Thread: lithograph engraving

The browm/bronze look is due to the pipe being painted metalic first. Thats another trick Your eye picks up more contrast if the frame is much darker than the object of interest.
As far as ballnose versus V bits there are tradeoffs.. Think of it this way how sharp are the corners of text when you use a straight or bullnose versus V carving versus how flat a background area is. V bits will give you very fine detail like strands of hair and detail in the eyes (very important as we focus on this) and a sharper angle will make white to black boundries sharper but require a smaller stepover to have an acceptable sawtooth in flat areas. a flatter angle (say 90 derees) or ball end bit will give cleaner flats and less need for tight stepover but loose it in the tight corners.

Another benefit of combined XY movements is that it will hide backlash better so banding is less apparent. I'm not sure why you get slower results when using combined moves... I use a smoothstepper so maybe that helps?


Like everything its a comprimise and the scal of the Litho would have an inffluence on the best cutter/approach

Cheers

Mark

Yes, it is a constant compromise, trial and post-moretem, trial & postmoretem...
Write everything down, so you can revisit your conclusions later after you've forgotten them!
No need for a fine cutter or fine stepover if the detail & scale does not warrant it.

I think the loss of detail in thicker materials might be due to the material casting its own shadows on the front side, which might help to counter the good effects of the transparency of the lithophane behind it.

We haven't found small banding to be an issue- you can see it up close in the surface, but can't perceive it in the litho when backlit.

"Smoothstepper" is not something I've heard of-and isn't an option with our software, but what I've found does help enormously is to select the unimportant background aspects of a photo, and blurr them a bit, and also reduce the contrast in them (when in Photoshop). This will help the router churn through the 'lack-of-essential-detail areas' much more rapidly.
Also I use the airbrush tool, or the paintbrush tool to add a reflected highlight to each eyeball, and darken the iris of the subject's eyes. Where the scale or magnification is useful, this little bit of work really helps make a nicer picture-especially if the subject is children.

Re the 45 degree angle of cut- we do a bit of screenprinting of halftones, and also often play around with dot frequencies. Similarly, you have to tweak the curves (greys), to allow for got-gain or bleeding in the darker shadows, and for screen clogging in the highlights, so you get in the end what you should have got, but wouldn't have had if you hadn't allowed in advance for the ink & screen's characteristics.

I've tried to not have too many supersharp contrast areas in a lithophane if I'm going to be using a cutter finer than 1/8" dia, as the smaller ones have a 1/8" shank, and you can't drop down into a groove and get finer detail where a fatter shank won't let you go.
If the cutter & the shank are the same, it is fine.
Alternately we use a long tapered cutter, like the USA Carvewright ones, but still program the file as if there's a 1/16" BN endmill being used.

Yep do a Gausian blur on the pics of people, patch blemishes etc, and then use a mask to bring back sharpness in areas like eyes or jewelry (like wedding rings etc) Back in the day of cigerette ads they used to whiten the ciggie so that it "jumped out" at you.

Very low res pics can still look amazing in Lithos as the eye and brain fill in missing detail... just got to get rid of the distracting stuff in the background like you say. I'd say the majourity of the work is doing the pic prep prior to the cutting.

BTW a Smoothstepper is a motion controller board that uses either USB or now Ethernet connection rather than the parallel port and can generally pulse better than a strat connection ie higher step rates.

Aah, OK, thanks. Our router uses servos, not steppers though, and connects via the old 9-pin serial port.

You're right about low-res pic's, abd blurr anything where detail is unimportant-the file time difference it makes, makes it really woirthwhile, and the difference is an improvement in the lithophane.

Originally Posted by mhasting2004

The trick with these is to find a material with the following characteristics

• cuts well
• holds fine detail
• thin (less work, faster cutting and sharper detail)
• uniform thickness
• opaqueness gradiant that allows for bright whites in the thin parts while still having enough mechaical strength and dark enough in the thick areas to offer a decent gray scale. Note the gradient of Corian I tried was quite shallow so to get a decent greyscale range required a thick (12mm or more) piece. Too steep and it becomes unworkable as the variances in depth become miniscule.

Here's a crappy pic of one I did on a bit or PVC gutter pipe. The tube is 68mm diameter and has a wall thickness of 1.6mm. White is cut to within 0.1 mm of breaking thru and black is 0.1mm below the outside surface. Cut with a 45degree V bit at a 45 degree angle to the pic. Wrapped using CNC wrapper step over 0.1 to 0.2mm. Tweaked in photoshop to push the contrast up. (mote subject and picture contrast play a big role in getting a nice end result)

Ive had very good results cutting melimine like you find in picnic plates but its rarely flat and uniform but is unreal a holding detail and very thin. If I could find sheets on that I'd be very happy.
Cheers
Mark

Have you tried contacting this place?
Surteco Australia: Surteco Australia
They may have something suitable. Pity they are so far away from me.
Cheers
Wolffie