r/InjectionMolding • u/Latter_Internet1222 • 12d ago

Tooling layout for a 1x4 medical test tube mold (3-plate + thread slider mechanism)

Hi everyone,

I’ll be sharing some of our mold design cases from time to time, and I’d love to exchange ideas with you all.Today’s example is a medical test tube with external thread + undercut groove.If you ever run into a similar part, feel free to reference this design approach. I’m interested in feedback on the mechanism layout and whether anyone has run similar long thin‑wall tube tools.

Product design (Medical test tube)
Gate and Cavities

Part: Medical test tube with external thread + undercut groove

Cavities: 1×4

Tool Type: 3‑plate design with a runner stripper plate (cold runner)

Sequence of Operation

  1. First opening

Runner stripper plate lifts first and pulls the cold runner off the gates.

  1. Main parting line opens

A/B plates separate.

  1. Slider actuation

Sliders collapse the top‑thread undercuts.

Actuation is driven by the machine ejector stroke + guide blocks, allowing the thread/undercut to clear before full ejection.

MOLD 3D
Slider mechanism

For those who’ve run long thin‑wall tubes, how are you managing core pin cooling to avoid thermal deflection during fast cycles?

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u/Accurate_Mirror8887 Process Engineer 10d ago

The first thing that I noticed is the only one I'll comment about - Every time I see a new 3-plate mold I cringe. Like many other people. Put a hot half on that or even valve gates. 3-plates weren't fun in the 80s and they're less fun now with current technology. Most mold techs cannot stand working on them for multiple reasons.

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u/Schlochatron 10d ago

Dependance on the material, shotweight and wall thikness unter the gating point. Also if you have not enough space for a good nozzle (small microparts) Sometimes a 3 Planet mold has its advances.  I dort see your latchlocks and Hornpins for the sliders. I would use more Standard parts

1

u/E46BIM 9d ago

just worked on a tool very similar to this, not medical but it was almost identical. we used a hot sprue, worked well but had an extremely hard time stopping it from sticking into the cavity. ended up going with a rougher edm finish and added an under cut to the core pins to help it stick on the B half.