Sheet Metal Fabrication Guide

Sheet Metal Fabrication: From Cutting to Welding, A Complete Guide

Category: Casting & Forming Reading time: 8 min Meta description: A complete guide to sheet metal fabrication covering laser cutting, bending, welding, punching, and finishing. Learn how to design parts for sheet metal. URL: /blog/sheet-metal-fabrication-guide/ Tags: sheet-metal, fabrication, laser-cutting, bending, welding

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Sheet metal fabrication is one of the most widely used manufacturing processes. From electronics enclosures to structural brackets, industrial equipment to architectural panels — sheet metal is everywhere.

This guide covers the key processes, design rules, and cost factors for sheet metal fabrication.

The Core Processes

Sheet metal fabrication combines several distinct processes:

1. Cutting

The first step — cutting flat sheet into the part outline.

Method	Thickness	Accuracy	Edge Quality	Best For
Laser cutting	0.5-25mm (steel)	±0.1mm	Excellent, clean	Most parts, complex shapes
Plasma cutting	3-50mm (steel)	±1.0mm	Moderate, slight taper	Thick plates, structural
Waterjet cutting	0.5-100mm	±0.2mm	Excellent, no HAZ	Thick or heat-sensitive materials
Punching (CNC turret)	0.5-6mm	±0.1mm	Good, fast for repeats	High-volume, simple shapes

Laser cutting is the most versatile option for custom fabrication. fiber laser machines are now standard, cutting mild steel up to 25mm and stainless up to 12mm.

2. Bending / Forming

The sheet is bent along straight lines using a press brake.

Factor	Standard V-Die	Air Bending	Coining
Accuracy	±1°	±0.5°	±0.25°
Tooling cost	Low	Moderate	High
Springback	Yes (compensated)	Yes	Minimal

Key parameter: The V-die opening should be 6-12x the material thickness. A standard rule: V-opening = 8 × material thickness.

Minimum bend length: The flange being bent should be at least 4× material thickness + the inside bend radius.

3. Welding

Used to join multiple sheet metal parts into assemblies.

Method	Thickness	Appearance	Speed
MIG welding	1-12mm	Moderate	Fast
TIG welding	0.5-6mm	Excellent (cosmetic)	Slower
Spot welding	0.5-3mm	Clean, no filler	Very fast
Laser welding	0.5-3mm	Excellent	Fast (high equipment cost)

For cosmetic welds: TIG is preferred. It requires more skill but produces clean, smooth welds that require minimal grinding.

4. Punching & Forming

Secondary operations on turret punch presses or press brakes:

• Punching — round and shaped holes
• Louvers — ventilation slots
• Extrusions — threaded holes formed from the sheet
• Embossing — raised features for branding or stiffness
• Lancing — partial cuts with formed tabs

Design Rules for Sheet Metal

Minimum Bend Radius

Material	Bend Direction Relative to Grain
	Perpendicular	Parallel
Mild steel	0.4-0.5t	0.8-1.0t
Stainless steel	0.5-0.6t	1.0-1.5t
Aluminum	0.3-0.5t	0.6-1.0t
Galvanized	0.5t	1.0t

Minimum Feature Sizes

Feature	Minimum Dimension
Hole diameter	1.0t (0.8mm minimum)
Hole to edge distance	1.5t
Slot width	1.5t
Tab width	2t
Corner notch size	3t
Emboss diameter	3t
Lanced tab height	2t

K-Factor and Bend Allowance

When sheet metal bends, the material on the inside compresses and the outside stretches. The K-factor defines the neutral axis position — typically 0.33 for most materials.

Bend allowance formula (approximate):

BA = (π/180) × θ × (R + K × t)

Where θ = bend angle in degrees, R = inside radius, t = thickness, K = 0.33

For quick estimates, fabricators use bend deduction tables specific to their tooling.

Material Selection

Material	Typical Thickness	Cost Factor	Applications
Mild steel (SPCC/DC01)	0.5-6mm	1x (baseline)	Enclosures, brackets, frames
Galvanized (SGCC/DX51D)	0.5-3mm	1.1-1.3x	Outdoor, electrical enclosures
Stainless 304	0.5-3mm	2-3x	Kitchen, medical, food equipment
Aluminum 5052	0.5-4mm	2-2.5x	Marine, electronics, lightweight
Aluminum 6061	0.5-4mm	2-3x	Structural, precision parts
Copper	0.3-2mm	3-5x	Electrical contacts, roofing

Finishing Options

Finish	Application	Cost Impact
Powder coating	Most steel parts	+$10-50 per part lot
Painting (liquid)	Small parts, matched colors	+$5-30 per part lot
Zinc plating	Corrosion resistance, fasteners	+$0.10-1.00/kg
Anodizing	Aluminum only	+$0.50-5.00/part
Passivation	Stainless steel	+$0.50-2.00/part
Silk screening	Labels, brand markings	+$20-100 setup + $1-5/part

Cost Factors

The biggest drivers of sheet metal cost:

1. Setup time — Programming and tooling changeover ($50-150)
2. Material cost — Varies by type and gauge
3. Cutting time — Laser cutting is charged per minute ($1-3/min)
4. Number of bends — Each bend is a setup on the press brake
5. Tolerances — Tighter than ±0.2mm requires special handling
6. Welding — Complex welded assemblies add significant labor
7. Finishing — Multiple steps add cost and lead time

Cost-Saving Tips

• Avoid tight tolerances on formed dimensions — Bending springback makes ±0.2mm difficult.
• Design for common material gauges — 1.2mm, 1.5mm, 2.0mm are most available.
• Consolidate parts — A single assembly with welds is often cheaper than multiple separate parts.
• Design self-locating tabs — Reduces fixturing cost for welding.
• Avoid multiple bend radii — One standard radius simplifies tooling.

Quality Standards

Class	Typical Use	Tolerance
Commercial	General enclosures, brackets	±0.5mm
Precision	Electronics, medical	±0.2mm
High precision	Aerospace, optical mounts	±0.1mm

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