tapered bit calculations

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tapered bit calculations

Postby Dale Yeager » Sat May 20, 2017 11:49 pm

When making a design with a tapered bit, and it requires multiple passes, it seems that all of the passes are calculated at the OD of the bit when at it deepest pass. This means, as you go deeper, the last pass on the is cutting material at the full depth of that pass. Is there a way to avoid this other then making multiple toolpaths?
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Re: tapered bit calculations

Postby Mark's Wood Chips » Sun May 21, 2017 12:34 am

If it's a profile tool path, you can apply an offset, positive or negative. If it's a V-carve tool path, you can specify a maximum depth of cut but you may have to apply offsets to your vectors to widen or narrow your lines if that is your intention.

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Re: tapered bit calculations

Postby Dale Yeager » Sun May 21, 2017 1:17 am

I am trying a pocket path. Imagine a circle pocket that requires 3 passes going .12 deeper each time, each pass has the exact same path, just at different depth. On the second and third pass, the bit is cutting material at the full depth on the OD. Then when you program the same circle with only 1 pass at .12, the OD is the same. The only way I can figure to do this is to program one path at .12, then program a second pocket, but tell it to cut the full depth of 2 passes, and then a third pocket toolpath at the full depth.
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Re: tapered bit calculations

Postby Mark's Wood Chips » Sun May 21, 2017 2:44 pm

Dale Yeager wrote:I am trying a pocket path. Imagine a circle pocket that requires 3 passes going .12 deeper each time, each pass has the exact same path, just at different depth. On the second and third pass, the bit is cutting material at the full depth on the OD. Then when you program the same circle with only 1 pass at .12, the OD is the same. The only way I can figure to do this is to program one path at .12, then program a second pocket, but tell it to cut the full depth of 2 passes, and then a third pocket toolpath at the full depth.

Sorry, I'm not quite sure what you are asking. If you are cutting a pocket tool path with a tapered bit, the tool path will compensate for the taper, maintaining the circle diameter at the top of the material. Anyone else care to help this gentleman?

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Re: tapered bit calculations

Postby ger21 » Sun May 21, 2017 3:39 pm

You could also make 3 different sized pockets, one for each depth.
But, what is the problem with cutting full depth? You'll get a better edge finish on the side walls with this full depth final pass. And it won't be removing that much material.
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Re: tapered bit calculations

Postby IslaWW » Sun May 21, 2017 7:52 pm

Dale....
Since tapered ball nose bits are not the best tools for removing material, why don't you pocket with an endmill and use an allowance, then do a stepped down profile pass with the ball nose?
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Re: tapered bit calculations

Postby Leo » Sun May 21, 2017 8:23 pm

I was also going to suggest a straight end mill.

Why do you want to use a tapered cutter to make a pocket?
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Re: tapered bit calculations

Postby Dale Yeager » Sun May 28, 2017 3:25 am

Ok, A little confusion here. The bit I have has a .25 inch flat bottom, with a 30 degree side angle. What I am seeing is that the software does make the correct calculations to determine the bit OD at whatever I set as the full depth. However, this means that the first pass does not cut to the correct OD. Then when the machine goes deeper, the outside pass is being cut at the full depth. My little hobby machine does not like this.

So, as suggested, in my project I program a different toolpath for each depth. Also, to help maintain the clean edge, I set the first toolpaths with a very minor offset of .005 inches. Then let the last pass gets it all, but not as much as if I did it with 1 toolpath.
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Re: tapered bit calculations

Postby scottp55 » Sun May 28, 2017 2:38 pm

Sounds like you may want to enter it as a Form Tool?
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