They are machined from aluminium or lithium billet for motorsport race cars and high-performance road cars, as well as from cast iron for military vehicles.
Similar to the original automated system installed in February 2007, the latest configuration is based on a bigger Hermle 5-axis vertical machining centre, a model C 32 U with 650 x 650 x 500mm axis travels, reflecting the fact that brake calipers have become larger during the past decade.
Supplied by Geo Kingsbury, UK agent for the German machine manufacturer, the C 32 U has been equipped with an Erowa Robot Easy that stores twelve 210mm diameter pallets, which are transferred to and from the working area by a horizontally travelling load/unload arm.
When the first cell was installed, it allowed brake calipers to be produced in two operations totalling about eight hours. Total cycle times were halved compared with the former process of producing them in four, five or six operations on 4-axis, horizontal-spindle, twin-pallet machining centres. Handling times, floor-to-floor times and work-in-progress were also drastically reduced.
Alcon’s production engineering manager Brian Cutler comments: “The first automated system from Geo Kingsbury for machining calipers proved so successful that we had no hesitation in following a similar route this time. All of the production benefits apply to the second cell as well.
“The Erowa pallet pool is positioned a little differently, in front of the machine rather than to the side, but it is set back far enough for the operator to have unrestricted access to the working area. This is important, as much of the day shift is spent setting and proving-out new prototypes, with the remainder of the 24 hours devoted to running production batches.”
As on the previous Hermle C 20 U, the latest full 5-axis machine is equipped with Blum laser tool breakage monitoring and length setting, Renishaw part probing, an 18,000rpm HSK 63 spindle, 80 bar through-tool coolant and a 117-position tool magazine. Comprehensive swarf management has been provided, consistent with unattended production from light alloys.
Designs are produced in SolidWorks and Open Mind’s hyperMILL CAM software is mainly used for creating the cutter paths prior to program transfer to the Heidenhain control fitted to the Hermle C 32 U.
Brake caliper production is a natural application for 5-axis machining, as Alcon discovered 10 years ago. Compared with 4-axis metalcutting, it is not only faster but also inherently more accurate, as approach angles can be adjusted to allow shorter and hence more rigid toolholders to access awkward areas of a component. Tolerances down to 13µmicrons are held easily, according to Mr Cutler.
Additionally, 5-axis capability gives Alcon’s designers more flexibility when developing products, as they can include complex surfaces and holes at compound angles, without increasing the number of set-ups or unduly lengthening cutting cycles. Consequently, in respect of the modern design of its products, the company has had a lot of positive feedback from the market.
Geo Kingsbury www.geokingsbury.com
Alcon Components www.alcon.co.uk
