2/15/1999 | 3 MINUTE READ

Hydraulic or Electric

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UBE Machinery (Ann Arbor, MI) has long been known by people who are involved in plastic part production as a manufacturer of highly reliable, long-lasting injection molding machines.


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UBE Machinery (Ann Arbor, MI) has long been known by people who are involved in plastic part production as a manufacturer of highly reliable, long-lasting injection molding machines. There are 37 UBE machines at Saturn's Spring Hill facility being used to produce body panels. Last year Visteon Automotive Systems named UBE a preferred supplier for molding machines larger than 300 tons of clamping force (machines that could be used to produce parts including bumpers, interior trim, and instrument panels.).

UBE has focused on toggle-type machines rather than ram-type injection molders. Benefits of using the link system, compared to the ram, are that there isn't a need for as big a hydraulic cylinder for clamping force, which leads, in turn, to energy efficiency and speed. By way of example, there is a line of machines UBE offers, the UM Series, which are offered in 500-, 720-, 1,000-, and 1,500-ton clamping sizes. The pressure needed to operate these machines range from 500 to 2,000 psi, as compared with 2,500 to 3,000 psi for hydraulic ram-type machines. The die closing, opening, and pressure build-up are said to be up to 20% faster.

Of course, that's in the hydraulic line-up. There is, UBE's Taku Tawarada admits, a trend toward the implementation of electric machines instead of hydraulic machines.

So UBE is now offering a series of electric toggle-style machines. There is a series of 35- to 385-ton machines built by Niigata Engineering of Tokyo that are private labeled as the UBE ULTIMA UN Series for North American applications. UBE's parent company in Japan and Niigata jointly developed 720-, 950-, and 1,100-ton electric machines. A 950-ton AC electric servo machine is to be installed in May 1999 in North America for an automotive application; Tawarada says that it is the largest electric molding machine in the world.

The argument for electric versus hydraulic is somewhat more compelling than that of toggle-style versus ram-type. Among the benefits that Tawarada cites are:

  1. The servo motors are energized only when needed. Hydraulic machines need the pumps to be running all the time. Consequently, there are energy savings of as much as 80% with the electric machines.
  2. The electric machines provide a better environment. There aren't oil leaks. The electric machines are quieter (e.g., no pumps).
  3. Electric machines tend to be more consistent. Setup correctly, this means better repeatability. And done right, repeatable accuracy.
  4. The cycle time is shorter for electric machines. Hydraulic machines use oil, which means that there is time spent actuating valves and other components. With the electric machine, it is a matter of sending a signal to the motor and the equipment starts running.

But perhaps not surprisingly, there is a bit of a delay in all of this. Electric machines are more expensive than hydraulic machines.

Tawarada points out, however, that the prices for electric machines are coming down. Apparently, electric machines are finding wider use in Japan than in the U.S. because of the higher cost of energy there. But Tawarada says that UBE recently sold an electric machine to a U.S. OEM that was interested in the accuracy and cleanliness characteristics of the machine. "They didn't even talk energy," he notes.

UBE isn't turning away from hydraulic technology. In fact, it is now offering a skin-insert molding process called DIEPREST for hydraulic machines; the software for the electric machines is still under development. This process permits the production of plastic parts with a fabric, vinyl foam, film, or skin insert, right in the mold. This means that it isn't necessary to, say, mold a piece of interior trim and then adhesively bond a fabric to it.

Tawarada says that in-mold laminating processes have been around for a while, but a difficulty has been the high scrap rate that tended to result. With DIEPREST, the approach is to input six values related to the part and the materials into a controller. Then a trial shot is performed based on that input. Once a part is produced and inspected, information related to the part quality is input, which is used to recalibrate a new recipe. One interesting aspect of DIEPREST is that the equipment isn't dedicated to the process alone; conventional molding can be performed, as well.


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