Sheet metal work is four stages in a fixed order: get the flat blank out of the sheet, fold or form it into shape, join it to whatever it must be joined to, and finish the surface. Almost every decision that affects the price of a fabricated part is a decision about which method is used at one of those four stages, and most of them are made by the designer without realising it.
Cutting the blank: the first step of sheet metal processing
Laser cutting is the general answer: fast, no part specific tooling, good edge quality on most thicknesses. Punching is faster on high volume repeat holes and leaves a different edge. Waterjet cuts anything and imparts no heat, which matters on hardened or heat sensitive material. Plasma is the thick plate answer. Blanking dies beat all of them on volume and cost tooling money to set up.
Forming: bending and rolling in sheet metal working
Press braking folds the blank against a die with a punch, one bend at a time, using standard tooling. Roll forming produces long constant sections continuously. Deep drawing pulls a blank into a cup or box shape in a die and is a tooling investment. Most fabricated parts are brake formed, which is why bend radius, flange length and bend sequence dominate design for cost.
Joining
Welding, spot welding, riveting, self clinching hardware and adhesive all appear. Self clinching nuts and studs pressed into the sheet are usually the cheapest way to get a threaded feature and avoid the distortion welding brings. Welded assemblies need fixtures, and fixtures are a real cost that many quotes hide inside the part price.
Finishing and what it constrains
Deburring, graining, powder coating, plating, anodising and passivation each have their own lead time and their own masking requirements. Finish decisions reach backwards into design: threads must be masked or chased, ground straps need a bare area, and a coating thickness that nobody accounted for will make a press fit interfere.
Questions people ask about sheet metal manufacturing
What is the sheet metal process, start to finish?
The set of processes that turn flat sheet into finished parts: cutting the blank, forming it, joining it and finishing it. It covers everything from a single bracket to a welded enclosure.
What thickness counts as sheet metal?
In practice, material thin enough to be cut and formed on standard fabrication equipment rather than machined or plate rolled. The boundary is set by the shop's brake tonnage more than by any definition.
Which cutting process should I ask a sheet metal factory for?
Usually none. Give the fabricator the geometry, the material and the edge quality you need, and let them choose the process their shop does best.
Why does sheet metal production cost more than expected on a simple part?
Usually setups. Different thicknesses, different bend radii, welded sub assemblies and multiple finishes each add a setup, and setups dominate at low volume.
All about sheet metal: which of the four stages decides the cost?
Joining and finishing, more often than the cutting and forming people focus on. Cutting is largely process choice and forming is mostly standard brake tooling, but a welded assembly needs fixtures and a fixture is a real cost that only pays back over quantity, while self clinching nuts and studs pressed into the sheet are usually the cheapest route to a threaded feature. Finishing then reaches backwards into the design: threads need masking or chasing, a ground strap needs a bare area, and a coating thickness nobody accounted for changes a fit.