Polycarbonate
- Very tough, clear, and stiff enough for lock luer threads
- Prone to stress cracking with lipids, some solvents, and alcohols
- Needs low-stress hub design where those fluids are present
Molded part guide: IV components
Injection Molded IV Components
An infusion set is a chain of small molded parts joined by tapers, threads, and tubing sockets. Each joint has to seal with parts made by other suppliers, and many of them sit in contact with drugs and carriers that can attack a stressed plastic. Fit and stress are the two things to get right.
The fluid path
Small parts that all have to seal to each other
Luer connectors, needle-free access parts, stopcocks, spikes, drip chambers, roller clamps, and Y-sites.
Most joints in an infusion set are luer connections. A male taper pushes into a female taper and seals by wedging, and a lock luer adds a threaded collar that holds the joint together. Because any male must mate with any female, the tapers follow the dimensions in ISO 80369-7. A taper that is slightly out of angle seals on a line instead of an area and can leak under pressure or pull apart.
The taper surface must be clean steel. A parting line, flash, or a gate vestige on the sealing surface creates a leak path. Tapers are formed in solid core or cavity steel, gates go on non-sealing faces, and the female bore is formed on a polished core pin that must stay centered in a thin-walled part.
Chemical attack is the less obvious risk. Lipid emulsions, some drug carriers and solvents, and alcohol-based disinfectants can crack amorphous resins such as polycarbonate where the part is under stress. A lock luer tightened hard puts the female hub in hoop tension, which is exactly where cracks appear. Lower-stress hub designs and resins with better chemical resistance, such as some copolyesters, are the usual responses.
Moving parts add fits of their own. A stopcock plug rotates in a body and seals by interference along its length, so plug and body are usually different resins, a softer plug in a stiffer body, to seal without seizing. Roller clamps must pinch tubing consistently without cutting it, and drip chambers need clear, even walls so drops can be counted.
Parts
Common IV parts and what decides whether they work
Each part has one fit or surface that carries most of the risk.
| Part | Critical feature | Design and molding focus |
|---|---|---|
| Male and female luer | Taper angle and surface | Taper in solid steel, gate on a non-sealing face |
| Lock luer collar | Internal thread that holds the joint | Thread release method, and hub stress when tightened |
| Stopcock body and plug | Seal along a rotating fit | Paired resins, roundness of both bores, and turning torque |
| Tubing socket | Depth and clearance for bonding tubing | Socket sized to the tubing and the bonding method used |
| Spike | Sharp point and clear flow channel | Point formed without flash, and a stiff resin |
| Roller clamp | Even pinch on the tubing | Ramp profile and wheel fit held consistent |
Lock luer threads
Getting the lock luer thread off the core
The female collar thread is internal, so the tool has to release it.
- Stiff resins like polycarbonate cannot be stripped, so the collar needs an unscrewing or collapsing core
- Some designs split the thread into segments that side actions can release
- Grip features on the collar outside also hold the part still while the core unscrews
- The release method is set early because it shapes the whole tool
Connector resin
Polycarbonate or a chemically resistant copolyester
Both are clear and tough. They behave very differently around aggressive drugs.
Chemically resistant copolyester
- Better resistance to many lipids and disinfectants under strain
- Clear and tough, though usually less stiff than polycarbonate
- Different shrink and flow, so the tool is cut for the chosen resin
Drawing
What to send with IV components
Fits with mating parts matter most, so include them.
CAD for each part, with luer, thread, and socket details
Mating parts: tubing size, connectors, and stopcock plug or body
Drugs, carriers, and disinfectants the part will contact
Resin, and the sterilization method the product uses
Pressure the joint must hold, and tightening torque for lock luers
Color coding or marking requirements
Keep reading
Related guides
Other fluid path parts and the tooling behind threads and small bores.
Syringe components
Barrels, plungers, and luer tips.
Syringe componentsInhaler components
Small dosing parts with tight holes.
Inhaler componentsMedical device housings
Housings that face daily disinfectants.
Medical device housingsThreaded caps
Ways to release internal threads.
Threaded capsPolycarbonate
Tough and clear, with chemical limits.
PolycarbonateUndercuts
Features that lock a part in the tool.
UndercutsFlash
Why sealing surfaces must be clean.
FlashUltrasonic welding vs adhesive
Joining molded parts in an assembly.
Ultrasonic welding vs adhesiveMolded parts hub
Every part-type guide, grouped by family.
Molded parts hubFAQ
Questions about molded IV components
Our female luers crack after lipid infusions. Why?
The lipid carrier attacks stressed polycarbonate, and a tightened lock luer puts the hub in hoop tension. A lower-stress hub design, a more resistant resin, or both usually resolve it.
The luer leaks only with some connectors. What should we check?
Check the taper angle and surface, especially for a parting line, flash, or a gate mark on the sealing area. A taper at the edge of its tolerance seals with some mating parts and not others.
Why are stopcock plug and body different resins?
A rotating seal of two identical rigid resins tends to either leak or seize. A softer plug in a stiffer body seals by slight deformation and still turns smoothly.
Can several IV parts share one tool?
Small parts of similar size and resin often run together in a family mold, which keeps a matched set of parts in one production run.
Next step
Quote IV parts with their mating parts
Upload the parts, the mating connectors or tubing, and the fluids they contact. DFM feedback covers tapers, thread release, gating, and hub stress.