Off-the-shelf nozzles cover a surprising amount of process work, but they stop short as soon as the deposit is unusual: a very short tip to reach into a cavity, an offset bend to clear a component, a wall thickness chosen to fit a specific fixture, or an inner diameter that sits between two standard sizes. At that point the part has to be made to a specification, and the specification is where most custom projects succeed or fail. This guide sets out the sequence an engineer should follow, from defining the deposit to agreeing the packaging, using the requirements that a stainless steel nozzles dispensing needle supplier needs in order to quote and manufacture without ambiguity.

Step 1: Define the Deposit, Not the Nozzle

The first document in a custom project should not be a nozzle drawing. It should be a statement of what the deposit must be: target volume or mass, allowable tolerance, adhesive type and viscosity range at application temperature, cycle time, standoff, and the substrate the material lands on.

Why this order matters

A geometry chosen from a catalogue habit often proves wrong when the numbers are written down. A target of a fraction of a microlitre at a high viscosity may need a shorter, larger-bore tip than intuition suggests, because the system cannot deliver the volume through a long, narrow channel within the cycle time. Starting from the deposit lets the supplier propose a flow path that actually works.

Step 2: Choose the Flow Geometry

With the deposit defined, the bore and taper can be selected. For micro-volume work, inner diameters between 0.1 mm and 0.8 mm cover most applications, with the exact value set by the volume, viscosity and available pressure.

Straight bore or tapered

A straight bore is easier to inspect and to predict, and it suits low-viscosity fluids and short channels. A taper reduces pressure loss and improves droplet detachment, which matters for viscous materials and for very small deposits. Where the taper runs only over the last few millimetres, the part retains most of the pressure advantage without adding much length.

Tip form and wall thickness

A flat tip suits contact and non-contact dispensing onto flat surfaces. A chamfered or radiused outer edge is less prone to damage but can interfere with close-proximity work. Thin walls improve access, at the cost of robustness; specify the wall as a range rather than a nominal value so the supplier can manufacture consistently.

Step 3: Fix the Interface and Hub

Most dispensing systems use a Luer lock connection, and the hub is the part of the nozzle where quality most often varies.

The requirement to write down

Specify the hub as flash-free at the bore and at the inlet, with the thread fully formed so the part seats squarely. A moulded hub with a thin lip of flash at the core pin narrows the flow path, and the resulting under-volume is easy to blame on the valve.

What a good hub supplier does

Inspection at the cavity level, with records, is the difference between a promise and a control. Where the process is safety-related, an ISO13485 quality system provides the framework for lot traceability, deviation handling and change notification.

Step 4: Put the Tolerances That Matter on the Drawing

A drawing with a dozen tolerances on unimportant features and none on the bore is worse than a drawing with three critical ones.

Tolerance these

Bore diameter, because it dominates flow. Orifice edge condition, because it dominates detachment. Hub concentricity, because it dominates landing position. Overall length, where standoff is set by the tip. Seat angle or Luer taper, because it dominates alignment and leaks.

Do not over-tolerance these

Cosmetic features that do not touch fluid or a datum, and dimensions that the manufacturing route holds naturally. Over-specification raises cost without improving the deposit, and it invites unnecessary deviation requests.

Step 5: Specify Surface Condition and Edge Quality

For very small orifices, surface condition is functional. Specify burr-free edges, a polished exterior where handling marks would otherwise create nucleation points, and passivation for stainless parts to restore the corrosion-resistant oxide layer after machining.

Why polishing and passivation belong together

Polishing removes the mechanical damage that holds residue; passivation removes free iron and restores the passive film. Together they produce a surface that wets, drains and cleans predictably, which is what consistent and repeatable deposit placement depends on.

Step 6: Decide How the Part Will Be Inspected

Decide before production, not after the first delivery, how conformity will be checked. Options include dimensional reports on the critical characteristics, sample deposits on film, and visual inspection at magnification.

Making inspection usable

Ask for the inspection plan in writing with the quotation. A dimensional report on a bore of 0.2 mm is only useful if the measurement method is stated and capable; otherwise the numbers look precise without being informative.

Step 7: Agree Packaging and Traceability

Packaging protects geometry. Standard cartons are adequate for most standard parts, but custom tips with fine or thin-wall ends often need individual protection.

What to request

Specify the packaging that fits your handling: bulk cartons, trays, or individual tubes, labelled with part number, lot and quantity. Where the part is custom, confirm that the approved drawing revision travels with the lot, and agree how changes will be notified. Parts supplied in packaging chosen by the customer reduce damage and speed receiving inspection.

From Sample to Drawing

Many projects start the other way round: the customer has a nozzle that works, and needs it reproduced. A physical sample is a legitimate basis for manufacture, provided the critical characteristics are measured and written into a drawing before production. Reproducing a sample without measurement risks copying wear as if it were design.

Drawings That Cannot Be Quoted

Conflicting information

A model that differs from the drawing, or a bore stated in one place and implied in another, forces the supplier to guess. Guessing produces either a query or a wrong part, and both cost time.

Requirements without capability statements

A specification that demands a finish or a tolerance without saying how it will be verified leaves the supplier free to interpret. State the measurement method or ask the supplier to propose one, and confirm it before production.

Missing interface detail

The Luer taper, hub length and thread form are frequently omitted because they are assumed. They are the features that determine whether the part seats squarely, so they belong on the drawing even when they follow a standard.

FAQ

How many drawings do I need to provide?

One controlled drawing with a revision number is enough, provided it carries the critical characteristics. Where a 3D model is supplied, state which dimensions are defined by the model and which by the drawing.

Can a supplier work from a sample only?

Yes, for straightforward parts. The supplier measures the sample, proposes a drawing, and production starts after the customer approves it. For fine bores, the measurement should be confirmed by both parties.

What lead time should I expect?

It depends on geometry and quantity rather than on the nozzle itself. Prototype parts from a stock material are usually quick; new tooling or special surface treatments extend the schedule, so ask for the sequence rather than a single number.

How do I know the parts will be consistent between lots?

Agree on the controlled characteristics, ask for lot records, and qualify each new lot with a deposit test before release to production. Traceability plus a functional check is a stronger control than dimensional inspection alone.

The Sequence in One Line

Define the deposit, choose the flow geometry, fix the hub, tolerance what matters, specify surface and edges, agree inspection, and settle packaging and traceability. A stainless steel nozzles dispensing needle built to that sequence behaves predictably, because each decision has been made deliberately rather than inherited. Where standard parts cannot satisfy the geometry, a supplier able to work from 2D or 3D drawings or from a sample, to ISO13485 where required, and to pack to customer specification, removes most of the risk from the project.