Sheet Metal Design Guide & Drawing Considerations

Parts made from sheets of metal, whether it is aluminum, steel or copper, have specifc design considerations for a manufacturable part. The intent of this guide is to provide insight into the thought process necessary to create detailed sheet metal parts that are manufacturable in a production environment.

Design Purpose

Before beginning the design, capture what the goals are of the part and the requirements it needs to meet.

Goals of the Part Design

Prioritize the key use of the part . Generally, parts fall into these main categories:

Protection from environmental elements
System coooling
Shielding for electromagnetic Interference (EMI)
Electrical grounding
Structural

Design Requirements

Identify additional requirements that influence all design decisions:

EMI
FCC, FAA, FDA
RoHS
WEEE
Regulatory (UL, CSA, CE)

Production Volume vs. Complexity

The number of parts produced in production influences design decisions. The costs accepted at low-volume are intolerable at high volume and should be mitigated. Consider the practical impact of the number of parts produced and/or stored:

Time to assemble
Warehouse space to store pieces or assemblies
How inventory will be managed
Managing the suppy chain

Consolidating parts into more complex assemblies limits the supply base, but saves in assembly time and reduces the number of parts in inventory.

Design Considerations

Fabrication Processes

Considering the fabrication process will improve yields during production. Suppliers can point to the most cost-effective way to design parts that works best with their processes.

Cutting

Laser cutting is great for short runs
Punch presses are better for mid-volume
Progressive tooling for high volume

Forming

Can be done in punch via tooling for lances, dimples, and hole extrusions
Press break required for bends

Joining

Provide features to self-align parts prior to joining

Welding

Spot welding may create plating issues
Slot & Tab construction conrols locations and can prevent plating traps

Finishing

Bolt or rivet parts together post plating
Provide flow paths for plating fluids to exit part to control leaching chemicals from causing surface finish issues
Prevent trapping of plating fluids by using slot and tab construction instead of spot-welded flanges

Functional Requirements

The funciton of the parts dictates some of the design decisions.

Rigidity

Add bends or bosses in critical areas to stiffen material
May allow you to reduce material thickness to reduce weight and cost

Tolerances

Tighten where needed; otherwise, keep loose overall
Be aware of manufacturing requirements which may conflict with the ability to have tight tolerances (e.g. hole position over multiple bends is difficult to maintain)

Materials

Steel

Suppliers can point to the most cost-effective way to design parts that works bst with their processes

Cold Rolled

Good general-purpose material
Consider low carbon steel such as 1008 or 1010 for lowest cost

Preplated

Good for enclosures that are screwed or riveted together since welding will burn off or discolor the plating
Requires care during processing
Plating will protect cut edges from corrosion in most environments

Stainless

304 is better for forming
316 is better for corrosion resistance but more difficult to form

Other Materials

Aluminum

Will need to be 3x thicker to maintain the same strength of steel
3x lighter than steel for the same thickness
5052-H32 good multi-purpose material for forming, welding, and corrosion resistance
6061-T6 is good for structural material, but is more difficult to form, requiring larger bend radii

Copper

Great conductor of heat and electricity