From 3D printing to injection molding, these five tips need to be considered

There are several technologies for making plastic parts. Around the world, plastics are cut, low volume manufacturingextruded and molded into moldable parts by injection molding machines, 3D printers and CNC machines. All of these machines have their own unique benefits.

Injection molding (the process of injecting liquid plastic into a metal mold) is the most widely used process for making plastic parts, but alternative technologies such as vacuum casting and FDM 3D printing offer different advantages and provide designers and manufacturers with great flexibility. After all, different projects may require different types of machines.

However, in many problematic situations, different technologies can be used to carry out different stages of manufacturing development. For example, 3D printing is often preferred for prototyping because it is simple, portable and has a very low start-up time cost. Whereas injection molding is usually the preferred process for end-use parts through extensive research because it is fast and highly repeatable in China. 3D printing information technology primarily serves the R&D work phase, while injection molding is responsible for safe production.

But what happens when you create a 3D printed prototype and need to produce it through injection molding? Given the fundamental differences between the two manufacturing technologies, how do you ensure that the molded part meets custom part manufacturerthe specifications of the printed part? How do you plan ahead to ensure the success of your prototype and production?

Global Economy Rapid Prototyping & Manufacturing, LLC 3ERP offers the following five key technical tips for companies looking to transition from 3D printing to injection molding for development.

Design injection molding whenever possible

It's not always easy to think ahead. When your first task is to make a 3D printed prototype, the natural instinct is to create the best printed part possible, which means applying DFM (design for manufacturing) principles to the 3D printing process.

But if you plan to make the eventual move from 3D printing technology to injection molding, 3D printed prototypes must be designed to be not only printable, but we can mold them quickly.

In practice, this means following injection molding design principles even during the 3D printing phase. It should include mold pulling angles, avoiding overhangs, and sharp angles should be rounded. In addition, because the mold cannot replicate those complex filling patterns, complex filling patterns (which can actually increase the strength and efficiency of 3D printed parts) should be discarded in favor of simple ribbing.

Designing injection molding from the start reduces the need for drastic pre-production changes and simplifies the transition from one process to another.

Printing with production materials

A useful prototype does not necessarily have to have the highest standard of appearance and performance. Rather, a useful prototype is one that best represents the end-use part, including its strengths and weaknesses.

This may mean that companies make certain compromises, including in the choice of materials for one aspect.

Injection molding is a highly flexible process that is compatible with a variety of plastics, while 3D printing is more limited in terms of available materials. However, when designing a 3D printed prototype, it is important to prototype machining serviceschoose materials that match or at least mimic the materials used in the production process.

It is important to note that this may not be a natural choice for a successful 3D printing job. Some effective molding materials are actually difficult to 3D print, requiring additional time and more thorough post-processing. However, choosing a representative material will result in a prototype that more realistically represents the final part, allowing for a smooth transition to production.

Polished prototypes are "molded" surface finishes.

For Chinese mechanical or aesthetic parts, it is important to create a prototype with a surface finish of the final part. Mechanical parts may require a degree of friction or smoothness that we need to pass through, so it would not be particularly useful for companies to have prototypes that fully satisfy different textures. (In addition, prototypes with a managed professional appearance can provide help to improve a company's marketing or promotion of their products.)

Thankfully, surface finishes can be used to change the appearance of 3D printed prototypes. The surface roughness of printed parts can be significantly reduced, and even a mirror shine can be produced by professional polishing using cloth or polishing wheels.

The result is a 3D printed part with no layers and no rough texture that actually looks and feels like a molded part.

Beyond FDM

FDM (Fused Deposition Modeling) 3D printers are a very popular choice for prototyping. It's inexpensive, easy to use, and compatible with a wide variety of plastic filaments, and many companies can iterate quickly by simply installing them in their offices.

With that said, FDM 3D printing technology produces parts of a much different quality than molded parts. The structurally important composition and surface finish also meet completely differently, so FDM-made prototype systems do not easily manage the transition to molded parts.

On the other hand, higher quality FDM alternatives can produce parts in a wider range of shapes. PolyJet 3D printers, for example, can produce parts with tight tolerances and smooth surfaces, as can light-based processes such as SLA. (SLA, however, may only be suitable for aesthetic prototypes, as it can create rather fragile components.)

Seek expert advice

Obviously, one of the easiest ways to ensure a smooth transition between 3 d printed prototypes and final injection mold making is to discuss the entire project with an expert.

If you plan to order a prototype through a professional service provider, be sure to let them know that the parts to be used in the end will be molded through injection molding. Better yet, use the same service provider for prototyping and production, allowing them to leverage their expertise to bridge the two processes.