The hottest debate within the injection moulding industry is which technology is best – all-electric machines, or conventional, hydraulic driven machines.
Perhaps the answer to this question lies in a combination of both. The new Eclipse series from Sodick (Sodick Plustech, Ishikawa, Japan) is based on this concept.
The design is said to be the first non-toggle, servo-driven, direct pressure clamp on the market. Servo actuated ball-screw technology is used for clamp open and close, as well as ejector forward and ejector return. Once the clamp meets the preset ‘kiss-point’ a pneumatic locking mechanism is set, and clamp pressure build up is generated via a hydraulic accumulator and pump.
This clamp design also features extensive use of linear guide technology, which results in extremely accurate clamp movement (a straightness specification of 5 microns per 100mm of travel). The 80 EH machine 88(US ton) uses 10 gallons of oil, a sharp contrast to the 70 gallons of oil used by typical hydraulic clamp machines in that size range.
The result is significant energy reduction (40% reduction from conventional hydraulic machines, and within 7 to 10% of all-electric machinery).
Another key advantage to the Eclipse design is the easy integration of specific moulding functions such as core-pull. Unlike all-electric machines, the Eclipse series integrates the core-pull function into the machine, thus eliminating a need for a separate core-pull unit. Another unique aspect of the Eclipse series in the injection unit. Like the clamp unit, the injection unit, combines servo technology with hydraulic accumulators to provide the user with a greater processing window. High injection rates and pressures (500mm/sec; 33,930 psi on the 80EH with 3.8 ounce shot size) are standard. Unlike conventional in-line injection units, the Eclipse series unique V-style design separates the functions of plasticising and injection.
The screw section of the V-style design has two primary functions. The first is to meter material into the injection chamber (plasticising achieved via a AC servo motor), and secondly, upon completion of material metering, seal the injection chamber, via positive mechanical pressure from the hydraulic screw touch cylinder, thus eliminating any back flow of material. After the exact amount of material, as determined by an encoder, is metered into the injection chamber, the injection plunger injects the material into the cavity. This method eliminates the need for a check valve, the primary source of material degradation, and shot weight inconsistency.
The company claims that for close tolerance lens, medical, connector, electronic, and automotive applications, this is an ideal machine.