Rotary Axis Feed Rates

Mill
1

I have a Micro Arc 4 on a PCNC1100. I tried the 4th for the first time today. When the X or Z are moving with the A, the feedrate is good, 20ipm. When the A is moving alone, it seems to switch to 20°/m.

Is there a setting to control this? Should the post be modifying the feed rate for A axis only moves?

2

The A feed is a lot less than the others because circumference distance is about 3 times linear distance. Plus depending where your tool is you can get material coming up into the end cut. The loads are a lot higher for radial paths. That said 20 deg a min is a bit slow. I think fusion uses the ramp feed rate for these cuts.
What material, tool diameter, number of flutes, tool radius and rpm are you cutting.

3

Might look at the what the code is doing. Now and then I get code that has thousands of micro distance moves and this slows the 4th axis even with a higher feed rate set in the code. My only fix was to change settings until most of that went away. Still on certain types of operations the coded posted was filled with the micro moves and they slowed everything down. Never had time to chase my tail on it so no real solution.

4

Nick,

You are correct, for rotary only moves the feed value is taken as degrees per minute. However, all coordinated moves must have the axes finish movement at the same time so in most cases the linear feedrate is applied and the rotary axis moves at whatever speed necessary to keep up. If the max speed of the rotary axis is hit during the move then the linear axes will be slowed down to honor the simultaneous finishing requirement.

The changing of speed is dependent on the distance of the commanded move, if you need to control the speed of axes during simultaneous motion inverse time feed is needed.

Thank you,

Norman

5

8mm, 3 flutes, 4500rpm, 20ipm. Chipload 0.0015ipt. Linear moves were cutting good.

I did. It’s how I figured that it was moving 20°pm on the rotary only moves.

Perfect. Thanks for that description.

I’ll make a python program to post my post and set the angular feedrate of those moves to the feed in IPM at the height of the tool from center. It might take me 30 minutes to make but it’ll save hours at the machine.

6

If anyone wants it, this python script solves the problem for my VCarve created code:

#! /bin/env python3

import sys

f=0.0
newF = -1
z=0.0
newZ = 0.0

outFile = open(sys.argv[2], "w")

with open(sys.argv[1], "r") as inFile:
	for line in inFile:
		if "(" not in line and ";" not in line:	# Ignore comments
			if "Z" in line:
				newZ = float(line.split("Z")[1].split("F")[0])
			if "F" in line:
				f = float(line.split("F")[1])
			else:
				if "A" in line and "X" not in line and z == newZ:
					c = 2 * newZ * 3.1415
					newF = (f * 360) / c
					line = line[:-1] + "F" + '{0:.1f}'.format(newF) + "\n"
				else:
					if f is not newF:
						line = line[:-1] + "F" + '{0:.1f}'.format(f) + "\n"
						newF = f
		outFile.write(line)
		z = newZ
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