Demystifying Injection Molding: From Wire Spools to Lego Bricks

Have you ever wondered how a 32-teeth plastic comb slips into your pocket so easily? Would you believe if I say that the plastic chair, which augments the decorum of your dining table goes through the same procedure of manufacturing as the miniature comb? And it’s not only about chairs or combs, but every plastic product that is introduced in the market through mass manufacture also has the same initiation. These little marvels are created through a process called Injection Molding.

Injection molding is apparently, a simple process where the plastic is melted and injected into a mold and allowed to cool in the desired shape, which is finally popped out as a finished plastic product. However, in reality, it is an intricate and vividly complex procedure. The machine mainly consists of three important parts the injection unit, the mold, and the clamp. 

Plastic pellets in the hopper feed directly into the barrel of the injection unit that consists of a reciprocating screw clamped with hot bands that heat the interior by conduction. Once the plastic reaches the front end of the unit, it is almost in the molten state. The reciprocating screw then rams it forward, similar to the plunger of a syringe, and is allowed to solidify inside the cavity image. When the desired shape is achieved, the clamp is pulled back and the piece is extracted. The procedure is repeated multiple times. The plastic pellets are often mixed with granular substances known as ‘colorants’ and up to 15% of recycled materials, which enhances the reuse of a number of waste products.

Older molding machines are used to heat the entire barrel externally followed by the introduction of plastic. Now, plastic being a poor conductor of heat, the material was subjected to uneven temperatures. To solve this problem, engineers came up with the idea of the reciprocating screw, often considered as the device that revolutionized the plastic sector. Today, far advanced technologies are deployed for the process of fabrication. 

Sumitomo (SHI) Demag Plastics Machinery GmbH, is a Japanese-German company that deals with the production of injection molding machineries and equipment. They provide all-electric, hybrid, and hydraulic machines with clamping forces in the range of 180 to 20k Newton. Multiple component injection techniques have been put forward that simplifies the task and also aggrandizes the quality of plastic. Sandwich Technologies mainly consists of co-injection, mono-sandwich, gas injection technique (GIT), and water injection technique (WIT). In GIT, the gas used is mostly nitrogen, which is injected into the part to replace the melt in the core and create a hollow space. GIT is used to produce parts with high wall-thicknesses or material accumulations. It provides more strength and stiffness at lower or equal part weight. It also enables reduction of weight up to 50% and helps in decreasing of the material costs.

There is a wide range of applications of injection molding. It is employed to generate high-end engineering tools with immaculate precision as well as plastic toys and even Lego bricks. It is utilized for the production of drug inhaling units for medicinal purposes. In the electrical sector, injection molding comes in handy in manufacturing of electrical switches and large cable spools. Other common products include disposable razors, electronic equipment cases, plastic chairs, and wheelie bins. 

Unfortunately, like all engineering procedures and formulations, injection molding inherently contains some minor shortcomings. The primary disadvantage is the enormous price of the injection molding machine that can make it a setback for many start-up ventures and slow-growing companies. Another disadvantage of injection molding is that the designs will have to be formed before any process can begin. This could put production behind schedule for the company. The process could be a possible setback for certain companies who don’t have a set of rules to follow. Lastly, there are some limitations as to what may be designed while using the injection molding process, which could put the finished product behind schedule.          

Injection molding has significant contributions to the development and growth of various prominent industrial sectors across the country. As for example the food and beverage industry adheres to FDA-certified and GMA-safe regulations on every product for the optimal safety of human health through plastic injection molding. 

Injection molding is a cost-effective way for large scale manufacturing of plastic goods of indelible necessity. It permits a cut-down in workload because the product is near completion as soon as the mold is ready. This feature demands less labor for production, which in turn is efficient for the companies. As the future starts envisioning more advancements, injection molding will continue to play a significant role in shaping plastic as well as the lives of people so vehemently attached to such impressive creations.