Metal Fabrication — Engineering Decision Guide

Laser for thin-to-medium steel and stainless (roughly up to 1 in.), tight tolerance, intricate detail, and high speed with a clean edge. Plasma for thick mild-steel plate and fast, lower-cost cuts where edge quality matters less. Waterjet for very thick material, heat-sensitive or non-metallic parts, and anywhere a zero heat-affected-zone is required (no thermal distortion or edge hardening). CNC/turret punch for high-volume simple holes and forms in thin sheet, especially when you also need to form louvers, tabs, or countersinks in the same operation.

Each process trades speed, thickness, edge quality, and heat. Laser is fast and precise but leaves a heat-affected zone and slows on very thick or highly reflective stock. Plasma is cheap and fast on heavy plate but rougher and hotter. Waterjet cuts any material with no heat at all — the reason it wins on titanium, composites, stone, and pre-hardened parts — but it is slower and carries abrasive cost. Punching is unbeatable for repetitive thin-sheet features and integrated forming, at the cost of tooling and shape flexibility.

Laser on very thick or reflective plate is slow and costly. Plasma where tolerance or a clean, hardening-free edge matters. Waterjet where throughput is the priority. Punching a one-off or a complex contour that a laser would nest and cut in minutes.

Use air bending as the default: one V-die covers a range of angles, tonnage is lowest, and it is the most flexible. Step to bottoming when you need tighter, more repeatable angles — at roughly 2–3× the tonnage. Reserve coining for parts needing a precise inside radius and minimal springback, accepting 5–8× the tonnage and heavier tooling wear.

In air bending the punch only presses the sheet against the die shoulders, so the angle is set by ram depth and the radius floats near ~0.16× the die opening — flexible and low-force, but springback must be over-bent out. Coining forces the material fully into the die and against the punch nose, which sets the radius and largely eliminates springback — but only because it applies enormous, tooling-punishing force.

Coining everywhere destroys tooling and demands a much larger press for no benefit on non-critical parts. Air bending a part with a hard angle tolerance leaves batch-to-batch angle variation as material springback shifts with lot and grain.

The finished angle opens up wider than programmed (springback), or the outer fibre cracks along the bend line — most often in high-strength or hardened material, or when bending parallel to the grain.

Springback grows with material strength, larger inside radius, and air bending. Cracking comes from a bend radius too tight for the alloy, bending parallel to the rolling grain, cold or age-hardened material, and a burr left on the outside (tension) face of the bend.

For springback: over-bend to compensate, or switch to bottoming/coining for repeatability. For cracking: increase the inside radius to at least the material minimum (often ≥ 1× thickness for mild steel, more for high-strength and aluminum), orient the bend line across the grain, put the burr on the inside (compression) face, and warm or anneal difficult alloys.