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Author Topic: radial curved slots - won't cut to dimension.  (Read 4284 times)

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radial curved slots - won't cut to dimension.
« on: September 15, 2008, 08:46:42 AM »
Newbie here.  I can't get this file to stay on dimension while cutting.  All four slots end up .004" larger on the end opposite the tool lead-in.  I've tried incremental & absolute settings with no difference.  If anyone has any ideas I sure would appreciate your thoughts,  I'm running out of aluminum.  Thank you.
Re: radial curved slots - won't cut to dimension.
« Reply #1 on: September 15, 2008, 09:34:22 AM »
Could be backlash in your system.
Determine if there is any and try to eliminate it or compensate for it with Mach.
RC
Re: radial curved slots - won't cut to dimension.
« Reply #2 on: September 15, 2008, 01:41:19 PM »
Thank you for your reply.  I should have mentioned the machine stats in my initial post.  I have .00005" backlash on the X axis and "0" on the Y axis.  On the full G-code file for this part, the center hole cuts out fairly correct, (within .001" diameter variance at clockwise position of 1:30, 4:40, 7:30, & 10:30.  The 12, 3, 6, & 9 o'clock positions measure exact.)
Thank's again for the reply and we'll keep searching.
Re: radial curved slots - won't cut to dimension.
« Reply #3 on: September 15, 2008, 01:53:00 PM »
Well that certainly rules out backlash....thats a pretty tight rig you got there.
 

Offline docltf

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Re: radial curved slots - won't cut to dimension.
« Reply #4 on: September 15, 2008, 05:10:56 PM »
you did not describe the cutting tool you are using. your TAP file is ok ,but you did not put in a finish cut. you just poked it through the piece. so chances are your feed is to fast
causing the bit to flex, when the machine slows to make the direction change the bit cuts smoother and straighter.

bill

Re: radial curved slots - won't cut to dimension.
« Reply #5 on: September 16, 2008, 05:33:48 AM »
Thanks for your suggestion Bill.  I'm using a Niagara 1/4" 2F HSS cutter with 3/8" shank and tried the feed at 7 ipm, last night but it's still .004" larger on the opposite end of the lead-in.  I also goofed on typing my backlash on the X axis it should have been .0005", not .00005".  Thank you all for your time.

Offline docltf

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Re: radial curved slots - won't cut to dimension.
« Reply #6 on: September 16, 2008, 06:43:00 PM »
endo
when i looked at your tap file and did the numbers the .004 is not written in the file. so it must be a mechanical problem. check your table ways for slop.
something must be moving around.

bill

Offline Graham Waterworth

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Re: radial curved slots - won't cut to dimension.
« Reply #7 on: September 17, 2008, 06:27:45 PM »
Is this a travelling quill machine, is so keep the quill movement as small as possible.

It may also be a good idea to take a finish pass around the part and see if that makes a difference.

Graham
America gave us powered flight, England the steam train and Germany the car.  Who invented the first boat?