What is Plastic injection molding?
Plastic Injection Molding Manufacturer is a way to make a lot of plastic parts that are very similar and have good tolerances. In Injection Molding, polymer granules are first melted and then pushed into a mould under a lot of pressure. There, the liquid plastic cools and hardens, and the mould is removed. People who make things with Injection Molding use thermoplastic polymers that can be coloured or filled with other things, like paint.
Injection moulding is used to make almost all of the plastic parts you see around you, from car parts to electronic enclosures to kitchen appliances.
Injection moulding is so popular because it costs a lot less per unit when you make a lot of things. Injection moulding is a good way to make a lot of the same thing over and over again. It also allows for a lot of different Injection Molding usually has a lot of limitations because it costs a lot to make a mould. Also, the time it takes to go from design to production is very long (at least 4 weeks).
There are many different types of injection moulding, but what is one? When and how does it work?
In this section, we answer these questions and show you common examples of injection molded parts to help you familiarize yourself with the basic mechanics and applications of the technology.
A machine called an injection moulding machine is used to make things :
- Polypropylene (PP): ~38% of global production
- ABS: ~27% of global production
- Polyethylene (PE): ~15% of global production
- Polystyrene (PS): ~8% of global production
A look back at the history of Injection moulding:
Plastics replace ivory:
In 1869, John Wesley Hyatt came up with celluloid, the first practical artificial plastic that could be used to make billiard balls instead of ivory. Early machines used a barrel to heat up the plastic and a plunger to push it into the mould.
A revolutionary invention:
In the mid-1950s, the reciprocating screw was invented, and it completely changed the plastics business. The reciprocating screw solved a lot of problems with uneven heating of the plastic that previous systems had. It also opened up new possibilities for the mass production of plastic parts, which was not possible before.
Plastic Injection molding today:
This is how much money injection moulding makes today: It’s worth about $300 billion. Each year, more than 5 million metric tonnes of plastic parts are made with injection moulding all over the world. Recently, there has been a rise in demand for biodegradable materials because they are better for the environment.
It’s important to know how these machines work:
If you want to make something with an injection moulding machine, there are three main parts. The injection unit, the mould (the heart of the whole process), and the clamping or ejector unit.
As we look at each of these systems in this section, we’ll talk about what they do, and how their basic operation mechanics can affect how well the process works.
Here, you can see a big injection moulding machine at work, making 72 bottle caps a second.
The Plastic injection unit:
The goal of the injection unit is to melt the raw plastic and guide it into the mould, so that it can be used. There are three parts to this machine: the hopper, the barrel, and the reciprocating screw.
In this video, we show you how the process works.
- The polymer granules are first dried and put into a hopper. There, they are mixed with the colour pigment or other reinforcing additives, and then put into the mould.
- As soon as the grains are put into the barrel they are heated together with other ingredients. A variable pitch screw moves them towards the mould as they move towards the barrel. The shape of the screw and the barrel are made to help build up the pressure and melt the material, so they work together.
- Then, the ram moves forward, and the melted plastic is pushed into the mould through the runner system. It fills the whole mould. As the material cools down, it resolidifies and forms into the shape of the mould, just like when you melt chocolate.
- Finally, the mould comes out, and the now-solid part is pushed out by the pins that push it out. The mould then closes, and the process starts again.
In about 30 to 90 seconds, depending on how big the part is, the whole process can be done again.
After the part is thrown away, it is put on a conveyor belt or in a holding box. Most of the time, injection moulded parts can be used right away and don’t need a lot of extra work.
Plastic Injecting Manufacturing the mold:
The mould is like the negative of a picture: its shape and surface texture are directly transferred to the part that is made by injection moulding.
When you start making things with injection moulding, the cost of a mould is usually the biggest part of the costs. A simple mould costs about $2,000-5,000, but a more complex mould can cost up to $100,000 for full-scale production (100,000 units or more).
This is because it takes a lot of skill to design and build a high-quality mould that can make thousands (or even hundreds of thousands) of parts that are exactly the same.
Molds are usually made out of aluminium or tool steel and then finished to meet the needs of the project. Also, they have a runner system that makes it easier for material to get in and water channels inside the mould that make it easier and faster to cool the part.
Plastic Injecting material into the mold: The runner system:
Runnner systems are channels that help the melted plastic get to where it needs to go in the mould. Is in charge of the flow and pressure of the liquid plastic. After it’s injected into the cavity, the plastic is removed and flushed down the drain (it snaps off). The runner system usually has three main parts:
- Plastic that has melted first goes through the sprue. It’s where most of it goes when it comes into contact with the mould.
- One of the runners spreads hot glue along the face where two parts of the mould come together. The spur is then connected to a gate with a piece of hot glue. There may be one or more runners, who help the material go to one or more parts. After the part is thrown out, the runner system is cut off from the rest of the piece. This is the only waste that comes from injection moulding, and 15% to 30% of it can be recycled and reused again.
- In a mould, the gate is where the material comes into the mould. Its shape and where it is is important, because it affects how the plastic moves.
