Making the Vigotec safe

Lasers
1

I am thinking about laser safety on my L7X.

Let me know what you think and/or alternate ideas…

Some thoughts on laser diode module exposure modes [plan to test these]:

  • The laser focus is 10mm off the surface and it’s not likely that a beam is reflected upward to a user?
  • The laser is low power therefore it’s unlikely a reflection will penetrate a clear acrylic cover above and a couple of inches away from the laser head.

The design concept I am thinking of is:

  • The side frames are solid material (colored acrylic) the top is clear acrylic with a hinge and interlock switch. A shield above the laser module may be effective protection.
  • There is a plate above the laser module shielding light from reflecting upward.
  • Put NO microswitches on the bottom edge of the frame of the unit. They shut down the lasers 12V when the frame is lifted off the surface or tilted.
  • I am thinking of a 12V relay whose contacts are in series with the lasers 12V and also indicate with a flashing light when the laser is enabled. [not as fail-safe as inline switches but good enough?]
  • An Estop switch on the main 120V input. [not really an Estop, do not directly stop steppers, but good enough since everything in this machine is very low mass?]

Alternate sensing:

  • Tilt switches [never had good luck with these at low voltage]
  • Arduino-managed accelerometer and 12V relay (complex & not really fail-safe?).

Laser Sheild
Here is a simple method some use to shield the laser module on CNC units. I cannot see any glaring practical flaws using this on a portable machine if it is combined with the interlocks above. Do you see any use cases where this could be unsafe??

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Notes:

  • I could use filter material on the entire enclosure but that would not meet my goal of low cost.
    This material is expensive: 250nm to 520nm Laser Shielding | J Tech Photonics, Inc.

  • I plan on an enclosed cabinet with an evacuation port that connects to a fume filter box that is about the size of a small vacuum cleaner.

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2

The thing I don’t like about the side sheld/box approach is how it traps the smoke in the lens chamber. Even with an air assist nozzle blowing sideways in there it’s not going to blow the smoke outside the chamber.

The only solution to this I can think of is a double walled side shield/box where a vacuum was pulled on the space between the 2 walls so the smoke was pulled out and most air was pulled down through the fins of the heatsink around the laser. Hey, you could probably remove the fan on top in this case if there was sufficient radiant heatflow for anything getting hot on the pcb driver board up there.

3

Instead of switching a few amps of power with the lid switches why not switch the PWM? IIRC the laser PWM needs a 5V signal level to turn on the LED so if there is a pull-down onboard the diode driver board you can use a much lower power switch for turn the laser off and a quick release of the lid will allow the project to continue with little effect on the engraving.

4

Good idea but turning off the pwm doesn’t really make the unit safe as the laser itself could be stuck on. Removing 12v does that.

5

I’m going with the type where there is a shield on one plane above the lens. I think when combined with side frames it will be safe.

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