Universal clamping systems accurately move parts around the shop floor.
By Charles Bates,
After turning operation, Competitive's parts remain fixtured and travel through three milling operations via a KPT/Unilock workholding system.
Loading a KPT/Unilock quick-change fixture onto a Haas rotary table takes a few seconds at Competitive Engineering.
Its KPT/Unilock system lets Competitive Engineering quickly and accurately move parts from one machining operation to the next.
Universal clamping systems solve two of manufacturing's toughest setup problems: repeatability of location from one fixture or workpiece blank to another and transfer of work from one machine tool to another. They do so through the relative location of a receiver chuck and a mating preloaded pallet. Once this location is established, it repeats for any subsequent operations.
Accurate and repeatable part transfers are especially beneficial to shops with processintense workpieces. One such shop is Competitive Engineering Inc. in Tucson, which makes hundreds of large-volume parts in successive small-run quantities. Typically, the shop performs multiple operations — turning, milling, and grinding — on the same workpiece using several different machine tools.
One of Competitive's jobs requires four lathe and milling operations. By incorporating a universal clamping system, Competitive combines two of these operations. Parts loaded on fixtures run through a lathe operation first, then go through two milling operations done in one cycle with two workpieces running simultaneously.
Universal clamping reduces the time it takes for Competitive to move these parts between different operations. As a result, it saves $7,500 on this job yearly.
For another of Competitive's jobs, universal clamping cut total setup from 10 to 3 hr and production from 25 to 15 hr. Applying a burden rate of $100/hr, the shop nets a gain of $1,700. Prior to the universal clamping system, total setup and production time was 35 hr.
Competitive uses the KPT/Unilock universal clamping system from KPT/Kaiser Precision Tooling Inc. in Elk Grove Village, Ill. The system combines a precision clamping chuck with a clamping knob that holds the fixture or workpiece with up to 11,240 lb of clamping force, achieving a repeatability of 0.0002 in. or better. Central datums provide the ability to transfer a workpiece from operation to operation and machine to machine, while maintaining the same position without losing the datum points.
With KPT/Unilock, a workpiece reference location is established once. Alignments for the chuck are determined from its centerline, and that data is captured electronically and kept in the machine's CNC program. Workpieces then move from a turning center to a grinder or from a machining center to a CMM without re-establishing the reference point. The system is then universal throughout the shop, slashing machine-setup time.
"The KPT/Unilock uses quick change to help manufacturers standardize the workholding process. It achieves interchangeability in workpiece fixturing the same as standard tool tapers and spindles do in toolholding," says Jack Burley, KPT's vice president of engineering.
Because of its modularity, the system adapts to workpieces of virtually any shape or size. Zero-point clamping chucks are available in different configurations for integration onto all types of machine tools, such as mills, lathes, grinders, and EDMs, as well as measuring equipment such as CMMs. Standard pallets are offered in steel and aluminum, or customers can produce their own pallet by purchasing the positioning components. Position and clamping elements can also mount directly to workpieces or existing fixtures.