7 MPa Planning
Planning Your Power Workholding System...
Successful powered workholding does not just happen. Like any other manufacturing process, it must be carefully planned. But that does not mean you need to be a hydraulics engineer to implement a powered workholding system. Designing a system involves nothing more than the common-sense application of a few basic workholding concepts. Applications for power workholding fall into two categories: retrofits to replace and upgrade clamping on existing fixtures; and new fixtures designed from the outset with power workholding. In both cases it is imperative you keep in mind the forces that can be generated by power workholding devices. A single device, small enough to hold in your hand, can generate 26 kN of clamping force. If you are replacing existing manual bolt and nut clamping or toggle clamps, make sure the fixture or machine tool base will withstand the forces.
You should select "realistic" cycle times . . . the shorter the cycle time, the larger the power source required. For example, a pump with a 1/3-hp electric motor may be satisfactory to reach clamping pressure on a given system in three seconds. However, to accomplish the same task in one second may require a pump with a 1-hp electric motor — at a considerable increase in both initial expense and operating costs. So before you specify "instantaneous" cycling, be sure the increased clamping speed is really worth the higher costs for your particular installation. Ask yourself if you can productively utilize the seconds saved. With this in mind, let’s proceed step by step through a plan of attack for designing your system.
Using power workholding does not in any way invalidate the principles of sound fixture design. The 3-2-1 concept as it relates to the location of the work piece in three planes is just as applicable when using power workholding devices as when using manual methods. Workholding devices should be positioned in such a way as to ensure firm contact between the work piece and locating buttons, pins or surfaces. Begin the planning process by asking yourself the following: n What do you want your system to accomplish? n What sort of operation is going to use this system? n What clamping "speed" is appropriate for the speed at which your production line runs?
© Vektek January 2019
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