Hybrid moulds: effect of the moulding blocks on the morphology and dimensional properties

Abstract

Purpose -This paper aims to explore the influence of the materials used in moulding blocks of hybrid moulds on the injection moulding setup and the properties of the mouldings. Design/methodology/approach -An instrumented (pressure and temperature) hybrid mould with exchangeable moulding blocks, produced by rapid prototyping and tooling techniques (RPT), was used to produce polypropylene tubular mouldings. The configuration of the mould was varied with combinations of moulding block materials, namely, an epoxy resin composite processed by vacuum casting and steel. The processing conditions were adjusted to obtained steady processing conditions. The mouldings were assessed in terms of the microstructure and the shrinkage. Findings -Due to the properties of the moulding block obtained by RPT being different from tool steel, the injection moulding processing conditions and the plastics parts properties are different when hybrid moulds are used. The cycle time depends on the moulding block properties and must be adjusted to the desired running temperature. The morphology of the mouldings is strongly affected by the thermal properties of the moulding block materials. When different materials are used in the core and the cavity asymmetric structures develop in the part. The shrinkage of the mouldings, when resin cores are used is also affected by the deformation of the core caused by the injection pressure. Originality/value -This paper makes a contribution to understanding the morphology of semi-crystalline mouldings obtained using hybrid moulds and enhances the importance of the core deformation on the shrinkage of the mouldings.

Hybrid Mold: Comparative Study of Rapid and Hard Tooling for Injection Molding Application Using Metal Epoxy Composite (MEC)

“…In addition, the market also demands products of a higher quality, cheaper costs, shorter product development cycles, and that fulfill the environmental requirements for sustainability [ 3 , 8 ]. Therefore, innovations in appliance methods and materials need to be adopted to meet the product manufacturing cycle requirements [ 9 , 10 , 11 ].…”

“…In the last two decades, in order to meet the new trends within the plastics industry, the concept of a hybrid mold ( Figure 1 ) has been developed for injection molding applications. A hybrid mold is a novel method in the fabrication of injection molds which combines the conventional machining for mold-based and Rapid Tooling (RT) techniques for mold inserts (core and cavity inserts) [ 10 , 12 , 13 ]. The advantages of this type of mold are efficiency in minimizing waste and energy consumption; agility to customize and ease of flexibility to change and incorporate design concepts [ 14 , 15 , 16 ].…”

“…The advantages of this type of mold are efficiency in minimizing waste and energy consumption; agility to customize and ease of flexibility to change and incorporate design concepts [ 2 , 3 , 8 ]. Manufacturers have sought the non-conventional process for tooling fabrication which includes RT and explored alternative materials with faster delivery, increased quality, reduced product development time, and compatible with global trends [ 10 ].…”

“…On the other hand, S. Rahmati and P. Dickens [ 25 ] pointed out that resin temperature (Tg), thermal conductivity of filler and fabrication process are important factors in considering how the molded component is affected by the molding process using mold inserts fabricated using the RT technique. There are still some difficulties in the manufacturing of plastic parts using hybrid molds which are related to the thermal properties, mechanical data and behavior of the materials which are either inaccessible or misunderstood [ 10 ]. One of the main issues encountered during the development of RT for the molding process is its low thermal conductivity, which results in slow heat transfer from the molten plastic to the coolant through the mold inserts.…”

Adjusting process parameters in zamak-8 prototype tooling to obtain functional prototypes in PP

“…In either case, these alternative materials have different mechanical strengths and thermal conductivities than conventional steel molds. Mold material strength influences its durability, while its thermal conductivity leads to different cooling rates and, consequently, affects the mechanical properties of the moldings [3][4][5]. This is more evident when using polymeric inserts.…”