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Subject: Re: How to figure 4th axis feedrates?

Date: 06/07/02 at 7:47 PM
Posted by: Sam
E-mail: ehrichwebster@bluefrognet.net
Message Posted:

In Reply to: Re: How to figure 4th axis feedrates? posted by Neal on 06/07/02 at 10:53 AM:

I'm not sure I understand you, Neal. The 4th axis is hardwired into the control. If I make an X and an A axis move in G1, the control synchronizes the 2 axis' to create a straight line. That's not the problem, the problem is snapping off tooling and not getting consistent finishes due to guesswork on feedrate calculation. If I want to cut at, say, 750sfpm and .0035"/tooth along a slot with various angles and straight moves in it, I can figure the straight moves, but am guessing on the angles. I am basically dropping my endmill into the outside of this ring and feeding back and forth in X as I index to get different angles and straight slot sections. So your saying that if I have a straight section and I've figured my speeds and feeds to be S4500 and F45., then to figure the speeds and feeds on a section of slot that trigs out to be 5" long about 20 degrees, I would just insert the values into your formula?
Ex. Slot angles to the right 15 degrees about 20 degrees of rotation (I'm making up the numbers):

Feed = (20 degrees)/(5"long move/45"per min.) = F300.ipm?

G1G91X3.5A20.F300.

I don't have the rough program I ended up with by trial and error in front of me but that seems high to me. Am I telling just the A axis to move at F300 and the X axis to just keep up to make the move come out straight? If I was to make another move where the A axis only moved, say, 5 deg. but the X axis moved over 5", the X axis effective feedrate would be very fast indeed( I know this from trial and broken endmills;)).

I was thinking this has to be tied into the diameter I'm cutting at as well. (Like on a lathe) The effective feedrate as an end mill cuts around a 10" dia. as the A axis rotates at F300. will be a lot higher than at a diameter of, oh, say, 3.14".
Its been a couple months since I last ran this job and I've been thinking about it but just don't have enough information. Any help or a book on 4 and 5 axis programming technique is appreciated greatly.

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