Gleason Corporation manufactures automated Phoenix II 275G gear grinding machines that create fine finishes on surfaces of bevel gears. To ensure product quality, the company’s machines must be well lubricated and not overheat during grinding processes. The gear grinding machines produce the best finish on the gear surfaces because a flow of lubricating coolant is precisely directed at the grinding wheel’s point of contact with the gear at all times. Gleason design engineer George Chamberlain said, “Positional accuracy of the coolant heads is necessary because you have to flood the point of contact with coolant so you don’t burn the part. The coolant also provides lubrication and flushes away the grinding debris created from the process.”
Gleason Corporation’s Phoenix II 275G gear grinding machine creates a fine finish on the mating surfaces of bevel gears that have already been rough cut. When the company needed a replacement actuator to position the machine’s heavy coolant head, it turned to Tolomatic for a solution.
In the original design of one of the company’s machines, an electric actuator moved a 50-lb manifold of coolant jets in small increments as the grinding wheel was consumed and changed dimensions. However, the original motor/actuator used in the machine sometimes lacked the necessary torque to move the heavy coolant manifold. When the actuator was overloaded due to increased friction in the system, it would stop and sometimes lose its position. “This would cause the machine to send a message to the operator to investigate the situation before the start of the next cycle,” added Chamberlain. “The machine would indicate a positional error and then you would have to re-reference the position of the coolant.” This was non-productive time that reduced overall productivity for some Gleason customers.
One solution would have been to replace the original actuator’s stepper motor with a more powerful servo motor, but the actuator Gleason was using didn’t allow such a replacement. In addition, there was insufficient space inside the machine’s grinding chamber to accommodate a motor that was physically larger or more powerful
Chamberlain investigated Tolomatic actuators and learned that they could accept a more powerful servo motor. He also learned that the RSM rod-style screw actuator was more powerful and extremely compact. “The most important factors in choosing the Tolomatic brand actuator were its overall torque and its compact design,” said Chamberlain. Most rod-style actuators have an inline screw that is driven by a motor. Tolomatic’s RSM actuators feature a reverse-parallel motor drive where the motor is mounted on the side of the actuator and drives the screw through a toothed belt and pulley system. He noted, “Every other actuator we looked at had the motor bolted to the backside of the actuator, making the units too long to fit into our design window.”
The Tolomatic RSM rod-style actuator series is designed for high performance, high thrust, durability, and compact mounting flexibility. With thrust capability ranging from 70 to 7,000 lb, even the smallest 12-in. model had enough power for Gleason’s application. The product line also features a black anodized extrusion designed for rigidity and strength. It also comes with ball screw, roller screw, or acme screw options, and it has robust internal guide bearings to support the screw assembly throughout its stroke.
The Tolomatic RSM rod-style actuator designed for Gleason Corporation was customized to meet Gleason’s gear grinding specification.
Tolomatic’s in-house design department can modify its standard products to meet special needs. In Gleason’s case, modifications were made to the RSM actuator, including:
Sealed actuator: The mating surfaces of the motor mount, drive belt housing, and inspection lid had to be fully gasketed to prevent spraying coolant from getting into the actuator.
Optional motor mounts: The actuator was supplied with two motor mounting flanges to accommodate different brands of servo motors. This gave Gleason the flexibility to match either a Fanuc or Moog servo motor to the production demands of its customers.
Secondary lead screw bearing: The end of the actuator was fitted with a secondary support bearing to accommodate the high radial loads due to drive belt tensioning.
Custom front flange: The ends of the rod was fitted with a custom mounting flange to mate with Gleason’s coolant head assembly, allowing drop-in compatibility during manufacture or in the field.
Additional sensor: In the unlikely event the drive belt broke, Gleason wanted the machine to have a feedback loop to avoid process problems associated with the coolant header being out of position. This was accomplished by installing a toothed rotor to the end of the screw and mounting a Balluff sensor. The sensor reports the position of the screw within 0.1 mm and signals the machine if a belt failure occurs.
The heavy, C-shaped coolant manifold on the Phoenix II 275G gear grinding machine is moved incrementally by a Tolomatic RSM actuator as the circular grinding wheel wears away. This keeps the coolant flow precisely directed at the point of contact with the gear face.
Since incorporating the Tolomatic RSM actuator, there have been no reports of coolant system or machine fault issues. “We also have a retrofit kit available for machines in the field with the old style actuators. The Tolomatic actuator has pretty much eliminated all of our problems with the coolant heads,” added Chamberlain.
Filed Under: Actuators, Machine tool industry + subtractive manufacturing, Linear motion • slides, Motion control • motor controls