Fanuc has developed their own brand of 4th axis, with linear motors. These systems offer no backlash, with no worm gear drive. Running at 100 RPM, the DDR system is fast and accurate, as well as being less expensive than traditional worm drive 4th axis systems.
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Fanuc DDR Linear Motor 4th Axis
The DDR's high-speed 4th axis dramatically reduces part cycle times by eliminating the positioning delays of traditional rotary tables and enabling the RoboDrill to machine at the high speeds of its other 3 axes. Its gear-free, zero-backlash linear motors are capable of unclamping, rotating 180°, and reclamping in approximately 0.4 seconds at a table-rotation speed of 150 rpm. Indexing precision is ± 0.0055 degrees (±20 seconds). The DDR's clamping force — up to 220 ft-lbs — is unusual for its size. The 140-mm unit has a maximum torque of 192 ft-lbs and a maximum loading capacity of 220 pounds. A large 40-mm through-hole allows for pneumatic or hydraulic fixture actuation.
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