Fire in the hole

[George Elston]

Well it finally happened to me. In cutting a large order of 3/8" plexi today, the plexi caught on fire. We caught it quick enough to no have much damage but it did get hot enough to damage a part of the aluminum screen that is in the cutting table, soo time to replace. There is someone here that sells cutting table screens but I can't remember who, (need web address). I was also thinking that with a complete machine shop, CNC routers etc. I might be able to make my own and get back up tomorrow instead of waiting for delivery. Anybody have any plans or ideas?

[Jim Good]

Mike has vector grids and can take care of you.

Jim

[Richard Rumancik]

You could consider an "eggcrate grille" from aluminum. It might get you by. Not sure what spacing you want; these are often .50" or so grid which may be a bit smaller than you want. Sometimes you can get larger spacing. A heating/ventilation supplier may stock something suitable. (To see a picture search on Google images for "eggcrate grille".)

[Joe Pelonio]

Why did it happen? Were you using air assist, and if so, how much pressure?

[George Elston]

Why did it happen? Were you using air assist, and if so, how much pressure?

Not sure, no air assist, BUT, I suspect a small piece of paper from a previous cutting job (found the burned piece) caught fire and ignited the rest of the plastic above it, which was already hot due to the extensive cutting.

[Jeanette Brewer]

Here's the link to Mike Null's cutting grid: http://www.stl-laser.com/laser-cutting-grid.html

[Joe Pelonio]

Not sure, no air assist, BUT, I suspect a small piece of paper from a previous cutting job (found the burned piece) caught fire and ignited the rest of the plastic above it, which was already hot due to the extensive cutting.

If your machine is set up for air assist you should use it. I cut a lot of acrylic and it does blow out any flames as it cuts. The only problem I have had was when I had transfer tape on a piece that went past the edges of the vector grid, and when it cut close to that edge it caught fire. I was watching and
caught it quick and have learned a lesson from that.

[Jim Huston]

I didn't set the laser on fire BUT.... I cut some delrin one day (3/8") and was in a hurry. Took the piece out of the laser, removed the parts I needed and put the scrap on the bench. About a half hour later someone came into the shop and pointed out that it was smoking inside. I went upstairs to the laser room, opened the door, and had flames to the ceiling! Put it out with an extinguisher. No damage to paser or computer but had to take everything out of the room, repaint, clean, and spend a lot of time cleaning the leaser, printers, computer, etc. It appeared that the scrap was still hot when I laid it on the bench and had smoldered for some time before starting flames. We do some welding here also and are VERY careful about sparks -- someone in building for at least an hour after cutting, welding or grinding but had never thought about the laser room being a fire hazard -- DO NOW!
They say confession is good for the sole - I have never sharded this story, mostly because I was embarrassed, but sometimes it is good to tell these things as it MAY help someone else avoid a problem.
JimH

[Phil Salvati]

We have set several fires as well. The air assist is the way to go!

The worst time....fortunately our machine is still under warranty... we replaced just about everything in the box to remedy a bad tracking situation. Universal was very patient with us and sent new parts over night every day!

Turns out the fire in the box melted the rubber wheels on the lens carriage! Go figure!

Anyway... I think Universal carries the honey comb material to go in their cutting table. Engravers Network in Texas has been very helpful to us when we needed replacement parts.

Phil & Gayla

[George Elston]

Actually, I ordered a cutting table from Mike today, and will limp by with a peg table I cut on the cnc machine till it arrives. Luckily there were three of us in the shop, one of my guys came and got me when he smelled it, but I will pay closer attention in the future.