Low-volume wireforms: how to buy 50 parts without a tooling programme

Why 50 parts is a different problem

A production wireform quote spreads a one-time charge over tens of thousands of parts. At 50 parts, the same charge sits on every piece. A tooling programme that adds 40 pence per part at 50,000 pieces adds £400 per part at 50, so the route has to change.

The good news is that most formed wire parts do not need a hard tool at all. A CNC former can make a part from a program and a set of standard pins. A bench fitter can make a small batch around a simple fixture.

Before asking for a price, decide what the 50 parts are for. Are they engineering samples to prove a shape, a pilot batch for an assembly trial, or a bridge supply while a production tool is built? The answer changes the route and the inspection plan.

Route one: hand forming around a fixture

For a simple part with generous tolerances, hand forming is the lowest entry route. The supplier makes a bench fixture or uses a set of pins and a stop, then bends each part against the fixture. The cost is mostly labour and a small fixture, so there is no program to write.

The limit is repeatability. Two parts from the same batch can differ in leg angle and bend position, especially if the wire has coil set or the temper varies. That may be acceptable for a bracket that is adjusted at assembly. It is not acceptable for a spring that has to deliver a stated load, or for a part that feeds an automated line.

Hand forming is also a poor way to prove a production design. A shape that a skilled fitter can coax into place may be impossible to run at speed, so say if the batch is a design validation.

Route two: CNC forming from a program

A CNC wire former is the usual answer for a small batch. The supplier writes a program, installs standard tools, sets the feed and cut length, and runs the parts. The one-time cost is engineering and setup rather than a part-specific die, so the entry point is far lower than a four-slide.

The batch size that suits CNC forming depends on the bend count and the tolerance. A simple part may be economic at 20 pieces. A part with a difficult sequence and a tight angular call may need a longer trial, but it is still usually cheaper than building a dedicated tool.

Ask for the program charge as a separate line. If the design moves to production later, the same program can often be reused. Ask whether the program is tied to the machine and whether it can be transferred.

Route three: soft fixtures and printed guides

A printed bend guide or a laser-cut plate can hold the wire in the right position while an operator makes the bends. This is not a production tool, but it is a useful way to make 20 to 200 parts with less variation than free-hand work. It also gives the inspector a repeatable way to check the shape.

The design of the fixture matters more than the material. The wire has to sit in a groove or against pins that locate the bend, and the operator needs a stop for the leg length. A guide that only shows the outline does not control springback or bend position.

Use this route when the part is simple and no CNC former is free. Do not treat a printed fixture as a process capability study.

Route four: start from a catalogue part

Sometimes the fastest route is not to make a new part at all. A stock spring, clip or wireform may be close enough to modify: cut a leg, open a loop, add a bend or change the end. Catalogue parts come with known material and published dimensions, and they are available in small quantities.

Modification has limits. Cutting a spring changes the number of active coils and therefore the rate. Re-bending a spring temper part can crack the outside of the bend or reduce the load. If the part carries a load or a fatigue duty, a modified catalogue part needs the same check as a new design.

Use this route for a proof of concept or a temporary fix, not for a drawing that has to be released. If the modified part works, document the change before a supplier makes the final geometry.

Writing an RFQ for 50 parts

The RFQ should say what the batch is for. A supplier who knows the parts are engineering samples will price a route that gets samples quickly. A supplier who thinks the order is the start of production may price a tool you do not need.

Send the drawing, the CAD file, the wire specification and the finish. State the quantity, the delivery date and the inspection level. If the drawing has a general tolerance, say whether it applies to the prototype. A prototype often needs a looser call on non-functional features and a tighter call on the features that are being tested.

Ask for the one-time charge and the piece price separately. Ask what the supplier would change if the volume rose to 5,000 pieces. That question shows whether the prototype route can scale.

• State that the order is a prototype, a pilot or a bridge batch
• Give the quantity and the date the parts are needed
• Name the features that the trial is meant to prove
• Ask for the program charge and the setup charge as separate lines
• Ask whether the program can be reused for a later production order
• Ask for a material certificate with the batch

From 50 parts to 5,000

A small batch is a chance to learn. Check the bend angles, the leg positions and the load before the design is frozen. If the part is hand formed, compare the spread across the batch with the tolerance the assembly needs.

Keep the records. The program, the setup sheet, the first article and the material certificate should carry forward to the production order. If the supplier changes, the records are the only way to avoid repeating the trial.

Finally, do not let a prototype tolerance become a production expectation. The drawing should say what the function needs, not what the prototype happened to achieve.