4/1/18 Laser Cutter Fire

Identifiers

Date/Time: 4/1/18 11pm

Equipment: Thunderlaser laser cutter

Collaborators:

  • Jake Lee (maintenance, writeup)
  • Thomas Orr (consultation)

Images Album: https://imgur.com/a/VvAG3

Relevant Terms

  • The air assist cone is the blue cone from which "the laser comes out"
  • The elbow joint connects the blue air hose into the air asssist cone
  • The head mirror redirects the incoming laser downwards onto the material on the bed

Symptoms

  • When cutting a thick piece of wood, a large flame consistently flared up from the material up onto the head. This flame was clearly abnormally large.

Diagnosis

  • The compressor was not plugged in - it was previously unplugged due to the sound during filming (the laser cutter had to look like it was on)
    • Note: always place a large sign or indicating a major equipment change or modification.
  • As soon as the compressor was plugged in again, the flame completely subsided, but left significant damage.
    • The elbow joint, made of plastic, was burnt and boiled. A significant leak can be seen. See Figure 1 and Figure 3
    • The aluminum nozzle was covered with a layer of soot.
    • The head mirror had significant soot residue. Note that this may be due to regular usage. See Figure 4

Solution

  • Elbow joint
    • We had a spare elbow joint of the same specifications from a previous nozzle that was damaged. See Figure 2
    • The air hose detaches by pushing down on the white ring and pulling up on the air hose. Much like a bowden tube on the ultimaker 3D printer.
    • The joint can be removed from the cone by using a wrench on the hex nut.
    • Replace the joint.
  • Soot buildup
    • While cleaning this is not critical to operation, consider it preventative maintenance.
    • To remove soot buildup:
      • Wipe off the parts with paper towel to remove the uppermost layer. This should be good enough for indirectly affected parts.
      • The air assist cone can be screwed off of the head.
      • Use paper towel with 99% IPA to remove more soot.
      • Some particularly difficult soot can be removed with a light abraisive, such as fine-grain sandpaper or fine steel wool. I used steel wool myself and it worked very well.
      • Replace the air assist cone.
  • Head mirror
    • Unscrew the three silver spring-loaded screws, taking care not to turn the brass alignment screws. Some tape would work.
    • Saturate the mirror with optical cleaning solution, or 99% IPA.
    • Dry the lens with a microfiber cloth, using a second one to completely dry if necessary. See Figure 5 for the result.
    • Replace the mirror.
    • If the brass alignment screws were changed, realigning the mirror can take time and finesse. Take time to adjust the alignment knobs back and forth to find alignment.

Figures

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5