Z axis trick to save spoilboard carving

Special Interest Groups CNC Milling
#1

In the quest to try and keep my spoilboard from looking like a modern art painting will all sorts of random grooves and lines from various projects I like to play with my Z axis coordinates with with the following technique on profile or deep pockets cuts that go entirely through the piece. Here is what I do.

  1. Think about the thickness of the material. Even though I’m using a 1/2 in board it will likely vary over the surface in different places.

  2. Put 1/2 inch for the depth of the profile or pocket cut in VCarve (or whatever SW you are using)

  3. Using the probe or manual on the CNC set the X and Y 0,0’s as you normally would.

  4. Using a piece of paper and VERY CAREFUL lowering of the router / spindle bring the endmill down to the surface of the spoilboard, NOT the surface of the material. Lower until the paper is just unmovable. I like to stay here or a bit higher for “onion skin” bits of material left that can be easily broken off or sanded.

  5. In your CNC control SW (mach3, CM or whatever) manually enter the Z coordinate of -0.5. This makes the lowest dimension that the bit will travel be the surface of the spoilboard.

One important point that you should include in your pre cutting checklist (you do have a checklist, right?) is to do a sanity check before hitting GO that X,Y and Z zeros “look right” by lowering your bit to the material and verifying the coordinates.

Let me know if you have questions,

Perry

#2

(you do have a checklist, right?)

Courtesy of you, yes we do!

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#3

Perry, I too am a fan of onion skins. But I would like to offer up an alternative. If you use your reference off your already flat bed, instead, and you have set your clearance properly on the Material settings, then you’ll never go into the spoilboard unless you intend to. As I see material vary .008 pretty quickly, if I have spoilboard (like on my shark its aluminum) then going off the bed ensures I don’t make an oops. Now you do need to make sure the spoilboard is leveled and that the test area is not something different.

For those wondering if this really works, I use the tape method frequently and add the thickness of 1 layer of tape to my Z0, I consistently cut only thru the top layer of tape, leaving the underlying intact. So its easy to lift off the bed. No tabs, no fuss.

#4

You can set up your VCarve file to reference the bottom of the piece and then set Z zero on top of the spoilboard.

Another trick to zero your Z is to loosen the collet and let the bit drop to the board and retighten the collet.