Lithophane

Gallery of projects completed with MeshCAM

Lithophane

Postby Randy » Thu Mar 19, 2009 6:54 am

Lithophane literally means "light in stone". It is basically a monochrome transparency, but instead of a varying density optical coating on a piece of film, the optical density variations are due to differing thicknesses of a translucent material. The Lithophane Museum has a much better description that I could pen at http://www.lithophanemuseum.org/lithophanes.html so read some history there.

I've been wanting to try a lithophane since I learned about them (which is about two weeks ;) ) and MeshCAM is ideally suited for the task. This is my first "artistic" usage of MC.

My first experimental piece is made from 6mm ("1/4-inch") white acrylic, which is .236" thick. I cropped the picture I was working from to a 4:3 aspect ratio and converted it to an 8-bit grayscale. I imported it into MC and sized it for 4x3 inches and kept the .100" depth range. I kept the material size the same X and Y dimensions as the image, but set the thickness to .236" and set the top margin to .100". This meant that the machining would be from Z-.100" thru Z-.200".

My actual blank was 4.5 x 3.5 inches, so I set the machine origin to X-.250, Y-.250 and the top of the material. I made two "finishing" passes. The first used a .125" ball-end mill with a .040" stepover, X passes only. That was my roughing step. The actual finish pass used a .031" ball-end mill with .007" stepover, X passes only. "Roughing" took about 25 minutes at 12ipm and finishing took a little under 4 hours at 8ipm.

I made a simple frame from black acrylic. Lit from the front, the lithophane looks like a weird bas-relief. But back-lit, espcially against a sunny sky, it is magical. It is a true grayscale image using no pigment. The digital photo does not begin to do it justice... It is well worth the little effort (mostly planning) it took to make.

What I will do differently the next time:

1. Offset the finishing pass by .005" or so deeper. The roughing "scanlines" are still visible in flatter sections of the image.

2. Find some 1/4" thick white Corian or similar pigmented acrylic as a raw material. The white acryilc I used is not as densely pigmented as Corian, which limits the dynamic range of the image.

3. Try a .020" ball-end mill for this size of image, and adjust the resolution of the bitmap so that there is one finish pass stepover per pixel line. Say, .005" stepover and an image of 800x600 pixels for a 4x3" image.

There are quite a few webpages on lithophanes about, and photos of both traditional hand-carved and modern CNC-carved examples. I recommend giving it a try!

Randy
Attachments
IMG_0301_backlit.jpg
IMG_0301_backlit.jpg (38.58 KiB) Viewed 26510 times
IMG_0301-frontlit.jpg
IMG_0301-frontlit.jpg (155.75 KiB) Viewed 26510 times
IMG_0301_original.jpg
IMG_0301_original.jpg (281.2 KiB) Viewed 26510 times
Last edited by Randy on Wed Dec 14, 2016 11:11 pm, edited 3 times in total.
Reason: replaced corrupted images
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
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Re: Lithophane

Postby jeffD » Thu Mar 19, 2009 6:26 pm

Randy,

Very impressive. Did you convert the greyscale to a height field with CAD and use standard MC or was this done just with Art MC?

jeffD
I have no financial interests in MeshCam. Nothing I say here has had any approval from MC. Any errors or omissions are mine alone. Use at your own risk.
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Re: Lithophane

Postby Randy » Thu Mar 19, 2009 9:22 pm

Jeff, no, this is just standard MeshCAM. My license doesn't include Art. (I can see how my wording could be confusing so I've changed "art" to "artistic".) I just loaded the bitmap (actually a TIFF--I just converted to a JPG to attach to my post for size reasons) and MC put up the bitmap import dialog. On the MC "More Info" page it says "MeshCAM can load BMP, JPG, PNG, and TIFF image files and automatically generate a 3D object from them." And that's what it did. :D

And the impressiveness credit goes to MC. All I did was tell it how large and high to generate the STL and from there it was just like machining any other STL. It's a really neat capability that I never had a reason to utilize until now.

Randy
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
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Re: Lithophane

Postby jeffD » Fri Mar 20, 2009 6:46 pm

Randy,

Still impressive. I tend to like the control I get from rhino, it never even occurred to me to work straight from a bitmap. I do attempt to avoid photo editing software whenever possible (haha... I did a quick test using a rhino render bit map) but it might be time to follow some of my 'harsh' advice about re-reading the manual :shock:

jeffD
I have no financial interests in MeshCam. Nothing I say here has had any approval from MC. Any errors or omissions are mine alone. Use at your own risk.
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Re: Lithophane

Postby Randy » Sat Mar 21, 2009 7:36 am

Thank you, Jeff. It is really amazing "in the flesh" and I'm tickled silly at how well it came out for a first effort.

Randy
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
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Re: Lithophane

Postby bobmorey » Fri Aug 14, 2009 11:20 pm

That is really cool! I gotta try that. I saw a couple of Marilyn Monroe lithopaines on another sw site that were amazing. What is neat concept. I say your first litho came out fantastic!
Bob
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Re: Lithophane

Postby BlueFin » Sun Nov 22, 2009 6:11 pm

Randy, found your post here. I have been making Lithos for a year now and never knew MC could be involved with this. I have Vectric V Carve and today I loaded my favorite example image into MC and generated a relief preview. At first loading the MC preview is identical to that of Vetric (first wow), but then I bumped the smooth relief tool down to 40 to see what kind of noise I could remove and the image cleaned up very clearly and appears to reduce the machining time. I am going to have to try one and see how it turns out.
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Re: Lithophane

Postby Randy » Tue Nov 24, 2009 2:20 am

Do post your results here, BlueFin! It is a neat application for MC, and one that comes out really well, even for a techie (rather than artsy) guy like me. :) I think it's time to buy a supply of 1/4" Corian sheet and start working on Christmas presents... :D

Randy
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
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Re: Lithophane

Postby LouisBrown » Fri Sep 09, 2011 11:15 pm

Hello,

Is there a practical limit on the size of a lithophane that can be cut on meshcam? I'm trying to work with an 8x10 image that is 300 dpi. I can't get it to smooth without crashing the program. I tried to get a toolpath without smoothing and its taking forever to offset the surface. I'm going to drop the dpi significantly and try again, but thought I might ask if anyone else has experience on "practical" limits.

Louis
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Re: Lithophane

Postby Randy » Sat Sep 10, 2011 5:53 am

Louis, the only limit I know of is Windows' memory limit of 2GB per program. Practically speaking, MeshCAM seems to lock up around 1.5GB actual memory usage. Pop up Task Manager and watch MC's memory usage and you'll quickly find out if that is the problem or not.

I don't know if you gain anything by having a DPI much finer than the stepover you're using. Sharp valleys (highlights in the picture) will be bridged over by the nose of your cutter if it is larger than the stepover, and sharp peaks (shadows in the image) will likewise be fairly softened. The ball-end is acting as a mechanical low-pass filter.

Randy
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
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