Smoke gets in your eyes

A project log for DIY Space Grade PCBs

3D print circuits using silver ink and ceramic substrates to make high performance, multilayer, fine line < 3mil, PCBs

chuck-glasserChuck Glasser 06/28/2016 at 01:170 Comments

If you go to a hacker space and use a laser cutter, all the magic behind the curtain goes without notice. To get a visceral understanding of what's involved, take a ceramic plate, fill it with wood chips, say a pack of popsicle sticks, pile them high, set it ablaze, right there in the sink. In a few moments, say thirty, you'll have as much smoke as pours out of a laser in the first few milliseconds. To be accurate, it's not the laser that's smoking, it's the workpiece that's in the focal point of a death ray.

So, behind the curtain your going to find a big blower and flue system sucking away your general ignorance.

Wait, there's more! The smoke is different than that you have seen from a flickering campfire late at night. The smoke is more like that from a blow torch, a blast of smoke propelled by a death ray. It's very impressive. Of course, the idea is that the smoke system is effective and the nieve go about their day making their gizmos without a care of the physics involved.

In this case, I would prefer to remain ignorant. Here is what it takes.

The exhaust plenum took a huge effort. Someday I'll have to powder coat it black.

Typically, most cutting is done on a replaceable hexagon grating with sufficient depth that the beam has diverged from it's focus when it reaches the bottom of the cutting chamber. In this system the workpiece is rigidly mounted to the cutting table, so air must be drawn across, rather than down.

The giant gaping maw of the exhaust system is just visible above the edge of the vacuum hold down.

Smoke condensation from the underlying MDF used in the vacuum platen.

Cleaned up with a bit of IPA.

The cover sheet used to support the ceramic green tape is still intact. Can it be that the power level of the laser was perfect? Doubtful. If the energy was not absorbed, and the MDF beneath it was not cut then it must have been reflected back. Interesting! Do not look into laser with remaining eye!

You can see a small tear in the material in the lower left corner. Ignore the divot on the right side. Too many things going on for two hands to coordinate.

The shiny side of the tape. Tear is very visible. The system was out of focus. A great opportunity for a new series of DOEs (Design of Experiments)

Later this week the MDF will be replaced with a refractory Perlite vacuum plate that will eliminate the smoke and surface contamination.