Do not understand Lithophane Tutorial

[kristenanne77]

I was watching the "Photovcarve-Getting started with Lithophanes" tutorial (link below) and about 5 minutes into the video, it shows the finishing bit specs as having a diameter of .04 inches and a pass depth of .125 inches.
I would think it would be the other way around????
Also it mentions NOT to have a cutting depth of more than .1 inch. What if you have a thick piece of material? Isn't the ideal of a lithophane supposed to be cutting "almost all the way through" so light can pass through the material? I think only .1 inch cut off the top wouldn't be deep enough. Right?
Can someone explain what I am missing?




thanks
K

[Frunple]

You want .04" of material left at it's thinnest point. The pass depth depends on the tool being used.
If you have thicker material, you're going to have to take it down to .25" before making the lithophane so why not just use .25" to start with?

[kristenanne77]

I agree. That's why I was wondering why the video shows a "Carv Max Depth" of .1 inch (at about 1minute into the video).
I would choose something like .2 inch or a little more for a piece that is about .25 inch.

K

[calgrdnr]

Here is a pdf tutorial with settings we have been using for years works fine . it is how to do ovals but has advance settings on how to use Vbit one pass 0.21 deep

http://forum.vectric.com/viewtopic.php?f=7&t=7175

[Xxray]

When I cut .25 corian my cut depth would be .21, pass depth same.

Most .25" sheet good are just nominal, so you have to measure them to be sure. You'd almost certainly overcut if you went .21 into a .23 sheet so just leave yourself a little margin. Yes, you do want to cut as much as possible without going through, can be a fine line with much depending on your machines trueness and your zeroing accurately.
If you end up not cutting quite enough, you can always sand the back with a belt/drum sander to get it down in specs. Better that than punching through, in which case there is nothing you can do to remedy it.

[dhellew2]

Since Corian is seldom uniform in thickness i start by setting the reference at the table which solves the potential problem of cutting too deep.

I start by making certain I have a perfectly flat table but planing the spoil-board with the CNC router
Clamp the material so it is flat on the table; often the Corian surface will be slightly curved so I put the side down that has the center on the spoil-board then push the edges down with clamps.

Using this method you will always leave the amount of material you intend to leave.

http://forum.vectric.com/viewtopic.php? ... df#p164196
Maybe this pdf will be helpful.

Dale

[Bob Reda]

I believe the u-tube tutorial forgets one important step it starts the cut down in the material, I've attached some photos to reference. use the pdf document for pvc on lithos to find the finish toolpath

Bob

[dhellew2]

When cutting lithophanes using the 135 degree angle the first cut is a drilled hole, every other cut is the step-over only. If your bit can cut to the deepest part of the lithophane then you can more than likely cut using a finish pass only.

90% of my lithophanes are cut with a 3/64" bit and I never rough cut. I use a feed rate of 55, 16k rpm and haven't broken a bit while cutting yet.

I use the same settings in oak too when cutting 'raised' lithophanes.

Dale