Prioritize batch consistency
Dimensions and appearance must match the previous batch. Narrower process windows make it harder to control batch-to-batch drift.
Application
Medical supplies and devices
Pipette tips, blood collection tubes, test card housings, and device shells: prioritize batch consistency and cleanliness over molding speed.
Common components
Pipette tips, blood collection tubes, culture dishes and test card housings, fluid connectors, device enclosures
Common resins
PP, PS, COC/COP, PC, PEEK, PSU
Shot Weight and Wall Thickness
0.1–10 g per part
walls 0.2–0.8 mm
Long cores in blood collection tubes increase the flow rate.
Three constraints that determine the gate
Shot weight, wall thickness, and flow ratio determine the gate; appearance and cleanliness requirements determine the nozzle type.
Black specks result from stagnant material, not inspection.
Material accumulates at runner corners, threaded joints, and the tip/manifold interface. Screening at the end of the line only adds cost.
Concentricity of thin walls on long cores
The core obstructs flow during filling. Shear and temperature changes alter viscosity, shifting the core off-center and resulting in uneven walls and a bent tube.
Common parts and matching exercises
Different gate practices are required for different components and requirements within the same industry. This table is organized by component, not by model.
Part | Common resins | Size and cavitation | Practice |
|---|---|---|---|
| Part Pipette tips | Common resins PP | Size and cavitation 0.2–0.8 mm, multi-cavity | Practice Multi-cavity SD or TP with independent temperature control per cavity |
| Part Blood collection tubes | Common resins PP, PS | Size and cavitation long core, high flow ratio | Practice Multi-cavity SD: Align core and gate; record gate freeze time per cavity. |
| Part Culture dishes and test card enclosures | Common resins PS, COC/COP, PC | Size and cavitation 0.3–0.8 mm | Practice SD; monitor ejection and gate residue |
| Part Fluid connectors and device enclosures | Common resins PEEK, PSU, PC | Size and cavitation 0.5–2.0 mm | Practice High-temperature SD with dynamic control for PEEK and PSU; VG for aesthetic components |
Molding Challenges and Our Solutions
Each item first explains the mechanism, then our scope of work. Mold temperature, clamping, and drying are out of scope.
Black specks and discoloration
Material accumulates at runner corners, threaded joints, and the tip interface, then degrades.
PRACTICE
Radius runner corners without steps; allow tip removal for inspection; purge per resin requirements. Eliminate dead zones in the structure instead of relying on end-of-line sorting.
Core eccentricity and bending
Shear and temperature changes affect viscosity during filling, while the core shifts under lateral force.
PRACTICE
Control each cavity independently to minimize variation between cavities; align the core and gate; perform flow analysis on thin-wall, long-core parts to verify the flow front.
High-temperature degradation of PEEK and PSU
High processing temperatures and long residence times degrade the melt and release gas.
PRACTICE
Place the sensor close to the melt to reduce control lag; configure a stop/purge procedure for the resin; and avoid prolonged hot standby.
Selection and responsibility boundaries
Scope of services and exclusions are outlined before the proposal and quotation.
SERIES
Open SD and TP, along with valve-gate VG and PVG, are suitable for medical consumables and devices. The specific model is determined by gate position, appearance requirements, and cavity count.
What We Don't Promise
Mold temperature, melt temperature, clamping force, and drying are part of the mold and molding process. A hot runner cannot replace them.
The no-clogging guarantee applies only to straight-through nozzles. Pin-point and valve-gate types have small sections and mating surfaces, so we cannot guarantee they will be clog-free.
We explain any out-of-range calculations at the proposal stage.
Related technical articles
Articles on materials and applications in this industry, sorted by newest first.
LCP Medical Connectors: Purity, Extractables, and Dimensional Control
Medical connectors must be reliable, clean, and compatible with repeated disinfection. LCP is ideal for miniature medical components due to its resistance to disinfectants and dimensional stability, though gate black spots, residue, and marks require stricter process control.
Insufficient Packing and Weight Instability: Once Gate Seals, Additional Pressure Is Useless
Weighing individual products from the same mold shows weight and dimension fluctuations, with occasional short shots at the end. This indicates insufficient packing and unstable weight.
Dimensional Out-of-Tolerance: Distinguish Systematic vs. Random Drift
Critical dimensions are consistently out of tolerance, batch consistency is poor, and assembly fit varies.
Stress Cracking: Delayed Failure Is No Coincidence
Parts appear normal upon ejection but develop cracks after several days or when exposed to solvents, with cracks initiating at gates or corners. This phenomenon is known as stress cracking.
Customer case studies
Practice and results only; customer names are not disclosed.
Customer case studies for this industry are being prepared.
Drawings first, then the proposal
Send the mold 2D layout, part 3D data, resin grade, wall thickness (including the thinnest section), number of cavities, shot weight, current process parameters, and defect photos.