Cutting off the end of a ruler sized stick

New user here. I searched for an answer in the forum, but apologies if this is one of those things already asked and answered 100 times already.

I’m trying to put a ‘fancy’ cut on the end of some sticks that are about the size of a one foot ruler. The thing I am struggling with is that to use the nice boolean operations I’d like to use to build up my complex line, the software requires the use full 2D shapes, but when cutting, I don’t want to do a full 2D shape which would either cut off the fancy shape from the rest of the ‘ruler’ or force the toolpath to wrap around outside of the object very slowly following a cutting toolpath where really there is air. OR I’ve found I can draw a spline curve to make a single fancy shape cut, but first, the spline curve is only a rough approximation of the cut that I want, and second, sometimes I’ve found, even with a single contiguous spline curve the created toolpath tries to close the loop and cuts through the ‘ruler’. In the screenshot I’ve got two examples of my attempts. In some drawing packages there is a command like ‘explode’ that takes a shape and breaks it into all the separate segments which can then be individually deleted or regrouped as desired. I don’t see a function like that. The big picture question is how do I make a cut-off cut rather than a looping cut?

Thanks for any hints (particularly if the hint is that my approach is all wrong.)

not quite sure I understand what you need. “Trim” is the command you normally use to help clean up a 2D sketch with overlapping lines.

Make those two vertical lines (pink/blue) go from top to bottom then use the “Trim” command to remove the unwanted geometry.

(I just tried this in carbon create and could not find a trim command… really no trim in CC?)

I normally use another CAD program (V-Carve, Fusion360, or even Illustrator) to design so maybe I’m just not finding it in CC.

You want to:

  • inset the design to get the desired limit to that portion of the pocket
  • draw the balance of the cut as a narrow rectangle
  • do Boolean operations to make a closed shape which defines the area which you wish to cut

Assign a toolpath to that shape and position it as desired and you should get the desired cut.

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Sorry, the picture I posted was after a half dozen attempts so it wasn’t the most obvious. Here is a cleaner version where I try to make the cut using a solid shape, which causes the toolpath to loop around (left) and separately (on the right) make the cut using the spline type line (which is only an approximation.) The blue lines are the toolpath created from the design.

A “Trim” command seems similar to an “explode” command that would let you delete portions of a more complex shape, and yes, I can’t find that either.

Hi Will, I had seen your uses narrow rectangles on your post about making miter cuts but it isn’t obvious to me on how to size the narrowness of the rectangle to get a perfect single width cut and not have it too fat so that it is cutting an area, or too skinny such that it is cutting over the borders. Is it as simple as having the width of the rectangle be exactly the width of the cutting tool? I was worried there might be some hidden offsets that make that not work. Also in your mitering examples you had narrow rectangles with half circle ends. They seem to not be necessary, but then I wasn’t sure why you had them. Thanks for the guidance!

You would want the rectangle to be at least 10% greater in size than the endmill you wish to use.

Alternately, just draw the whole thing as a polyline:

and assign a suitable toolpath based on its position:

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Yes, the polyline is what I meant when I said spline curve. The problem is that with a bit more complexity for the desired cut (I simplified my shape for the discussion) then the polyline is only an approximation of the desired line. However, I do like how you made a pretty perfect match for this simpler drawing so I’ll have to practice with that for a bit to see if I can get it to be what I need.

Using the narrow rectangle technique it seems that the toolpath will always be a small area cut that only does the useful cutting in one direction and then is cutting the throwaway wood in the other direction and therefore taking twice as long. Of course I have spent much more time than that trying to figure out a solution, but I’m just trying to learn the various ‘right’ ways of doing things.

Also, I left unsaid, in the end I am trying to make the cut on one stick of wood and then the ‘opposite’ cut on another piece of wood such that they can fit together like puzzle pieces. Using the rectangle technique I’ll have to make two designs, one for the original piece and one of the opposite, whereas for a complex line (or polyline) I was hoping to just use the left hand tool path and the right hand tool path from the single creation of the complex line design.

Either way, you have given me a lot to play with to help my progress. Thanks very much.

The polyline technique will only work if you shape the polyine so that it has the radius to accommodate the endmill — that’s easier with a closed path.

Making the extra pass is good machining practice — slotting (making a cut w/ 100% tool engagement) is hard and liable to lost steps which are the bane of machining on a CNC with belts and no positional feedback. See:

Ahhh. Now I’ve learned several new things, including that slotting is bad and that there is a tutorial section of the forum to read up on these kinds of things.

Thanks again.

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