The manufacture of steel wire
forms and welded wire assemblies demands
a tremendous amount of knowledge and experience. The final product
can only be optimally achieved after matching the materials, processes,
equipment design and quantities with the application. The designer
should be aware that a practical and reasonable approach to tolerance
is important to the overall cost of a part. Generally tighter tolerances
will increase the product cost.
Wire shape, size and selection of the alloy
(low carbon steel, stainless steel, aluminum or hard drawn) is
where it all begins. Wire is typically purchased in coil form and
is straightened and cut automatically on high-speed machines to
tolerances within +/-.010”
Many wire fabricators recommend that the minimum bend or radius
should be equal to the wire diameter. There are exceptions due to
product function. In some instances the inside radius must be smaller
than the wire diameter. When requiring a smaller radius, a crimping
operation could be done, but with special tooling.
Wire is bent or formed with a variety of equipment.
Rotary air benders, press brakes, punch presses, CNC wire benders
and four-slide formers are used. Steel and
stainless steel wire forms, wire
formed products, wire parts and
problematic wire forms are all formed on this type of equipment. Depending on the equipment,
standard or special tooling is required. Typical tolerances for
wire forming fall into a range from +/- .015” to +/- .030”
Another major consideration in wire forming is the design of mechanical
joints in wire forms to fasten and assemble formed
wire products together. Other considerations include threading (by die cutting
or rolling); swaged, pierced and upset ends; fasteners and fastening
systems; and sheet metal brackets. Resistance welding
of wire products (cross wire, butt, tee, projection and line) along with gas arc welding
should be considered.
Multiple-wire products such as cross-wire panels
and other skeletonized shapes are usually readied for welding by
being assembled in special jigs and fixtures made from plastic,
wood and metal. These fixtures hold the formed
wire parts in place
during welding. Some specialized machines weld multiple-
wire products without utilizing a jig or fixture. The fixture is actually built
into the machine and is part of the “set-up” of the machine. Typical tolerances fall
into a range from +/- .010” to +\- .060”. Wire is resistance
welded using a variety of equipment configurations. Single-head welders,
projection welders and higher-volume multiple-head welders are used
to provide complete flexibility during processing.
The finishing of wire products is also an important consideration.
Basically, the wire product is completely manufactured before applying
a finish. The finishing choices are nickel/chrome, zinc, powder coating,
nylon or vinyl coating, black oxide, electropolish or passivation.
A full-service wire forming and welded
wire assembly company provides
product design assistance, prototypes, in-house tooling fixturing,
short runs and production. The company should be capable of recommending
simplified designs and practical solutions to your processing problems.