Bumpers are safety devices on CNC-machining centres, which are directly mounted on moving parts (usually the aggregate head). Bumpers must cover all areas of the machine, which in case of a collision can affect a person. Bumpers need to be padded have to cause an immediate stop of the machine movement in case of a collision. The operator must not be overturned.

Advantages:

• No restriction of the working range for the operator. Especially for alternate loading there is no limiting safety zone in the middle.
• The safety system requires no additional space, as it is attached to the machine.
• A machine accessible from all sides can be relatively easily-realised.

Disadvantages:

• Especially at high feedrate, it is technically difficult to achieve the required immediate stop of the machine without overturning the operator. In the field of validity of the CE regulation the restriction from the working velocity. Thus machines with bumpers exist whose process speed is maximum 25 m/min. Even with higher, technological effort mostly only process speeds up to max. 38 m/min can be reached.

Because of the irrefutable advantages of the bumper systems, two-step systems are being used nowadays with high-performing machines, where bumpers with other systems, e.g. light barriers or laser surveillance are combined. If people are outside of both systems, the machine works in full speed. If one person enters the exterior security area the process speed reduces, the machine comes only to a halt by contact with the bumper.

At older machines you often find a bumper-like safety system with loosely attached metal plates or rods, which will cause an immediate stop of the machine in case of a collision. These systems are not allowed anymore.

See also: SCM Pro-Space, SCM Pro-Speed, HOMAG safeScan