MHI Injection Molding Machinery Inc., which sells Mitsubishi presses, is touting a newly patented process that molds with multiple cavities, filling one part at a time. The process is called SCS, which stands for “sequential cavity separation.”
SCS allows parts with vastly different dimensions to be made using the same mold. The technology opens and closes hot-runner valve gates to fill first one part and then another — controlling the fill velocity, pressure, position and hold time of each cavity independently.
Originally, MHI used mold cavity pressure to control the proc-ess, but after beta testing, the firm discovered that not all customers had that capability. The company went back to the drawing board and developed a machine control version of SCS to allow for standard injection molding.
MHI of Bensenville, Ill., listed several advantages of sequential cavity separation:
* The clamp tonnage required to fill one cavity at a time is much less than when multiple cavities are filled at the same time. That means a smaller machine can be used. One example: automotive wheel covers with a surface area of 188 square inches per part. Normally, that part would require a press with 1,200 tons of clamping force, but MHI has molded the parts successfully on a 610-ton machine. The press size must be large enough to mold the largest part in a family mold.
* The same principle means a family of parts can be molded on one press and one work cell, such as all four major components of a laptop computer. That ability dramatically cuts costs compared with using four presses and the required auxiliary equipment.
* Material costs can be reduced by eliminating over-packing conditions often seen in multi-cavity molding, according to MHI.
* SCS also can reduce or eliminate problems with color matching, since all parts are molded on the same machine.
* The technology can be used for low-pressure molding of textiles onto automotive parts. On a door panel, for example, the machine first molds a cloth insert for the upper section, then pull back the slides that provide a seal-off between the main panel and the cloth area of the door panel. Then the substrate is injected around the cloth insert.
MHI said customers are running 12 Mitsubishi presses with the SCS option, with 11 more presses on order for delivery later this year.
Applications include automotive parts, office equipment and toilet seats and lids, although an MHI spokesman said the company would not identify customers.
Tel. (630) 693-4880, fax (630) 693-0915, e-mail [email protected]
