3d tool set

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lestes
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3d tool set

Post by lestes »

I am sure this question has been answered many times but I couldn't find a specific answer.
When doing a 3d carving, do I zero the bits from the surface since the surface changes during the carving or do I zero from the table/spoil board?

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adze_cnc
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Re: 3d tool set

Post by adze_cnc »

Zeroing should be done from a known spot. If you are zeroing the roughing bit (square-end) from the surface of the material the finishing (ball-end) needs to be done from the same surface. If you've milled that surface away you now have to figure out a compensatory strategy.

Some examples:
  1. can you make the material larger than your cut area so that the surface will remain in the extra material?
  2. do you have a scrap piece of material the same thickness so that you can use that with the ball-end cutter?
  3. can you zero off the table surface and then move the machine in a known distance in the Z axis to the top of the material
How number 3 might work:
  • before the roughing cut: zero off the table surface
  • move to the surface of the material
  • before zeroing to that spot write down the distance we've moved in the Z axis
  • zero the bit
Now, when you want to zero off the ball-end cutter:
  • zero the ball-end to the table surface
  • manually move in the Z axis to the value written down above
  • zero to that height

lestes
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Re: 3d tool set

Post by lestes »

Thanks much. Using the scrap or leaving a border seems to make the most sense.

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martin54
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Re: 3d tool set

Post by martin54 »

I am not sure there is a right or a wrong way as both methods will work OK so I think It is really down to personal choice & how you like to set things up. some people will use the table surface/spoilboard, others will use the material surface, use whatever works best for you & the way you like to work. :lol: :lol:

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SteveNelson46
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Re: 3d tool set

Post by SteveNelson46 »

I think it also depends on your machine and how you have it configured. With mine, I always try to set the Z-zero to the spoilboard. There is a touch-off switch that measures the tool length after a tool change so I never have to set Z-zero again unless I surface the spoilboard or use the recoil indexing lathe. That said, there are times when setting Z-zero to the surface of the material is more convenient. So I guess my answer to the question would be to learn and understand each setting and set it to what ever is appropriate for the project.
Steve

wood_fly
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Re: 3d tool set

Post by wood_fly »

Zero from the surface also works if the stock is uneven. Good explanations for the other methods by the other guru's. Wise to listen to them... :D

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TReischl
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Re: 3d tool set

Post by TReischl »

There are a few fine points that are never discussed when this topic comes up.

If the job is zeroed from the surface and then an issue develops later concerning depths of cut or clearance it is very easy to look at the G code and see what is going on. All clearance heights will be a positive value, all moves within the material will be negative Z values.

Here is another method to set Z zero after all the surface material has been removed:

When the initial Z zero is set to the top surface, note the position of the Z axis in MACHINE COORDINATE. Those are not the same as the work piece offset coordinates which most of us see and use. Most control software will show them as small numbers or require the the user to select a button to make them visible. After the first cut, subsequent tools can be set by zeroing off the spoil board, then move the machine to the Z axis MACHINE COORDINATE noted earlier and press the Z set axis zero button.

BTW, this also works with the X and Y axis.

It does not work with machines that do not have homing switches.
"If you see a good fight, get in it." Dr. Vernon Johns

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