These Lithos make my head hurt (depth settings questions)

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wingarcher
Posts: 46
Joined: Thu Dec 30, 2010 11:32 pm

These Lithos make my head hurt (depth settings questions)

Post by wingarcher »

Hopefully someone will either send aspirin or help me make sense of all this!

I made a litho last night by following the PDF directions from the Vectric site to the letter. Worked good, but it's a bit too thick, I think because the Avonite stuff I have is thicker than .25 and I didn't pay attention. I now have modified my image to be a bit more contrasty and wish to create another snow-storm in the shop. :roll:

I do not have a V bit yet, I'm using a 1/8 ballmill for rough and a 1/16 ballmill for finish.

I can't seem to get my head around the relationships between max carving depth (pdf says .100), the re-zeroing of Z below the surface, the material thickness established in the beginning, etc. There usually is a simple explanation but my searches are missing it I guess. A single pass is pretty easy to figure out (start it at .040 + .100 above the table, no matter the thickness). I want to figure out the roughing pass and finish pass combination AND how to deal with my thicker material (.27? )

Does the max carving depth establish the thickness differences between black and white? A shallower depth will produce a less contrasty image, and a deeper max depth will do the reverse? Thus leave it at .100?

Nat

wingarcher
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Joined: Thu Dec 30, 2010 11:32 pm

Re: These Lithos make my head hurt (depth settings questions)

Post by wingarcher »

Update: Just measured this material (that I got from ebay, precut to 5x7) and it has some variation in thickness (.010 or so on some pieces) so I'm inclined to think I should base my Z zero on the table and not the top of the material, just to be safe. I wonder if this will make the paths easier to comprehend!

N

fixtureman
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Re: These Lithos make my head hurt (depth settings questions)

Post by fixtureman »

I like to zero off my table but it takes a lot longer to create the file. I haven't gotten an answer to this. Let me know if this happens to you

JMD
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Re: These Lithos make my head hurt (depth settings questions)

Post by JMD »

wingarcher wrote:Update: Just measured this material (that I got from ebay, precut to 5x7) and it has some variation in thickness (.010 or so on some pieces) so I'm inclined to think I should base my Z zero on the table and not the top of the material, just to be safe. I wonder if this will make the paths easier to comprehend!

N
I have done several lithos and have had good luck setting max cutting depth to .160. I have never used Avonite so don't know anything about how it may cut. I would think if you think the litho is too dark you should set the cut depth a little deeper. I never mess with the contrast, seems to work good as is.
Hope this is of some help.
John
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wingarcher
Posts: 46
Joined: Thu Dec 30, 2010 11:32 pm

Re: These Lithos make my head hurt (depth settings questions)

Post by wingarcher »

I'm currently wearing earmuffs next to a screaming router in the midst of the finish path on my second litho. 7 minutes in... a while to go. The rough only took about 10 minutes!

I did some more reading. Told PVC that I was zeroing on the surface, material was .25 (yeah, right, sure it is) and then set the bit down against the table of the router with the collet loose. Zeroed it and tightened the bit up properly. Entered -0.160 into Z, and re-zeroed. Ran the rough pass with a max dept of .100 which left me .060 above the table at max cut.

The finish path is a smaller bit and set-up like the rough- off the table. Instead I entered -0.140 and re-zeroed, same .100 max dept of cut, that'll leave me with the desired .040 thickness for the whites.

The contrast- my photo was a pretty flat shot of a sleeping baby, not ideal lighting. I edited the photograph in Gimp (linux!) to increase the contrast. Brightening up the first attempt would help a little, but there still wasn't enough range in the photo to begin with.

I think I need to get some of those there V-bits and stop having to change bits and sort out what depth I need to fake the Z into!

Nat

calgrdnr
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Re: These Lithos make my head hurt (depth settings questions)

Post by calgrdnr »

Your making this a heck of alot harder then you need too. measure your stock , if it varies not a problem mark where you measure it . well say 0.27 we want to leave 0.04 for the whites. Get a vbit 45 degree will work 30 would be better or find http://www.amazon.com/SOLID-CARBIDE-CAR ... B0012K7154.

now when working it up in PVC tell it it is 0.27 thick zero from top of material. Now tell the software you are using a 0.31 Ball nose , set your max depth of cut to 0.23. line spacing 8-10 percent Line angle 315

this will start the cut at 0x,0y cutting at 45 degree angle will make the bit make a hole to start with but from then on just slice away 0.003 lines .

now zero at the area you marked and start cutting ... no rough cut so it will faster then the way you are doing it now ..


If you are cutting large litho 8x10 with one face in it you can use 0.125 ball nose same way


good luck .

Kent

calgrdnr
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Re: These Lithos make my head hurt (depth settings questions)

Post by calgrdnr »

opps should be 0.03 ball nose ....

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ssflyer
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Re: These Lithos make my head hurt (depth settings questions)

Post by ssflyer »

It's a late night, but I've done a lot of these - zero to the table, set depth to zero minus 0.04 and cut it. I cut at a 315 degrees) maybe - long night - remember :D ) That lets you cut with a finish path, only. Zeroing to the table, assuming it's flat, guarantees a consistent cut.
Ron Sloan

wingarcher
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Re: These Lithos make my head hurt (depth settings questions)

Post by wingarcher »

I've got at least one handle on this now.

I'm running a Romaxx with the ground aluminum plate table, which seems flat enough for a 5x7/6x4 litho. I don't have a V-bit so I'm using what I do have- .125 and .0625 ball nose. The rough pass takes about 9 minutes with the .125 and then just short of an hour with the .0625 (I walk away then).

I measure off the table and reset to .160 for the rough and then .140 for the finish... .100 depth of cut, leaves .04 at the deepest.

N

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