Support Pillars Information


Support Pillar

Support pillars are mold components that are mounted between the back-up plate and the rear clamping plate of a mold. They greatly increase the mold’s capacity to support the projected cavity area, preventing deflection during injection pressure. Typically, support pillars are used when building larger molds. They provide an alternative to cutting a manifold pocket from a single plate. During injection, support pillars keep closed the two halves of the plastic injection mold. In this way, the mold supports distribute the force and minimize the stresses on the mold plates. Without adequate support pillars, flashing of the parting line faces and bowing of the plates may occur. Support pillar suppliers can help determine the number of pillars that are necessary for specific applications. 


Support pillars have either tapped holes or drilled and counter bored holes for mounting a locating pin. For support pillars with tapped holes, product specifications include:

  • outside diameter (OD)
  • tap diameter
  • dowel locating hold diameter
  • length

The minimum locating-hole depth and minimum tap depth are also important to consider. For support pillars with drilled and counter bored holes, product specifications include:

  • outside diameter
  • through-hole diameter
  • counter bore diameter
  • counter bore depth
  • length

Generally, both types of support pillars are made of steel and measured in millimeters (mm). One row of support pillars can increase the permissible cavity area by up to four times, while two rows can increase it up to nine times.


Support pillars are used in plastic injection molding, the most common plastic processing method. Injection molding machines reduce pelletized raw materials into a hot liquid or melt that is then forced into a cooled mold under tremendous pressure. After the material solidifies, the mold is unclamped and the finished part is ejected. In addition to support pillars, plastic molding equipment uses guide pins, locating rings, guide pin bushings, angle pins, and sprue bushings. Centering bushings, tubular dowels, and dowels are also available, along with bolts, screw, and lock washers. Stop disks are designed for ejector plates. Specialized mold components may also be available from some support pillar suppliers.

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