Blow forming through injection mould

Processors who want to integrate functional channels into thin- walled parts, e.g. cable channels or pipes, have to use a multi- stage process such as welding or bonding together of parts that had been previously injection- or blow-moulded. Now, an optional process, an integration of gas-assisted injection moulding with an inflation process, is gaining interest. The idea behind the process is to further inflate the channel being generated by gas injection. Although parts manufactured by gas-assisted injection moulding are hollow, only a very limited gas-bubble cross-section can be achieved. The process combination with inflation makes greater demands on the mould technology than pure gas-assisted technology. But this method can produce large channels and if required very lowwall thicknesses. The thin-walled region, as common with injection moulding, can be as complex as required, and has a high surface quality. This clearly distinguishes these parts from extrusion blow moulding, which imposes strict limits on the formation of 2D regions. GITBlow thus extends injection moulding with new possibilities for functional integration and part design. Two variants, one- and two-stage processes, are available, and differ in their process sequence, thermal management and design freedom. Energy-efficient process In the single-stage process, a preform geometry is first developed. To this end, a channel is produced in the melt-filled cavity by the injection of nitrogen. After a gas holding time, in which the gas performs the function of the holding pressure, the gas pressure is reduced again. To inflate the part, the injection mould cavity can be enlarged by means of a hydraulically operated core puller. After, or during the cavity enlargement, nitrogen is again injected into the existing gas bubble, enlarging the channel by stretching the residual wall of the gas-assist-generated part. The temperature of the residual wall is still in a thermoelastic to thermoplastic range of the materials being processed. The gas pressure is maintained for a few seconds to allow the final part to be deformed. Geometrical advantage The two-stage process is characterised by the transfer of the gas-assist preform (with or without intermediate heating). In a gas-assist process performed in a similar way, the mould is opened and the preform is transported to a second, larger cavity using a turntable. With the mould open, the temperature profile in the corresponding part regions can be optimised for stretching by means of infrared radiators, moved into the mould by a handling system. In the closed mould, a preform is then inflated to form a finished part, while the other is already being manufactured in the other cavity. A significant advantage of the twostage process over the single- stage process can be seen in the greater geometrical freedom. While the latter only enables the cavity to be enlarged within certain limits, the two-stage process allows almost any conceivable geometrical possibilities; an undercut was therefore deliberately provided in the prototype part, generated by two splits in the injection mould. The prototype molds were subjected to a series of tests, intended to prove the process' practicability. Both parts were deliberately designed so that standard injection moulding, fluid-assisted moulding and blow moulding processes were out of the question for their manufacture. Networked components The tests were carried out on an injection moulding machine by Arburg GmbH + Co. KG, Lossburg, Germany equipped with a completely new control system from Phoenix Contact GmbH & Co. KG, Blomberg, Germany. This control allows all components of the system like machine, robots, two gas-control modules, radiant heaters, removal system, temperaturecontrol units, turntables, safety equipment and conveyor belts to be net worked via bus systems. The GITBlow process seqShop Women's Sneakers by Brand