In order to comply with Federal NHTS standards, our customer – a tire manufacturer, operates machines to measure and record precise forces at failure in a variety of destructive tests. The test must be accurate to the nearest 1% of the measured force, which could be up to 20,000 lbs. Traditionally, hydraulic cylinders were used for this type of application, however there were environmental and safety regulatory concerns overseas that drove the customer to consider electro-mechanical alternatives.
The criteria we had to meet included:
- EM cylinder would be required to handle the 15,000 lb. force
- Maintain the required +/- 1% accuracy of measured force
- Compact design to physically replace the hydraulic cylinder
- Availability of a variety of actuator mounting options to accommodate various machine concepts
- The servo drive must interface with the customer specified control, utilizing the existing software and programming
By using the Parker ETH125 actuator, PX gearbox and MPP motor, combined with a Compax3 servo drive, the customer completely eliminated the environmental concern. At the same time, they greatly reduced the complexity of safety compliance by eliminating hydraulics altogether. We could maintain a force consistently and accurately by modulating current in the drive, measuring the error with loadcell and looping to the force setpoint from the control.
While the ETH cylinder has outstanding power density for a ballscrew actuator, all EM cylinders have larger footprints than hydraulics of similar force ratings. However, the ETH does offer an industry leading variety of mounting options, which allowed the customer the convenience and flexibility to accommodate the larger actuator into the design when replacing the hydraulic cylinder.
– Far exceeded the 1% force control requirement. Ultimately, the customer achieved an accuracy of +/- 2 lb. on loads exceeding 11,000 lbs. This outperformed their previous (hydraulic) machine, making this the most accurate machine of this type that the customer had ever built
– Environmental; no hydraulic fluid
– Simplified safety standard conformance by eliminating pressurized liquid “stored energy”
– Very little maintenance required
– Ability to utilize the existing control, program and code from previous machines, despite introducing an entirely new technology
– Positioning was simplified and more repeatable
– No energy required to maintain pressure when machine is not in use
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