Rapid Injection Molding
Produce high-quality components for production or pre-series with the speed of rapid prototyping.
What is Rapid Injection Molding?
Injection molding or plastic injection is a process that is commonly used in the manufacturing industry, which allows the fabrication of plastic parts, starting from the raw material in a state of heat fusion and using molds for this purpose.
Through a mold, which is closed with an opening for the filling of the plastic material, a molten polymer is injected under pressure, which is cooled inside the mold. Once cooled, the mold is opened to be able to eject the pieces already molded.
Injection molding used for mass production uses steel molds that require several weeks to manufacture and is designed for high volume production (hundreds of thousands to millions of pieces). However, rapid injection molding uses rapid manufacturing molds or also known as prototyping molds, made of aluminum, in a few days. Naturally the durability of the mold is much lower and therefore they are intended for the production of a few hundred or a few thousand plastic pieces.
In recent years and thanks to additive manufacturing technologies, these molds can also be manufactured in plastic materials allowing greater flexibility in design and lower production cost. Although the most important advantage is the possibility of having the first units of molded parts in less than a week.
Main applications for rapid injection molding:
Low volume series
As the mold is cheaper, it is possible to manufacture small volumes of parts and assemblies for the final product, at an affordable cost, but without sacrificing precision.
Pre-series
Given the flexibility and low cost, it is possible to use this method for product validation, before mass production.
Mass Production
In many cases, when the final runs are not large, this technology can be used to launch final products on the market.
Advantages and Limitations of Rapid injection molding
Main advantages
- Speed of mold construction
- High precision and high quality of parts
- Wide variety of plastic materials for the manufacturing of parts
- Lower upfront costs.
Main limitations
- Not suitable for long runs (> 20,000)
- Design limitations due to the mold construction.
- Parts may vary due to the injection process.
Types of rapid injection molding
Single cavity
In this case, the mold is small, producing a single piece per injection. Although the cost of the mold is lower, the cost per injection is higher and the number of parts that will be manufactured throughout the life of said mold is reduced.
Multi-cavity
In order to increase the number of parts produced during the life of the mold or simply to be able to achieve several different parts per injection, it is possible to build molds with several cavities. In this case, the cost of the mold is higher, but its amortization per piece will be significantly lower.
Overmolding
It is based on the injection of different materials in two steps. First the substrate material is injected into a cavity and in a second step a second material is injected onto the substrate. Through this process it is possible to create plastic pieces in different colors or with hard and soft materials.
Insert molding
Prior to the injection process, one or more metal pieces are inserted into the mold cavity. The plastic is injected onto the metal insert and when it cools, they remain joined as if it were a single piece. In this way, we can reinforce joint areas or integrate metallic or ferromagnetic elements for different purposes.
Materials for Rapid Injection Molding
One of the advantages of this manufacturing technique lies in the great diversity of materials that can be used for the production of parts. The most common are:
ABS
This thermoplastic is characterized by a high level of impact resistance. Although it is vulnerable to many solvents, its low cost and low density make it a widely used material in this technology.
PP
Polypropylene is possibly the most widely used plastic. It has good chemical resistance and is available in food grade. However, it does not have good mechanical characteristics.
PA
Polyamide or Nylon is an ideal material for functional applications, thanks to its excellent mechanical properties and high resistance to abrasion and chemical attacks.
PC
Polycarbonate is the plastic with the highest mechanical resistance to impacts. It has good temperature resistance, suitable for outdoors use and has excellent toughness. It is possible to have this material as transparent or opaque, at the same time that it is susceptible to being dyed. It is widely used in the automotive industry.
PE
Polyethylene, thanks to its resistance to impacts and its excellent behavior outdors, has become another of the preferred plastics in the injection molding industry.
TPU
Thermoplastic Polyurethane is an elastomer with the look and feel of natural rubber. By formulation it is available in different hardnesses although, by varying its thickness in the injection process, it is possible to adjust it in different areas.
Finishes in Rapid Injection Molding
Different finishing options for your parts:
Natural
In this case, the pieces are delivered as they come out of the mold, although this technology offers incredibly good finishes.
Polish
By controlling the roughness of the mold, it is possible to directly obtain plastic parts with mirror polished finishes.
Spray painted
The pieces, once manufactured, can be painted with sprays of different colors.
Texture
Using different textures inside the mold, these are replicated in the injected plastic components.
Metal plating
Through electrochemical processes, the pieces can be finished with layers of gold, silver, nickel, among others.
Soft feel
By using special resins, it is possible to give the pieces a soft touch far from conventional plastic.
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