Parameters related to selection

Generally speaking, the following information must be collected before choosing the injection molding machine, and the more detailed the better.

  • Mold size, weight, special design, etc.

  • The characteristics of using plastics;

  • The size and weight of injection products;

  • Molding requirements, including a few, production speed, product quality requirements and so on.

Selection steps and principles

After having the above information, you can choose the right injection molding machine according to the following steps.

  • Choose the right type: decide the type and series according to the characteristics of products and plastics. Please consult our business personnel or related technical personnel in detail.

  • Put it down: according to the size of the mold, determine whether the “column spacing” and “minimum die thickness” of the machine are applicable.

  • Get: according to the mold size and product size to determine whether the “maximum opening distance” and “ejection height” is applicable.

  • It can be locked: according to the characteristics of products and plastics, the “clamping force” is determined.

  • Shot full: according to the weight of each mold of the product to determine the “injection” and select the appropriate “screw diameter”.

  • Good shooting: according to the plastic properties, determine whether the “length diameter ratio” and “ejection pressure” are applicable. Please consult our business personnel or related technical personnel in detail.

  • Shoot fast: determine the shooting speed according to the “ejection rate”.

Matters needing attention

  • The output is the measured weight of the PS emitted from the machine in full travel.When choosing injection molding machine, you need to convert the indirect conversion algorithm according to the density (specific gravity) of the processed plastics.

  • Under normal circumstances, the actual ejection volume is the best between the maximum ejection 35%~85%. The smaller the ratio is, the longer the residence time of plastic in the tube is, the greater the possibility of degradation. The larger the ratio, the greater the probability of deviation in theory. Moreover, the residence time of plastic in the pipe is relatively short, which may affect the quality of the melt. It can be seen that the proportion of plastics should be considered comprehensively.But one thing is for sure: do not choose the screw that just meets the requirement. In addition to the above reasons, even if the new machine can do the product, but once the screw wear, the product can not do well.

  • Try not to increase the injection volume by increasing the standard stroke. If the feeding stroke exceeds 3-5 times the screw diameter, the homogeneity of the melt is unlikely to meet the high quality requirements. There is also the danger of air entering the melt, which inevitably leads to stains on the surface of the product.

  • Do not choose a machine with a large modulus. Small dies with large formwork will increase the deformation of formwork and column, which is not conducive to more precise forming, and long-term use will lead to the formwork and column due to fatigue and fracture. Therefore, it is best to use the mold with a size of not less than 2/3 of the machine spacing.

  • Clear relationship between injection rate and plasticizing ability:
    Ejection rate, also known as injection rate, is the injection volume per unit time of the cylinder at the highest theoretical speed, not the actual injection volume, the unit is CM³/S.Plasticizing capacity is defined as the amount of PS that can be uniformly plasticized or heated to a certain molding temperature in kg/h or g/s per hour during the maximum screw speed and zero back pressure of the injection molding machine. It has a great relationship with the size of screw and the movement characteristics of plastic in screw.The injection rate is the performance parameter in the injection stage, and plasticizing ability is the performance parameter when the screw moves backward. They constitute the minimum cycle of the machine.

  • Clear the relationship between ejection pressure and clamping force:
    The ejector produces a force that separates the mold, which is equal to the product of cavity pressure and cavity orthographic projection area. The clamping force must be greater than this force. Therefore, estimating the clamping force through the cavity pressure is the closest to the actual requirement.

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