Mold with interchangeable matrices

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At Coesum we have always dealt with rapid prototyping and the design and creation of injection molds for plastic. Usually the development cycle of a product passes through design, engineering, prototyping and series production. If we are talking about a complex product with multiple assembly elements, each of them will have its own “matrix” in the production mold. However, there are limit cases, in which some conditions or factors external to the “pure” design influence the choices to the point of determining them.

This is the case of the Polaris device, a portable analyzer for VOC (Volatile Organic Compounds) analysis. Designed by Pollution s.r.l. overall it is compact and light, despite being made up of two large half-shells, 350x360x111mm each. Pollution s.r.l. has relied on us to obtain the best solution for the creation of the mould. Given the large size of the shells, the investment for two traditional molds would certainly have been expensive and there was the risk of not finding adequate compensation in the sales volumes expected for the first years of product launch.

When we started following the project, the customer had already defined a design draft and created productions through rapid prototyping processes.

After the first tests, the customer’s need was to start a definitive production to be used for marketing the product.

By analyzing the files, the dimensions of the shells, and optimizing production costs as best as possible, there could be two alternatives:

  • Prototype mold is a solution suitable for the production of batches contained in plastic material, including co-molded ones; it is convenient when it is not necessary to purchase production equipment, and it is necessary to have low volume production, with final material in 5/6 weeks. It is temporary equipment that remains available for molding for 12 months; after this period it is necessary to produce the definitive mold or a new prototype mould.

  • Mold with interchangeable matrices is a solution in which, on a single mould, it is possible to insert multiple figures and therefore produce different geometries. In this specific case, since the two half-shells are the same size, it could have been a viable solution.

Mold with interchangeable matrices

Pollution has chosen the second solution to have the guarantee of continuous production over time on short runs.

The first step, after choosing the production process, was to engineer the files for the production process with optimization of thicknesses, insertion of draft angles to facilitate extractability, insertion of internal ribs, elimination of undercuts, standardizing the positioning of the screws for post-production hot insertion

This first phase starts with the feasibility study up to the final preparation of the 3D CAD. Once the geometry was defined we started designing the molds. In this phase, software filling simulations were performed and all specifications were shared with the customer regarding the finishing of the molded piece, the injection point, the embossing level.

Analysis of plastic injection in mold with interchangeable matrices

At the end of the mold production we performed a molding test, a fundamental step for dimensional control and mold acceptance.

The injection molding production is carried out in PA6+15%GF – Color RAL 5019.

An interesting and challenging project also considering the large dimensions of the shells.

All the co-design activities and the excellent collaboration with the customer have contributed to optimizing internal processing and quality control costs by reducing product non-conformities by 98% compared to previous production technologies.

Download the case history in .pdf format

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