When UK-based Valeo Climate Control in Swansea, Wales, set out to reduce mold changing times on its three 1,000-ton presses, it achieved dramatic results. Downtime went from about 3 hours to about 30 minutes. However, the company still wanted to achieve greater flexibility, and it needed even speedier mold changes to do that. So it turned to the use of magnetic platens to further reduce mold change time.
Valeo Climate Control is one of the 80 manufacturing units around the world operated by the French-owned automotive supplier Valeo SA. The facility in Swansea makes heating and air conditioning systems for carmakers including Rover, Opel, Saab and others.
Going from 3-hour to 30-minute mold changes was accomplished by streamlining mold-handling procedures and with the use of a pair of cranes. As the search for further setup reductions continued, Valeo began looking at mold mounting, or clamping, as a place to save time. When Valeo was looking in early 1994, magnetic platens had not yet been used to hold molds of up to 9 tons in 1,000-ton presses. The existing applications were for smaller molds. However, the company knew that magnetic platens had been holding large die pieces for many years. So Valeo chose to try a magnetic platen made by Tecnomagnete of Lainate, Italy (Troy, Michigan, in the United States.).
Using the magnetic platens, the mold is lowered in and set against the platen using a standard locating ring. The platen is magnetized (in less than two seconds) and the hoses and lines are connected. The procedure is then repeated for the other mold half. There are no technicians moving over, around, and in particular, under the machine to tighten clamp bolts. One technician can do the procedure, but Valeo uses two for speed.
For added security, after both mold pieces are attached, Valeo's procedure calls for closing the mold and re-magnetizing the platens. There was some initial wariness over holding large molds magnetically until it was understood that the magnetism is only switched on and off by an electrical pulse. It is not maintained by electrical power. Therefore, the mold will not fall if the electricity fails because magnetism, not electricity, is holding it on. For an extra measure of safety, technicians also attach safety chains to each mold, which would limit a fall to a few centimeters if a mold became detached. In more than five years of frequent mold changes, however, there have been no problems with magnetic platens holding the molds.
The Tecnomagnete platens, which attach to standard holes in a machine platen, were retrofitted to Valeo's three 1,000-ton machines on site. Valeo subsequently installed two 1,300-ton machines. The supplier, Engel, incorporated the Tecnomagnete platens and integrated the magnetizing procedure into the machine controllers. In the retrofit, the only interface is a relay into the safety cut-off circuit of the machine. If the integrated proximity switches in the magnetic platens detect that the mold is not properly against the platen, the machine stops. Tecnomagnete platens take 52 mm of mold height on each platen, or 104 mm in total.
Valeo's present average mold change time is down from 30 to about 16 minutes. The goal is to be around 10 minutes. Valeo is already able to change a one-cavity, 4-ton mold in 8.5 minutes. Part of the bottom line results is that Valeo is gaining roughly 30 moldings per change in a plant that does 12 to 15 changes per shift among the five machines. The same two technicians accomplish all those changes. Because of these improvements, magnetic platens are now specified on every new machine purchased by Valeo.