I'm trying to do some trochoidal milling to mill a slot which entails simply milling circles with every circle offset with a certain stepover. The trouble is I'm having a problem with the machine "bumping" everytime the circle completes. I'm running at 200IPM with a 0.25 radius toolpath and a 0.04" stepover. I've called HAAS and they've told me to adjust setting 191 (rough-medium-finish). The rough setting is certainly the bumpiest. The finish setting is a little smoother but moslty just seems to slow the feedrate. Is there any way (adjusting a parameter perhaps?) that will allow me to smoothly run the machine in this manner?
I think the bumping could be due to a feedrate change switching from circular to linear interpolation, as well as the sudden change in direction. If you are doing this in CAM you could draw a path which would involve fewer changes in direction.
Here is a snippet of code, the tool looping towards the left along the X axis. The gist of the method is to have the tool move 270° at your .250 radius, then change radius to .210 from 270 to 360, enough to provide the .040 advance. Then add a straight line to join the end of this movement with the start of the next 270° circle.
This code sequence has a definite pattern to it that would be fairly easy to copy and paste multiple copies in a text editor, if you had to, then modify one value to advance to each loop.
You can reduce the 'bumping' if you write the program to have tangential changes between the G01 and G03 and you can save a lot of time if you do not do a full circle but just use a semi-circle. You can also save a lot of coding by putting things in a subroutine and making the X incremental.
I subsequently re-worked the program to take out all the air cutting and cut the cycle time in half. The program I posted was before the rework but I can dig out the reworked version and post it if you like.
An open mind is a virtue...so long as all the common sense has not leaked out.
OK so here is how it would look from TrueMill which does write a large program for sure. I made some guessaments as to length and material. the program below is for a 1/2" slot in the center of a 2"x2" block of 1018 steel with a TiALN coated carbide 3/8" EM cutting 1/2 inch deep with a 79degree TEA. I would not program it this way by hand for sure. I am cutting at 589.SFM 6000 RPM 60 inches per minute 1/2 inch deep no coolant and the plunge is in open air. There is a finishing cut on the walls.
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