New Mold Cooling Approach Eliminates Surface Blemishes

Applications are growing for an interesting process for improving the surface finish of cosmetic parts.

Called BF Mold technology, the system replaces cooling channels with a space under the mold cavity that is packed with steel balls and flooded with a heating/cooling medium. The ball-filled space provides mechanical support and is placed extremely close to the cavity.

Raimund Au (Sanit) and Klaus Ehlig (Wittman Battenfeld) in front of a display panel of BF Molded parts.

As a result, the tempering media is very close to the mold cavity and is evenly distributed below its entire surface. That means that the whole area below the cavity is heated and cooled.

It works best with “Variotherm” heat/cool molding in which a mold is heated during injection and quickly switches over to cooling after the cavity fills. That allows easier filling of thin walls, glossier surfaces, better replication of mold detail, and reduction of stresses and weld lines.The Tempro plus C 2/160 VARIO multi-zone temperature controller was specially developed for use with the BFMold system.

It works well for relatively flat parts, such as TV frames or cellphone covers.

Wittmann Battenfeld acquired the patent rights and now licenses the technology for a one-time fee. “Ball-filled mold” technology was developed by the Plastics Institute in Ludenscheid, Germany.

One customer is a German company called Sanit which uses BF Mold technology to produce a designer frame with a high-quality surface. The designer frame is part of the flush panel assembly for a water closet.

It’s an alternative to expensive glass panels. The frame is produced by a variothermic process, with the integration of BFMOLD technology in the mold. Sanit says the new approach eliminates surface defects such as blushing and weld lines.

Wittman Battenfeld showed two other applications at K2010.

In heating with BFMOLD technology, the downtimes are used for heating up, so that cycles are normally not lengthened. It also enables fast cooling. With large, flat spaces, a homogeneous cavity wall temperature can be generated to provide an extremely fine surface texture. Sink marks are prevented and joint lines and warpage minimized through an extended holding pressure phase. The process window of parameter settings is wider, and process optimization can be achieved quickly. In this way, the newly developed technology.

 

About Doug Smock

Former Chief Editor at Plastics World and Senior Technical Editor Design News
Consumer Goods, Cooling/Heating, Europe, Injection Molding ,

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