Large-Part Injection Molding

Large-part injection molding is a manufacturing process for producing large parts in high volumes. It is commonly utilized in mass production processes in which the same part is recreated thousands or even millions of times in succession. The main benefit of injection molding is the ability to produce parts en masse and cost-effectively.

During the injection molding process, hydraulic pressures exceeding 20,000 psi are utilized to push the two halves of the mold apart. Typically, injection molding machines are rated by “clamping force” in tonnage. “Clamping force” refers to the force used to clamp the two halves of the mold together. Notably, molded parts with a larger surface area require greater tonnage and vice versa. Usually, the machines rated as “large tonnage” come with 500 or more tons of clamping force.

What Makes Plastic Injection Molding for Large Parts Different From the Standard Plastic Injection?

Plastic injection molding presses can be rated or classified depending on tonnage or clamping pressure and force. Presses run in sizes from as few as five tons of clamping pressure to as high as 3,000 tons of clamping pressure. Notably, the higher the press ton rating, the larger the specific plastic injection molding machine.

A large-tonnage injection molding machine naturally requires a massive amount of resources. Large-tonnage machines require a footprint of approximately 40′ x 15′ x 15′ and cost anywhere from $250,000 to over $1MM. The injection molds processed with these machines exceed 10,000 pounds and need special lifting equipment.

In essence, the big difference between plastic injection molding machines for a large part and those for standard plastic injections is that large machines typically run more complex parts. They are also more expensive to acquire while requiring massive space for staging, packaging, and storing parts. This is the main reason why fewer companies choose to offer machines greater than 500 tons. This also explains why these machines are unique and scarcer than standard injection molding machines.

How to Determine If Your Part Requires a Large-Ton Machine

There are several factors to consider when deciding on the size of the press. These include the size of the part, the polymer used, and the safety factor. Specifically, the safety factor refers to an extra numerical percentage buffer added to the calculation to help eliminate the risk of defects on the final product. Experts recommend adding 10% to allow for the safety factor.

The general rule of thumb for measuring the amount of tonnage needed for any given plastic under production is 2-8 tons per square inch. This means that a 10″ x 10″ part (100 square inches x 2 tons/sq. in.) will require 200 tons. Remember, the larger the part, the more clamp force is needed to hold the two halves of the mold together during the injection process.

Large-Part Injection Molding Capabilities at Lerner Molded Plastics

As the leading Ohio plastic parts manufacturer, Lerner Molded Plastics is committed to providing all our clients with precision, custom plastic injection molding services that deliver premium quality components. We leverage our ISO 9001 2015-certified facility to offer custom molded plastic parts with diverse materials. We can produce high-volume small and large parts with shot sizes ranging from 3 to 600 ounces. Our advanced plastic molding equipment boasts unmatched pressure clamping force, ranging from 30-3,000 tons and up to 64 cavities. We also provide large-part rotational molding, blow molding, and thermoforming with custom coloring capabilities. Some of the plastic materials that we offer for large-part injection molding include:

  • Polypropylene (PP) ○ Polystyrene (PS)
  • High-Density Polyethylene (HDPE)
  • ABS
  • Nylon
  • Acetal
  • Polyester (PET / PETG) ○ Acrylic
  • Polycarbonate (PE)

Our experts are committed to helping you create a product that offers maximum quality at lower production costs. We combine the power of cutting-edge infrastructure, innovation, and experience to produce high-quality and cost-effective parts that meet your specific needs. We also offer a full line of value-added services to complete your manufacturing requirements. To learn more about our custom plastic injection molding services, contact us today or request a quote.