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Author Topic: Very small parts of another kind  (Read 1943 times)
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cncorbust
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« on: November 13, 2010, 06:33:23 PM »

Didn't want to hi jack some one elses post on small size engraving but thought this might be of interest to any one wanting to see how small one can one go with the inverse of engraving (embossing?).  I'm sure with the right equipment it is possible to go smaller but what I am showing is about my smallest limit.

The picture shows an embossed (raised lettering) of a plaque for a 1/2" scale model of a steam loco I am building.

I made the cutter from 1/8" round tungsten carbide. I ground the stock down to a 60 deg point, with the point as dead center as possible. I then changed the angle of the stock from 30 degs from the diamond stone surface to 60 degs. As carefully as possible I moved the tip into the grinding surface to a depth of 0.001" (not really sure if I achieved the 0.001" depth, I don't have the tools to be sure. I did try 3 times!). This puts a flat surface that retains curvature at the tip of the point with a slight offset. In effect it produces a very small round nose cutter. The cutting is done using a raster cut with Gcode derived from a high contrast image of the lettering on the plaque.  With an X step over of 0.001" and Y resolution of 0.001"  and 3 passes to a depth of 0.005" the result is quite surprising.

Mike


* SuperHeaterPlaque.jpg (157.76 KB, 778x597 - viewed 469 times.)
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Tweakie.CNC
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« Reply #1 on: November 15, 2010, 04:03:53 AM »

More than surprising Mike that is just excellent.

Which software did you use to create the raster toolpath from your image please ?

Tweakie.
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cncorbust
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« Reply #2 on: November 15, 2010, 10:27:49 AM »

HiTweekie, I used DeskCNC, although there are other readily available softwares that will convert BMP to Gcode.  You need to massage the grey scale image to get the best results for the lettering. Just take the BMP and make the image as contrasty as possible, sharpen up the edges etc, there are several choices of photo packages to do this. Once the image is processed then you just pass it to DesckCNC and set the parameters.  With really small cutters I found that exceeding 0.003' depth is asking for trouble, so take more than one pass if you want more depth.  When I did the plaque I had my machine as tight as possible with back lash <0.002 so if you have good ball screws and no backlash you're in business. I had cheap all thread 1/2" X 20.  My table runs on linear bearings.

If you look at the "Golden wedding anniversary gift" topic you can see 3d relief images done also using DeskCNC.

Mike
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Tweakie.CNC
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« Reply #3 on: November 15, 2010, 12:06:32 PM »

Thanks for all the information Mike.

I had always thought of DeskCNC as working with it's own  proprietary controller rather than a creation tool for GCode to use with Mach.
I can see the need for an accurate and rigid machine construction for this small stuff.  Wink
Keep up the excellent work and of course keep posting the pictures.

Tweakie.
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Glad
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« Reply #4 on: November 15, 2010, 12:20:24 PM »

Hi Mike,
nice job. Could you show us cutter you've made to do this project?

Glad
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cncorbust
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« Reply #5 on: November 15, 2010, 08:06:39 PM »

Can't show the actual cutter because I can't find it! I made it three years ago. What I can try is to show a drawing which might actually be better than trying to photograph the cutter any way.  I hope the drawing will show OK

Mike


* SpecialCutter.jpg (121.39 KB, 1223x728 - viewed 237 times.)
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Jammerm
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« Reply #6 on: November 16, 2010, 03:30:37 PM »

Well, that answered my question I put on the other post. Smiley

That is small, and would be interesting to try to cut some printing plates.
I have old letterpress equipment and am always looking for other ways to use it.
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