First lithophane in corian

[Stickman]

Following the tips from this forum, I did my first lithophane in corian today. The results are stunning (better than I can capture on camera) but this project raises yet more questions.

My material was cut exactly to 6" x 4.125". My material size in PVC was 5.871" x 3.5". I probably should have given myself more margin, but I figured this would work. My bottom and right edges of the carving are pretty straight, but the left side is pretty crooked and the top edge in that corner pretty much wanders off the material. I measured the corian at 2.4" thick, and I set my cutting depth at .21. I think I could have reduced that slightly and been happy with it. At arms length this looks great, but a bit closer and the light areas seem just a little too recessed.

Also, I noticed corian has both a smooth and textured surface. At first I was going to cut into the rougher side, thinking that it wouldn't matter much if that were cut away, but then I thought that the smooth side is probably the one presented, so the smoother margins were my reason to cut on that side. Feedback?

The other thing is PVC said this was a 2 hour 9 minute project. Well, my CNCShark disagrees. Even running it at full speed, this took more like 71/2 hours on the machine. I used a 30° v-bit without a roughing cut, but I have to wonder if the time "saved" by a single pass might have been better spent with a roughing profile.

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[calgrdnr]

Yep the learning curve will bring up many questions

I do not understand , If you have dialed in the speed of your router and the estimated times you should not be that far off. What speed are you cutting at ?

all the corian I have is smooth on both sides ...


gotta run will get back Kent

[Stickman]

I don't know the actual speed of the CNCShark; there's not a lot of information available on it. I just dialed it up at full speed, same for the router. The setting for the .0313" ball nose says 100"/minute. With a depth of .072", that's 3 passes in Z to the max of .21", and there were 1320 lines. Still, that's part of the calculation. My other lithophanes (the test pieces in acrylic) took slightly longer than the estimated time, but those were very shallow cuts in thin material.

One other screw-up is I ran this with my new dust shoe on. It worked, but it's clearly designed for longer bits and the brushes now look squashed like an old broom.

[calgrdnr]

The setting for the .0313" ball nose says 100"/minute. With a depth of .072", that's 3 passes in Z to the max of .21"

This is why it took so long . It did not cut in one pass, but 3. I don't know why the shark does this .

Maybe with the shark you need to do roughing pass ....

1320 line sounds about right . as stated your problem is the fact that your machine or setup is not cutting the full depth in one pass.


good luck .

By the way the Corian litho looks great


Kent

[Stickman]

Thanks for the compliment. It does look great at arm's length, but a little closer and the depth of carving gives me a bit of vertigo. Looking at the back, I can see how thin the deepest cuts went. I don't think there was much margin for error there!

I did check with the manufacturer and the Shark does feed at 100ips. Regarding the 3 passes to reach full depth, that was from the PVC setting for the .0313 bit. Are you saying it's safe/reasonable to edit that for a single pass on the deep cuts?

I also saw a tip to use a text editor (notepad) to zero the end-of-line rapid clearance gap, that this can speed up the carving. I may try that on my next piece.

[calgrdnr]

Yep with the bits and settings I have recommended , you can cut in one pass just adjust tool Pass depth to .23
that is how I do it anyways

[Stickman]

OK, I just edited a new .031 bit just for this kind of project. I presume that setting the tool pass depth at .23" is so there's no problem with single-pass cutting at .21 depth (that took me a moment to figure out).

Also, I've figured out why this took so much longer than the projected time. When I was having problems with the machine (turns out I needed to use a different controller software than the one initially provided for my operating system) I though perhaps vibration was causing the machine to lose position, so the manufacturer had me tweak some hidden settings to slow down acceleration from 100ips to 50ips. I'd forgotten about that!

[Stickman]

I guess I didn't figure out the time-to-completion problem. I'm re-cutting this piece (for another family member) using the new settings, where I put the feed at 50ips instead of 100. The program still told me 3.5 hours for the project, and here I am 7.25 hours later, waiting for the project to end. It looks like about another 30 minutes ... Anyone have a suggestion what other parameters need to be changed to get an accurate projection?

[Stickman]

OK, further frustration on the learning curve. A couple of family members expressed an interest in this lithophane so today I cut it for the second time in corian. I made the following changes in the program from the first one.
1) I slightly reduced the size, by about 1/8" height (and proportionate width) to better fit my material;
2) I reduced the depth of the cut from .21" to .2"
3) I changed the settings for the .031" ball nose bit, lowering the feed from 100ips to 50ips to try to get a closer estimate of time to completion (it didn't work). Also, in another attempt to reduce cutting time, I changed the depth of cut from .072" (requiring 3 passes) to .23, so the machine could cut in a single pass, and I lowered the rapid clearance gap from .06 to .01"

Overall time to cut this 5.75 x 3.5" piece was slightly over 8 hours, even longer than the first piece!

Here's the bad part, though, because regardless of cutting time, the results speak for themselves. If you look at the attached image, once again the upper left margin is uneven. Worse, though, this time the depth of cut changed where the margin shifts, so there is clearly a visible difference in the contrast of the upper left corner to the rest of the image, right across the baby's face. I have no idea why this occurred, especially as the previous piece didn't do this. I was intending to send this to my father-in-law (it's his granddaughter and great-grandson) but with this flaw, I'm not so sure it'll create the right impression.

[MikeUSNRet]

Both that you have posted pics of look fantastic.

Can't explain why the jagged edges either as I get the same thing on mine, except they are usually along the bottom edges.

Not sure what to recommend as far as the cutting time goes. I know that I do have one small one I want to cut out of my mom when she was very young, but VCP says it will take approx 21 hours to do this...eeek.

[calgrdnr]

First off, it was slower because you told it to run half the speed it was first time ie 100 to 50. ( are you setting the speed in the tool setup ? The depth change
means your machine lost steps ( Zaxis) or the tip broke off. if that was the corner it started from and if you would of caught it you could of stop the cutting re-zeroed and started over. That is what I do when the tip breaks ...


If you send me the photo I can work it you and see what times it should take ... looking at the size and detail I would say at least 5 hours so the 7-8 might not be out of line for that size ... Lithophanes are fantastic , but do take lots of time to cut when asking for the resolution that you are cutting.

Kent


calgrdnr ( at ) sbcglobal.net

[Stickman]

Yep, I changed the speed in the tool profile. The idea was to try to get PVC to give me a more accurate time estimate. In the end, this slightly smaller lithophane took about 30 minutes more than the previous version. I'm less concerned with how long it takes than with having an idea of how long it takes. I don't want to start an 8 hour project late in the day because I don't want the noise going into the small hours of the night, or having to stay up later than planned so I can shut off the machine when it's done.

The depth change was the LAST part of the piece! I'm using a 45° line angle, so the cut is starting in the lower right. That means it went deeper towards the end, and the tip seems as sharp as ever. I've also started using a dust brush, which makes it difficult to monitor what is happening. Not that I would have necessarily caught this, or started over so late in the process.

Wish list? To be able to highlight a line in the code and have the machine resume operation from there without having to start over from the very beginning (not that it would help my problem with the depth increase at the end).