In the field of injection molding, back-injection technology refers to a specialized processing application. The production of decorated molded parts involves the utilization of a thermoplastic carrier in conjunction with a decorative material. As part of the process, the ornamental material, which may be a film or a cloth, is back-injected with plastic.
Process and sequence of back-injection technology
Back-injection technology involves the ornamental material being introduced into the open injection molding tool in the beginning of the process. When the mold is closed, the decorative material is clamped between the side of the injection molding machine that is responsible for closing and the side that is responsible for nozzles. Some options to this include electrostatic adhesion or fixation achieved by the application of negative pressure within the cavity.
In the following step, the plastic is pumped into the cavity. At various points throughout the tool, the thermoplastic is dispersed and combines with the substance that is used for decoration. When it cools, the plastic becomes more solid. When this is complete, the component can be extracted from the mold. What you will receive is a plastic component that has been decorated.
There is no need for glue to be used in order to link the thermoplastic and the decor, which is one of the advantages of the method.
Back-injection technology process
The procedure is frequently constrained by the mechanical and thermal sensitivity of the material that is being used for decoration. An further drawback is that the decorating causes the molded object to lose heat at a slower rate than it would otherwise. It is common practice to employ combinations of back-injection technology and low-pressure injection molding or thermoplastic foam injection molding (TSG) in order to circumvent these constraints. The two techniques are more friendly on the ornamental material because they allow for a pressure distribution that is both flat and homogeneous, and they also result in less distortion of the components.
Application of back-injection technology
In particular, the automotive sector makes extensive use of back-injection technology in a range of different applications. Components that are typical of this business and that make use of films and fabrics as ornamental materials include the following:
- door side panel,
- A, B and C pillar trim,
- Dashboard,
- front wall paneling,
- trunk cover,
- Cable duct cover and
- Hat rack.