3D finishing

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3D finishing

Postby electrictermite » Sat Nov 09, 2019 5:38 pm

After the roughing pass and the finishing bit has been put in, do you move Z back to zero or Do you jog Z down to the new surface that the roughing created.
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Re: 3D finishing

Postby Adrian » Sat Nov 09, 2019 5:43 pm

You re-zero to the same level you zeroed the roughing bit at. You can't go back to the original zero as the bits are almost certainly not exactly the same length.
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Re: 3D finishing

Postby electrictermite » Sat Nov 09, 2019 6:15 pm

so you are saying to go back to original zero which was the surface point before ruffing. but at the same time you are saying you will never get true zero because of bit length. if this is what you are saying then i understand. the finishing file will plunge down to ruffing area just done.
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Re: 3D finishing

Postby BigC » Sat Nov 09, 2019 6:45 pm

Where have you set your XYZ datum point? (hoping you haven't milled this away with the roughing pass)
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Re: 3D finishing

Postby electrictermite » Sat Nov 09, 2019 7:09 pm

X0, Y0, Z0...This will be my first attempt at 3d and hope to learn before taking a run at it.
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Re: 3D finishing

Postby Adrian » Sat Nov 09, 2019 7:49 pm

electrictermite wrote:so you are saying to go back to original zero which was the surface point before ruffing. but at the same time you are saying you will never get true zero because of bit length. if this is what you are saying then i understand. the finishing file will plunge down to ruffing area just done.

Use the original zero point but not the original zero value. When you set the initial z-zero you should use a point that won't be removed by the roughing tool pass. If you've removed all the material at the level that was the original zero point then you've got a problem.
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Re: 3D finishing

Postby electrictermite » Sat Nov 09, 2019 8:28 pm

I thought you could jog back and watch the X,Y,Z change until the G code sender showed x0, y0, z0 and that would put you at the original pre ruffing start point.
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Re: 3D finishing

Postby kstrauss » Sat Nov 09, 2019 9:03 pm

If you've removed all the material at the level that was the original zero point then you've got a problem.

If you are using CNC software (LinuxCNC or Mach3 or PathPilot or...) that uses its tool table to compensate for the length of your tools, removing the material is not an issue.
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Re: 3D finishing

Postby TReischl » Sat Nov 09, 2019 11:37 pm

Another way of saying this:

You must use the same plane for setting both tools.
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Re: 3D finishing

Postby Xxray » Sat Nov 09, 2019 11:58 pm

Always Z on top of original material for all passes, if you Z what has been cut you will be in for an unpleasant surprise of the finishing pass going way too deep, perhaps through the material into the spoilboard.
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Re: 3D finishing

Postby martin54 » Sun Nov 10, 2019 12:21 am

electrictermite wrote:I thought you could jog back and watch the X,Y,Z change until the G code sender showed x0, y0, z0 and that would put you at the original pre ruffing start point.


The point people are trying to make is that you will zero your "Z" axis on the material surface with the bit you use for roughing. Once the roughing pass is complete you would then normally change to a different bit for the finish pass. The bit used for the finish pass is unlikely to finish up at exactly the same length below the collet as the roughing bit which would give you a false z zero position unless you had some way to set it. There are ways to do this but a lot of people will just re-set the zero position for the z axis on the material surface the same way they set the z zero position for the roughing bit in the first place :lol: :lol: :lol:
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Re: 3D finishing

Postby electrictermite » Sun Nov 10, 2019 3:42 am

That was the answer I was looking for is just jog down Z to new surface and reset Z to zero before running finishing gcode.
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Re: 3D finishing

Postby gkas » Sun Nov 10, 2019 3:52 am

electrictermite wrote:That was the answer I was looking for is just jog down Z to new surface and reset Z to zero before running finishing gcode.


The key is NOT using a NEW surface. You should set your Z to the same spot for ALL of your bits. Pick a spot that won't get machined. If you use 3 different spots, you may be picking 3 different thicknesses of wood.
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Re: 3D finishing

Postby Adrian » Sun Nov 10, 2019 9:59 am

electrictermite wrote:That was the answer I was looking for is just jog down Z to new surface and reset Z to zero before running finishing gcode.

Wrong. You use the old (uncut) surface not the new surface. Both bits are zeroed at the same level (plane).

Of course we're assuming that you have set the z-zero in VCarve to be the material surface. If it's the table surface then you have to zero to that. Either way you zero to the same level (plane) for both toolpaths.
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Re: 3D finishing

Postby martin54 » Mon Nov 11, 2019 4:30 am

pick a spot on the material surface that isn't going to be machined by any of your toolpaths & use that spot after any bit change to reset your z zero. I generally put a small pen or pencil mark on the surface so I don't have to try & remember where I first set my z zero position :lol: :lol: :lol:
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