Injection molding machines use a processing method in mass production of plastic parts with complex shapes. The advantages of the injection molding machines are fast production speed, high efficiency, automatic operation, variety of colors, shapes from simple to complex, the size can be from large to small, and the size of the injection molded part is accurate, the product is easy to be replaced, and injection molded parts with complex shape can be molded.
According to Wikipedia, “Injection molding uses a special-purpose machine that has three parts: the injection unit, the mold and the clamp. Parts to be injection-molded must be very carefully designed to facilitate the molding process; the material used for the part, the desired shape and features of the part, the material of the mold, and the properties of the molding machine must all be taken into account. The versatility of injection molding is facilitated by this breadth of design considerations and possibilities.”.
Click on any image below to view details
The “tonnage” is the measure of force that is required to keep the tool closed during the injection process. This force is the main factor in determining the injection moldier machine size required for producing the part.
Plastic injection molding machines are classified or rated based on tonnage, or more specifically the clamping pressure or force. Smaller presses have tie bar spacing too narrow to accommodate larger products. Lower tonnage machines such as 10 to 100 Ton injection molding machines are great for smaller plastic parts such as those used in medical devices and can also accommodate a wide variety of parts in the aforementioned industries as well.
Most injection molding machines will recommend 2.5 times the surface square inches of the part and an additional 10% as a safety factor. If you have a part that is 120 square inches, you would need a press size with 300 tons of pressure. When you add the 10% safety factor, the required press size would have 330 tons of clamping force.
While large-tonnage injection molder machines require some big investments in infrastructure, the markets that require large parts offer some great business opportunities to Injection molders. These Plastic injection molders are classified or rated based on tonnage, or more specifically the clamping pressure or force. Larger presses can accommodate larger molds and multi-cavity molds often reducing the cost per part.
A machine rated for 100 tons can deliver 100 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.
While plastic injection molding machines 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.
In the end, your plastic injection molding machine 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.
Injection Molding Machine for Plastic Parts Production
Stack of polypropylene food containers on conveyor belt of automatic plastic injection molding machine at fabric, exhibition, trade show. Manufacturing, industry, automated technology concept.
The Machinery Center, also known as MCI was founded in 1990 by both Richard Stone and Richard Todd. Combined they have over 60+ years’ experience in both the Plastics and Metal Industry. They are proud to be the leading providers as well as the largest “stocking” dealer of quality pre-owned equipment for the US, Mexico, Canada and Overseas Market. Call us at (561) 953-9100 and we will be happy to help you.
We carry a wide assortment of injection molding machines from many different manufacturers. Click on one of the links below to see the manufacturers and injection molding machines the offer.
Injection Molders 10 To 100 Ton
Injection Molders 101 To 200 Ton
Injection Molders 201 To 300 Ton
Injection Molders 301 To 400 Ton
Injection Molders 401 To 500 Ton
Injection Molders 501 To 600 Ton
Injection Molders 601 To 700 Ton
Injection Molders 701 To 800 Ton
Injection Molders 801 To 900 Ton
Injection Molders 901 Ton & Over
Injection Molders – Electric
Injection Molders – Liquid Type
Injection Molders – Rotary Type
Injection Molders – Shuttle Type
Injection Molders – Thermoset Type
Injection Molders – Tie Bar Less
Injection Molders – Two Color
Injection Molders – Vertical Type
Injection Molding – Horizontal
Injection Unit – Only
For more information on Injection molding Machines or other machines you might need please see our article about What Type of Plastics and Metal Machinery do I Need?
Interested in Blow Molding Machines? Get more information at What are Blow Molding Machines?
Interested in Extrusion Molding Machines? Get more information at What are Extrusion Molding Machines?