View Full Version : First move problem

07-29-2013, 01:47 AM
When I do a 4 axis flip tool path with a .127 mm tapered ball mill and less than .025mm step over I get a problem with the first move showing up randomly hundreds of times in the Gcode . I like to used a high z home so the cutter does not hit the part during flip. If I leave the Gcode as it is, every few cuts back and forth I get a home move. For the time being I am setting a 2 to 3 mm z home move in madcam ( just enough to clear the stock ) and changing the Gcode to have the home move on the flip be higher .

Any one want to try and see if they get the same type of output?

The cutter is a 3.175 shaft with a 5 degree taper each side 15 mm long cutting section the tip diameter is .127 with a radius of .0635

Also madcam outputs the A180 flip on the same line after the x,y,z call for the cut on the new side so the z slowly moves down as the flip is happening , some times just missing the part. Should the A180 flip not be before the line to move the x,y,z to the new location for the cut on the second side?

07-30-2013, 10:11 PM
It turns out I have over 5 thousand first moves in the post. This is causing all sorts of little problems .
Earlier today I was cutting and getting all sorts of random plunges in the cut on the reverse of the A axis . Took me a while to figure out they were left over Z3 moves from the first move section it worked fine with that home position on the A0 but on the A180 .... Problems

Now I am editing the whole first move section out in the post

I hope some one gets the same results so that joakim can fix it soon.

08-05-2013, 01:49 AM
Which post processor are you using?

08-06-2013, 01:17 AM
We were using EMC 2 4 axis. I think we were using a first move change that Dan had recomended here a few weeks back, for some one that was having a problem with the cutter not moving out of the way on a rotary. My computer since had a problem and I lost our post change so we started from scratch with me just added home moves to the post by hand where needed. But it would be nice to know if this is a bug that exists or something to do with the way we changed the post.

This post

08-06-2013, 02:28 AM
I haven't seen that homing thing, on the other hand we are using different setups.
What happens if you are using the post called LinuxCNC? There are some differences in those two.
You need to add the fourth axis config, but it's not difficult.

Dan B
08-06-2013, 06:11 AM
Please post the post you are using. It's probably an easy fix.


08-08-2013, 01:21 AM
I had a computer problem and lost our mod to the madcam post change that we did . Though I do believe we did exactly as Dan mention. If I did a step over of more than 0.025 mm with a cutter of .127 mm then all was normal it was only when the step over was smaller than this. So it must be a quirk in madcam. I will try to redo the post prosessor set up some time this week end and see if I can get the same results.

Dan B
08-08-2013, 02:03 PM
You may have 2 issues here. The issue with the A180 flip is probably just due to the lack of the FIRST_MOVE section where you can control how the tool approaches. The other issue may be a bug. I'll create a path with your tool and step overs and see if I can replicate it. It may be specific to the tapered tool, as I don't use tapered tools, and haven't seen this bug before.

I'll get back to you...


Dan B
08-08-2013, 02:08 PM
Can you post the file? I can"t make my test case misbehave. If you prefer, you could send it to cncdanb@gmail.com