Plastic Die Mould

Introduction to Plastic Die Moulds

Non-metallic, synthetically produced materials are called plastics. For commercial use, they can be moulded into many different shapes and hardened. Products made from plastic moulding are widely available. Jars, safety caps, plastic tubes, handles, toys, bottles, cases, accessories, kitchen utensils and many other items are examples.

Even the keyboard and mouse you use are made of plastic through the moulding process. Even the plastic components of the chair you are sitting in are made using this process.

The basic principle of plastic moulding is to pour molten liquid plastic into a ready-made mould, such as a bottle mould. Once it has cooled, the mould is removed to expose the plastic bottle.

Types of Mouldings

Extrusion Moulding

Extrusion moulding involves forcing hot, molten plastic through a pre-formed hole to produce a long, shaped plastic object. A die is the flexible shape through which the molten plastic is forced. This die is specifically designed to produce the desired result. Making moulded biscuits is almost like running dough through a press.

Extrusion is also used in other types of plastic moulding to get the raw liquid into the moulds, but instead of using moulds to create the desired shape, extrusion uses the shape of the die to create the shape. 

Compression Moulding

This technique involves pouring raw liquid plastic into a heated mould, which is then crushed to create the desired shape. The high temperature throughout the process ensures good strength in the finished product. The liquid plastic is cooled to maintain its shape before being trimmed and removed from the mould to complete the process.

Blow Moulding

The hollow and thin-walled bespoke plastic parts produced by blow moulding are hollow. This method is ideal when the plastic part needs to have a uniform wall thickness. Glass blowing is very similar to this process.

The machine melts the raw plastic until it becomes liquid and then inflates it like a balloon by blowing air into it. After being blown into a mould with a specific shape, the plastic begins to take on that shape as it grows and presses against the walls of the mould. The liquid balloon is cooled to maintain its shape after filling the mould. In a 12-hour working day, the process can produce up to 1400 pieces.

Using Injection Moulds

Extrusion and injection moulding are similar processes. Injection moulding is different because molten plastic is pumped directly into a unique mould. High pressure is used during injection to fill the mould and create solid parts. The plastic is cooled to maintain its new shape once the mould is filled, similar to the previous processes, and the mould is then opened.

This is similar to a jelly mould where the final product is created by filling and cooling the mould.

Movement in Rotation

In this process, sometimes called rotomoulding, the resin or liquid is poured into the mould and then rapidly rotated. The liquid is then evenly distributed over the entire surface of the mould to create a cavity with uniformly thick walls. The liquid plastic is removed from the mould after it has cooled and taken its new shape.

This process is cheaper and more environmentally friendly because it uses a small amount of material efficiently and produces very little waste.

Benefits of Using Plastic Die Moulds

1. Effective high output

Once the moulds are created, the process is incredibly fast, with cycle times as low as 10 seconds. Depending on the moulds you choose, it is suitable for medium and high volume production runs from 10,000 to well over 100,000 parts. 

Occasionally, the use of a multi-cavity or family mould, which produces many parts from a single press, can help to increase productivity.

Consider an efficient front-end design and ordering process when outsourcing your tooling; take a look at our on-demand production.

2. Reasonable component costs

The cost per part for high volume production is quite reasonable. By using aluminium moulds instead of steel moulds, you can save costs even for medium volumes, i.e. between 10,000 and 25,000 parts.

3. Repetition

Multiple copies of the same product can be produced. If you need parts with tight tolerances and high reliability, this is the best option.

4. Wide range of materials

You can choose from a wide range of plastic materials depending on the properties you require from your end product. Protolabs also offers liquid silicone rubber moulding, so you are not restricted to using plastic. 

A wide range of colours are available and you can even incorporate fillers into the moulding process to make the finished item more robust.  Talk to us about what you need your part to achieve; there are usually a variety of options.

Plastic Die Mould Manufacturing Process

Blow moulding- Best suited for hollow objects

Suitable for hollow products such as bottles, blow moulds, the process follows the basic steps of glass blowing. Air is used to inflate a parison, a heated mass of plastic, often a tube. To create the desired shape, the air forces the plastic against the mould. After cooling, the plastic is ejected.

Blow moulding is used to make hollow, one-piece, large volume items. It is ideal if you need to produce a large number of bottles. Blow moulding produces very consistent, thin-walled containers. It can also be very cost effective.

Compression molding- suited for larger objects

Larger things, such as car parts, are best suited to compression moulding.
The name of this moulding technique says it all.  A heated piece of plastic is pressed into shape using a heated mould. Plastic can be bought in bulk, but it often comes in sheets. The finished item retains its integrity thanks to the heating process, known as curing. The item is then removed from the mould after moulding, as with other moulding techniques. If plastic sheeting is used, the plastic must first be cut to size in the mould before the part can be removed.

Extrusion molding- suited for long hollow formed applications  

Larger things, such as car parts, are best suited to compression moulding.
The name of this moulding technique says it all.  A heated piece of plastic is pressed into shape using a heated mould. Plastic can be bought in bulk, but it often comes in sheets. The finished item retains its integrity thanks to the heating process, known as curing. The item is then removed from the mould after moulding, as with other moulding techniques. If plastic sheeting is used, the plastic must first be cut to size in the mould before the part can be removed.

How to Choose the Right Plastic Die Mould

• Hardness: The resistance of a material to compression and indentation is a measure of its hardness. Shore hardness, which can be divided into Type A and Type D, is measured using an indenter. Each category has a scale from 0 to 100 to better gauge the hardness of the material in question, with Shore A referring to softer plastics and Shore D referring to tougher plastics.
• Cost considerations: When deciding which material to use for your injection moulding project, cost is a key consideration. This choice requires careful consideration, as it also needs to take into account how the product will be used. Choosing a more expensive material up front can pay off in the long run, whereas cheaper solutions can sometimes lead to costly failures later on.
• Weight: The fourth and final factor to consider when selecting an injection moulding material is weight. This is because both the weight of the finished product and the weight of the moulded part depend on the density of the polymer. Weight can be a critical issue because lightweight consumer products often contain injection moulded parts.