Smart Molding International 3-2022

38 molding technologies smart_molding international 3/2022 F FP2 masks are everywhere. What should be done with the scrap created during production? It should be recycled, of course. The sta- ple fiber fleece made of polypropylene is as liquid as water (melt volume rate MVR 800-1000), entirely different from shredded gummy scraps of HDPE from the production of blow-molded parts from the toy industry (MVR < 1). If you also add HDPE from injection molding production with a consistency similar to honey (MVR 5-15), you have the three components that are being combined into one new material at K 2022. KraussMaffei is focusing its trade show presence on circular economy - and the DCIM direct compounder with its single-screw extruder plays a central role. It is suitable for shot weights from 50 to 2000 grams and thereby complements the IMC system (Injection Molding Compounder, with twin-screw extruder), which has been tried-and-tested for 20 years and is ec- onomically attractive for shot weights of 1500 grams or more. Saving costs with DCIM The current costs of polymers re- sult in material dealers no longer be- ing able to purchase enough recycled materials to cover their demand. So it´s necessary to take action your- self. The DCIM process (Direct Com- pounding Injection Molding) makes this easy by blending, modifying with additives, reinforcing or filling and feeding the material directly into the injection molding process. “The DCIM process saves costs for external compounding (on average, about 0.6 €/kg) and gives the proces- sor maximum control over the mate- rials used.” Franz-Xaver Keilbach, Global Prod- uct Owner Circular Economy / Recy- cling Injection molding and compounding in a single heating process For DCIM, a single-screw extruder is installed in a piggyback position directly over the injection unit of a standard hydraulic machine (usually from the GX series). Both produce in intermittent operation, which means that the extruder stops when the in- jection volume for the next cycle has been reached. For the trade show application, the three materials are additionally mixed with the masterbatch, stabiliz- er additive and micaceous iron oxide as fillers. The last of these results in a cooling time reduced by up to ten percent. Turning the six individual components into a homogeneous melt is achieved by the special screw of the extruder. It has an optimized design and an extraordinarily length. The ratio of length to diameter is usu- ally about 17-23 L/D (standard injec- tion molding machines), but for DCIM it is an impressive 30 L/D. Production in one heat saves valuable energy In view of the current energy prob- lem, it is also of particular interest that all production is accomplished in a single heating process, so the compounded melt goes directly from the extruder into the plasticizing Live at K 2022: Reusable crates made with three recyclates At K 2022, a GX 1100-4300 DCIM produces returnable crates from three different recyclates (all pictures: KraussMaffei) When it comes to recycling plastics, aspirations and reality often diverge. This is because pure polymer is only available in limited quantities. Therefore, as many sources as possible must be used to achieve the necessary volume of recyclate. With Direct Compounding Injection Molding (DCIM), KraussMaffei is demonstrating at K 2022 how a new material can be compounded from three recyclates of different viscosities.