High-grade multi-colour styling, complex mouldings with two or more components, decoration, printing, back injection of textiles and foils, injection moulding with assembling… Multi-component technology has undergone rapid development in recent years: ever new variants of the processes, plastics and material combinations have been added for ever new applications in automotive, medical and communication technologies, in the electronics, packaging and sports industries. New applications have emerged that were unthought-of only a few years ago. We in Sumitomo (SHI) Demag take the credit for having made important contributions: The Multi has proved its mettle in hundreds of manufacturing facilities: With innovative, user-specific solutions that combine a high standard of moulding quality with a high level of productivity.
An overview of processing techniques
- Bi-injection – simultaneous or sequenced injection of two components into one cavity
- Core-back technique – injection of two components into one cavity one after the other, the space for the second component being accessed by shifting a valve
- Transfer technique – the preform is transferred manually or by means of a robot into the second cavity or second machine
- Rotary technique – transfer is by axial or vertical rotation with the rotary function provided for in the machine or in the mould
- Sandwich technique – different plastics are laminated together to produce a skin-and-core structure.
However different they may be, most multi-component techniques offer similar advantages:
- Cycle times are signifi cantly shorter
- Setting-up of the machine is simpler and faster compared to two “mono material” machines
- Operations are simplified
- Assembly effort is reduced
- Quality assurance and reproducibility are enhanced
- Less floor space is required
- Energy consumption is lower
The range of applications
The term “multi-component technology” denotes a variety of methods employing specially designed mould and machine features. Basically, they all use two or more injection units to inject two or more materials onto each other or in between each other. If injected onto each other, the components will either form an integral moulding (say an automotive taillight) or a split moulding (say, a closure with a seal ring). If injection is with a shot in between the other shots, referred to as the sandwich technique, a “laminated” structure is obtained, for instance, with a soft skin and a hard core (typically, regrind may be used for the core and virgin material to provide a high-quality surface).