A large amount of machining is required to produce the pneumatic cylinders, valve assemblies and other automation equipment manufactured by Univer at its Bradford factory. Many components are awkwardly shaped and difficult to secure for machining, so the company relies on Chick work-holding equipment to ensure rigid clamping as well as short set-up times.
Around 70% of Univer’s standard products — and all of its special systems — involve machining, as well as kitting and assembly. The automation equipment is supplied to distributors or directly to manufacturers of specialised machinery for the automotive, gas, packaging, brewing, computer and other industries. Moreover, on-site machining sets the company apart from its competitors, with a recent expansion seeing the addition of R&D facilities for special projects.
Production manager Brian Hodgson says: “We have come to rely on Chick products to underpin our work-holding requirements throughout the factory. It was about 12 years ago that we read an article on Chick Multi-Lok tombstone-type work-holding and subsequently saw it demonstrated at a MACH show in Birmingham. At that time, we were introducing a new pump component that was machined from 316 stainless steel, and it was taking us 3.5hr to set up all four faces of our existing tombstone. The Chick Multi-Lok is four- to five-times quicker to set. Change-over takes typically 45min, so our machining centres are more productive and unit manufacturing costs are lower.”
Mr Hodgson adds that components are held more securely in the Chick Multi-Lok from Salisbury-based 1st Machine Tool Accessories Ltd (
www.1mta.com) than in conventional fixtures, resulting in better milled finishes, especially when machining stainless steels that include Duplex. In one instance, 1.6Ra is achieved on a gasket surface by milling alone, avoiding the expense of a subsequent grinding operation. The absence of vibration also prolongs tool life, leading to further savings.
There are currently three Chick Multi-Loks in use at Univer’s Bradford factory. Two are mounted vertically on rotary tables on the pallets of a 2APC Doosan horizontal machining centre, while the other is indexed horizontally on a Haas VF6 vertical machining centre fitted with the manufacturer’s own rotary indexer and a tailstock.
Clamping repeatability
On each face of a Multi-Lok, there is a single- or dual-station jaw set that uses Chick’s QwikChange snap-on/snap-off interface. Round and diamond location when mounting onto a Chick foundation plate gives a high degree of clamping repeatability and consistency of machining from one batch to the next. If the components are small enough for dual-station jaws to be used, more-productive options are available, such as accessing extra faces in a single production cycle and minimising the number of tool changes needed to machine a given number of parts.
Ideally, for maximum productivity and extended periods of unattended machining, components are set up on all four faces of a Multi-Lok. However, there are occasions when Univer uses only two opposing faces — such as if components are longer than the tombstone width and overhang the sides. Another reason for loading only two faces is if stainless steel is being cut and the machine tool does not have laser-based tool-breakage detection. Halving the number of components limits the potential for material wastage if a cutter failure goes undetected. All four faces are normally used if solid or extruded aluminium or brass is being machined, as cutter life is longer and any material wastage less costly.
Machinable aluminium QwikChange jaws are used across the three Multi-Loks, as well as on eight Chick Qwik-Lok work-holding arrangements at Univer. Such jaws allow parts of irregular shape to be held more securely and heavier cuts to be taken than when using hard jaws. “The soft-jaw option is financially viable for quantities of more than 500 per month,” says Mr Hodgson. “If a batch falls below 10-off, we generally hold components in hard jaws. The choice depends on how frequently we have to repeat the manufacture of the part. We are prepared to accept longer and perhaps more frequent set-ups in hard jaws if the overall cost is less than producing dedicated aluminium jaws.”
The Chick Qwik-Loks at Univer have the same quick-change snap-on/snap-off jaws as are used on each face of a Multi-Lok, allowing considerable flexibility across the different fixturing platforms. With dual-station jaw sets, turning a single handle causes two moveable jaws to be squeezed from either end against a common fixed jaw at the centre, cancelling the opposing forces and providing a reliable reference point.
Furthermore, profiling in the Chick jaws creates a pull-down action when they close, thereby providing added clamping security. Sometimes, two or more Qwik-Loks are ganged on a machining-centre table to allow large components to be clamped.