Round positioning pillars and interlocks, made to your drawing. The hardened round interlocks fitted between mold halves to hold cavity-to-core alignment at the moment of closing — the job the guide pillars cannot do on their own once the mold is hot and under clamp. Send a drawing, a sketch with dimensions, or the worn part next to a caliper, and we quote in writing, normally within one business day.

Why a mold needs these when it already has guide pillars

Guide pillars align the plates as they travel. They are relatively long, running in clearance, and they are not there to resist sideways force at the parting line. Once the mold is closed and injection pressure is pushing the cavity off centre — or once the mold has been running hot long enough for the plates to grow — the final alignment has to come from something short, stiff and close to the cavity. That is what a positioning pillar or interlock does.

The symptom that sends people looking for these: a step or mismatch across the parting line on the part, flash on one side only, or a core that walks over a production run. If your guide pillars are fine and the part still shows a mismatch, alignment at closing is where to look.

The two dimensions that decide whether it works

• The taper or lead-in. The pillar has to find its bore before the mold faces meet, otherwise it is being asked to correct misalignment at full clamp force, which is how interlocks get sheared. A generous lead-in does the finding; the parallel land does the holding.
• The fit on the parallel section. Too loose and it is decoration. Too tight and it binds as the mold heats up and the plates grow — a fit that is perfect on the bench can seize at 80°C. Tell us the operating temperature and the plate material and we will take thermal growth into account rather than quoting a cold fit.

Hardness and wear

The pillar and its bushing or bore should not be similarly hardened — two comparable hardened steel surfaces gall rather than wear. Normal practice is a hardened pillar running in a replaceable bushing that is deliberately the softer, cheaper, sacrificial half. Decide which part you want to be replacing in two years, and that answer sets the hardness pair.

What to send us

• Pillar diameter, overall length, and the length of the parallel land
• Taper angle or lead-in form, and how much engagement you need before the faces meet
• Shoulder, flange and retention detail, and the mounting bore in the plate
• Required fit class, and the operating temperature the mold runs at
• Mating bore or bushing: material, hardness, and whether it is replaceable
• Material, heat treatment and hardness preference, or describe the duty
• Tolerances on the diameter and on concentricity; quantity and destination

Replacing a worn set? Tell us how it wore — evenly, on one flank, or galled — and whether the mold shows a parting-line mismatch. That points at fit, alignment or hardness respectively, and it changes what we would recommend.

Documentation and confidentiality

Material certificates, hardness results and dimensional inspection reports are available on request, with scope and any cost stated 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.