302 Spring Wire - Cast and Helix for Auto Feeding
302 spring wire for auto feeding
,cast stainless steel spring wire
,helix 302 spring wire
302 Spring Wire - Cast and Helix for Auto Feeding
Cast and helix are the two descriptions of coil shape that appear on almost every spring wire specification and are ignored on almost every purchase order. They decide whether a coil feeds smoothly into an automatic coiler, whether the wire tangles when the machine stops, and whether the spring comes off the tool with the pitch the designer intended. This page explains what the two terms measure, how they are checked on a shop floor, and what to write on the order when the wire is going onto high speed equipment rather than a hand winder.
Product Specifications
| Item | Specification |
|---|---|
| Product Name | 302 Stainless Steel Spring Wire |
| Material | AISI 302 / SUS302 / UNS S30200 |
| Diameter Range | 0.15-12 mm |
| Diameter Tolerance | ±0.01 mm (fine wire), ±0.02 mm (0.5-3 mm), ±0.03 mm (above 3 mm) |
| Tensile Strength | 1400-1800 MPa, spring temper (size dependent) |
| Cast Diameter | 300-600 mm typical for spring temper, or as agreed |
| Helix | ≤ 25 mm per metre typical, or as agreed |
| Surface | Bright drawn, soap coated on request |
| Coil Weight | 1-100 kg |
| Applicable Standards | ASTM A313, EN 10270-3, GB/T 24588 |
What Cast and Helix Describe
Cast Is the Diameter of the Free Coil
Cast is the diameter a length of wire takes when it is laid flat and allowed to relax, with one end held and the rest free. A tight cast means the wire naturally forms a small circle; a loose cast means it forms a large one. The value is a direct reflection of how the wire was wound and how much residual bending stress remains from that winding. It changes with coil size, with the tension applied during coiling, and with the annealing history of the wire.
Helix Is the Out-of-Plane Deviation
Helix describes how far the wire departs from a single plane. If one end of a length is lifted and the rest is allowed to hang, a wire with no helix stays flat; a wire with helix twists away. The value is normally quoted as a deviation per unit length. Helix is the harder of the two to control and the more damaging when it is out of specification, because it cannot be corrected by adjusting the feed rolls.
Why They Matter on the Coiler
Feeding and Tangling
A cast that is too loose lets the wire swing when the coil is paid off, which shows up as a wandering feed line and inconsistent spring position on the tool. A cast that is too tight makes the coils of the supply pack press against each other, and at low tension the wire can cross over itself and tangle. Both faults stop the machine, and the second one takes far longer to clear than the first.
Pitch Consistency
Helix carries into the finished spring. A wire with residual twist tends to wind with a pitch that varies along the coil, so the free length scatters within a batch. On compression springs with an open pitch this is visible as an uneven coil spacing, and it cannot be corrected by grinding the ends.
Measuring and Specifying
How It Is Checked
Cut a length of two to three metres, lay it on a flat floor and let it settle. The cast is the diameter of the circle the wire forms. For helix, lift one end to a defined height and measure the lateral offset at the other end over a known length. Both checks are quick, need no equipment beyond a tape measure and a flat surface, and are worth doing on arrival rather than after the coil has been loaded.
Typical Values and How to Specify
For spring temper wire in the 0.5-6 mm range, a cast diameter of 300-600 mm covers most coiling equipment, with a helix limit around 25 mm per metre. These are starting points rather than universal values: a small coiler with a short pay-off path tolerates a looser cast than a high speed machine with a long run. Specify the value the machine actually needs, and state the measurement method, because two labs measuring helix differently will report different numbers on the same wire.
Applications
High Speed Coiling
CNC coilers running several hundred parts per minute are the most sensitive application. A stable cast keeps the wire centred in the feed rolls, and a low helix keeps the pitch uniform without the machine having to compensate. Wire that performs acceptably on a hand winder can fail continuously on this equipment.
Wire Forms and Bending Machines
Bending machines index the wire by length, and a twisted wire arrives at the bend die rotated relative to the tool. On a two dimensional form this shows as an out-of-plane leg; on a three dimensional form it shows as a part that will not sit flat. Cast and helix belong in the specification for these parts as much as diameter does.
Weaving and Knitting
Warp knitting and wire weaving use many ends in parallel, and each end has to arrive at the same tension. A coil with a tight cast pays off unevenly as it is consumed, which changes the tension and shows up as a mesh with varying aperture. Uniform cast across the coil, not only at the start, is what the process needs.
Product Advantages
- Cast and helix controlled and stated on the certificate, so the wire can be checked against the coiler requirement on arrival.
- Coil winding tension controlled during packing, avoiding the tight cast that causes tangling at low feed tension.
- Diameter tolerance of ±0.01 mm on fine sizes, keeping feed alignment stable on automatic equipment.
- Consistent temper along the coil, so the cast does not drift from the outside to the inside of the pack.
- Bright drawn surface free of seams, reducing friction in the feed rolls and the risk of a snag stopping the machine.
Quality Control
Cast and helix are checked on a sample from each packing lot, using the agreed method and length. Diameter, tensile strength and elongation are tested per lot. Surface is inspected for seams, laps and die marks over the full coil length. Where a customer specifies a cast range for a particular machine, the measurement procedure is written into the agreement so that the supplier and the customer are not measuring different things under the same name.
Selection and Ordering Notes
- State the cast diameter range and the helix limit, together with the measurement method and the sample length used.
- Describe the equipment: a high speed CNC coiler and a hand winder need different values from the same wire size.
- Mention the pay-off arrangement, since the distance from the pack to the feed rolls changes how much a given cast matters.
- For weaving and knitting, ask for cast to be controlled across the full coil rather than only at the outer end.
- Confirm the coil weight and the packing form, as level wound spools and free coils behave differently in the same machine.
Cast and helix are cheap to measure, hard to correct after the fact, and decisive on automatic equipment. Send the machine type, the wire diameter and the spring pitch requirement, and the coil shape can be specified together with the temper instead of being discovered at the coiler.
