Auto focus on the fly

qa

#1

So correct me if I am wrong. One of the capabilities of the GF that I am most excited for is the Autofocus feature. I’m super stoked to engrave on wood with heavy grain, or other irregular objects.
On the main page they say this “The lens moves as the laser travels, so you can cut & engrave materials that are curved, uneven, or irregular.”

My question is how irregular?

For example if I was planning on engraving the top of a Lego piece (pre GF). I would set two paths. on that hits the top of the nubs, and one for the bottom/root. Because as the laser travels the change in z would be almost instant. Does the GF need this step? Does it automatically break up the work into layers?

It seems to me that the GF would be limited by how fast the Z can adjust. So, when the GF is rastering how steep of a slope can it compensate for? Does it scan the whole piece and develop a 3D Z tool path?

So many questions on how they pull this off. I haven’t seen much conversation about this feature in the forums. Anyone else thought much about this?


#2

ABS (What legos are made out of) doesn’t laser very well… its messy since it melts…alot.
I’m pretty sure I read that it can handle the sloped sides of say an ipad, but I doubt it can jump from a lower surface to an immediate higher surface like the pips on a lego piece.


#3

With the accuracy/resolution specified, it seems that for a drop off, the laser could pause while focus is obtained and gantry is positioned correctly for start of next cut? Obviously it would not be as practical for a “randomly irregular” surface. Didn’t Dan state that the system is making a 3D map of the object to be lasered before the run - or am I imagining things (it’s possible lol).

In the camera world we have depth of field, which for a very brief definition is the range of what’s in suitable focus and what’s not. I’m sure their is something similar in the laser world but don’t know what the verbiage would be. What is the typical range in distance the laser is typically considered “in-focus”?


#4

It’s up to you. You can engrave and cut things with an out of focus laser, if there is still enough power to ablate it in a satisfactory manner. What is satisfactory? You tell us :slight_smile:

I can’t find it now but I seem to recall that the Glowforge did a pass over the material before the cut to measure height, rather than trying to do it during the cut. If that’s the case then sudden vertical changes shouldn’t pose any problem

The macro cam has a resolution of 0.05mm and they can measure distance to the material within 0.13mm, so following the contour of a lego block should be well within the Glowforge’s technical capabilities


#5

So in the demo video they show it engraving a macbook. which has a general curve to it.

So you could measure the variation as a ratio, for instance 1/10. or 1in vertical for 10in horizonatal.

The ipad would have a pretty low ratio or at least smooth. but the lego would have an infinite ratio (1/0). It would be cool to know what the GL max ratio would be.

And i agree with @Sam, i remember them saying the height was measured before hand. thats where i got the z-tool path ahead of time idea.


#6

For the lego case, the easy solution is a two-pass engrave, where you engrave once at the top and once on the lower portions. The actual angle that it can trace depends on the x-speed.