bill.french wrote:Ok, since I don't have a functioning laser yet, and have never used one, hopefully I am understanding what is happening.
Normally, the laser is turned on, then the head starts moving, then the laser is turned off. This causes extra burning at the start and end of a path as there is a delay in the commands. The laser is on the whole time the head is moving. You can compensate for the extra start/stop burnings with "lead ins" which are the little ears I am seeing on the shapes?
..but the leadins bring their own issues, such as the cosmetics of the ears.
So, now you have your laser set up to turn the laser on more in time with the motion, and as well, you are pulsing the laser on and off very quickly while the head is moving, which gives you an added benefit of more effective power, which results in more vaporization and less burning.
Am I in the ballpark?
That's pretty close. In the old way of doing stuff, the laser would get a command to turn on, then there would be a lag (because of the relatively slow command processes), the head would start to move and do its stuff, then it would stop at the end, another pause, and then the laser would receive the command to turn off. The pauses are only a few tens of milliseconds, but that is enough. Those pauses cause a wide kerf when stopped which look like drill holes. That was why I would use the quarter circle lead in and outs. Even still, putting heat into the material at the start and end would cause a minor disturbance to the cut. This way makes no discernible impact.
This way of doing things make sure that the stepper motors receive the stepper motors receive pulses before the laser receives a signal to turn on and make sure that the laser is off when they stop, thus no drill holes.
Basically you are right in the last part... the pulses are short enough that things vaporize and don't have enough sustained heat in the material to cause the solids to burn to any appreciable extent. This is amplified by the fact that we can get nearly double the power in the first millisecond as the laser is rated for.
I can't wait to cut some acrylic. That stuff used to sustain a flame on the bottom of the piece as it cuts which used to mar the bottom of the cut. I am willing to bet that the flame will not sustain with this method... it usually didn't ignite for a second or two so I think this will help.
You can hear an audible "buzz" as the material is being cut. I am sure that is due to the shock waves that form as the material explodes off the surface. The laser makes a bit of a pop too as the plasma forms, but is much louder when I cut something.