Injection molding is a manufacturing process that involves the production of parts by injecting molten plastic into a mold cavity. The mold creates an exact replica of the product to be mass-produced. It is the most commonly used process to fabricate most plastic items as we know them today.
The process involves feeding the material for the item into a hot barrel. It is heated and mixed using a helical-shaped screw till molten. The molten material is pushed into the mold cavity through a mechanism that simulates the hypodermic syringe. Here, it cools and hardens into the configuration of the mold.
Molds are created after an industrial designer or engineer has designed a product, usually from steel or aluminum. They are made to scale to form the features of the desired part. Injection molding is used in mass-production where the same part or
component is created in tens of thousands in quick successions.
The injection molding process is a repetitive cycle that takes between two seconds and two minutes. The cycle consists of the following four stages:
Molds come in two halves that must be securely closed before the injection of the molten material. Bringing together the two halves of the mold and securing them is called clamping. It is hydraulically operated.
The raw material in the form of plastic pellets is put into the molding machine and gradually pushed toward the mold cavity. During this process, the material is melted by heat and pressure. The molten plastic is injected swiftly into the mold to take shape.
Cooling starts immediately after the shot comes into contact with the interior of the mold surfaces. It solidifies to the shape of the desired item. Shrinkage may occur, but the injection stage allows additional material to flow in and compensate.
After the item has sufficiently cooled and has solidified, it must be ejected. Some force may be required because shrinkage has occurred and the item is more attached to the molds. The ejection system is attached to the rear half of the mold. The mold release agent can be sprayed onto the mold cavity surfaces to aid mechanical ejection.
Post-processing is required, and it involves trimming any excess material using cutters.
3D printing, also known as additive manufacturing, is a process that involves the transformation of a three-dimensional digital model into a physical object. You create a digital design of an object using software, and then a 3D printer creates a physical object by adding successive thin layers.
A concept is actualized by laying thin layers (layer by layer) of material in 3D printing.
A 3D printed object is achieved through an additive process. Here successful layers of material, which can be visualized as a thinly sliced cross-section of the object, are laid down.
How Does 3D Printing Work?
The next step is slicing, which involves digitally slicing the model earlier generated for printing. This is critical because the 3D printer cannot conceptualize the item as a whole. Slicing breaks down the model into many layers. The design of each layer is sent to the printer to print. You either use the Craftware or Astroprint program; these are special slicer programs that complete Slicing.
Once Slicing is done, you deploy the 3Dprinter. It prints out the model as instructed by the slicer program using a different method. The process varies with different printers. Listed are the different options of 3D printing.
- Direct 3D printing: This technology is similar to inkjet; the nozzle moves back and forth, dispensing molten plastic, which cools and solidifies to form a layer of the model’s cross-section.
- Multi-jet: This technology uses several jets working at the same time to dispense the plastic polymer, making it faster.
- Binder 3D printing: The jet nozzles apply fine dry powder and liquid glue, which binds the powder to form a layer.
- Photopolymerization: Involves exposure of drops of liquid plastic to a laser beam of ultraviolet light. The beam converts the liquid to solid.
- Sintering: This technology involves melting and fusing particles to print each layer. The process is repeated for each successive layer.
Regardless of the 3D printer used, the printing process is similar across each type:
- Production of a 3D model using CAD software
- Conversion of tessellation language (STL) format
- Transfer of the STL file to the computer that controls the 3D printer
- Set up of the 3D printer setup requirements, such as refilling the polymers and other necessary consumables
- Startup of the machine and regular checking to ensure progress as planned
- Removal of the printed object
- Post-processing (You may need to brush off any remaining powder or wash your finished item.)
Difference Between Injection Molding and 3D Printing
Whereas 3D printing is a digitally guided technology that converts a digital model into a physical three-dimensional object through an additive process and is achieved through laying successive thin layers on the cross-section of the model, injection molding uses a mold that is designed like the object to be manufactured. The mold is filled with the molten material by injection. The material is left to cool and harden to produce the desired object or product.
Injection Molding vs. 3D Printing
The choice you make between the two manufacturing processes depends, of course, on your particular project.
Injection molding offers a significant advantage in mass production, with great reliability in precision and repeatability. You’re assured of a quick turnaround time due to the speed of production. You also have a wide range of materials you can use with this method that can potentially create more durable parts.
3D printing is an additive technology that has been regarded as a rapid prototyping technique. 3D printing is also flexible—you can easily change your design using 3D modeling software. It not only saves you money and time but helps you improve your product design. With 3D, you can curb material wastage, making it cost-effective.
As to which is objectively “better,” there is no definite answer. Our experts can help you decide which method suits your project’s purposes in your consultation.
How Do 3D Printing and Injection Molding Work in Tandem?
3D printing can enhance the role of injection molding due to the technique’s inherent advantage of precision, and details. 3D printing is a better process for prototyping. Once you have your prototype, you can use the comparative advantage of injection molding to mass produce the items.
Quality, Competitively Priced Parts at Rapid Axis
No matter which method you decide to use, Rapid Axis has the experience and capabilities to provide you with the best custom injection molding and 3D printing services in the industry. We offer SLA, FDM, and SLS printing for all your prototyping needs with the fastest lead times, guaranteed. Call today and receive a free quote in just a few hours!