Episode 94 ~2:00 Fabrication

CNC cutting, punch, laser & plasma

Three ways to turn a flat sheet into a part. Edge quality, slug control, thickness limits, and which cutter the workshop reaches for when the BOQ doesn't say.

Animated explainer, press play to watch the concepts now; the filmed cut publishes once production wraps.

What you'll walk away with

01

Punch wins thin sheet at volume.

Below 2 mm steel and at quantities of 50+, a turret punch outruns laser. Each hit is milliseconds, and the tooling pays back over runs.

02

Fibre laser owns 1–12 mm steel.

A 6 kW fibre laser cuts 1 mm stainless at 30 m/min and 10 mm mild steel at 1.2 m/min. Kerf is 0.15 mm. The edge is square enough to weld on without dressing.

03

Plasma is for thick steel and forgiving tolerances.

20–40 mm plate where laser tops out and waterjet is too slow. Edge is angled and HAZ is wide. Spec a 1 mm secondary machining allowance.

04

Slug control dominates the cost.

A laser cuts to scrap, a punch makes slugs you have to evacuate. Lose track of slugs in a hole pattern and the next part jams. Workshop time, not material, drives price.

Cutter × material × thickness × edge

Indicative cut speeds. Exact rates depend on machine power, assist gas, and material grade.

CutterThickness · SpeedEdge · Use
Turret punch0.5–3 mm · burstHoles & forms, sharp edge, high volume
Fibre laser 3 kW0.5–8 mm · 1–20 m/minClean weld-ready edge
Fibre laser 6 kW0.5–12 mm · 1.2–30 m/minProduction standard for enclosures
Fibre laser 12 kW+to 25 mm steelHeavy fabrication, switchgear
Plasma (HD)3–40 mm · 0.5–4 m/minThick steel, 1 mm finish allowance
Waterjetto 150 mm · 0.1–1 m/minNo HAZ, any material, slow

Five things to lock before cutting

Decisions at programming time that compound across the whole run.

Common-line cutting saves 20% of cycle time.

Two parts sharing an edge get cut once. Programmers who think in single parts leave the saving on the table. Spec common-line nesting in the workshop RFP.

Hole-to-edge minimum is 2× the thickness.

Cut a 10 mm hole 5 mm from the edge in 3 mm steel and the edge bows during cooling. Designers think in pixels, the metal thinks in heat.

Lead-in and lead-out leave a mark.

The pierce point is hotter and rougher than the rest of the cut. Move the lead-in to a non-cosmetic edge or inside a relief slot. Customers see pierce marks before they see your drawing.

N₂ for stainless, O₂ for fast mild steel.

Nitrogen assist gas gives an oxide-free edge on stainless and aluminium, paintable, weldable. Oxygen on mild steel doubles cut speed but leaves an oxide layer that needs cleaning before paint.

Cut order = thermal management.

Small features first, large perimeters last. The sheet stays cool, parts hold position on the slats, and the kerf width stays inside tolerance across the run.

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