This article is about Injection molding and 3D printing and why they are still not in the same page? Let’s see the why in detail
Injection molding is one of the most versatile process to make mass production of the plastic parts. This process also helps in making complicated parts in less time and therefore the capital expenditure is reduced. An injection mould is required prior this process and molten material will occupy the hollow space in mould cavity which forms a defined shape. Repeatability is the major highlight of this process.
On the other hand 3D printing is an additive manufacturing process. It works by adding one layer over the top of the other until it reaches its dimension. Molding is not required and you can start from base and work up to the surface.
Factors to consider while choosing the right manufacturing techniques
If we talk about 3D printing, it creates three-dimensional object from computer design using various 3D printing methods like SLS (Selective Laser Sintering) printer or FDM (Fused Deposition Modeling) printers etc. 3D printing is seen as a cost-effective way to make parts but I think it has is own limitations. 3D printing factors that we should consider while putting injection molding on the same page depends majorly upon batch size or the production volume, repeatability, material type and the rigidity of the material.
On the other hand, injection molding needs an initial big investment in terms of injection machine and the critical part that is injection mould. Imagine you have an initial order for say 1000 parts and you have to send 10 piece prototypes for inspection with in a limited time. Now if you follow to make an injection mould, it has a minimum lead time of 4-6 weeks – then molding, finishing and inspection. Also if some discrepancies come up, all of these process go to waste and you will have to start from the beginning. Here if you take the 3D printer, you can have rapid prototyping within some hours to a day in large cases depending upon the complexity of geometry.
Comparing strength and weakness of Injection molding and 3D printing
Injection molding and 3D printing both have their own advantages and disadvantages. In case of injection molding – production volume, repeatability and cost /piece play a big role. If we set aside initial investment like setup cost and injection mould cost once in practice can make a large volume of material in very cost-effective way efficiently. Also, machines runs for 24X7 keeping the same consistent workflow. Composite material like a polyurethane with metal inserted material can easily get molded in injection molding. Surface finish and finishing operation can be easily done or completely avoided in some cases. So we have a very less time constraints in meeting the supply chain demand. One more interesting fact is that as the whole material is kind of poured in one single shot therefore the strength of the objects manufactured is pretty solid.
For 3D printing one thing that come to my mind very first is making anything anytime possible within a short duration without pouring out a lot of budget. Say we have to inspect and determine whether a prototype will work or not, we can do that. The lead time therefore gets reduced. Also if there is anything that we do not like in the prototype, we can change it in the design model and the second one we print will bear the changes. So, this customization at any point gives a big advantage whereas in injection molding scraping a mould will cost us a lot of money and most importantly time. Although it becomes impractical to print tens or thousands of similar material using 3D printing due to the cost involve to it and post printing operations. Like we discussed before, injection molded material can be mould finished or some post molding operations required but in 3D printing the cutting and finishing of structure tree and surface finish is required after printing which takes long time in post production.
Therefore in my opinion we should not compare injection molding and 3D printing and put them on the same page rather both can work alongside for our benefit. For example a workflow could be like using 3D printing for prototyping and inspection, once approved we can go for injection mold and repeat the process for larger batch. So depending upon the industry and budget both manufacturing technique should be weighed before making a final decision. Hope this opinion and the content above help you to make the right choice.
Content by
Nabin Kamal Haldar: Application Engineer at Futurescape
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