The dynamics of raster engraving

[AustinT]

I would like to know which scenario is used by the controller . Suppose the laser head is sweeping across and comes to the end of the drawing. There is a certain time - distance where the head comes to a stop and changes directions. Also the gantry moves to a new position during this time. When does the controller tell the gantry to move?
1. does it start moving as soon as the last dot is done and the head is still in motion?
2.Does it move as soon as the head comes to a stop and then both axis accelerate from a stop
3. Does it move as soon as the head comes to a stop and the head waits until the carriage moves before it accelerates?

Hope this makes sense

[Tweakie]

Hi AustinT,

I think I understand what you mean here.

In my case this is all taken care of by the trajectory planner part of the control system. As the X axis nears the end of it's travel it's speed starts to decrease (deceleration) and the planner starts to reduce the available laser power level to match the reducing speed ending with zero speed and zero laser power level. Then the Y axis is incremented for the next line. The planner then increases laser power as speed is increased (acceleration) at the start of the next line until max speed and max available laser power is achieved. And so on.......

I presume most planners work this same way.

Tweakie.

[AustinT]

Thank you for the reply, This is probably a little deeper than I need to think about it right now but I find it fascinating.
Thanks again!

[zax15uk]

In my case this is all taken care of by the trajectory planner part of the control system.

Tweakie.

Tweakie, would you mind refreshing my memory - what control system are you using?

Zax.

[Tweakie]

Hi Zax,

I was referring to the operation of the Impact Engraver / Laser plugin as part of Mach3 using the Tempest trajectory planner.
This is the only system I have studied in detail but as laser cutting depth and speed are so closely related I am assuming that all systems must reduce the available laser power at the beginning and end of raster scan lines otherwise they would cut deeper as the axis slows.

Tweakie.

[zax15uk]

Thanks Tweakie. That was the answer I was looking for 'Mach3 laser plug in'.

Zax.