Laser cutting machine bellows : FR or Flameproof ?

With the development of laser fibers and the increase of the general level of performance in laser cutting technologies, laser cutting processing has become widely used in the manufacturing industry. The protective bellow is often overlooked but plays an important role in the preservation of the machine.

What are the bellows for ?

Bellows on a machine tools are set up on Linear Motion (LM) guides :

To prevent accidents involving the operator
To protect the LM guides from dust, particles and liquids.

Dust and particles affect the precision and lifespan of the machine in the long run. Therefore it is important to keep those parts clean with a protective cover.

FR or Flameproof ?

Because of the nature of the process, Laser cutting machines are prone to fire hazards. The laser beam (from 2 to 10kW) generates enough heat to melt or vaporize matter, allowing it to cut, pierce or engrave various kind of materials (such as wood, paper, cloth, glass, aluminum, steel, etc). However not all materials can be processed safely and extra care has to be given to avoid the following hazards :

Toxic fumes (PVC, PTFE or coated carbon fibers can emit toxic fumes when processed with laser)
Fire hazards (cardboard, polystyrene foam, HDPE, etc, catches fires when processed with laser)

Bellows are potential combustibles if the machine catches fire and therefore need to be carefully selected to prevent such accidents.

Fire Retardant (FR) materials are sometime chosen for their low cost, but Flameproof (FP) materials are an absolute must. Indeed, both FR or FP bellows are designed to prevent the starting of a fire. However, while a flameproof bellow does stop the fire propagation (in case it has been caused by something else like processed materials), a FR bellow cannot offer the same protection.

Sparks and holes :

When used to process metal, gas are used to blow the molten metal out of the kerf (to obtain a clean finish), creating incandescent sparks. Those sparks can hit the bellows, burning through the FR fabric to create tiny holes. Once pierced, the bellow will less efficient to protect the LM guides potentially causing more frequent downtime.