Johnford SDMC Series – Sliding Column Bridge Mills
The six machines in the Johnford SDMC series of heavy duty sliding double column machining centers feature a moving column and fixed table for unlimited table loads. With standard accessories the Meehanite cast iron machines weigh nearly 150,000 lbs. The machines can be configured to fulfill any large-part production requirements.
The SDMC series can be expanded from 5 meters (196″) up to 20 meters (787″) of X axis travel. A rugged 90˚ bridge with offset Y-axis ways and a 48″ (1,220 mm) wide saddle keeps the spindle center line extremely close to the bridge for rigidity. This design also gives a full 48″ (1,220 mm) span across the Y-axis ways for optimum support of the massive headstock. The bridge and traveling head feature square box ways coated with Turcite and have been designed with diagonally arranged ribs that will help reduce the amount of distortion that can result from years of continued service.
Column traverse is accomplished via two sets of heavy duty Schneeberger linear ways under each column and twin 3.15″ (80 mm)-dia. ballscrews up to 9 meters (354″) long in the X axis. To eliminate whip and vibration, the X-axis ballscrews are fixed and the ball nuts are spun by servo motors. SDMC machines with 10 meters of X travel and larger use twin precision rack and pinion drives. The CNC synchronizes the servo motors to eliminate crabbing effect. Twin Heidenhain glass scales are standard on the X-axis to enhance positioning accuracy. W-axis capability is optional.
A spindle motor of 35 hp delivers power through a two speed gearbox. Tooling is CT-50 (HSK-100), and the machines feature a 40-tool capacity automatic toolchanger.