Ask the Expert: Zero-Point Workholding

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by Kip Hanson 

What is zero-point workholding, and how can it help machine shops achieve greater efficiency?

For machine shops faced with frequent prototypes, unexpected rush orders, and high-mix, low-volume manufacturing, changeover times can spell the difference between a winner job and one you would just as soon never see again. It’s for this reason that shops should do everything they can to make machine setups as fast and efficient as possible, and one of the best ways to accomplish this is with zero-point workholding. 

A quick Google search for the term reveals multiple suppliers, among them Jergens, BIG Kaiser (now BIG Daishowa), Gerardi, Schunk, and many others. Almost all suggest that a zero-point strategy reduces setup times by 90 per cent, increases positioning accuracy over traditional clamping methods, and paves the way to lights-out manufacturing. Are they right?

Before answering that question, it might be time to ask another: what is zero-point workholding, anyway? The technology and associated patents behind each company’s products vary, but all are similar in function and construction. (I’ll leave performance claims to the manufacturers.)

It starts with a donut-shaped receiver that can be attached to a subplate or directly to the machine table. With it comes a mating retention knob that closely resembles the pull-stud used on any steep taper CAT or BT-flange toolholder. As with a machining centre spindle, this retention knob slides into the receiver bore, where it engages with a spring-powered clamping mechanism. When the machining operation is complete, the springs are compressed via air, hydraulic, or mechanical means and the knob is released. 

Most systems require at least two receivers and a pair of retention knobs. More are needed for larger workpieces or pallets—sometimes, lots more. This last point is an important one. Because the knobs can be attached to a pallet, vise, fixture, vacuum chuck, or even the part itself, these systems provide great flexibility, and can serve as the basis for a virtually universal clamping solution. 

As for lights-out manufacturing, most zero-point systems come equipped with force-sensing capabilities, as well as integrated blow-off nozzles to keep positioning surfaces clear of chips and grit during robotic loading operations. Each of these is critical to predictable automated machine operation.

For shops still using the all-too-common 20 x 40 machining centre setup with two or three 6-inch machinist’s vises bolted to the table, do yourself a favour. Talk to a few of the companies that come up in your Google search. They’ll probably suggest the following: mount each of those vises to a baseplate, thread some retention knobs into the other side, bolt a series of zero-point receivers to the table, and start enjoying the benefits of far shorter setup times and the ability to break into a job for a drop-in order or prototype at will. 

Zero-point is a no-brainer. SMT

Technical Editor Kip Hanson has more than 40 years experience in the manufacturing industry. He is the author of Machining for Dummies and Fabricating for Dummies, and has written over 1500 articles (and counting) on a diverse range of topics, among them machining, sheet metal fabrication, 3D printing, automation, software systems, Industry 4.0, and the Industrial Internet of Things.

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