Point of view: Injection moulding will be no longer the same

They have recently developed new injection moulding processes of polymeric materials, not all necessarily characterized by simple execution but anyway featuring peculiar characteristics that allow satisfying the more and more articulated and complex market demands. As it happens more and more frequently, the market does not ask “please, manufacture that product by using that particular technique”, but it provides instead some indications about the characteristics of the product to be implemented, leaving then the freedom of developing new products and identifying the correct technologies to manufacture them to engineers and sector experts. The continuous training of sector players is then essential and it cannot be left to chance or to the simple collection of information, performed in uncoordinated way or in fortuitous occasions. It is necessary to invest in education (but how many times have I already stated that?) and to lavish time and resources in this target. Technical engineers (both those who design the product to be manufactured and those who design the mould or devise the process and define its characteristics and machining parameters) cannot spend all of their time with a mouse in their hand, in front of a computer monitor where a CAD turns. It is instead necessary that they collaborate, dialogue, consider alternative ways of designing and producing, daring, sometimes, to give up the prefixed solutions and undertaking new ways. Moreover, it is necessary to invest in research and development to become or to remain competitive not only from the economic point of view but especially in terms of technology and quality of the manufactured products. The target of this effort is precisely outlined by the market demands. Nowadays the borders of the injection plastic production have widened: there are demands that provides for the replacement of components generally manufactured with standard materials with products implemented (or partially manufactured) with plastic materials, requests that provide for the realization of components with minor mass (due to clear reasons of energy consumption decrease in their implementation, use and disposal). All these aspects leave then great design freedom. Among the latest developments in the plastic injection ambit, there are certainly multi-component injection techniques, the plastic micro injection, the new machines equipped with computer permitting the constant control of all injection operations based on the information coming from sensors distributed in the machine and in the mould, thus granting notable improvements in the quality of the manufactured products. Among the multi-component technologies, it is worth mentioning those called “sandwich technologies”. They include the conventional co-injection in which two melted materials are injected one after the other into the mould, the mono-sandwich where two materials are simultaneously injected into the mould, the gas injection technique (GIT) and the water injection technique (WIT). In GIT, the gas (nitrogen is generally used) is injected to replace the central part of the product, thus attaining hollow parts with big-thickness walls, to achieve products with higher resistance and stiffness, reducing or keeping constant the quantity of injected material. In some cases it was possible to reach a 50% mass reduction with an increment of the cooling speed resulting in an evident cost reduction. The technique defined WIT provides for the use of water instead of gas. Further advantages of this technique derive from the incompressibility of water compared to gas, which can generate a process with faster cycles, with minor and more uniform thicknesses of the produced components, meanwhile decreasing the part distortion and proving to be suitable for bigger-size components, too. The application fields of these techniques are enormous and can offer notable advantages also for products deemed more traditional, provided that we realize and understand their potentialities and we have the courage in investing in equipment and, especially, in knowledge.

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