Constant surface feed rate in 4 axes

[Oliver Coelho]

I use mill 9 to generate 4 axes G codes for sinumerik controller using a VMC. I am not able to achieve constant surface feed rates. I can get a constant feed rate output .nc file, but when I run it on the machine the 4th axes surface feed rate far exceeds the other 3 axes.

 

Inverse time feed rates make the cutting too slow at localized points. Is there a solution?

[jeff]

Im not very familiar with 4 axes machining,but have you tried the highfeed option?

HTH.

[Oliver Coelho]

I have not tried high feed. I will give it a go tommorrow and see if it is fruitful.

[Glenn Stephens. from CCCS]

Lesson time

 

The problem is almost always the inability of the control to keep up with the code. Say for instance you are trying to cut at 600 mm/min. Making a 30mm move takes 3 seconds, but if you're cutting around a corner, the tip of the tool may only move .001 mm whereas the rotary might have to move 90 degrees in say 10 steps. That means each move is theoretically .0001 mm. At 600 mm/min each move would have to be processed in .00001 seconds. Not to many controls can process 100,000 blocks per second.

 

I always liked the Fadal control because it showed you all the lines of code that were in the buffer, say 12 lines on the screen. When the code was too fast for the control, you could see the buffer get smaller to the point that there was only 1 line of code on the screen at a time. It flashed and changed faster than you could read it, but if you turned down the feedrate until you had at least 2 lines on the screen at once, you got a constant feedrate through the whole program.