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Tips for CNC'ing box hinge recesses.

Discussion in 'General Talk' started by Ethan Maloy, Feb 21, 2024.

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  1. Ethan Maloy

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    I need to make 12 wooden boxes with quadrant hinges and I would ideally like to use the CNC machine to do the carving for the hinge. I have tried to use the CNC machine to do this in the past and have had dissapointing results. Can anyone help with some tips or specific things to pay attention too?

    Thank you!
     
  2. Giarc

    Giarc OpenBuilds Team
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    I would think that all you have to do is draw a pocket the depth you want where the hinges go.

    What were your issues before that caused disappointing results? Knowing that may help us to help you.
     
  3. Giarc

    Giarc OpenBuilds Team
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    One thing I should add is that your spoil board needs to be surfaced flat so it is parallel to your x gantry. Otherwise the pockets may all be different depths. Also, you z should be accurately calibrated.
     
  4. Ethan Maloy

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    The primary issue I have ran into is the pockets being carved do not line up with where I have drawn them in VCarve, however I have already confirmed that the X,Y, and Z have had their movement distances calibrated.

    Currently I will measure the box to the highest degree of accuracy possible and draw this in Vcarve and add the hinges. The pockets will then be carved off center from where I expected them to be. Doing this previously I had the dust shoe on the router too low and as I learned on a more recent project this causes the router to lose position when changing direction. I have not tested hinge pockets without the dust shoe yet and will be soon. Are there any other problem areas I should be inspecting before/during the carve to produce more favorable outcomes?
     
  5. Rink

    Rink Well-Known
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    With little room for error, be sure to zero all three axes very, very carefully.
     
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  6. Giarc

    Giarc OpenBuilds Team
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    To add to that, get a very accurate tool with no flutes to do your probing. When I need high precision I use one of these Vermont gages. It is exactly 1/4 inch. I got mine elsewhere but here is an amazon one:

    Amazon.com

    Another option is buy a really nice 1/4" Sharkbit down cut Down-Cut 2 Flutes Solid Carbide End Mill 1/4" and accidentally choose that one when milling aluminum. The shafts are exactly 1/4 inch (at least mine was) and after it breaks in the aluminum (downcut is the wrong choice) you have a nice "Vermont gage."

    I also use my broken 1/4 inch endmills for locating pins for two sided carves. They work so well it was almost worth breaking them.
     
  7. Ethan Maloy

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    Would the innacuracy of using an endmill for your X and Y zeroing be the cause of this misalignment? (This mis-alignment is .015" off if it helps guide your answer)
     

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  8. Ethan Maloy

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    I am having some troubles with the CNC machine also not carving at different depts. I have leveled the bed before, but is there a test I can do to see if I am still level to the bed with my gantry?

    *This issue is likely a table saw issue, but I want to be able to test and rule out the CNC if possible.*
     

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  9. Giarc

    Giarc OpenBuilds Team
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    Re-flatten the spoil board. Just skim off about 0.25mm. Or mount you box and flatten the surface you plan to place the hinges before running the pocketing tool paths. This will ensure the gantry is parallel to the box edges.
     
  10. Ethan Maloy

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    If I am using an 1/8" bit for the carve, but use a 1/4" tool for the probe, which dimension should I enter into the probe function for the approximate diameter?
     
  11. Ethan Maloy

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    This is a perfect example of the missalignment issue I mentioned at the top of this thread. When I made the origianl cut file for the hinge pockets, the lid was misaligned by 0.015."

    This is the box I carved pockets into yesterday. This box is the exact same dimensions as the box from post #7 and the same cut file was used. However this came out misaligned by 0.107."

    Where should I start to diagnosis this because I don't see how the same dimension box and the same cut file can produce such erratic results.
     

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  12. Alex Chambers

    Alex Chambers Master
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    A), whatever the actual diameter of the bit is.

    B), better still, don't use any bit for probing X and Y - use an accurately turned pin (sometimes called a guage pin or dowel) - the orientation of the flutes on the bit can (will) cause errors in measurement.

    Alex.
     
  13. Ethan Maloy

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    Thanks for the input, I ordered a guage pin from an earlier suggestion.
     
  14. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    You enter the dimension of whatever is in the collet at the moment you are probing XY. Probes sets the "centerline" of the tool. To do that, it needs to know the diameter of the tool, because ZERO origin, center of the tool for the upcoming toolpath - is 1/2 the Bit/Pin diameter + shoulder of the probe away from where it touches. To do that math, it relies on the value you enter to match what's there in reality. Once centerline is set you can swop tools, XY Zero is still where it was. Center of a 6mm bit is center of 3mm bit. You do need to reprobe Z after toolchanges though as inserting it into the collet is not always the same exact depth

    Toolpaths run along the center of the tool. CAM did the Offset (half endmill diameter away from the CAD lines) already, the gcode runs along the center of the bit. And that's why your CAM workflow needs to know the size of the endmill to be used for the cut (so that offset is calculated correctly)
     
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  15. Ethan Maloy

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    Bumping this post for anyone that might have missed it but could have inputs.
     
  16. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    I think we're all waiting for your Guage pin to come in so you can report back if probing more accurately (and with your understanding regarding endmill diameter clarified per my reply above) gives any improvements. Ball was in your court
     

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