Force Needed to Break Safety Glass?

This should be one of the CR4 challenge questions...Couple questions: Any *rough* idea on shape or size of the object? Did it just break or did punch clear threw the glass? Size of the hole - Bonus point for a picture. Someone leave something in the machine? Oops, Glad no one was hurt!

The machine was running normal, it was the 15th or 18th part, no one was around, the glass broke but remained intact, that's a good thing, now I know I can stand in front of the machine and not get hurt. Anyway, we don't have a clue as to the size of the object, that's why I asked the question, what force could cause it as we didn't find anything larger then a machining chip. Hint, the supervisor heard a loud bang and went and saw the broken glass, and the machine in a normal cut mode, he pressed option stop and called the engineers.

Hmm...Are you certain is wasn't something impacting the glass from the outside? I once watched a horizontal mill hurl a wrench across a shop and puncture an empty air tank. Scary stuff.....

I was standing talking to my boss once and a fellow worker turned on the drill press without removing the chuck key. It buried itself in the drywall about 2 feet from us. Lovely.

Were any of the parts missing? I'm guessing this is a multi-bed CNC lathe, so if there's a part missing you know the impact came from inside - and if they're all accounted for, it must have been from outside, as suggested above.

Good luck.

Sometimes lathes produce a high pitched screech from the cutting tool - could your mysterious glass smasher be a sound frequency? Opera singers used to demonstrate their high pitch by smashing wine glasses.

Another possibility is thermal differential on both sides of the glass panel. Warm room on one side and cold workshop on the other?

Finally, toughened glass sometimes breaks on its own with no obvious cause - something to do with stresses in the glass during manufacture. Your door will deliver quite a bit of shock to the glass panel each time it is closed and this can build up the stress until the glass cracks.

My neighbour's oven door safety-glass panel 'exploded' two weeks ago. The oven was only 3 months old wasn't switched on and no one was in the kitchen when it happened - Scarey stuff!!!

I once saw a wind screen on a FB111A shatter because a tiny screwdriver fell on it from a few feet above...Later it was determined the glass surface was covered by fine scratches. The other aircraft were inspected and quite a few wind screens were replaced.

In rescue, we use a spring activated center punch to shatter a car's laminated safety glass, then attack it with a battery operated demo saw to cut it from the frame. Time matters....