Injection Molding: One of the Reasons Plastic Parts Are So Cheap

It’s amazing what you can buy these days without spending a whole lot of money. Products that used to cost a lot when I was a little kid now cost next to nothing thanks to cheap plastic parts that keep the retail cost of finished goods in check. Plastic parts are cheap because they can be produced cheaply. Injection molding is the key to it all.

Although injection molding is only one of several methods of plastic manufacturing, it is arguably the easiest and most popular. Manufacturers love it because it’s efficient, cost effective, and highly repeatable. Most parts can be produced via injection molding for pennies. And as for the waste the process produces, it is fully recyclable.

The Basic Premise


The basic premise of injection molding is in the name itself. Stainless steel molds are carefully engineered and manufactured. One placed into an injection mold machine a mold is injected with molten plastic that cools nearly instantly. The mold opens, the part falls out, it closes back up, and the process repeats.

The most difficult aspect of injection molding is creating the molds themselves. These are precision molds made by skilled craftsmen who train for years before being allowed to work on their own. A well-constructed mold will provide years of reliable service.

A major benefit of injection mold manufacturing is the ability to make plastic parts in nearly any shape. If you can think it up, someone can probably manufacture a mold to make it happen. It’s just a question of how difficult a particular design might be from an engineering standpoint. But once a mold is complete and ready to go, you get consistent parts run after run.

Plastic Purge and Cutoffs

Plastic Purge and Cutoffs

Injection mold manufacturing produces two types of plastic waste. Both are recyclable. Companies like Tennessee-based Seraphim Plastics often purchase this waste, transform it into a product known as regrind, and sell that product back to manufacturers. They utilize a mechanical recycling process that reduces the scrap to small pellets that can be mixed with virgin plastic for new parts.

As for the two types of waste, here they are:

  •       Plastic Purge – Injection mold machines need to be cleaned every now and again. Cleaning forces engineers to purge a machine of any and all molten plastic still inside it. This plastic is known as purge.
  •       Cutoffs – Completed parts produced by injection molding are attached to plastic frames. They need to be removed from those frames and trimmed. The frames and any trimmed plastic are discarded as waste. They are known in the industry as cutoffs.

The beauty of both plastic purge and cutoffs is that injection mold companies can either send them to recyclers for processing or handle it in-house themselves. Most send it to recyclers rather than invest in the grinders and shredders needed to reduce the waste to regrind.

Environmental Benefits of Recycling Plastic Waste in Injection Molding

Recycling Plastic Waste

Injection molding is a remarkable process that revolutionized the manufacturing industry by making plastic parts affordable. While it’s primarily known for its cost-effective production capabilities, it’s equally important to recognize the environmental benefits it offers through the recycling of such waste.

Plastic production has been a vital part of the modern world, but its environmental footprint has been a growing concern. One of the main advantages of injection molding is its inherent efficiency, which translates into less waste. However, it’s essential to address the plastic waste that is generated, which is where recycling comes into play.

Injection molding yields two types of plastic waste: that of purge and cutoffs. These waste materials can be recycled, contributing to a more sustainable manufacturing process. Many companies have recognized the value of recycling these plastic wastes. Through a mechanical recycling process, they transform purge and cutoffs into a product called regrind, which can be mixed with virgin plastic to create new parts.

The environmental benefits of recycling plastic waste are multifaceted. First and foremost, it reduces the amount of waste ending up in landfills, where plastic can take centuries to decompose fully. Recycling gives these materials a new lease on life, preventing the environmental harm associated with improper disposal.

Moreover, recycling helps conserve valuable resources. By reusing plastic waste to create new parts, there is less reliance on virgin plastic production, which demands significant energy and resources. This reduction in the need for virgin material helps mitigate the environmental impact associated with extracting and processing raw materials.

Additionally, recycling plastic waste reduces the carbon footprint associated with the production. The energy required to create plastic from scratch is substantial, but recycling requires significantly less energy, thereby reducing greenhouse gas emissions.

Furthermore, the use of recycled plastics in injection molding contributes to a circular economy, where materials are continually reused, extending their lifecycle and reducing the need for constant production of new materials. This circular approach aligns with sustainability goals and helps preserve natural resources.

Incorporating recycling into injection molding practices is not only environmentally responsible but also economically sound. Companies can collaborate with recycling facilities to minimize waste and lower production costs, demonstrating that sustainability and cost-effectiveness can go hand in hand.

Producing Parts for Pennies

The limited expense of injection mold manufacturing is rooted in repeatability. A stainless-steel mold will hold up for years. Based on the size of a part and its setup, it’s theoretically possible for a single mold to spit out thousands of parts per hour. Every one of those parts will be identical. Best of all, the entire process is automated.

A large volume of parts, repeatability, and automation make it possible to produce plastic parts for mere pennies. If you’ve never seen injection molding in person, it really is fascinating. Search for some videos online and take a look. You’ll soon understand why plastic helps keep consumer prices in check.