Introduction: Injection molding is a super cool way to make stuff. It’s been around for a long time and it’s made making things way faster. When you’re making a lot of stuff, it’s important to make it fast and easy. That’s because it’s cheaper to make stuff, you can make more stuff, you can make stuff better and you can sell more stuff.

In injection molding project , molten plastic is quickly cooled through cooling lines to form material forming , which is suitable for high volumes . Although injection molding has so many advantages, what are the disadvantages of injection molding? This article will explain this issue.

What is Injection Molding?

Injection molding is a manufacturing processes where you take some melted stuff and squirt it into a mold. Then you let it cool down and harden. After that, you take it out of the mold. You can use this process to make one thing, but usually you use it to make a lot of the same thing. The stuff you squirt into the mold is usually plastic materials or rubber.

How Does Injection Molding Work?

Injection molding is done using a special injection molding machine. The manufacturing process is divided into the following steps:

Creating the Mold

The first step in injection molding is to make the injection mold . Using computer-aided design (CAD) software, follow several injection molding guidelines to design the injection molds for the part you want to make, based on the part’s 3D model. Then, make the mold in two parts, usually using computer numerical control (CNC) machining. The mold is made of metal, usually steel or aluminum.

Injection

The two halves of the mold are put in the clamping unit of the injection molding machine and held together tightly by the clamping unit. The raw material is put into the barrel as granules or pellets, where it is heated at high temperature and pressure until it melts. The material, now melted, is shot into the mold cavity, filling the whole space in the mold. It then cools and hardens, taking the shape of the mold.

Demolding and Finishing

Once the material has cooled down and hardened, the mold is opened using the clamping device and the hardened finished part is pushed out. Some finishing operations are done on the finished part. These operations include removing extra material and support structures, smoothing the surface, and, if needed, painting, plating, heat treating, etc.

What are the Commonly Used Materials for Injection Molding?

Polypropylene (PP)

PP, or polypropylene, is a versatile thermoplastic that’s used in injection molding. It’s lightweight, resists chemicals and holds up well under stress. That’s why it’s a top choice for making things like packaging, containers and car parts.

Polyethylene (PE)

Polyethylene (PE) is a lightweight plastic known for its flexibility and low cost. It has different types like HDPE and LDPE and can be used in a bunch of different industries from packaging and containers to agricultural products and toys.

Polystyrene (PS)

Polystyrene (PS) is clear, hard, and cheap. It’s used a lot in throwaway stuff like packaging, food containers, and throwaway cutlery because it’s easy to shape and doesn’t cost much.

Nylon (PA 6)

Nylon, specifically nylon 6 or PA 6, is known for being strong, tough, and resistant to wear. It’s great for making mechanical parts and is used a lot in things like gears, bearings, and other parts that need to be made high output production, last a long time, and be made very precisely.

Polycarbonate (PC)

PC, or polycarbonate, is known for being see-through, tough, and able to handle high heat. That’s why it’s used to make things like eyeglass lenses, computer parts, and clear stuff that doesn’t break in lots of different industries.

What are the Limitations of Injection Molding?

High Initial Mold Cost

One of the big downsides of injection molding is the high cost of making the mold. Designing and making a mold to fit a specific part shape can be very expensive, especially for complex or fancy designs. For companies with smaller production or limited budgets, this initial investment can be a deal breaker.

Injection molding is a precision manufacturing technology that requires high costs to ensure product quality and consistency. The production of injection molding requires a lot of equipment, processes and human resources, resulting in high production costs. In addition, the injection molding process requires the use of high-quality raw materials and additives, which further increases costs.

Design Limitations

Injection molding is super versatile for making all kinds of shapes and details, but there are still some things you gotta think about. Some shapes, like sharp corners, thin walls, or deep grooves, can make it hard to fill the mold, cool the part, or get it out of the mold.

When you design parts for injection molding, you gotta think about things like draft angles, wall thicknesses, and other stuff to make sure the mold works and the parts come out good. Sometimes you gotta add extra stuff to the mold or do extra things to the part to make it work, and that can make it more expensive.

Visible Defects in the Finished Product

While the process is extremely accurate, the finished product may still have minor defects that remain in the injection molding process. Please note that such defects do not affect the functionality of the part. Defects include distortion, nozzle drooling, sink marks, flow marks, and weld marks.

Higher Cost

Injection molding requires a lot of equipment, including injection molding machines, molds, automatic transport equipment, and related auxiliary equipment. These equipment need to be strictly maintained and managed, and once a failure occurs, the repair cost is relatively high.

Injection molding also requires high-precision temperature control systems and pressure control systems, and the equipment must have a high degree of stability and reliability.

The setup cost of injection molding is high. The equipment and tools required are very expensive. Mold prototypes also need to be repeatedly manufactured and tested. In addition, experienced technical workers are required to design molds to avoid additional costs in the production process.

Long Production Cycle

The production cycle of plastic injection molding is relatively long, generally taking several days to several weeks. This is mainly because injection molding requires multiple links such as mold making, mold trial, and mass production, and each link takes a long time. This also makes the injection molding production cycle not conducive to the processing of urgent orders.

Compared to some rapid prototyping methods like 3D printing, plastic injection moulding usually takes longer to set up and get started. The process includes designing and making molds, running mold trials, and dialing in process parameters before you can start making parts in large quantities. So the time from concept to finished parts can be longer than with faster prototyping methods.

Environmental Pollution

When you make stuff with injection moulding , you can make some bad stuff too. Generate unused or waste plastic , Like, you can make gas and water that’s bad for the world. And you need a lot of energy and stuff to make things with injection molding, which is also bad for the world.

Limitations in Materials

The materials for injection molding are usually thermoplastics, such as polypropylene, polyurethane, etc. These materials have certain chemical and physical properties, so their specific performance also has limitations.

In injection molding, it is necessary to consider the fluidity and melt index of the material, so some special materials are not suitable for injection molding, such as some materials with high requirements for high temperature performance and chemical corrosion resistance.

Limitations in Size

Injection molding has some limitations when it comes to part size. Generally, injection molding is good for small and medium-sized parts. But if you’re making big parts, you have to think about things like how complicated the mold is and how much it costs.

Also, injection molding is usually for parts that are 300mm or smaller. If you’re making parts that are bigger than 300mm, you have to use other molding methods.

Injection molding can be limited in size, especially for big parts. The size of the injection molding machine and the size of the mold cavity can limit the biggest part you can make. If you want to make a part that’s too big, you might need special equipment or multiple mold cavities, which makes it more expensive and complicated.

Limitations in Shape

Injection molding has some limitations on the shape of the part. Injection molding is best for molding parts with simple shapes, such as cylindrical, box-shaped, etc. For parts with complex shapes, multiple injection molding and post-processing operations are required, which increase cost and complexity.

Conclusion

Injection molding is a great way to make a lot of parts fast. It can make parts that are really precise and have a lot of detail. But it has some problems. It costs a lot to make the molds. It takes a long time to make the parts.

You can’t make parts that are too complicated. You have to use the right kind of plastic and make the parts the right size. It costs a lot to buy the machines and keep them running. It can make a mess and hurt the environment. You can’t use it to make everything.