tapered bits

Topics related to wrapped rotary machining in Aspire or VCarve Pro
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jseiler
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tapered bits

Post by jseiler »

I created wrapped object using a 2" dowel. I like to center to the left and on the surface. When I use a tapered bit, I get this ridge that's pretty huge at the 0 and 360 degree crossover point. Anyone else have this issue? The bit is a 1/8 roundnose to 1/4" 5.4 degree bit. I'm cutting now with a new toolpath that I created telling aspire its not tapered (just 1/8 roundnose) to see if the problem goes away. Just curious if anyone else has seen this and has a solution that doesn't involve faking out aspire.

John

jseiler
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Re: tapered bits

Post by jseiler »

I think my tapered bit wasn't quite long enough to cut what I wanted to cut. When it was trying to "index", it was occasionally losing steps, just enough to throw everything off by .1" over a 2" diameter. Gonna try a bit with a longer cutting length and see if that fixes it.

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dealguy11
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Re: tapered bits

Post by dealguy11 »

Yes, get it regularly. Nope, don't know how to address this without "faking out" Aspire. I usually increase the dimension of the part in the wrapped direction, and make sure the component goes a little beyond the edges of the part to address it.
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Greolt
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Re: tapered bits

Post by Greolt »

jseiler wrote:I think my tapered bit wasn't quite long enough to cut what I wanted to cut. When it was trying to "index", it was occasionally losing steps, just enough to throw everything off by .1" over a 2" diameter.
Yes it sounds to me like you are losing positional integrity.

The cutting length of the tool being insufficient for the depth of cut could be enough for the machine to miss steps.

If the machine is solid and acurate, and no steps are lost, then you will not get that ridge of uncut material.

Having said that, I often set up a rotary job to cut slightly over 360 degrees. Although when I don't, I don't get a ridge left either.

Greg

jseiler
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Re: tapered bits

Post by jseiler »

I'm pretty sure I am not losing steps. I am thinking that maybe my 15 to 1 gearbox isn't exactly 15 to 1. Need to take some data there. How do you cut more than 360 degrees?

jseiler
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Re: tapered bits

Post by jseiler »

I swapped out for a bit with a longer cutting edge, cut less aggressively, lowered the speed and acceleration of the a axis and nothing changed. Rib was evactly the same width. That makes me wonder about the 15 to 1 ratio being just a little bit off.

jseiler
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Re: tapered bits

Post by jseiler »

Had a loose set screw on the chuck adapter. This was throwing things off because plunging with a tapered bit was pushing the chuck around on the first pass. Thanks for making me look closer at the setup.

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Re: tapered bits

Post by jseiler »

Just a note to say how I troubleshot this thing so when this happens again, I can find it. :)

I loaded up a centurion v bit and set it to make a very shallow line cut. I moved it up and down the x axis to draw a line on a piece of 2" scrap dowel. Once I did that, I cut 360 around. Came right back to zero. Did the other direction... Still good. Did 3600 degrees in both directions. Lined up perfectly. If the ratio had been off, the error would have stacked up and it would have shown off. Put a wrench on the chuck and gave it a good tug and it moved. Made sure the motor shaft stayed put. It took a suprising amount of force to shift it. The set screw was loose and that fixed it.

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Re: tapered bits

Post by Greolt »

Glad to hear you have got it fixed. :)

Greg

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Re: tapered bits

Post by jseiler »

Greg... how do you get it to cut past 360 degrees?

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