Conformal Cooling

to slash	скорочувати	to fuse	сплавляти
a rate	норма, доля	a core	центр, ядро
a part	деталь	to eliminate	ліквідувати
to remove	видаляти	a housing	корпус
evenly	рівномірно	to be around	активно працювати
account manager	рекламний агент	durable	міцний, стійкий
molding	лиття, формовка	to withstand	витримувати
sintering	спікання	to bedevil	мучити
to account for	складати	gunk	багнюка
to warp	деформувати	a bump	вигин, гуля

A new way to make molds for injection molding promises to slash cycle times and scrap rates for complex parts. Creating conformal rather than straight-drilled cooling channels in molds removes heat faster and more evenly. “While performance varies with part size and complexity, some companies have reduced cycle times by 60 percent and scrap by 50 percent”, said Augustin Niavas. Niavas is a key account manager for Germany’s EOS GmbH Electro Optical Systems, which makes equipment that builds the molds directly from CAD files.

Injection molding is the most widely used plastics processing technology. The process melts thermoplastics and forces them into a metal mold. After the plastics cool, the mold opens to reveal the finished part. To speed cooling, molders run liquid through cooling channels they drill into the mold.

Direct metal laser sintering builds molds with integral cooling channels layer by layer. Shaping the cooling channels to the part speeds cycle times and slashes scrap.

Cooling channels work great when molding parts with regular features. Add curves and irregular geometries, and manufacturers run into problems. Straight drilled channels cannot follow the contours of the part. As a result, they remove heat unevenly, so operators must wait until the material farthest away from the cooling channel cools before they remove it from the mold. No wonder cooling time can account for up to 70 percent of each injection molding cycle. Uneven cooling can also warp parts and increase scrap rates.

This is where EOS comes in. The company’s equipment produces molds from 3-D CAD data by direct metal laser-sintering, fusing metal powders into solids one layer at a time. The company’s equipment has no problem creating cooling channels that curve, arch, and branch to conform to any shape, because channels are built into the mold as it is formed, not drilled afterwards.

EOS application engineer Siegfried Mayer pointed to a German service bureau, LaserBearbeitungs-Center outside Stuttgart, which was having trouble molding long, thin, cylindrical lipstick caps. It was easy to remove heat from the outside of the part with standard cooling, but it was hard to build an effective cooling channel inside the mold’s core. This produced a hot spot on the cap of the tube. Using conformal cooling eliminated the hot spot and reduced cycle time by more than 60 percent.

Mayer also mentioned a filter housing that had a problem with warpage. “Its core was so thin, it was impossible to create a cooling channel,” he explained. “There were different cooling gradients within the mold. They had to keep the whole mold enclosed until the energy flowed out.” Even then, the processor had to scrap 50 percent of its output. Conformal cooling not only reduced cycle times, but also slashed scrap rates to nearly zero.

While direct metal laser sintering has been around for decades, it was not until 2007 that EOS developed a maraging steel that it could use to make molds durable to withstand mass production.

Conformal cooling also solves a problem that bedevils drilled cooling channels, flow blockage as gunk accumulates at right-angle turns. “We don’t have that problem because we have very regular paths,” said Niavas. “We can also build structures like bumps into the pathway to generate turbulence to clean the channel.”

Дата добавления: 2015-10-30