Helical _ought_ to be fairly easy. But I have not tried it yet.
I know that I claimed to have done so above, but I haven't hooked it up yet.
In theory you just need to add some proportion of the absolute X position to the workpiece angle.
I currently use this HAL component:
Code:
component hobbing "synchronise a rotary axis to the spindle";
pin in float teeth;
pin in float starts = 1;
pin in float spindle-pos;
pin in float spindle-vel;
pin in float A-pos-cmd;
pin in float gear-pos-fb;
pin out float gear-pos;
pin out float gear-vel;
pin out float A-pos-fb;
author "andypugh";
license "GPL v2+";
function _;
;;
FUNCTION(_){
static double pos_ref;
static double spindle_ref;
static int old_teeth;
if (old_teeth != teeth){
pos_ref = gear_pos_fb;
spindle_ref = spindle_pos;
old_teeth = teeth;
}
if (teeth != 0) {
gear_pos = pos_ref + 360*starts*(spindle_pos - spindle_ref)/teeth + A_pos_cmd;
gear_vel = spindle_vel / teeth;
A_pos_fb = gear_pos_fb - pos_ref - 360*starts*(spindle_pos - spindle_ref)/teeth;
} else {
gear_pos = pos_ref + A_pos_cmd;
gear_vel = 0;
A_pos_fb = gear_pos_fb - pos_ref;
}
}
To cut a helical you would need to add:
Code:
pin in float y-pos
pin in float lead
Then in the calculation section:
Code:
gear_pos = pos_ref + 360*starts*(spindle_pos - spindle_ref)/teeth + (lead * y_pos) + A_pos_cmd;
Note that in this example the helix is defined as an angular lead / mm so that the HAL component does not need to know the gear diameter.
In practice I think that I woild have my GUI calculate that, based on helix angle and the gear parameters (because that _does_ know the pitch diameter.
