One classic example of a precisionapplication is an indexing table with several stations for machining or assembly. Precision gearboxes and servosystems fit well when the table is relatively heavy and needs to be accurately positioned and when high-speed operation is not as important.
In this case, the gearbox is being used simply for accurate torque multiplication. The servomotor’s top speed of 3,000 to 5,000 rpm is not required at the load, so the gear reduction ratio and corresponding torque multiplication can be large. This allows a relatively small servosystem to handle the task. The servosystem might even use its built-in indexer to control the motion based on discrete I/O signals from a PLC, or even a simple selector switch, depending on the required level of automation.
Another example of a gearbox application is a high-speed pick-and-place device, such as part removal from an injection-molding machine. The cycle time of these machines is often critical to meet production quotas, and the designer typically wishes to remove parts as quickly as possible after the mold opens.
The moving arms of the pick-and-place device are designed to be as lightweight as possible, but inertia mismatch can still be a factor. The gearbox can minimize the mismatch so that the pick-and-place mechanism is extremely responsive.
The PLC in this example might be much more involved in controlling the motion, commanding moves with pulse and direction signals. In some cases, the PLC also passes recipe tuning values to the servodrive when the motion profile or the picked-part’s inertia changes.
Precision gearboxes and servosystems can be used to meet a wide range of automation challenges. Machine builders should purchase the required components from a knowledgeable vendor who will stand behind their products. Using online selection tools can simplify the choices, although the system will require tuning after installation. When properly designed, specified, and tuned, these systems provide accurate, repeatable results for many years.