The total cost for spindle repair/replacement can often exceed the price of the unit itself. GF Machining says its Machine and Spindle Protection (MSP) feature for its Mikron machining centres has been developed to reduce and eliminate these issues.
The MSP feature is comparable to the Integrated Collision Protection capability that has been available on AgieCharmilles wire EDM machines for some time. The system for the wire machines has energy-absorbing, spring-loaded ball-screws on the linear axes and two types of positioning sensors for each axis – a rotary encoder and a glass scale. The system stops machine motion within microseconds if the location detected by the rotary encoder and glass scale for a given axis differs by a predetermined amount (meaning a collision is occurring), before damage occurs, GF explains.
The MSP feature for milling machines uses a mechanical system that enables the spindle to deflect slightly in X, Y and Z axes during a collision. A sensor system detects this deflection and stops machine motion before the spindle/spindle bearings are damaged. The company guarantees that the MSP feature will prevent spindle damage at travel speeds of 12 m/min. or less; an M304 code was developed to cap the rapid feed of the linear axes at that rate. Once a new part program is proven out and it is determined that there will be no collisions during the operation, a subsequent M305 code disables the MSP feature and enables the machine to run at normal speeds.