Injection molding is a manufacturing process of making parts by injecting material into a mold.
Injection molding is one of the main processes used to manufacture plastic items. It’s a fast process that can deliver a large number of identical items – from high-precision engineering components to small, single-use consumer items.
The use of this process has enabled the expansion of the design boundaries in plastics and has also contributed to the replacement of traditional materials, reducing the weight of the end product and creating immense design freedom.
Companies involved in injection molding
Below are some of the major companies involved in injection molding:
- Ferromatik Milacron GmbH, Malterdingen, develops, manufactures and sells injection molding machines. The latest creation is the modular F-series, which can be configured as a fully electric, hydraulic or hybrid machine. The company is part of the American Milacron group.
- KraussMaffei is one of the world’s leading manufacturers of injection molding machines. The injection molding machines offered by the German company are the AX, CX, CX-ClassiX, EX, GX, MX and C3 series.
- Sumitomo (SHI) Demag Plastics Machinery GmbH, Schwaig, is a Japanese-German company that manufactures injection molding machines. They offer fully electric, hydraulic and hybrid injection molding machines with clamping forces between 180 and 20,000 kN.
- The German company Arburg is one of the world’s leading manufacturers of high-end injection molding machines for plastics processing. They are aimed at industries such as electronics, packaging, automotive, medicine / optics and many others.
- AIM Plastics covers a wide range of industries including healthcare / medical, electrical / electronics, automotive / auto aftermarket, retail / consumer, aerospace / defense, and action sports. They are located in Michigan, USA.
Recent improvements in injection molding
Below are some of the key improvements in injection molding:
- Multi-component injection technologies – Sandwich technologies are among the spectrum of multi-component injection technologies. Sandwich technologies include co-injection, mono-sandwich, gas injection technology (GIT) and water injection technology (WIT). With the co-injection method, two melts are injected one after the other through a gate into the cavity of the machine. In the mono-sandwich method, two materials are injected into the cavity through a passage using an injection unit. The GIT primarily uses nitrogen, which is injected into the part to replace the melt in the core and create a cavity. GIT enables the production of parts with high wall thicknesses and / or material accumulations. It offers increased strength and rigidity with less or the same part weight. It enables a weight reduction of up to 50% and a reduction in material costs. It also enables a reduction of the cooling / cycle time by up to 50%, lowers the clamping force and the machine costs. GIT enables fewer sink marks, parts with less distortion and improved part quality. There are two processes in WIT – the short-shot process and the full-shot process. The short shot method requires high speed shooting in a transparent tool during the filling process. Many consider WIT to be relatively more beneficial than GIT. WIT offers shorter cycle times, smaller and constant wall thicknesses with less distortion, large part diameters and smoother inner surfaces. In addition, water is cheaper than gas and is incompressible.
- Micro Injection Molding – In order to produce very small components using the injection molding process, maximum accuracy and precision is required. The core of the processing of plastics of minimal size is the microinjection unit. Sumitomo (SHI) Demag is one such company that offers customer-specific plasticizing systems for shot weights from 5 to 0.1 g in the field of miniaturization. Your microinjection unit can be integrated into any standard machine for a clamping force of up to 500 kN.
- Modern injection molding machines are controlled by a built-in computer. The computer controls all of the machine’s actions based on information fed by the sensor, ensuring consistent output and shot-to-shot quality.
Dual shot injection molding
Two-shot injection molding, or two-shot injection molding, is a process of making simple to complex parts from two different polymers, even with two different colors during a machine cycle.
The “two-shot” mold consists of two separate cavities from which a single part is made. The first step in this process is to create a substrate in the first cavity that will receive material from one of the two injection units. The tool then opens to allow 180 ° rotation to a secondary position after the finished part is removed from the second stage cavity. When the tool closes, the second step begins with positioning the previously formed substrate in the second cavity. The second cavity receives the material from the second injection unit, which completes a finished part. This happens at the same time as the substrate is being molded for another part.
When the tool opens again, the finished part is ejected and another substrate is ready to receive its overmold. Therefore, this simultaneous process enables continuous manufacturing operation by using an alternating rotary motion of the tool.
The main advantages of two-shot injection molding are as follows:
- Soft-touch functions and multi-colored on handles, handles, devices, housings and other components
- Backlit buttons, dials and other instrumentation products
- Noise / vibration dampening and isolation
- Air / water seal
- Shock absorption and protection
- Movable segments or components such as living hinges and spring mechanisms
Applications of modern injection molding
Injection molded parts make up almost most plastic products. Almost all manufacturing sectors use injection molded parts because of their flexibility in size and shape.
The following is a list of basic products that can be injection molded:
- Power tool housing
- Telephone receivers and DVDs
- TV cabinets
- Electrical switches
- Bumpers and dashboards for automobiles
- Battery case
- Drug inhalation units
- Disposable razors and syringes
- Garbage cans and boxes / recycling boxes
- Bottle caps / closures
However, this list is not exhaustive as there are many more products that can be made using injection molding.