Sheet Metal Prototyping

Why Sheet Metal Is a Different Engineering Problem

Sheet metal work is formed, not cut from solid. That single difference changes what a designer has to think about: not just geometry, but bend sequence, bend allowance, grain direction and what happens to a flat pattern when it is folded.

A CAD model of a folded bracket can look correct and still be unbuildable, because the unfold does not close or because the bend sequence traps a flange. This is the most common reason a sheet metal prototype quote comes back with questions.

Equipment and the Accuracy It Holds

Process	Machine	Documented accuracy	Envelope
Laser cutting	TRUMPF TruLaser 1030	±0.05 mm	1000 × 600 mm
Bending	Amada HG 2204	±0.1 mm	2200 mm bend length
Secondary machining	Mazak Variaxis i-600, Haas VF-2	±0.005 mm	For holes, pockets and features after forming
Verification	Zeiss Contura G2 CMM	±0.001 mm	700 × 700 × 600 mm

The 2200 mm bend length is worth noting plainly: most prototyping shops bend far shorter parts, and long folded sections are a common reason a job gets subcontracted badly.

The Design Rules That Actually Decide the Part

Bend radius versus thickness. A bend radius below material thickness risks cracking on the outside of the bend, especially in harder tempers. The minimum is a material property, not a preference.
Bend relief. A flange that meets a wall without relief tears. Relief notches are cheap at design time and awkward to add later.
Hole-to-bend distance. A hole placed too close to a bend distorts into an oval. The usual guide is at least material thickness plus bend radius away from the bend line.
Bend sequence. Some flanges block the punch for later bends. A part can be geometrically valid and still have no workable sequence.
Grain direction. Bending across the rolling direction cracks more readily than bending along it. For critical parts this has to be stated.
Flat pattern closure. The unfolded blank must actually exist. If the CAD unfold does not close, the part cannot be laser cut.

Where Sheet Metal Prototypes Fail

Tolerances tighter than forming allows. Laser cutting holds ±0.05 mm, but the bend operation afterwards moves material. A tolerance that ignores the forming step will fail even though the cut was accurate.
Cosmetic expectations on formed faces. Tooling marks at the bend, and slight orange-peel on the outside radius, are normal. A drawing demanding a pristine bend face is asking for a different process.
Finish applied before forming. Powder coating or plating before bending cracks at the bend line. Order of operations matters and belongs in the process route.
Holes used as datums after forming. A hole that was round in the flat becomes slightly oval after bending. If it is a datum, it has to be machined after forming, not cut before.

When Sheet Metal Is the Wrong Choice

Solid or thick parts. Sheet metal starts from flat stock. A solid block is a machining job.
Tolerances in the ±0.001 mm range. Forming cannot hold that. If a feature needs it, the feature is machined after forming, which is a different and more expensive route.
Deep drawn or complex 3D shapes. Press forming and deep drawing are production processes, not prototyping ones.
Organic or heavily curved surfaces. Sheet forming works with bends, not with freeform curvature.

From Prototype Sheet Part to Low-Volume Batch

Sheet metal is unusually well suited to the prototype-to-batch step, because laser cutting has no tooling cost. Going from one part to two hundred changes setup amortisation and material purchasing, not the process itself. What does change is inspection: a batch needs a sampling plan and recorded results rather than a final look.

Verification

Formed parts are measured on the Zeiss Contura G2 CMM at ±0.001 mm, with surface on a Mitutoyo Surftest SJ-210 across Ra 0.005 to 40 μm, and height and step features on a TESA Micro-Hite 600. ISO 9001:2015, qualification ratio above 99%, 50+ staff including 6 engineers, 4 designers and 2 dedicated inspectors.