A new hybrid process combining machining and selective laser melting to manufacture an advanced concept of conformal cooling channels for plastic injection molds

Firstly, this work investigates a new design of a conformal cooling channel for injection molding tools containing serial and parallel circuits. Secondly, a hybrid-manufacturing process, combining machining and metal powder additive manufacturing, was also evaluated to manufacture molds. Specimens were manufactured by selective laser melting (SLM) using stainless steel (Corrax®) powder, which was deposited on a pre-machined PH13-8Mo stainless steel substrate. The melting zone interface (MZI) between the two materials were assessed. The results showed that the laser-melted and machined surfaces were successfully melted and bonded. Thus, an injection mold was designed and manufactured. A pair of inserts containing the conformal cooling channels were manufactured by the hybrid process and another equivalent pair of inserts containing a conventional cooling system were produced only by machining. Injection molding was carried out alternating the two types of inserts. The results showed that the mold with the conformal cooling channels reduced the warpage of the injected plastic parts by a factor of ~7. The difference in temperature along the insert was reduced by a factor of ~10 and the molding cycle time was around 36% shorter compared with that of the conventional mold. Overall, the proposed hybrid manufacture of the inserts reduced the manufacturing costs and time by 53% and 60%, respectively. The results indicate the benefits of using the proposed conformal cooling design and the hybrid-manufacturing approach, which combines machining with additive manufacturing for injection mold production.