ROTATION SPEED FOR ROTARY PLUGIN NOT CORRECT?

[plasma]

did a search, not much there.
Having an issue in getting the rotating surface IMP for a given diameter to match the the X axis commanded IPM

Say I am cutting out a square hole in a tube. the hole traverses 180 degrees of the tube on the A axis and 1" on the X axis.

I have commanded the tool to cut at 20 IPM

when the tool travels along the X axis the code shows 20IPM and the machine moves at 20 IPM, but when it rotates it the code says something like 2291 IPM? it whips around way faster than 20IPM

I've looked into the posts to try and find a clue to no avail. I would assume, given a specific radius the post, or something, should interpret desired IPM then calculate the correct degrees per second needed to match the commanded IPM at the radius specified in the rotary plugin setup then write that IPM needed into the Gcode.

I do have the A axis settings correct and double checked. (as far as I can tell)

BASIC CODE PRODUCED AFTER PRE-POSITIONING AND TORCH START

N0240 G01 Z0.5900 A270.0002 F2291.8312
N0250 X-0.0000 F20.0
N0260 X0.0000 A89.9998 F2291.8312
N0270 X-1.0000 F20.0

For a surface speed of 20IPM on a 1" diameter, it should take about 10 seconds, 20 ipm/3.1416" traveled per rev = 6.366 revs. 60 seconds/6.366 revs = 9.42 seconds
if I enter G1 A360 F80 I get a full rotation in about 10 seconds. So my cave man intuition tells me instead of F2291.831 it should be F80? bigger dia less, smaller dia more.

If I tell the Sheetcam Rotary plugin that my diameter is 28" I get around 80 IPM during the A move but the Z is way off of course.
This problem makes for some radically different cutting speeds around a fish mouth cut on a tube which is real bad for dross and heat affected zone.
Any ideas??
Where am I missing it?

[yurapak]

Hello. did you solve the problem with the high speed of passing the pipe edge?

[Les Newell]

The high speed is correct. The feed rate you enter is the desired feed rate of the torch across the surface of the work. Now look at the corner of a square tube. The actual length of the corner is quite short. However to get around the corner the rotary axis has to turn 90 degrees as well as the X and Y axes moving to track the rotation. The combined movement of the axes ends up very high to maintain the surface speed.