some ideas about rapid travel, G00

Watching a guy work out a problem today, the machine was choking in rapid moves. To fix it he programmed the rapids as feed moves.
My theory on that was maybe the machine isnt bufferring the G00 moves, and reading them a line at a time, OR...the machine is making one rapid move, then decelerating to make it perfect, than do the next line, etc... making it pause. By posting as feed moves maybe it would smooth out the moves, and it worked. I was wondering... in the cam system is a box to post out rapids or feeds, is that there to do what we used it for or does it have another purpose?
Final conclusion: maybe we shouldn't be using rapid G00 on todays high speed mills? Just use only G1,G2,G3.???
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Rapid moves are fine with canned type cycles. Anything else, really, to take maximum advantage of the performance of today's modern controls/machine tools, feed moves are much better, faster and smoother.
JM2C
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On short rapids less than about an inch or so I set my rapid over ride down to 50%.Less strain on the machine and is actually as quick.Kind of like between stop lights,flooring it really doesn't get you any quicker because while you may reach a higher top speed your braking is longer so you don't get the most out of the top speed.

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vinny wrote:

Vinny, I've run both my mill and lathe at 50% rapid rate and haven't seen a big difference in cycle times, especially on the lathe. The lathe parts are generally short in length generally 3-4 inches or less to the distances aren't very far. On the mill the parts generally "busy" so I'm not drilling a hole and then rapiding 24 inches to do another hole.
Best, Steve
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Regards,
Steve Saling
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Depends on the controller. I know that on our MAM 72-63V (A fanuc 30i controller) the high speed is disabled when you do a rapid motion. Once again it is engaged when you go to a feed move. Granted, it does not take long to engage/disengage, but even .1 seconds (or even . 01...dunno what the exact time is) adds up when you have alot of rapids. Think of a peck drill cycle....I never use high speed when drilling...but just imagine turning on & off with each peck. even at . 01 seconds it would add up in a hurry. Now then....on a Siemens 840Di controller with the right options....when you turn high speed on...it stays ON. No delay between a rapid & a feed move. One can really see the difference you linearize a 5 axis rapid move (that is, correct for a 5 axis motion) with the 2 controllers. Difficult to explain without pictures....but basically you would break up the 5 axis rapid move into several lines. The Siemens controller runs through it like butter...The Fanuc chokes up. To put it more basic terms...rapid 20 inches in the X & Y directions...cept do it ten thou at a time.
Now then....I know that alot of CAM systems have many different "high speed" toolpath options. All the ones I have seen offer the option to output a high feed move (say 1500 IPM) rather than a feed move. The Fanuc controller likes this and will fly through the code.....
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Zymrgy wrote:

What are you refering to as "High Speed" - G5.1?
--
John R. Carroll



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All said & done rapid is machine/job function specific. Some times ya need it - long retracts back to starting position or most of the time max feedrate G1 is fine. If your machine is a jitter bug, slow down dufus. Its the rapid over ride button thats nice to know if its on or not, enable dis able- is that on or hit the deck! <g>
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Well little snot nose Tommy, that's about all the time
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