View this article by Siegfried Mayer on the Plastics Today website. 

Growing numbers of injection molders are discovering the advantages of using conformal cooling channels that follow the shape of the cavity and core, reach hot spots, and promote temperature uniformity in the plastic materials being molded. These molders are seeing striking results: shortened cycle times, improved plastic part quality, and—above all—cost reductions.

Even so, many manufacturers, some of them with long experience in the industry, still think conformal cooling is too difficult and too expensive. They think these things because both used to be true.

Up until four or five years ago, cooling channels for molds were (and mostly still are) drilled in secondary machining operations, and they followed straight lines. If more cooling was needed than a simple channel could provide, toolmakers might create an insert that had channels with baffles or helix baffles. In rare cases where more intricate cooling channels were unavoidable, toolmakers split the mold into segments, milled matching half-channels into the segments, and soldered the segments together to produce channels that didn’t follow straight lines. The milling was costly, and the mold life was shortened because the solder often deteriorated over time.

But recently, new technology has made conformal cooling channels both easy and affordable to produce. Direct metal laser sintering (DMLS) can create parts with highly complex external and internal geometries, “manufacturing” the cooling channels along with the tooling inserts—in a single process.

A cool solution

DMLS is an additive manufacturing technology that produces parts from 3D CAD models by melting metal powder with a focused laser beam, layer by layer, in strata as thin as 40 µm. The first DMLS material available to moldmakers was a bronze alloy ideal for molds and inserts used in low- and medium-volume production runs. The addition of EOS MaragingSteel MS1 (a prealloyed ultrahigh-strength steel in fine powder form) has made it possible to create tooling for high-volume applications as well. Both these materials are readily machined to create the desired mold surface.

Not only does DMLS eliminate the need for secondary drilling, but it also can be used to make optimized cooling channels that closely conform to the surface of the mold cavity, or that reach crucial hot spots that conventional channels can’t. In addition, the channels can be formed in shapes that add to the volume of coolant flow or that generate turbulence to carry off more heat—making the channels far more efficient and mold temperatures more uniform.

Still, some toolmakers and injection molding experts will hesitate to adopt a new technology because they think they’re doing fine with the old ones. They’re already making profits using proven methods; why replace something they know so well with something they don’t?

There are several convincing reasons. Discover them on the Plastics Today website. Siegfried Mayer is application engineer and Augustin Niavas is business development manager tooling for laser sintering systems manufacturer EOS GmbH (Munich, Germany).

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