Hydraulic workholding solutions

Whether for machining cumbersome workpieces, or machining operations that require precision finishing in a production environment or machining center, hydraulic vises and similar workholding systems offer a highly flexible and stable fixturing solution that can speed up work cycles and also cut down on waste.

In many situations today the machine shop can simply not afford to apply traditional mechanical vises and other clamping devices to hold workpieces in place. These include instances where it would very difficult to manually mount and apply the necessary consistent-and-even clamping pressure workpieces, thereby risking movement or vibrations that could render workpieces into scrap.

“In the past, one machine shop was having some difficulties machining welded beams that were perfectly straight—using a mechanical vise setup,” says Larry Johnson, president of Special Machined Components, Mason, Ohio. “Due to the size of the workpieces, mechanical vises were tough to load and control. I understand that they had to scrap quite a few of the beams during the first two or three months of production, perhaps 50 of them. However, at our shop, thanks to our hydraulic workholding system,

I don’t think we’ve had to scrap 10 workpieces over a 12-year period, certainly a huge improvement over the mechanical vises.”

The hydraulic workholding system that Johnson’s company installed in 2001 was a six-vise stacked ProHold model manufactured by Planet Products that is used by some job shops for welding and riveting as well as machining operations. One of the problems of using a mechanical vise for large or heavy workpieces is that it is difficult to set up the machine for consistent clamping. For example, if a powerful 300-lb. operator is working the first shift, then a much smaller man takes over on the next shift, there is likely to be a difference in the clamping power between the two shifts.

Those who are using hydraulic vises are quite often applying them to production runs, where the consistency of clamping grip and ease and quickness of operation are most important. You simple set the pressure, and it holds each production workpiece the same way.

“Our hydraulic vises have a pre-set, automatic clamping and release mechanism,” says Larry Johnson. “You just open or close the valve on it and the jaws open and close.”

The powered opening allows a 400 lb. part to rest on the vise and always open. This typically would not happen with a spring return vise.

“These beams we are machining weigh about 400 lbs. each. To use a mechanical vise you’d have to use a hammer to go around and make sure they’re tight enough. With the hydraulic vises, we’ve got much better control, and no concerns about operator errors.

Using the ProHold hydraulic I’ve never had a problem with workpieces coming loose. The hydraulic system is the only way to do it. It’s more expensive, but pays for itself,” explains Johnson.

For more information, visit www.planet-products.com.