Metal fabrication is the one route where prototype and production parts can be made by exactly the same process, because laser cutting and press braking need no part specific tooling. That makes a fabricated metal prototype fast and cheap and creates a trap: nothing about the prototype tells you whether the part could be stamped, cast or extruded at volume.
Why it is fast
The blank is cut straight from the file and folded with standard brake tooling. There is no die to cut, no pattern to make and no lead time beyond the shop's queue. Simple parts in stock material commonly ship within days, and several design iterations are affordable inside a single week, which is exactly what a prototype programme wants.
Building an assembly quickly
Tab and slot joints cut into the parts let a welded assembly locate itself, which removes the welding fixture that would otherwise be the main cost at prototype quantities. Self clinching hardware gives threads without tapping or welding. Together these two techniques let a complete fabricated assembly be built in a week without any tooling at all.
What it does not tell you
Whether the part nests efficiently for volume production. Whether a progressive die could form it. Whether the bend sequence that works by hand can be automated. And whether a casting or an extrusion would be far cheaper at volume. If the production route is different from the prototype route, get that reviewed while the prototype is still cheap to change.
Getting the most from it
Send the folded model and let the fabricator generate the flat with their own bend allowances. Order a few extra parts, since the marginal cost is small. Ask for a bend sequence review before cutting many. And decide whether the prototype needs its production finish, because plating and coating add days and are rarely necessary to answer a fit or function question.
Questions people ask about prototype metal fabrication
How fast is a fabricated metal prototype?
Often within a few working days for cut and formed parts in stock material, because there is no part specific tooling to make.
Can I build a welded assembly without a fixture?
Usually yes, by designing tab and slot joints into the parts so they locate each other. Laser cutting makes those features essentially free.
Does the prototype prove the production process?
Only if production uses the same process. If the part will be stamped, cast or extruded, get a review against that route while the design is cheap to change.
Should I supply a flat pattern?
No. Supply the folded model. The fabricator's bend allowances are tested against their own tooling and material.