Advanced Blow Molding
October 2006
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The UMA 20.SH blow-molding machine from Uniloy Milacron has advanced parison suction technology that is designed to economically produce elongated and curved 3D shapes, virtually flash-free, from high temperature engineering resins. The company says the machine can save production time and material waste for the appliance industry in the production of parts such as high-temperature lines and pipes for tumble dryers, washing machines and dishwashers. Parison suction is designed to eliminate parting lines as weak points while delivering superior wall-thickness uniformity. The machine can be equipped for sequential co-extrusion of two-material parisons, enabling molding of components with both stiff and flexible sections.
Modular machine design is said to allow easy interchangeability between suction blow and conventional blow molding, to give users enhanced flexibility and utilization from the accumulator head, especially in the early stages of developing suction blow business. The machine’s dimensions are designed to allow it to support processing of a wide range of products.
In parison suction, mold close comes first, then the parison is pushed out from the melt accumulator into the closed cavity. The parison floats on an air stream generated by a suction fan at the bottom of the cavity. The parison is drawn down through the mold contours, while support air is blown as needed inside the parison from the top to prevent parison collapse. When the mold is filled, sliders close off the top and bottom ends of the parison. The parison is inflated against the cavity walls via needles located at the parison ends. Additional needles can be used to enhance internal cooling/flushing air for reduced cycle times. Parison suction is said to permit exceptionally tall molds, enabling two or more parts to be molded end-to-end in one cycle, then separated afterwards.
The suction process eliminates flash along the length of components, in turn reducing trimming stations and waste handling. Parison suction leaves minimal flash material, just finishing of domes created by top and bottom close off. The machine is said to bring exceptional material utilization and process economies to blow molding of HDPE, PP, high-temperature nylons, glass-filled resins, thermoplastic rubber, and engineered materials. The machine is engineered for a 340°F (171°C) melt temperature.
According to the company, parison suction allows a compact machine to produce parts of exceptional dimensions and geometries for significant investment savings and energy savings. The process enables a smaller head and extruder and lower clamp force than would be required for traditional blow molding of the same shapes.
The machine offers shot sizes up to 1.3 L (1 kg of HDPE) with maximum output of 125 kg/hour HDPE. The unit accepts mold platens up to 700 mm by 650 mm (27.5 inches by 25.6 inches) and provides 1,000 mm opening daylight. An open access, tie-barless clamp unit, adapted from the company’s shuttle machines, permits easy access to the mold from three sides. The 200 kN clamp unit (300 kN optional) enables traditional blow molding, along with suction blow.
A touch-screen machine interface provides 100-point process control, configuration of valve sequences, record of all modified variables, and remote tele-service access to machine screens and sequences. Control-based SPC/QC capability is available as an option. Ethernet communications allow networking and high-speed signal transmission. The machine can be supplied as a complete production system with downstream equipment for automated parts handling and finishing (such as cutting, milling and welding). www.uniloy.com


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