Key takeaways
- Wire forming covers straightening, feeding, bending, cutting and finishing wire into a fixed shape.
- The material grade and temper decide the minimum bend radius more than the machine does.
- Every bend below one wire diameter deserves a DFM note before tooling is discussed.
- A quote needs the drawing revision, wire diameter, material, finish, volume and inspection level.
What wire forming is
Wire forming is the process of taking wire from a coil and turning it into a fixed shape: a clip, a spring, a hook, a cage, a contact or a bracket. The wire is straightened, fed to length, bent around tools, cut and finished. Some parts need one bend. Others need twenty, with a weld or a thread at the end.
The process sits between stamping and machining. It is faster than machining for a thin part with a constant cross-section, and it uses far less tooling than a progressive die when the volume is low. The trade-off is that wire forming is a geometry process. It can hold a bend, a loop and a leg, but it cannot add a pocket, a rib or a flat face without a secondary operation.
The five operations behind a formed wire part
Most wireforming lines run the same sequence, whether the machine is a CNC former or a four-slide. The difference is how the tools move and how much changeover the job needs.
- 01
Straighten and feed
The wire is pulled from a coil through straightening rolls and fed to a set length. Coil set, cast and helix affect how straight the finished leg will be.
- 02
Bend
Pins, rollers or slides form the wire around a radius. The tool geometry sets the inside radius; the material temper sets how much the wire springs back.
- 03
Cut and form ends
The part is cut to length. Ends may be looped, hooked, flattened, threaded or chamfered in the same cycle.
- 04
Join
Welding, crimping, staking or overmoulding adds a second element or a termination. Each joint needs its own inspection.
- 05
Finish and inspect
Plating, passivation, coating or stress relief follows. The final step is dimensional and functional inspection against the drawing.
Wire forming vs stamping: the practical split
Stamping starts with flat sheet and cuts a profile from it. Wire forming starts with a round cross-section and bends it. The choice is usually obvious once you look at the part, the volume and the tooling budget.
| Question | Wire forming | Stamping |
|---|---|---|
| Typical volume | Prototype to millions | Thousands to millions |
| Tooling entry cost | Low to medium | Medium to high |
| Best geometry | Bends, loops, hooks, springs, cages | Flat profiles, holes, tabs, contacts |
| Cross-section | Round wire, sometimes profiled wire | Sheet thickness |
| Change speed | Fast for a new bend or leg | Slow once a die is built |
| Typical limit | Bend radius and springback | Burr, strip layout and die wear |
Many parts use both processes. A stamped contact may be formed and a wire part may be welded to a stamped bracket.
The design calls that decide cost
A formed wire part has five cost drivers: material, wire diameter, number of bends, bend radius and finish. The first three are usually visible on the drawing. The last two are where quotes diverge.
- Material and temper: music wire, stainless, phosphor bronze and beryllium copper behave differently. State the grade and temper, not just the diameter.
- Bend radius: below one wire diameter, the outside of the bend carries high strain. In spring temper material this can crack or need stress relief.
- Number of bends: every bend adds cycle time and a tool position. A part with fourteen bends is not a scaled version of a part with four.
- Leg length and symmetry: long unsupported legs vibrate and distort. A small gusset or a change in bend order can fix it.
- Finish: plating thickness, masking and hydrogen embrittlement controls all change the process route.
A dimension without a tolerance is a question
Put a general tolerance in the title block, then add tighter tolerances only where the assembly needs them. A drawing with every dimension tight tells the supplier that nothing is critical.
Tolerances and inspection
Wire moves. A formed leg that measures correctly on the bench can move after plating, after packing or after a day under load. The drawing should distinguish between features that locate the part and features that only need to look right.
For a typical formed wire part, the critical calls are the distance between bend centres, the angle of a load-bearing leg, the free length and the load at a stated deflection. A general tolerance such as ISO 2768-m can cover the rest. For springs, load testing at a stated length is more useful than a stack of linear dimensions.
Ask for a first article that includes the dimensions, the material certificate and any functional test. If the part is plated, include plating thickness and an adhesion check. If it is welded, include a pull or shear result.
| Feature | What to record | Why it matters |
|---|---|---|
| Wire diameter | Measured diameter and material certificate | Load, fit and spring rate |
| Bend positions | Distance between bend centres | Assembly fit |
| Leg angles | Angle from the datum leg | Load direction and clearance |
| Free length | Length before loading | Spring fit |
| Load | Load at stated deflection | Function |
| Finish | Plating type, thickness and coverage | Corrosion and contact resistance |
Materials and finishes that fit the job
Music wire is the default for small springs where cost matters and the environment is dry. Stainless steel 302 or 316 adds corrosion resistance at a cost and changes the springback. Phosphor bronze is useful where conductivity and fatigue matter together. Beryllium copper is a specialist choice for contacts and springs that need high conductivity and good fatigue life.
Finishing is not cosmetic. Zinc plating on high-strength spring wire can introduce hydrogen embrittlement if the baking step is missed. Passivation is the usual finish for stainless. Powder coating adds thickness and can bridge a bend radius, so the coating callout needs to account for the geometry.
What to send for a useful quote
Send the current drawing revision, the native CAD file if one exists, the wire diameter and material grade, the temper, the finish, the annual volume and the delivery destination. Add the inspection level and any standard the part must meet.
If the part is still in design, send the concept and say which features are fixed. A supplier can then price a range and flag the features that will move the number. That is more useful than a single price built on an assumption.
- Drawing at the current revision, with a title block and general tolerance
- Native CAD file or a clean PDF
- Wire diameter, material grade and temper
- Finish, plating thickness and any masked areas
- Annual volume and release size
- Delivery destination and Incoterm
- Inspection level and any declaration
Frequently asked questions
What is the difference between wire forming and spring making?
Spring making is a subset of wire forming. A spring uses the elastic properties of the wire to store or release energy. A wireform may be a clip, cage, hook or bracket where the shape, not the spring rate, does the work. The machines overlap, but the drawing and inspection calls are different.
What is the minimum bend radius for wire?
It depends on the material and temper. As a starting point, keep the inside bend radius at or above one wire diameter for spring temper material. Below that, ask for a DFM note. The supplier should check for cracking, stress relief and tool access.
Can wireforms be made without tooling?
Yes for prototypes and small batches. CNC wire forming can produce a part from a program with little or no hard tooling. The trade-off is cycle time and unit cost at higher volumes.
How do I specify a wireform finish?
Name the finish, the standard and the thickness. For tin plating, state the standard and the minimum thickness. For stainless, state passivation. If the part sees flex or high stress, ask about hydrogen embrittlement controls before plating.
Sources and further reading
- ISO 2768-1:1989, General tolerances, linear and angular dimensions
- ISO 2768-2:1989, General tolerances, geometrical tolerances
- Qumek drawing review and DFM notes for formed wire parts
Qumek Engineering Desk
Engineering team
The engineering team behind Qumek drawings, DFM notes, tolerances and inspection standards. Every guide is reviewed against the drawings and processes used on live programmes.
Have a wireform drawing that needs a second opinion?
Send the current revision and the volume. The engineering desk will reply with a written DFM note on the bends, material and finish.
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