Things You Need to Know When Designing Products for Injection Molding


Injection molding is one of the most common manufacturing techniques in the world. It’s been used to create plastic goods in a variety of industries and it is arguably one of the best and most economical plastic molding techniques available.

Because of their lightweight, cost-effectiveness, and easy serializability, injection-molded plastic is a popular choice for many segments, including the health industry. The global injection molding market is expected to grow further as almost all plastic products are made using injection molding.

The following article will share everything you need to know about designing products for injection molding.

What Is Injection Molding?

The injection molding process is a way of getting objects to form. Hot, melted plastic is injected into a mold, and once it hardens, it takes on the shape of the mold, forming an object.

Injection molding can be done with a two-part or single-part mold. A two-part mold has the two halves assembled together around the object to be molded, then clamp them together and inject the material through an opening in one half of the mold.

A single-part mold has only one side, and it will have an opening for injecting the material through. It’s rarely used, as you cannot easily extract the object once it hardens, and you’ll probably have to ruin the mold.

The injection process is often used for mass production of parts because it produces parts that are symmetrical and interchangeable. For instance, injection molding is used in healthcare, for creating pregnancy test kits and blood sample analysis cuvettes.

Stages of Injection Molding

There are four stages of injection molding, and it usually takes anywhere from two seconds to two minutes to produce one object, depending on its size.

  • Clamping. The first part of the process is where the two parts of the mold are put together.
  • Injection. Hot, melted plastic is poured into the mold.
  • Cooling. It takes a short while for the plastic to cool down and harden.
  • Ejection. After the cooling process, the object is removed from the mold, and ready for usage.

Benefits of Injection Molding

Low Cost of Production

The process of injection molding is budget-friendly for the company because it allows for mass production with little labor costs. Not to mention that it is a fairly quick and easy process.

Moreover, there are many advantages to using this process including that it does not require any special equipment or materials, apart from the specially designed mold.

Repetitive Action

The injection molding process is a repetitive process, meaning the machine does not change much from one part to the next. This also means that there is not a lot of work for the operator to do. The machine does all of the work, and all that is required from the operator is to monitor and make sure everything stays in order.

Creating or finding the mold is the hardest part of the process. People often focus on the finished product, but there wouldn’t be a product without the mold. Once you purchase it, the hardest part of the job is over, but you shouldn’t overlook the mold design, as it’s an essential part that will guarantee consistency and repeatability of the process.

Small Amounts of Waste

The process is relatively clean, and there is no mess. But sometimes, there are extra pieces of plastic sticking out from the object, as the melted plastic found its way into the cracks of the mold. You can cut them easily and dispose of them.

Factors That Affect the Production

Object Wall Thickness

If your main goal is to produce as many objects as possible, you’ll need to create them with thin walls. The thinner the plastic wall, the quicker the object will cool down and harden. On average, wall thickness ranges from 2-4 mm, but there are injections as thin as 0.5 mm.


Depending on the mold, your object may have ribs on it, and sometimes, they can possess a problem for the final process as they tend to be thicker than normal walls. In order to avoid problems, try keeping the ribs at no more than 60% of the wall thickness.


Bosses are the parts where screws are attached, and they can easily sink in the process. In order to keep the desired bosses intact, you’ll need to keep the thickness at no more than 60% of the nominal wall thickness of the object.

Bottom Line

Injection molding has wide acceptance and widespread popularity. It has many advantages, making it the most efficient manufacturing method on the market. Injection molding can produce parts and components made of plastic that are precise, flexible, high-resistant, cost-efficient, and highly durable.