Averaged across the shot
- Quick, and fine for general dimensions
- One worn seat is diluted by all the good ones
- Volume complaints cannot be traced to a source
Molded part guide: pipette tips
Injection Molded Pipette Tips
A pipette tip is a thin cone molded over a slender core, with a small hole at the end where the liquid leaves. The volume it delivers depends on that hole, the wall around it, and how the tip seals on the pipette. Every tip from every cavity has to behave the same, because the user never knows which cavity made the one in their hand.
The tip
A thin cone where small differences change the volume
Standard, filter, low-retention, and extended-length tips for single and multichannel pipettes.
The tip is molded over a long, tapered core. Melt usually enters near the wide collar and flows down toward the narrow end, where the wall is thinnest and the plastic freezes fastest. The narrow end therefore fills last. If air is trapped there, or the melt slows too much, the end comes out short, rough, or burned, and the orifice shape suffers.
The core has to stay centered. It is slender and supported mainly at its base, so uneven filling can push it sideways and leave one side of the cone thinner. A tip with an off-center bore bends slightly as it cools, and a curved tip can touch the side of a well. In many designs the end of the core seats against the cavity steel at the orifice, which supports the core and forms the hole at the same time.
That seat is the most sensitive spot in the tool. A clean seat forms a crisp, round orifice. A worn or dirty one leaves a thin film of flash or a ragged edge, and droplets cling to it. Orifice size and edge are measured on tips from every cavity, and the seat is inspected on a schedule.
The inside surface matters too. Liquid that clings to the bore is not dispensed. A highly polished core and a polypropylene grade with few additives reduce retention, because some slip and antistatic additives can migrate to the surface and change how liquid wets it.
Features
Tip features and what each one affects
Most accuracy problems trace back to one of these.
| Feature | Affects | How it is controlled |
|---|---|---|
| Orifice at the end | Droplet release and delivered volume | Clean core seat, measured on every cavity |
| Thin wall near the end | Complete fill and straightness | Venting at the end, balanced fill, and core support |
| Upper bore | Seal on the pipette nose cone | Consistent bore with a smooth sealing band |
| Inside surface | Liquid clinging to the wall | Polished core and a resin with few additives |
| Cavity identification | Tracing a problem to its source | A small cavity mark molded into each tip |
Filling the end
The narrow end fills last, so it is designed first
Most tip defects appear at the end, where the wall is thinnest.
- Melt enters at the wide collar and reaches the thinnest section last
- Air trapped at the end causes short or burned tips, so the end is vented
- The core end seats in the steel at the orifice, supporting the core and forming the hole
- A worn or dirty seat leaves a film of flash across the orifice
Inspection
Checking tips as a shot average, or by cavity
A good average can hide one cavity that is drifting.
Measured by cavity
- Orifice and bore tracked for each cavity over time
- A drifting seat is found before tips go out of range
- Molded cavity marks tie field problems back to one cavity
Drawing
What to send with a pipette tip
The pipettes it fits and the volumes it serves shape the design.
Tip CAD with the orifice, upper bore, and wall near the end
The pipette models the tip must fit
Volume range, and any filter or low-retention requirement
Resin, and any limits on additives
Rack, refill, or bulk packing format
Expected annual volume, which sets the size of the tool
Keep reading
Related guides
Other lab parts, and the defects that show up at a thin end.
Syringe components
Another long, slender core.
Syringe componentsPetri dishes
Thin, clear, flat lab parts.
Petri dishesTrays
Racks and trays that hold parts in position.
TraysContainers
Why long cores shift, in more detail.
ContainersPolypropylene
The standard resin for tips.
PolypropyleneFlash
Thin films across a small hole.
FlashDraft angle
Releasing a tapered part from its core.
Draft angleSingle vs multi-cavity
When a larger tool often pays off at tip volumes.
Single vs multi-cavityMolded parts hub
Every part-type guide, grouped by family.
Molded parts hubFAQ
Questions about molded pipette tips
Why do some tips hold back a drop?
Usually the orifice edge or the inside surface. Flash or a ragged edge at the orifice, a rough core, or surface additives in the resin let liquid cling. Check the orifice by cavity and inspect the core seat.
Tips seal on one pipette model and leak on another. Why?
Nose cones differ in size and taper between pipette makers. The upper bore is designed for the models the tip must fit, often with a sealing band that tolerates small differences.
Why do tips come out slightly curved?
The core was pushed off center during filling, or the tip cooled unevenly. Balanced filling and support at the core end keep the cone straight.
Can filter tips be supplied?
The filter is a separate part pressed into the molded tip. Filter insertion can be quoted as an assembly step with the tips.
Next step
Quote the tip with the pipettes it fits
Upload the tip and list the pipette models. DFM feedback covers core support, venting at the end, the orifice seat, and cavity marking.