CNC Wire Bending
CNC wire bending feeds round or flat wire through a programmable head that bends it in sequence into a finished 2D or 3D form.
- Part
- Forming
- Revised
- 2026-08-11
At a glance
- Family
- Metal
- Typical tolerances
- Roughly ±0.020 in (±0.5 mm) on leg lengths and ±1–2° on bend angles, tightening to about ±0.010 in and ±1° with first-article correction; tolerances accumulate along multi-bend parts
- Surface finish
- Retains the incoming wire finish; cut ends carry a small shear burr unless chamfered or ground
- Typical volumes
- 100–1,000,000+ parts; a few hundred is enough to absorb the setup
- Lead time
- 1–3 weeks including programming and first articles; days for repeat orders. No tooling lead time
- Materials
- Metal
What it is
CNC wire bending feeds round, square, or flat wire from a coil through a programmable bending head that forms it into a finished 2D or 3D shape, then cuts it off. There is no part-specific tooling: the geometry lives entirely in the program, so a new part number is a setup rather than a tool build.
Wire diameters typically run 0.020–0.500 in (0.5–12 mm), with heavier machines going further, in low-carbon steel wire, music and spring wire, 302/304 stainless, aluminum, copper, and brass. Simple parts come off at cycle times measured in seconds.
It is the process behind display and retail racks, appliance and dishwasher baskets, seat and furniture frames, clips, hooks, handles, and formed springs. Because tooling is programmable, it covers a volume range no die-based process can — economic in hundreds and still competitive in the millions — and the whole part is made in one operation, with no weld or joint in the formed length.
How it works
- Payoff and straightening. Wire is drawn from a coil through a set of straightening rollers in two perpendicular planes. Getting this right is fundamental: residual coil curvature that survives the straightener shows up as bowed legs on every part.
- Feed. Servo-driven rollers or a gripper feed the wire a programmed length. Feed accuracy sets the leg length tolerance directly.
- Bend. A bending head forms the wire against a pin or die. On a 2D machine the head bends in a single plane; on a 3D machine the head rotates around the wire axis, or the wire itself is rotated between bends, so bends can be placed in any plane.
- Springback compensation. The machine overbends by a programmed amount. Springback is a function of the wire's yield strength and diameter, and it varies between material lots — which is why a first article is checked and the program trimmed for each new coil.
- Secondary in-line operations. Many machines integrate end forming, coiling, thread rolling, chamfering, punching, or flattening within the cycle.
- Cut off. The finished part is sheared free. The cut end carries a small burr and is often chamfered or ground in a secondary operation if it will be handled.
- Post-processing. Resistance or projection welding for assemblies, then zinc plating, powder coating, e-coating, or plastic dip.
Because there is no die, the process's accuracy is a function of feed servo precision, wire straightness, and material consistency rather than of tooling. That makes wire diameter and temper consistency an important purchasing specification, not an afterthought — a coil with tensile strength varying along its length will produce parts with varying angles no matter how good the machine is.
Design guidelines
Bend radius
Inside bend radius should be at least 1–2× wire diameter for annealed low-carbon steel and 2–3× for spring tempers and stainless. Tighter radii crack the outer fiber, and in spring wire the failure is sudden. The radius is set by the bend pin, so a design specifying several different radii needs several pins and, potentially, a tool change mid-cycle.
Distance between bends
Leave at least 2–3× wire diameter of straight length between bends. The bending head needs physical clearance around the wire, and adjacent bends interfere with tooling before they interfere with each other.
Tolerance stacking
Every bend adds angular error, and every leg adds feed error. Dimension from one end rather than chaining dimensions along the part, and put the tight tolerance on the feature that matters — usually a hook opening or a mounting hole spacing — rather than on the overall envelope.
2D before 3D
A part that can be formed in a single plane runs faster and holds tighter than one requiring rotation between bends. Where a design can be flattened into one plane without losing function, it should be.
Material and temper
Specify the alloy and temper, not just "steel wire." Annealed low-carbon wire forms to tight radii and stays where it is put; spring tempers hold load but need larger radii and show much more springback variation. See the material properties chart for a comparison of the base materials.
Closed forms and overlaps
A wire form that closes on itself — a ring, a closed rectangle — cannot be bent shut without the free end colliding with the machine head. Closed shapes are formed open and then welded, which is a separate operation with its own tolerance.
Design for the weld, if there is one
Resistance and projection welding of wire assemblies needs contact geometry: crossed wires weld well, parallel wires touching along a length do not. Where a wire form is welded into an assembly, make sure the joints are point contacts.
| Feature | Recommended | Limit | Why |
|---|---|---|---|
| Inside bend radius | 2× wire diameter | 1× diameter, annealed steel | Outer fiber cracks at tighter radii |
| Bend radius, spring temper | 3× wire diameter | 2× diameter | Hard tempers have little outer-fiber ductility |
| Straight between bends | 3× wire diameter | 2× diameter | Bending head needs physical clearance |
| Number of distinct radii | One | Each radius needs its own bend pin | Tool changes interrupt the cycle |
| Geometry | Single plane where possible | 3D needs rotation between bends | Planar parts run faster and hold tighter |
| Closed loops | Form open, weld closed | Cannot bend a loop shut in the head | The free end collides with the tooling |
| Leg length tolerance | ±0.020 in (±0.5 mm) | ±0.010 in (±0.25 mm) | Set by feed servo accuracy and wire straightness |
| Bend angle tolerance | ±1–2° | ±1° with first-article correction | Springback varies between material lots |
Cost drivers
There is no tooling to amortize, so cost is setup plus cycle time plus wire. Setup is the dominant term at low volume: threading and straightening the coil, loading the program, and correcting springback on first articles takes a few hours regardless of quantity. Cycle time is seconds per part, so at volume the wire itself and the secondary operations — welding, plating, coating — usually cost more than the bending.
Volume breakpoints: a few hundred parts is enough to absorb a setup. From 5,000 to 500,000, wire bending is at its most competitive, beating stamping outright because there is no die to build and no skeleton scrap. Very high volumes of a stable design may still move to a dedicated four-slide or multi-slide machine, which is faster but requires hard tooling.
- Reduce the bend count. Each bend is cycle time on every part.
- Keep the part planar. 3D bends require rotation, which slows the cycle and widens the tolerance.
- Use one wire diameter across an assembly. Changing diameters means changing straightener and feed setup.
- Avoid welded closures. A form that needs a closing weld doubles the operation count; redesigning it as an open form with a hooked overlap can remove the weld entirely.
- Choose a standard coating. Zinc plating and powder coating on wire are commodity operations; specialty finishes cost disproportionately on a low-mass part.
Questions
6 questionsWhat is the minimum bend radius for CNC wire bending?
About 1–2× wire diameter for annealed low-carbon steel and 2–3× for spring tempers and stainless. Below that the outer fiber cracks, and in spring wire that failure is sudden rather than progressive. The radius comes from the bend pin, so using one radius throughout avoids tool changes.
How close together can two bends be?
At least 2–3× wire diameter of straight length between them. The limit is physical clearance for the bending head, not the metal — adjacent bends run into the tooling before they run into each other. Very close bends may require a different machine or a secondary forming operation.
What tolerance can CNC wire bending hold?
Roughly ±0.020 in (±0.5 mm) on leg lengths and ±1–2° on bend angles, improving to about ±0.010 in and ±1° once first articles have been used to correct the program. Because tolerances accumulate along the part, dimension from one end rather than chaining dimensions bend to bend.
Does CNC wire bending require tooling?
No part-specific tooling. The geometry lives in the program, and the only hard tooling is standard bend pins and feed rollers. That is why the process is economic in the hundreds — there is no die to amortize — and why a design revision costs a reprogram rather than a tool build.
Can a closed wire loop be bent in one operation?
No. The free end would collide with the bending head before the loop closed. Closed shapes such as rings and closed rectangles are formed open and then joined by resistance or projection welding, which is a separate operation carrying its own tolerance.
Why do parts from a new coil come out at different angles?
Springback is a function of the wire's yield strength, which varies between coils and even along a coil. The machine compensates by overbending a programmed amount, so a first article is checked and the program trimmed each time material changes. Specifying alloy and temper tightly reduces the variation.