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Plastic Injection Moulding


What Is Plastic Injection Moulding?


Plastic injection moulding is a fast process in which we are able to produce a high amount of identical items, this can range from disposable consumer goods to highly precision engineering components.


The flexibility in size and shape possible from the use of plastic injection moulding has continually increased the boundaries of design in plastics. Therefore injection mouldings count for a large proportion of all plastic products.


Here at CJ Tool and Mouldings we meet the needs of every individual client despite the size of the job or the unique request, we have an experienced team and can manufacture a range of products using the plastic injection moulding process. We offer a unique innovative filter, this is applied at the beginning of every project right the way through till the completion of the project. This therefore means that at every stage of the plastic injection moulding process we help identify opportunities for improvement, and look to enhance your product to achieve the best results possible.


Why Should I choose Plastic Injection Moulding?


Plastic injection moulding is one of the most common technologies used in the 21st century, it’s accuracy is typically within 0.005 inches meaning the finished product is very precise. As well as this generally it only takes about 15 – 30 seconds to pass between cycle times, however this is dependent on the complexity of the mold itself and its labour cost is low due to the operating machines which require minimal supervision.  Not only this but as so much attention is being paid to sustainability, it’s common practice for our developers to choose processes in which benefit the environment and maximise waste. This is because we only use the necessary amount of plastic used to produce a product and if there is any excess plastic this can be ground up and recycled.

Added: 07 Aug 2018 14:42

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Plastic Injection Moulding new

What is Plastic Injection Moulding?

 Plastic injection Moulding is a key process for building plastic parts and is a quick process used to produce high volumes of identical items, these range from high precision engineering components to disposable consumer goods.

 There are multiple processes of plastic injection moulding each with their own benefits, our team at CJ Tool and Mouldings have the required skill and experience needed to execute each and every process. The injection moulding process is one of the most majorly used process and counts for a significant proportion of all plastic products.

 How does it work?

The plastic injection moulding process is when granules of plastic material are placed into an injection moulding machine through a range of conveying systems. The plastic will then be melted and induced under pressure via a runner system into the cavity. The moulding tool that provides the cavity defines the shape of the moulded part. The material will then cool down and eject from the mould as a finished part. The injection moulding process will then repeat each cycle producing an identical part.

What are the advantages?

There are many advantages to plastic injection moulding, one of which being it’s quick to produce large volumes of parts every hour, usually a typical cycle can be as short as 15 seconds. There is great flexibility in terms of material and colour choice and our team is happy to help you choose right. The  injection moulding process offers low labour costs, as parts can be made ready with little assembly needed. You can view our design guidelines here or get in touch with our experienced team! Another great advantage with plastic injection moulding is that there is very little waste, as often plastic waste can be recycled.

For more information when it comes to plastic injection moulding please contact our specialists today!

Added: 17 Jul 2018 14:22

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Plastic Injection Moulding


In the UK, plastic injection moulding is the main process for manufacturing plastic parts. The process of plastic moulding is fast and ideal for producing large numbers of identical plastic goods.


There are several plastic injection moulding processes, each method presents individual benefits, we’ve explained injection moulding in a separate article.

The process, consists of six steps, clamping, injection, dwelling, cooling, mould opening and ejection. To understand these steps in more detail, read our plastic injection moulding process article.


To manufacture plastic parts using the moulding process, an injection moulding machine is required. These machines can be hydraulic, mechanical, electrical or hybrid. Find out how an injection moulding machine works by reading our article. When choosing a company, consider their machinery. Do they have the latest technology, software and machinery to design and manufacture your product? At CJ Tool & Mouldings we have conventional and C.N.C milling and EDM machines as well as CAD software to produce 2D and 3D prototypes.


We are an experienced plastic injection moulder, with over 30 years’ experience working with customers across the UK. Here at CJ Tool & Mouldings, we offer a full range of injection services; design, tooling, moulding and assembly. We’re also proud to offer our unique innovation filter, which is applied to every project, free of charge. This added value service, evaluates your project at each stage to identify any improvement opportunities and cost-saving options. This service is unique to us because it is delivered by the people within our team, it is their experiences, skillset and knowledge that is being transferred.


We believe that investing in the future, our people and innovative technology that we stay one-step ahead. With a passionate and knowledgeable in-house team, we offer a customer centred and personal approach, delivering quality products with superior customer service.


Get in touch with our specialists to discuss your next project and see how we can help you today. Whether you have a new idea, a new part or an existing mould tool, we can help you.

Added: 22 May 2018 11:05

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Plastic Injection Moulding Jargon Buster

There is a wide range of injection moulding knowledge and experience that often comes with its own language. Therefore, we feel it is helpful to have a basic understanding of the main terms used in plastic injection moulding.


Below is our jargon buster, which explains some of the most commonly used words and phrases.


We hope you find it useful:


Injection Moulding Term.



The change of a material with time under defined environmental conditions, leading to improvement or deterioration of properties.



The part of the moulding press where resin is melted.


Bridge Tool

A temporary low production tool mould. It is made for the purpose of making production parts until a high-volume production mould is ready.



The round protrusions on plastic parts and moulds, often designed for fasteners.



Air pockets that have formed in the material of the component. Bubbles may vary in size.



Concave in mould, which usually forms the outer surface of the moulded part; depending on number of such depressions, moulds are designated as a single cavity or multi-cavity.



The pressure applied to the mould to keep it closed during a cycle, usually expressed in tons.



The complete sequence of operations in a process to complete one set of mouldings. The cycle is taken at a point in the operation and ends when this point is again reached and moving platens of the clamp unit in the fully open position.



The degree of taper of a mould-cavity sidewall or the angle of clearance designed to facilitate removal of parts from a mould. Generally, all plastic components should be designed with draft where possible.


The hardness of a material as measured by the Shore Durometer.



Electric Discharge Machining. Sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges. Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage.


Ejector Pins

Pins that are pushed into a mould cavity from the rear as the mould opens to force the finished part out of the mould. Also called knockout pins.


Family Mould

A multi-cavity mould where each of the cavities forms one of the component parts of an assembled finished part.



Any excess material that is formed with and attached to the component along a seam or mould parting line.


Flow Line

Marks visible on the finished items that indicate the direction of the flow of the melt into the mould.


Flow Marks

Wavy surface appearances on a moulded part caused by improper flow of the melt into the mould.



An orifice through which the melt enters the mould cavity.


Gate Trim

Remnant of plastic left over from cutting the component from the runner or sprue, usually to be cut flush with the edge of the component.


Hand Loads

For low production mould with undercut, steel fixture which create the undercut are manually removed from the mould during the part ejection process.



Refers to the portion of an automatic custom injection mould that keeps the slide in the forward position when the moulding machine is closed on the mould.


Hot-Runner Mould

A mould in which the runners are insulated from the chilled cavities and are kept hot. Hot-runner moulds make parts that have no scrap.


Insert Moulding

Insert moulding is the process of moulding plastic around preformed metal inserts. This process is compatible with both thermoplastic and thermoset materials.



Turbulent flow in the melt caused by an undersized gate or where a thin section rapidly becomes thicker.


Knit Lines

Where melted material flows together to form a line or lines that may cause weakening or breaking of the component.


Living Hinge

A thin flexible hinge made from the same material as the two rigid pieces it connects. It is typically thinned to allow the rigid pieces to bend along the line of the hinge to allow them to open and close. They require careful design and gate placement. A typical application would be the top and bottom of a box.


Mould Frame

A series of steel plates which contain mould components, including cavities, cores, runner system, cooling system, ejection system, etc.


Multi Cavity Mould

 A mould having two or more impressions for forming finished items in one machine cycle.


Over Moulding

A process in which a mould cavity is first partially filled with one plastic and then a second shot is injected to encapsulate the first shot.



The filling of the mould cavity or cavities as full as possible without causing undue stress on the moulds or causing flash to appear on the finished parts.
Over-packing or under-packing results in less than optimum fill.


Parting Line

On a finished part, this line shows where the two mould halves met when they were closed.



The forcing one moulding material out of the plasticiser with another material prior to moulding a new material. Special purging compounds are used.



A thin support features (usually triangle shape) on a part that are used for strengthening wall sections and bosses.



The channel that connects the sprue with the gate for transferring the melt to the cavities.



Refers to when plastic enters into the mould and the melt is maintained by friction produced by speed and pressure. Too much shear can cause the plastic material to burn, too little can cause the material to freeze off causing short shot.


Short Shot

Failure to completely fill the mould or cavities of the mould. Edges may appear melted.


Shrink Rate

The dimensional differences between a moulded part and the actual mould dimensions.


Slide Action

A sliding mechanism in the mould designed for the moulding of parts with undercuts. The undercut-steel fixture is held in place during the injection process and then slides out of the way prior to ejection.


Single Cavity Mould

A mould having only one cavity and producing only one finished part per cycle.


Sink Marks

A shallow depression or dimple on the surface of a finished part created by shrinkage or low fill of the cavity.



Area of the custom plastic injection moulds that is used for creating undercuts. Required for automatic injection moulds



The feed opening provided in injection moulding between the nozzle and cavity or runner system.


Steel (Metal) Safe

Part design change will only require when removing metal from mould instead of “weld-add” metal on the mould.


Straight Pull

No side actions.



A shallow channel or opening cut in the cavity to allow air or gases to escape as the melt fills the cavity.



A protuberance or indentation that impedes withdrawal from a two-piece rigid mould.



A mark created by trimming the injection moulded part gate.


Wall Thickness

The thickness of the cross section of the plastic part.



Dimensional distortion in a moulded object. Caused by internal stresses via un-even material flow, cooling, and compression



Where melted material flows together during moulding to form a visible line or lines on a finished part that may cause weakening or breaking of the component.


Added: 24 Apr 2018 10:14

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Plastic Injection Moulding UK

CJ Tool and Mouldings are a long-established plastic injection moulding manufacturer in the West Midlands. We strive to use our advanced experience to offer a customer centred personal approach, providing high quality and professional plastic moulding services within the UK.


There are many plastic injection moulding companies based in the UK, however CJ Tools and Mouldings provide the highest quality and delivery of plastic injection moulding. We always like to guarantee our clients an effective and smooth process from design to assembly.


CJ Tool and Mouldings are a UK plastic injection moulding firm that puts quality at the forefront of everything we do. We have and continue to develop the quality of our services and products to meet and exceed UK and worldwide standards. Learn about our quality and accreditations here.


We are proud to offer an added value service called the ‘innovation filter’. This is a single point of contact for all your plastic injection moulding and tool making requirements. This service is incorporated into each project, providing added value and potential customer savings. The customer benefits from dealing with just one supplier at no additional cost, saving time and money and ultimately receiving a more robust product.


CJ Tool and Mouldings is constantly maximising speed, quality and productivity as we aim to become one of the top plastic injection moulding manufacturers in the UK. We guarantee that you will not get a higher quality of plastic product and service within any other manufacturer in the UK. Our personal and customer centred approach sets us apart from other firms and ensures we build long-standing partnerships with our customers.


Our team are always happy to help, advise and quote for your requirements. For our specialist advice, please contact CJ Tool and Mouldings today or read our latest articles for tips and advice on plastic injection moulding.



Added: 20 Feb 2018 12:06

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Plastic Injection Moulders – 2017 a great year for CJ Tool & Mouldings

2017 has been a great year for CJ Tool & Mouldings as we have seen many achievements and developments throughout the course of the year.
Let’s recap on some of the fantastic highlights we have had!

In June, we launched our brand-new website. The website had a whole new look and modern feel to it, effectively representing the business and our core values; people, product, partnership. The new site was also tablet and mobile responsive, so easily scaled down to view and use on different devices. It has been a great success and a big hit with our customers and suppliers.  
In addition to this, we began our online social media presence.

We will continue to grow our online presence, connecting with UK business, to further establish our ‘people, product, partnership’ core value.


September saw the installation of our new and innovative water cooling system. It is one of the most energy efficient systems on the market. It has allowed for our business to reduce our carbon footprint and replaces two large conventional chiller units. Being eco-friendly is extremely important to us and we are actively establishing green initiatives.


Another great achievement in 2017 for CJ Tool & Mouldings was the renewal of our ISO Certification 9001:2008. This continued certification has allowed for significant improvements throughout the business and helped to further streamline the operations throughout our plastic injection moulding process. The 9001:2008 Certification has assisted in the businesses resilience and work ethic. ISO9001:2008 is currently changing to ISO9001:2015 which will apply risk strategies within our quality management system; which will aid CJ Tool and Mouldings in managing our business risks whilst applying controls to deliver consistency and increase customers satisfaction.


Our Business Support Manager, Miranda Woodhouse, has recently started a management development programme at Wolverhampton Science Park. She attends monthly seminars that provide learning experiences to compliment Miranda’s careers aspirations at CJ Tool & Mouldings. The programme covers a variety of aspects such as understanding the challenges managers face on a day to day basis and finding solutions to make the challenges much easier to deal with.
Overall, the management development programme helps Miranda to understand and use the core skills and values that are set within the business to aid her in becoming a fantastic manager for the team.


We’re extremely proud of our developments and achievements in 2017 and look forward to a successful year in 2018!

Added: 12 Dec 2017 09:17

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