|Home » Forums » CNC » Message||Login|
You are not logged in. Consider these WOODWEB Member advantages:
From a really old post:
Parametric programming is useful when used as an extension of the programmer. For instance, letís say that you have arcs and straight lines in your program. It can be useful to control feed-rate based on formulas that calculate chip load in a turn verses chipload on a straight line move.
Instead of programming different feed-rates, it is possible to have the control calculate feed on the fly. At the top of the program there is a list of variables for feed and rpm. Make subprogram to calculate feed-rate based on size of arc. If move is straight then make feed a specific sfm (surface feed per min). Tool companies list formulas for their tools. Remember that imagination is the key. See it and then sketch your point of logic path you want to accomplish and finally program it.
#101=.005;chipload per tooth
#102=4;number of flutes
This program becomes fun to the operator if he wants to experiment with tool life. Also these macros can be installed in posts to solve tool changer problems etc. I have even installed a macro in a post that automatically inserted tool comp and had a line of code that the operator could edit so he never had to go to his off-set page.
So, the question is, in a program that has lots of starts and stops, does it make sense to vary the RPM to keep the chipload constant or am I just chasing rainbows?
That would freak my ears out. I have dad-ears that hear everything in the shop, when a machine is out of whack. Varying CNC RPMs would take some getting used to for sure. On a more pragmatic note, I've noticed my own tool wear comes less from uniform wear from chip load and more from non-uniform wear (plywood glue lines and p-lam).
On my machine correct chip load is nearly never actually achieved. If it takes 12 inches of accelerating to hit 720 inches per minute no portion of any drawer part is cut at the correct chip load, and only a small amount of a cabinet side is cut at correct chip load.