We begin our series with information on the basics of plastic injection molding presses.  We hope you find this information useful.  If you have specific questions, please do not hesitate to contact us.

We make injection mold  and  produce many different final products..(include injection molding, assemble, painting,  silk-screen).

Often plastic injection companies will provide a molding equipment list on their website. It may look something like this:

From your initial thoughts on a part through to full scale production we can take you down the right pathway. As seen in the image a client’s initial thought was then designed by our R&D team, drawn, prototyped, mould designed and finally manufactured in masses.

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Once you have an estimate of the press size you will need, you can identify plastic injection molding companies that will meet your requirements. In general, molders with a greater number and wider selection of press sizes will be able to accommodate the needs of your project.  If you are not working with a completed mold, look for a plastic injection company who can design and build the mold. They will have a better understanding of how to maximize the manufacturing process and will often offer tooling allowances. This, in turn, will minimize the overall cost of your project.

Plastic injection molding presses are classified or rated based on tonnage, or more specifically the clamping pressure or force. Presses can run in size from less than 5 tons of clamping pressure to over 4000. The higher the press ton rating, the larger the machine.

There are many factors that are taken into consideration when determining the size of the press. The size of the part, the polymer being used and something called the safety factor. The safety factor is an additional numerical percentage buffer that is added to the calculation to help avoid defects in the final part. Some recommend adding 10% to allow for the safety factor. As mentioned earlier, the MFI (Melt Flow Index) of the plastic compound will also impact the pressure needed to produce the part. Many calculations include the platen size as well as the mold and part size, however, to get an estimate of the press size your project will need, we have simplified it even further.

Our team believes in a 100% safe working environment and procedures. We offer clean room facilities and a purpose built injection moulding workshop. We can assure you we can achieve great results and complete customer satisfaction.

We have the latest technology robotic Automation. Above are medical parts that have been removed from the injection moulding machine. Once these parts have been taken from the mould they go through a series of QA checks before being placed in the correct packaging for dispatch

While plastic injection molders will help you determine the size of the machine needed to get the best result, a project designer or engineer can get a good estimate based on some basic information. By knowing approximately what size machine will be required, you can better source a plastic injection molder that will meet your needs.

Many plastic injection professionals use a general rule of thumb of 2.5 times the surface square inches of the part to be produced. So, if you have a part with 42 square inches than you would need a press size with 105 tons of pressure. If you add 10% for a safety factor, you will need to use a press with a minimum of 115 tons of clamping force. A press size of 120 tons would be able to accommodate your plastic injection molded product.

Custom Plastic Injection moulding is the preferred manufacturing process when you need to produce amounts of the same plastic part. The process involves heating up small plastic granules, usually to a liquid state and then injecting it under pressure into the cavity of a mould. After you have finalised the custom design of the plastic part you want to make, the first step in getting the part injection moulded is to build the mould.

Posted by Kyle Coblentz | 07 / 17 / 13 5 Comments

Topics: Plastic Injection Molding, Injection Molding Basics, Plastic Injection Molds and Presses

Our quality management systems ensure our customer’s requirements are always exceeded. Developing processes and procedures aimed at continuously improving operations and meeting the never ending demands of the manufacturing sector.

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No components are too difficult , with an extensive range of injection moulding machines of all different sizes and tonnages there is no project we can’t look into.

Our machine capacity dynamically adapts to various requirements. Our ability to process all plastics is further highlighted through a specialised focus on engineering plastics. At Allmould Plastics our purpose built facility is equipped with the latest machines, automation and robotics, to ensure a lean manufacturing process of optimal production efficiency.

We can help you design &  manufacture all types of plastic parts, aluminum/zinc parts. Includes electronic assembling, silk-screen printing, oil-spout and packaging.

We offer a blend of traditional, and high tech mould making skills on site which enables us to produce every type of tool from prototype tools through to fully specified production tools.

In the end, your plastic injection molder will determine which machine would be best suited for your project. Larger presses can accommodate larger molds and multi-cavity molds often reducing the cost per part. However, larger molds are more expensive. Choosing the right press size can balance the upfront tooling expenditures with long-term manufacturing costs.

A machine rated for 68 tons can deliver 68 tons of clamping pressure. This pressure keeps the mold closed during the injection process. Too much or too little pressure can cause quality issues.  Too much or too little pressure can also cause flashing, where excess material appears on the part edge. Pressure also impacts the viscosity of the plastic being used in the project. Melt Flow Index or MFI is a measure of the ease of flow of the melt of a thermoplastic polymer. Plastic compounds react differently to pressure based on their MFI. The higher the MFI, the higher the pressure needed.

The building of a custom plastic mold requires great precision using design software and metal working equipment such as CNC milling stations, EDM machines etc. Custom Plastic Mold costs vary depending on:

By involving Plastic Parts Direct at an early stage in your injection moulding product development, we can offer you the best advice on how to save time and money whilst not compromising on standards or functionality. We are always on hand to work with you to obtain the most efficient and economical solution to your injection moulding requirements.

Our use of computer generated solid modelling allows us to ‘proof’ customers designs before any metal is cut and thus keep us at the forefront in the moulding industry.

Our website is frequently visited by product designers, engineers and purchasing agents who are looking for information on plastic injection molding.  With this in mind, we have created a new series of articles that are developed to give our readers a better understanding of the presses, processes and pitfalls in our industry.

Above is an injection mould we made to produce plastic bottle preforms. Countless hours are poured into the design of these types of moulds from our Engineers to guarantee maximum production along with short cycle times.