KO support pillars and mold foot spacers, made to your drawing. The columns that stand between the support plate and the clamping plate, carrying injection pressure that would otherwise bend the cavity plate down into the ejector space. Send a drawing, the required height, or the existing pillar photographed against a caliper, and we quote in writing, normally within one business day.

What these actually carry, and why the height is critical

Behind the cavity plate is a hollow — the ejector housing. Injection pressure pushes on the cavity face, and without support that plate deflects into the hollow. The result is flash that appears only at high pressure, a parting line that opens in the middle of the mold and not at the edges, or a dimension that changes with injection pressure rather than with temperature.

Support pillars stop that. Which makes their height match the specification that matters most:

• Too short and they do nothing. A pillar 0.03 mm under height carries no load until the plate has already deflected 0.03 mm — which is usually most of the deflection you were trying to prevent.
• Too tall and they pre-load the plate the wrong way, holding the mold open at the centre and causing flash at the parting line before injection even starts.
• They must match each other. As with parallel blocks, what matters is that the set is consistent, to a tighter band than any one is to nominal.

Normal practice is to make pillars very slightly proud — a few hundredths — so they take load as the plate begins to move. Tell us your convention, or ask and we will state on the quotation what we would hold.

Bearing area, not just strength

These fail by indenting their end faces into the plates rather than by crushing. A pillar with a small footprint under high clamp force beds in over time, and once it has bedded in, the height is wrong again. If you are increasing injection pressure on an existing mold, the pillar diameter is worth revisiting rather than assuming the original was sized with margin.

Through bores, threads and shoulders

Pillars are often bored to pass an ejector pin or a return pin, or threaded so they can be pulled out for service. If you need either, say so — a through bore changes both the load capacity and the machining, and a thread at one end changes how the end face bears. End-face flatness and parallelism should be called out where they matter, because they are what actually transmits the load.

What to send us

• Outside diameter, or the profile if it is not round
• Overall length, and the height tolerance and set-to-set match you need
• Through bore, counterbore, internal thread or shoulder dimensions
• End-face flatness and parallelism requirements
• Mounting method, and whether the pillar is dowelled, threaded or a slip fit
• Clamp force and injection pressure, if you want us to sanity-check the footprint
• Material, heat treatment, tolerance, quantity and destination

Replacing pillars on a mold that flashes under pressure? Measure all of them and send the numbers. If they differ, or if the end faces show a bright bedded ring, you have found the cause before anything is made.

Documentation and confidentiality

Material certificates, hardness results and dimensional inspection reports are available on request, with scope and cost confirmed in the quotation. Technical files are used to evaluate and fulfill your inquiry or order. They may be shared only with relevant manufacturing, inspection, logistics or service partners as needed. Send only files you are authorized to share. See our Privacy Policy. NDA on request from rfq@privleymold.com.