Close this search box.
Home » Blog » How should I purchase an injection molding machine?

How should I purchase an injection molding machine?

Generally speaking, enterprises or department managers and related technical personnel who have been engaged in the plastic products industry for many years are capable of making their judgment and choosing the suitable injection molding machine for purchase because they have experience in using injection molding machines.

However, many enterprises or department managers may not know much about injection molding machines or do not have professional technicians to provide references, so they need the assistance of injection molding machine manufacturers to decide which type, model, and parameters of injection molding machine to use, or even customers may only have samples or ideas of plastic products, and then directly ask the injection molding machine manufacturer whether the machine can be produced, or directly ask which model is more suitable.

In addition, some unique products may need to be paired with special devices such as accumulators, closed circuits, injection compression, etc., for more efficient production, which can only be known by senior technicians or after actual production.

As a result, how to choose a suitable injection molding machine for production is a problem many customers face.

The factors for choosing the type, specification, and brand of injection molding machine mainly include mold, product, plastic, molding requirements, etc. Therefore, the following information must be known before making the selection.

  1. The mold size (width, height, thickness), weight, exceptional design, etc., required for the plastic products.
  2. The type and quantity of plastics for the plastic product (single raw material or multiple plastics)
  3. The external dimensions (length, width, height, thickness), weight, etc. of the injection molded products
  4. The molding requirements of the plastic products, such as quality conditions, production speed, etc.

After the information is prepared, the injection molding machine can be selected in the following order.

  • Select the machine type and specification series by plastic products.

Since there are very many types of injection molding machines, it is necessary to correctly determine at the beginning which type of injection molding machine or which specification series of injection molding machine should be used to produce this plastic product, for example, whether it is a general thermoplastic or bakelite or PET material, whether it is single-color, two-color, multi-color, sandwich or mixed-color, etc. In addition, certain plastic products have special requirements: high stability (closed circuit), high precision, ultra-high injection speed, high injection pressure or rapid production (multi-loop), and other conditions. You must also choose the appropriate series to produce.

  • From the mold size to determine whether the machine’s “large column inner distance,” “mold thickness,” “mold minimum size,” and “mold tray size “To confirm whether the mold can fit or not.

  • From the mold and plastic products, determine whether the “mold opening stroke” and “mold holding stroke” are sufficient to allow the plastic products to be taken out.

  • The “clamping force” cargo is determined by the plastic product and plastic-type.

The clamping unit of the injection molding machine must provide enough “clamping force” to keep the mold from being opened.

  • The weight of the finished product and the number of cavities are used to determine the required “injection volume” and to select the appropriate “screw diameter.”

# The number of cavities in the mold (how many cavities in a mold) should be taken into account to calculate the weight of the finished product.
# For stability, the injection volume should be at least 1.35 times the weight of the finished product.

  • Screw compression ratio” and “injection pressure” are determined by the type of plastic.

Some engineering plastics require higher injection pressure and appropriate screw compression ratio design for better molding results. To improve the finished product shot, the need for injection pressure and compression ratio should also be considered when selecting a screw. Generally speaking, a smaller diameter screw can provide higher injection pressure.

  • Confirmation of “injection speed.”

In this case, it may be necessary to confirm whether the machine’s injection rate and speed are sufficient and whether it needs to be equipped with accumulator and closed-loop control devices. Under the same conditions, a screw that can provide a higher injection pressure usually has a lower injection speed. Conversely, a screw that can provide a lower injection pressure usually has a higher injection speed. Therefore, when choosing the screw diameter, the injection volume, pressure, and rate (injection speed) should be cross-considered and traded off.

Share this post