Working in an exclusive relationship with Bosch-Rexroth, the two developed a hybrid drive for the machine's closing system. The drive is optimized to handle the transition from rapid motion (mold close) to force motion, and is fully adjustable and stroke-independent. Maximum force build-up is available immediately after the switchover. Even with all of this force, the unit is a quiet 68 dB.
The Eblow is the commercially ready version of an electric extrusion blowmolding machine that Bekum displayed at the K show in 2007.
Karlheinz Moser, technical director at Bekum, said the company's customers asked Bekum for an electrically powered machine that offered more speed, precision and ease-of-use than other electric extrusion blowmolding equipment already in the market. The heart of the new clamping unit is a C-shaped base frame, similar to those used in injection molding machine manufacture for years. Moser, as it happens, came to Bekum in 2007 after more than two decades at injection molding machine maker Engel.
A C-clamp, although requiring more iron than a standard clamp, also has fewer parts, so that these Eblow models are priced about the same as models would be with conventional clamping systems, added Moser. Significant, he said, is that platen parallelism on these new machines is less than 0.1 mm over the entire stroke, better than on comparative machines without such a clamping system and freeing processors to attempt more complex parts. The position accuracy of the shuttle also is tight at about 0.01 mm. Top and bottom calibration is offered.
The Eblow at the K was the first manufactured by Bekum in its Berlin headquarters. Five models are available, sized with mold platen width running from 350mm to 700mm and clamping force available ranging from 10-24 tons (100-240 kN). Although called an "electric" machine, it does have a hydraulic transmission between the electric drive and the linear axis for the closing system. Gary Carr, national sales director for Bekum's U.S. operations, told MPW that this transmission helps convert the machine's rotary motion into linear motion, and so helps reduce the load on the drive side and the ball screw drive.
On the business front, the manufacturer's managing director, Michael Bamberger, said that Bekum is realizing about €55 million in annual sales, with 300 employees across its four sites (Germany, Austria, Brazil, and the U.S.). The company has an installed base of better than 16,000 machines. —Matt Defosse