Ingersoll Machine Tools (Rockford, Illinois) faced a formidable challenge in manufacturing North America’s largest five-axis gantry-type milling machine with a working envelope comprising a width of 8 m, a length of 62 m, and a height of approximately 2.5 m. But from the very start, it was clear to everyone that it would be equipped with position encoders from HEIDENHAIN because of their exceptionally good repeatability. Both the linear and rotary axes feature HEIDENHAIN encoders, which are responsible for the position feedback and have to guarantee the accuracy of this powerful machine. This was a new record both for Ingersoll and HEIDENHAIN: each of the X axes with lengths of 72 m is equipped with an LB 382 C linear encoder—the longest sealed linear encoder ever produced by HEIDENHAIN.
World-class linear measurement
These distance-coded reference marks on the HEIDENHAINLB incremental linear encoders simplify the homing process, particularly on large machines, and the reference position is found after no more than 80 mm of traverse. Engineers from HEIDENHAIN Corporation, USA, supported Ingersoll in installing the two 72 meter long linear encoders. Each detail up to the intermediate seals and scanning units had to be perfectly right. The housing was mounted with the aid of a dial gauge for flatness and parallelism within 0.1 mm. The scanning head, too, required very high precision during installation because the scanning gap of 1.5 mm ± 0.3 mm had to be maintained over the entire 72 m length. A calibration of the machine by an independent calibration service using laser trackers certified the work with outstanding measurement results and confirmed the required accuracy of the gantry machine.
Exceptional accuracy even at the spindle
The Cybermill’s spindle head rotates at 16,000 rpm with 50 kW of power. This results in machining with very high precision at a cutting speed of 25 m per minute—a very high speed for a machine of this size. Two absolute angle encoders from HEIDENHAIN are dedicated to angle measurement of the spindle: one on the C axis (joint between the turret slide and the spindle head), and the other on the B axis (joint at the tool, for angular movement).
Large parts with high dimensional accuracy
This extraordinary milling machine is operating at “W Industries” in Detroit, Michigan, originally a vendor for the auto industry, and has enabled it to greatly expand its range of services. Since last spring of this year, W Industries has been using its new gantry-type milling machine, christened “Cybermill,” to manufacture very large parts for the space and aeronautical industry, for example to produce dies and molds for connecting wings to the fuselage. However, it's also getting contracts from the regenerative energy industry, for example for molds for turbine impellers of wind power stations.