Extrusion value for any XYZ coordinate within a move?

[jazbaatbadalgaye]

Let us assume that we start at 0,0,0. When I give G0 X5 Y5 command via YAT, I can see the total extrusion value for that move through the DDA debug output. Now what I am interested in is the extrusion value at any arbitrary coordinate within that move. i.e. what would be the extrusion value when, say x = 3 y = 4. How can I get that value?

[alankilian]

@jazbaatbadalgaye I don't think your extruder should ever get to x=3,y=4 during that move, but anyway...

I think the extrusion is linear for the entire move, so if you have a move that's 20 units long, and you are 5 units into the move, you've extruded (5/20=0.25) of the whole amount of extrusion.

So you can calculate the total move distance and the distance traveled to your point and make a fraction.

[jazbaatbadalgaye]

@alankilian That makes sense but shouldn't the extrusion be more while acceleration, linear during the constant speed phase and less during the deceleration phase, to get uniform extrusion throughout the move? If its linear during accel. and decel wouldn't it cause under-extrusion and over-extrusion respectively? Hope I am making sense.

[dc42]

@jazbaatbadalgaye extrusion is linear with respect to distance moved, not linear in time. The extrusion speed accelerates and decelerates in step with the movement speed.

[engikeneer]

@dc42 is that still true when pressure advance is used?

[dc42]

@engikeneer said in Extrusion value for any XYZ coordinate within a move?:

@dc42 is that still true when pressure advance is used?

No, the commanded extrusion is modified when pressure advance is used in order to get the actual extrusion closer to being linear in distance moved.