Environment-friendly regulations requiring that new plastic objects contain a certain percentage of recycled content are beneficial to the environment. The downside is that they cause manufacturers headaches because it is now their responsibility to reconcile the unattractive appearance of recycled plastic with the aesthetic demands of the market. According to Engel Machinery, Injection Mold a manufacturer of production machinery, many brands do not want the dark-colored recycled core material to be visible at the injection point. It is in response to this that they have developed a new Duo Speed Injection Molding Machine, which they describe as "the beginning of the co-injection revolution."
According to the company, Engel's new machine can concentrate recycled material in the component's core and encapsulate it with a layer of virgin skin material before assembling the component. The virgin and recycled materials are of the same type in order to ensure that the sandwich-molded parts can be recycled as well at the end of their useful life cycle.
As an illustration, here's what a 5-gallon pail would look like if you simply dumped virgin plastic nurdles (shown in white) into the hopper of a conventional injection molding machine along with recycled plastic nurdles (shown in dark grey):
Engle's Duo machine, on the other hand, can combine the two molten plastics in the pail mold without the need to mix the plastics in the melt stream first. As a result, Packaging Mould a coinjection valve gate allows the system to switch between recycled and virgin material at the cavity injection point, plastic injection molding allowing for more efficient operation. This allows them to essentially sandwich the recycled material between two virgin materials, resulting in an appearance that is monochrome.
In addition, the company points out that because the core and skin material fractions are strictly separated from one another during the manufacturing process and because the core is encapsulated by the skin, including the injection point, the new coinjection process can be considered for use in the food industry as well, a panel discussion on plastics injection molding.
Engel, which collaborated with Canadian company Top Grade Molds to develop the new machine, claims that it has cycle times that are comparable to those of conventional injection molding machines and is extremely compact.