What Is A Short Shot In Injection Molding?

A short shot is the incomplete filling of a mold cavity which results in the production of an incomplete part.

If a part short shots, the plastic does not fill the cavity. The flow freezes off before the flow paths have completely filled.

To ensure the finished part is of good quality, the part must also be adequately packed with plastic. Therefore the question to ask is not only, “Will the part fill?” but also, “Can a good quality part be made?”


  • Flow restrictions. Due to channels freezing or inadequate runner design.
  • Hesitation and long or complex flow paths
  • Inadequate venting. Back pressure due to unvented air traps can cause a short shot.
  • Low melt and/or mold temperatures.
  • Insufficient material entering the cavity. An undersized machine, low shot volume, or inadequate ram speed.
  • Machine defects. Including an empty hopper, blocked feed throat, or a worn non-return (check) valve that causes loss of pressure or volume leakage.


Before you try one of the methods listed below, check all of the other results, so that you know the exact cause of the short shot.

  • Avoid hesitation.
  • Eliminate air traps. If air traps do exist, they should be positioned in areas that can be easily vented or ejection pins added so that air can be removed.
  • Increase mold and melt temperature. This will decrease the viscosity of the melt, making it easier for the plastic to flow through the part.
  • Increase ram speed. This can cause greater shear heating, which decreases the viscosity of the melt, making it easier for the plastic to flow through the part.
  • Change the part geometry. Balance flow paths so they fill in an equal time and an equal pressure. You may need to thicken thin sections, or reduce the complexity of a flow path.
  • Use a different material. Select a less viscous material (higher melt flow rate). By choosing a material with a higher melt flow rate, less injection pressure will be required to fill the part.
  • Increase the maximum injection pressure for this part.

Solving one problem can often introduce other problems to the injection molding process. Each option hence requires consideration of all relevant aspects of the mold design specification.

About JasonMould Industrial Company Limited

Jasonmould is a China mold maker of plastic molds- injection mold, die casting moulds, plastic blow molding, rotational molding, medical plastic injection molding, two shot plastic injection molding, insert molding, overmolding, metal injection molding, micro injection molding, powder injection molding, ceramic injection molding, liquid injection molding, husky injection molding, household mold, casting mold, die mold tool, custom molds, china moulds, rapid prototyping tooling, plastic prototyping tooling, punch press tooling, die and tooling for mobile/ cell phone parts, automotive parts, vacuum cleaners, rechargeable tools, telephones, copiers, computers, multimedia speakers, and many other electronic products and household appliances. And also a plastic product manufacturer, mold manufacturer China– plastic parts, plastic water tank, plastic balls, plastic containers, plastic buckle, plastic anchor, plastic hanger, plastic spoon, plastic pipe fitting, plastic tumble, plastic tableware, plastic cups, plastic bottles, plastic tray, plastic cosmetic container, plastic case, plastic food container, plastic chairs, plastic caps, plastic cap closure, plastic tubes, plastic water pipes, plastic knobs, plastic tubing, plastic utility boxes, plastic racks and so on.

Person: James Yuan
Company: JasonMould Industrial Company Limited
Add:  LongGang Village,LongXi Town,BoLuo County,HuiZhou City,GuangDong Province, China
Tel: 86-752-6682869
Email: [email protected]

Site: https://www.jasonmolding.com/company/

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