Additive Manufacturing - Applying foaming technologies in the injection moulding process usually means compromises in the surface quality. A special structure in the casting forms enables systematical heating and cooling. This geometry can be realised via additive laser melting.
Foaming technologies in the injection moulding process bring vital advantages. However, the process that results in material savings and speed gains is also associated with a loss of quality on the surfaces of the parts. Until now, however, this foaming procedure was only applicable to parts for which surface quality was not important.
The German laser specialist BKL-Lasertechnik has developed a process by which high-gloss areas can be achieved with the material-saving foam injection moulding technique. According to the company, they addressed this problem because the geometries necessary for the process of the conformal cooling of tools can only be realised with additive manufacturing in the laser melting process.
Controlling temperature by heating the form
The decisive step for the quality of the surfaces is the targeted heating and cooling of the casting form in the right places and at the right time of the injection moulding cycle. This works as follows: Using a newly developed temperature control technology, a special hot fluid is injected into the fine channels for continuous temperature control. By doing so, the surfaces are heated at the critical points before the plastic is injected into the casting form. After the injection process, the casting form can be cooled down rapidly with a cold fluid.
Advantageous process with savings in materials, time and energy
The geometry for such conformal cooling can only be realised with additive laser melting. In other places, however, the casting form has to be isolated so that it will not transfer the heat or store it in the wrong place. Laser technology comes into play in this case as well.
Apart from the surface quality, this injection moulding process provides a number of other advantages. In addition to material savings of up to 10%, the production time for the tools is reduced by up to 25% - thanks to additive manufacturing, BKL-Lasertechnik says. Furthermore, a significant amount of energy is saved due to the short heating-up times.
The load on the injection moulding machine is also reduced overall; hence, an injection pressure of only 200 bar is used. According to the company, the weight of the casting form is also considerably lower thanks to the fine honeycomb structures. As a consequence, the injection moulding machine has to apply less retention force.