A mould tool is critical to plastic production. Without it, you can’t form a component of any kind. It shapes every product that goes through the moulding process, from a simple plug to a detailed engineering component.
A well designed tool helps control the quality and consistency of each part, and supports an efficient production run. Even small choices in design can affect cycle time, surface finish, and the long term performance of the product. As a rule, the design of your tool has a direct impact on its lifespan too.
This means that the way the steel is selected, how the cooling channels are placed, and how the parts open and close will all influence how long the tool can run before it needs maintenance or repair. A thoughtful design helps prevent early wear, reduces stress on moving parts and keeps production stable over many cycles.
When we design a tool, we plan far more than the external shape. We think about how your plastic will flow, cool and release. Generally, a tool is made from steel or aluminium, and includes two main halves known as the core and cavity. Together, they form the profile of your product.
A good injection moulding tool design considers:
Each detail supports a stable moulding process.
During moulding, molten plastic travels through a channel inside the tool from the machine barrel into the cavity. Venting inside the tool lets trapped air escape so you can avoid voids or bubbles on the finished part.
The tool then cools the plastic. This is done by circulating water or oil through internal channels, similar to a car cooling system. Cooling is important because the plastic must set at the right speed to avoid stress marks or distortion.
Once the part has set, ejector pins gently push it out of the rool, and the cycle starts again.
Below is a guide to the main components you’ll find in most mould tools. This helps demonstrate how each section supports the moulding process.
1. Location ring – Aligns the tool with the moulding machine so everything sits in the correct position.
2. Fixed half clamp plate – Holds the fixed side of the tool in place and provides the structure for the cavity.
3. Pillars & bushes – Precision ground alignment pillars that ensure the fixed and moving halves of a tool lines up with one another.
4. Sprue bush – The entry point for molten plastic. This can be a hot or cold tip. A hot tip can reduce material waste and offer more control.
5. Fixed half cavity plate – Holds the cavity or female part of the tool and gives on half of the product its shape.
6. Slides – Used when the part needs undercuts or details that cannot be formed with a simple open and shut tool. Not all tools need slides.
7. Moving half core plate
This holds the other half of the product shape, known as the core or male half. During moulding, molten plastic flows into both the core and cavity and then sets into the final form. The plastic reaches these areas through two key features.
8. Ejector set – The ejector set includes the plate that holds the ejector pins in the right position, along with the pins themselves. Once the moulding has set and the tool opens, these pins push the part out of the mould so it can be collected and the next cycle can begin.
9. Risers – Provide space for the ejector plate to move.
10. Moving half clamp plate – Holds the moving half of the tool in position on the moulding machine.
Every project calls for a slightly different approach. A new injection mould tool can be the best choice if you’re planning for long term production. A fresh tool delivers better results for a product with complex features, tight tolerances and material flow. It also guarantees a longer lifespan for your tool.
In some situations, we can adapt or repair an existing tool instead. This can be helpful if you already have a mould tool that only needs small changes, such as an updated feature or a minor size adjustment. Reworking a tool can reduce both lead time and cost, as long as the original steel allows for it.
Our team always reviews the part design, the production volume, and your goals before giving advice. We look for the most practical and efficient path, whether that means creating a new tool or making the most of what you already have.
At Bowles & Walker, we provide support from tooling design right through to production. We work closely with our customers and give pragmatic advice at each stage so your tooling is cost effective and suited to the way you want to mould your parts.
If you would like to talk through a project or need guidance on your next tool, you can call us on 01953 885294 or email info@bowles-walker.com. We are always happy to help you create reliable products, manage costs and support UK manufacturing.
