How do I do a downward spiral cut/movement?

[klick0]

I'm trying to do a circular cut that goes down smoothly on the Z axis, i'm sure there's probably a term for this but I don't know what it is. Just to be clear, I want to move in circles while slowely moving Z down.

I've looked at drill g-codes but don't know exactly how they would work like this, perhaps the threading ones, not sure though.

Really I don't do arc's much, so perhaps there is a way with arcs, but is this the appropriate way? I know I could do this in small line segments, but that's less then ideal. Looking for the correct approach.

Thanks,
Ross

[Geof]

It is called helical interpolation.

The code is simple enough, if the machine has this option enabled, I do not know about other machines but it is a standard feature on Haas machines.

G91 G03 I. J-.5 Z-.1 F40. L5

On a Haas this will spiral down on a counterclockwise circle with the center located -.5 away from the start along the Y axis moving down Z distance of 0.1 for each circle to a total depth of 0.5.

[klick0]

Thanks so much, I use linux emc, i'll try it on it later.

[rfrenzl]

I don't know if EMC2 will implement a helix in this fashion (A single command). I seem to recall that you can not use a single G02/03 command to do a full circle in EMC2 (or was that TurboCNC?). I've written a number of routines and this just happens to be one of them. What I've done is set up several parameters in the file and then let it run. It uses a WHILE loop and 4 arc commands (one for each quadrant) with a Z component. Just edit the file for your specific cut and load it to EMC2. About the only thing that may be missing is the ability to supply any XY location for the center. Right now, it is set to have the center at 0,0.

The result is that I can cut a hole of any specific diameter including compensation for the cutter, or a disc of a given diameter. It is actually the same code but one is offset to the inside of the path, the other outside. You can not use tool compensation in G02/03 (at least that is what I remember). I've had good luck with this approach that I've not even looked to see if any of the new version of EMC2 will do helix cuts like they do with a Haas.

If you want, I'll post my code for you. I am not home so I won't be able to do anything until later today. The file is pretty short and easy to use. I think it has 25-30 lines total.

Ron