The way in which workpieces are clamped for milling and drilling can make a big difference to a manufacturer’s ‘bottom line’. With this in mind, Birmingham-based Armac Martin, which makes luxury fittings for kitchens and furniture, is now using Chick work-holding equipment from the USA to improve its profitability — and quality.

Salisbury-based 1st Machine Tool Accessories (www.1mta.com), Chick’s UK distributor, provided the equipment — and advice. Armac Martin’s first contract for luxury fittings was eight years ago, and it prompted the company to shift from using manual/CNC turret mills to vertical machining centres from XYZ.

The larger working areas of these VMCs were able to accommodate more components at a time in dual-station work-holding units. Instead of having just one component under the spindle of a turret mill, at least four —and sometimes six — components were mounted in two or three Chick Qwik-Loks on the 610 x 370mm table of a 560 Minimill.

When the first 710 VMC with its 760 x 430mm table was installed, the number of components under the spindle could be increased to eight.

Furthermore, if the parts are sufficiently small, two can be mounted in each jaw, doubling the number of parts fixtured.

While the amount of metal-cutting per component is unaltered, the number of tool changes is reduced by a factor equal to the number of parts on the table. The non-cutting time is therefore significantly less, shortening the overall cycle time per part.

Neil Nally, foreman at Armac Martin, said: “We went down this new work-holding route in 2007 when a customer that manufactures cubicles for changing rooms significantly increased the number of aluminium door fittings it was ordering to 3,000 a month.

"We calculated that by setting up four parts at a time on our first Minimill VMC, rather than just one on a turret mill, and replacing slow manual tool changes with rapid automatic changes on the machining centre, the manufacturing cost per part could be reduced by 20%. It was immediately obvious that this was the way to go, so a second Minimill — along with more Qwik-Loks — was installed within a year.”

Common fixed jaw

Furthermore, a Chick foundation plate fixed to the machine table allows quicker and more-flexible placement of the Qwik-Loks across an array of pre-drilled holes in the plate, thereby avoiding the use of toe clamps and T-nuts to anchor them to the table.

Moreover, the round and diamond pin sets supplied for mounting the clamps onto the foundation plate give a high degree of repeatability and consistency of machining from one batch to the next. Each Qwik-Lok allows two parts to be squeezed simultaneously against a common fixed jaw in the centre by turning a single handle.

Opposing forces are cancelled, and a reliable reference point is provided for machining. In addition, profiles in the Chick jaws create a pull-down action when they close, enhancing the rigidity of the set-up and prolonging tool life.

Sometimes, two or more Qwik-Loks are ganged together on a machining-centre table, so that large components can be clamped.

Phase two of Armac Martin’s work-holding make-over started in the summer of 2014, when the company again called in 1st MTA to advise on possible improvements to some workpiece-clamping arrangements.

Increasing numbers of handle blocks — as well as other window and door furniture such as bolts and catches — were having to be machined on the sides as well as on the face. If such components are held in a standard Qwik-Lok, further set-ups and separate operations are needed to complete each part, lengthening floor-to-floor times and potentially compromising accuracy due to repeated relocation.

The solution provided by 1st MTA was a four-sided Multi-Lok mounted horizontally between a rotary indexing table and a tailstock clamped to the machine table. The complete unit is referred to as a Chick ISS (indexing sub-system), and the first was delivered in August last year (essentially, this comprises four Qwik-Loks, one mounted on each face of a square-section column and using the same snap-on/snap-off interface, allowing jaw sets and other accessories to be interchangeable between Qwik-Lok and Multi-Lok/ISS systems).

After the faces of the first components have been machined on any given side of the ISS, one or two edges of each component (and potentially more) can be accessed after indexing for further operations to be performed, reducing the need for additional set-ups to a maximum of one; 90deg indexing is normally programmed, as workpieces are usually orthogonal, but occasionally components are set at intermediate angles for machining.

Minimised hand finishing

Some drawing tolerances are surprisingly tight for this type of product — down to ±0.1mm, the aim being to minimise subsequent hand finishing and preserve the form of the fittings. Handles installed in venues like the Dorchester Hotel in London or the Waldorf Astoria in Edinburgh can cost hundreds of pounds. Repeatability is also important in ensuring that the luxury items look identical when placed side by side in a top-end kitchen.

Armac Martin turns brass, aluminium, stainless steel and plastic components in a machine shop that dates back to 1918 but now sports the most up-to-date fixed-head and sliding-head CNC turning centres. Of some 6,660 part numbers, about one quarter require some prismatic machining, and the proportion is increasing as fittings become ever more complex.

Of those, 25% can be machined ‘in one hit’, but the remainder require a second operation. To produce these components, equal numbers of parts are secured in both halves of the jaw positions for Op1 and Op2 to be performed sequentially, thereby allowing finished parts to emerge each time the machine doors open at the end of a cycle.

There are now eight XYZ machining centres on Armac Martin’s shopfloor, including a relocatable 2-OP model. All these machines can be equipped with Qwik-Loks, of which there are two dozen on site, although two of the 710 VMCs use the two Multi-Lok/ISSs for most of the time.

Soft aluminium jaw sets — some machined for specific jobs and others used for families of parts — can be fitted to any of the work-holding units. Such jaws allow parts of irregular shape to be held more securely and heavier cuts to be taken when compared with the use of hard jaws.

In conclusion, Mr Nally said: “We are delighted with the performance of our Chick products. Right from the start, when 1st MTA sold us the first units, they transformed the productivity of our milling section. With the latest indexers, profitability has been increased further by avoiding unnecessary set-ups; this has the added bonus of improving the accuracy of our high-value fittings and reducing the amount of hand finishing required.”