Injection moulding: the underdog in the sustainable production world
Talent Plastics Tartu AS
A Swedish owned company from Estonia that supplies thermoplastic parts with injection moulding and inhouse assembly.
Injection moulding process produces virtually no waste! True story.
I have your attention now, right? We in Talent believe that being sustainable, cost effective and considerate of the environment is a must not an option anymore and that is why we are proud to say that we use technology that is advanced enough (and improving constantly) to provide just that. So, injection moulding – let’s talk about that.
Injection moudling is a plastic manufacturing process, where plastic granulates are melted and injected into moulds to mould the needed part, while being a cost effective solution for producing bigger volumes.
Obviously we here need to talk about important definitions in injection moulding but while looking for a good technical but not too cosmic definition explanation, well... They are all very different and maybe just touch one or the other aspect of the technology. So, here is our take: injection moulding is a plastic manufacturing process, where plastic granulates are melted and injected into moulds to mould the needed part, while being a cost effective solution for producing bigger volumes (1). Before any moulding can happen, an injection moulding tool is created but more about that in a separate article. Overall, injection moulding takes place in 5 different steps (2;3;5):
1)????Setup of the tool: material preparation, where a machine setter prepares for production by entering the specific tool settings into the machine.
2)????Injection phase: plastic pellets are fed into the moulding machine using a hopper and passed into a heated barrel to melt the granules. Within the barrel a reciprocating screw plasticises and compresses the material, driving the molten plastic towards the mould tool.
3)????Hold pressure time: a nozzle forms a seal between the barrel and the mould tool. Under high pressure the molten plastic is passed from the barrel, through the nozzle, and into the cavity of the mould tool.
4)????Cooling phase: temperature controlled water or oil circulates the body of the mould tool for a specific length of time to cool the plastic within. As the plastic cools it solidifies to the shape of the mould cavity or cavities.
5)????Ejection and closing: the moulding machine uses its moving platen to open the mould tool and ejector pins extend into the mould cavity to push the part out. Often a robot collects the finished moulding from the mould and places it on a conveyor belt or final working area. After that, close and repeat the cycle!
Injection moulding process illustration (4)
The injection moulding method was patented in the US back in 1872 by the Hyatt brothers who began producing billiard balls in celluloid. The type of machine used today (with screws) were first introduced in the 1950s. The history of injection moulding is as detailed as the process, when to analyse it on a more technical level but it is our hope that the above step-by-step overview at least gave a better indication of the process. The method is not perfect, which is why it seems right to bring out the most relevant pros and cons:
THE PROS
·??????Producing high volumes at high speed. Short cycle time enables to make a high number of parts and in turn during a production cycle (5).
·??????Complex design. The high pressure involved in injection moulding means that the molten material penetrates the nook and cranny of the mould before solidification and curing. This allows engineers to design complex parts, inscriptions, details, and elements (6). Important note: there is no 100% guarantee that everything is feasible since the combination of supplier machinery, tool concept possibilities and the specification of the part can cause issues but fortunately there always is a way/compromise ??
There is no 100% guarantee that everything is feasible since the combination of supplier machinery, tool concept possibilities and the specification of the part can cause issues but fortunately there always is a way/compromise.
·??????Low waste and reusing. ?As the plastic injection moulding process involves injecting plastic into an exacting mould, only the exact quantities of material are used to create and shape the final product. Any excess in channels or air vents can be re-ground, melted, and used to create the next moulding. The same plastic granules could be recycled into multiple different plastic products over the course of their lifetime (which as we know with plastics is hundreds of years). (3)
·??????Cost effectiveness. Even though the investment side of injection moulding is costly, the part cost can be improved with higher productivity (the bigger the cavity number, the better the productivity) and using optimized tool concept (for example hot runner system or having no undercuts where possible), therefore cost per part can be smaller then while producing with other methods. (2) On the other hand, less expensive prototype tools enable to scale up a product fast and improve the design if needed with lesser cost then while improving a series tool. (6)
·??????Quality consistency. This process follows a sequential pattern in the creation of identical parts. Therefore, the quality of the first would be like that of the second, third, and the next. (5)
·??????Variety of materials and finished surfaces. With this process, you can use multiple materials and colours simultaneously (5). With the proper process optimization techniques, injection moulded parts can be ejected ready-to-use or finished in an array of popular or custom methods to ensure that your part look and feel as intended. (6)
领英推荐
Talent Plastics Group gallery
Of course, there are more advantages but, as you can see above, the list is already quite long and detailed so it is only fair to give some spotlight to the disadvantages. They are given below.
THE CONS
·??????High investment costs. To have a high quality and long-lasting tool, a big investment needs to be considered. While creating the tool, sampling cost also needs to be planned, which makes the tooling process in total a costly process. (2)
·??????Time consuming. Even though the production process in series is fast, the process of having a ready for use tool is relatively long. With different testing, trimming and tool adjustments, altogether the project itself can be for example 6 months or longer.
·??????Size limitation. Items that are too large for an injection moulding machine’s capability need to be created as multiple parts and joined together later. (2)
·??????Quality issues. When there is an issue with the tool, the defect will be easily visible on the part. On the other hand, when set process parameters and tolerances of the parameters change, the quality of the injection moulded parts can decrease.
·??????Price sensitive. Even though there are many ways of improving cost basis and reducing cost drivers then it is unfortunately so that the raw material prices affect to a great extent the end price. This is evident in the current raw material crisis.
Like mentioned above, there are surely more advantages AND disadvantages. Feel free to share your take on the matter. In time, surely more and more new aspects come to light for every company: while processing a new material, using new more advanced tooling systems or even producing with latest technology machines. But if everything would be easy, where would be the fun in that? We love a challenge at Talent! But three different crisises at a time is perhaps too much of challenge in one take…Let's see how things develop in the future :)
We hope this was an interesting read for you. These busy times do not enable to write too often and one needs to wait until inspiration strikes.. However, we will do our best to be more productive! Anyway, the plan is to write the next article about injection moulding tools in the coming months. If you have any suggestions what to write about, feel free to write to us. In the meantime, we at Talent wish you a relaxing end of the week, stay safe and healthy and until we meet (again)!
Reference sources:
?
?