To keep a condensing lens from being directly affected, in a laser beam machine, even if protective glass for the lens is broken by spatters entering inside from the outgoing port of a machining nozzle during machining.
Between the condensing lens and the machining nozzle in a machining head 13, a first and a second protective glass plates are arranged successively from the nozzle side at a space apart; an assist gas to be supplied to the nozzle is partially branched and introduced through one directional valve 18 into the space enclosed with the two protective glass plates; and the state of the gas supply to the space is then monitored by a pressure sensor 19 and the signal is outputted to a controller 14 so that damage to the first protective glass plate is detected.
KUBA KAZUKI
MOMOI HITOSHI
TAKADA KIYOSHI
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