Manipulators – Part 4 of 8 Articles
The Qualifications of a Manipulator
Manipulator qualifications fall into three categories: fixed, controllable and programmable. When choosing a manipulator, make certain it is the correct choice for the job.
An overqualified manipulator may lead to unnecessarily high costs with respect to training, operation and maintenance or demand special skills for programming, operation and maintenance. In addition, an overqualified manipulator may be faced with early obsolescence
|The Qualifications of a Manipulator|
by Plasma Powder and Systems, Inc.
Manipulator qualifications fall into three categories: fixed, controllable and programmable.
The turntable can be used as an example of the three types of manipulator. An operation spraying a part at a fixed turntable speed can function with a turntable powered by a standard, AC motor/pulley drive.
If the turntable speed is fixed during the spraying of a part, but needs to be changed for different parts, a turntable driven by an adjustable belt drive, a DC motor or Variable Frequency AC drive is suitable.
If the turntable speed needs to be changed during the spraying operation, or if the speed needs to be changed for each part being sprayed, a programmable drive is usually needed.
A similar situation exists with gun drives. One operation is able to operate with something like a modified garage-door opener that cycled the gun across a panel as it was indexed after each pass (a fixed gun manipulator).
A number of roll coating operations use modified machine lathes where the traverse rate of the gun is fixed during the spraying operations. Traverse rates are set with change-gears standard in machine lathes and are, therefore, a controllable gun manipulator.
Programmable manipulators are often used in coating operations where motions are modified during the coating operations or where emotions are more complex than a simple X-Y motion.
Many years ago, programmable controllers, in general, were based on impressive mechanical systems. Outstanding examples of mechanical control systems in other fields include the Jacquard Loom, the Norden Bomb Sight and the cam-driven sewing machine.
The invention of the transistor, just about sixty-five years ago, made it possible to provide electronic control systems that are both cost-effective and reliable. Therefore, programmable manipulators are now being used in place of simple controllable manipulators.
An example of this is the Programmable X-Y traverse gun manipulator. It is often found in job shops that support the aerospace industry. Early versions of this manipulator used mechanical trips for programming the traverse limits while modern units are based on point-and-teach programming.
As stated, these modern programmable systems are cost-effective and reliable. Still, care needs to be used when selecting such systems. Will special operator training be required? Will the supplier maintain a stock of spare electronic modules? If repairs are required, will the spray shop be able to make the needed repairs? In the days of mechanical systems, shops were often able to make repairs with standard hardware store components. This is evidenced by a number of mechanical manipulators that are still in operation after many years of service. With many electronic-based manipulators, in-house repairs are no longer possible.
When choosing a manipulator, make certain it is the correct choice for the job. An overqualified manipulator may lead to unnecessarily high costs with respect to training, operation and maintenance or demand special skills for programming, operation and maintenance. In addition, an overqualified manipulator may be faced with early obsolescence.
The next and fifth article in the series addresses “The Programmable Manipulator”.