Slotting mode idea

[digiexchris]

How hard would it be to add a slotting mode? For example, for broaching an internal keyway using tiny infeeds of the cross slide, and moving the carriage left and right.

Example:
https://youtu.be/vk6msRj_tcQ?si=Dp1TDIgzHQsS9AoH&t=264

The way I do it on my 10x32" lathe is by barely touching, then move the carriage left to scrape one cut, then go to the start, feed in another .0005" (inch lathe) or .001" depending on how wide the slot is, and move it again. It would be nice to automate this with the H4, so I can say cut the slot to my X limit, and define the depth of each pass., and with a configurable left and right speed. The right speed can be much faster than the left speed due to the smaller torque requirement.

The difference with the turning mode is that the spindle obviously must not be turning, otherwise the automatic turning mode would do the job.

There is one complication for a blind slot (a slot that does not extend through the part entirely), the chips will pile up in the hole and prevent the tool from cutting the full depth. So I manually stop short as I'm progressing. For example, if my depth of cut is 0.0005, then the next pass must stop 0.0005" short of the left stop. If it's a through hole, that's not required though.

Just an idea. I was going to do a PR and implement it myself, but finding the time to dedicate to that is difficult for me at the moment. And I'm able to slot manually using the left and right moves anyway.

[kachurovskiy]

Hi Chris, great idea, would it be appropriate to move with SPEED_MANUAL_MOVE throughout?

[digiexchris]

SPEED_MANUAL_MOVE works for my case, because I use a large closed loop servo so the torque doesn't decrease as rpm increases, but the closed loop stepper I replaced did suffer from torque drop as rpm increases (as do all steppers). So for my use case, SPEED_MANUAL_MOVE would be fine. Later on though if people have trouble with it, we may want to consider a configurable slotting cut speed and then slotting retract speed can equal SPEED_MANUAL_MOVE.
#define SPEED_SLOTTING_CUT = SPEED_MANUAL_MOVE /2
#define SPEED_SLOTTING_RETRACT = SPEED_MANUAL_MOVE

or something. No big deal though, starting with SPEED_MANUAL_MOVE for everything and seeing how that works might be good enough.