-all useful and good for the library of knowledge. Thanks Fred
When we had a candy business, I remember a machine that imprinted logos on golf balls and anything else odd shaped. The image was inked on a wad of material that looked like an egg and was very flexible, then pressed on the object, in the case of this demonstration, a golf ball. Of course, it was not cheap and was cost effective only in major runs. I'll try and find the company, but it has been a long, long time ago.
Bill
Bill
rod
~ Elite 1000 Member ~
If it is a relatively simple design, then draw, and verify with your eye.
If it is a complex design, it can be projected, like, take a photo, 35 mm transparency, use slide projector, to project it onto any screen or object, flat, cylinder, or sphere. Then draw a trace on, say, the sphere. That should give you the accurate image that the eye will see as natural? Then engrave.
Rod
If it is a complex design, it can be projected, like, take a photo, 35 mm transparency, use slide projector, to project it onto any screen or object, flat, cylinder, or sphere. Then draw a trace on, say, the sphere. That should give you the accurate image that the eye will see as natural? Then engrave.
Rod
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