Electronics and electrical industries use sheet metal enclosures to enclose electronics and electrical components. Sheet metal enclosures has advantage of low manufacturing cost and turnaround time. In this article we will discuss step by step guide to design sheet metal enclosure. We suggest you also read this article on new product design and development process.
Step-1 : Understanding Product design Requirements
First step in any product design is to understand product design and functional requirements. Only after understanding complete requirements you can design a good sheet metal enclosure. Product requirements can include following points.
- Enclosure Application.
- Mounting Requirements: Table top, wall mounted, Pole mounted or rack mounted
- Enclosure Working Conditions: Minimum and maximum working temperature, Corrosion resistance, IP Rating and vibration resistance requirements etc.
- Size Constraints
- Product Aesthetics
- Details of the parts to be enclosed inside sheet metal enclosure.
Step-2: Preliminary Design
After enclosure design requirements are finalized. Next step is electronics enclosure industrial and assembly architecture design.
Sheet Metal Electronics Enclosure industrial Design
During industrial design phase product aesthetics are finalized. For consumer electronics products, enclosure Industrial design directly impact its sales. Buyers takes decision based on product aesthetics.
Designers creates various design options and best one is finalized. Sheet metal Enclosure industrial design also has an impact on product internal components, manufacturing and assembly process. Therefore product detail design starts only after the completion of industrial design.
Following points are considered to finalize enclosure industrial design.
- Internal PCB and other components positioning and their size.
- Position of interface connectors.
- Heat dissipation requirements.
- Functional and Performance Requirements.
- Mounting Requirements
- Assembly Process
- Manufacturing Process
- Cost Constraints
Electronics Enclosure Assembly Architecture Design
All interfaces and product requirements are considered during enclosure architecture design. Following are the outcomes of enclosure architecture design.
- Product top level BOM : A class components, fasteners etc.
- Assembly and Disassembly Process.
- Design and Development Risks.
- Manufacturing Process etc.
Step-3 : Detailed Design and Development
Sheet metal detailed design and development process involves the following points:
- Material Selection
- Fastener Selection
- CAD Modeling
- Finish Operations
- Assembly Operations
Material Selection For Sheet Metal Enclosure
Correct material selection ensures product reliability. Following factors affects the selection of type of material. Read this article to know in details about sheet metal enclosure material selection.
- Material Strength : Stainless steel and CRCA has high strength compared aluminium which is relatively softer material.
- Corrosion Resistance : If enclosure has applications in coastal area or highly corrosive environment. Highly corrosion resistance materials such as stainless steel, GI or Aluminum are recommended.
- Electronics Enclosure Weight Constraints : Aluminum has approximately 70% less weight compared to steel or GI.
- Assembly Process : Steel is easy to weld compared to aluminium. If Design requires a decent amount of welding, choosing aluminum can be risky.
- Cost : Lower material cost means more satisfied customers. This factor needs to be taken seriously at design stage as well.
- Thermal and Electrical Conductivity : Electrical and thermal conductivity of copper is very high. To increase heat dissipation rate, copper is a good choice.
Detailed Enclosure Design (CAD Modeling)
During detailed electronics enclosure design following activities are performed on cad tools.
- PCB Mounting Arrangement : Studs, standoff, metal/plastic brackets and spacers are used to mount PCB with electronics enclosure.
Cutout for Connectors and User Interfaces : Optimum clearance is required between pcb connectors and sheet metal cutout. It is advisable to perform tolerance stack-up analysis to ensure assembly.
Cutout for Ventilation and heat Dissipation : Heat dissipation is becoming very challenging due to miniaturization of electronics products. Ventilation holes are added to ensure product is not heated Up. Simulation studies are performed to manufacture first time right product.
Enclosure joining Operations and Assembly Fasteners : PEM clinching fasteners, welding fastener, riveting nut, studs and standoff are used for pcb assembly with enclosure. Read more about various sheet metal joining operations here.
- Design verification for assembly and manufacturing : After detailed part design designer verify the design for manufacturing and assembly.
Define Finish Operations
Final finish operation affects sheet metal enclosure aesthetics and corrosion resistance. Following points are considered during the selection of final finish operation.
- Sheet Metal Material
- Required Corrosion Resistance
- Product aesthetics requirements
- Conductivity requirements
Some of the commonly used finish operations are given below:
- Powder Coating : Powder coating is applied electrostatically and cured under heat to allow it to flow and form a skin. Powder coating is mainly used for coating metal parts.
- Chromate Conversion Coating : It is a type of conversion coating used to passivate zinc-plated Steel, aluminium, copper, silver, magnesium and tin alloys.
- Anodizing: It is an electrolytic process for producing thick oxide coatings, usually on aluminium and its alloys. Magnesium and Titanium can also anodized. It is used to give improved surface resistance to wear and corrosion, or as a decorative layer.
- Zinc Plating
- Nickel plating
- TIN Plating
Step-4 : Prototype Development and Verification
After design is finalized, the next step is sheet metal prototyping. Prototyping is done to ensure designed part will meet required expectations. Prototyping cost is high compared to production parts.
Prototype parts are verified and tested as per product functional, aesthetics and assembly requirements.
Step-5: Product Validation Testing
As per product functional requirements, validation tests are performed. If there is no major difference in production and prototyping parts. Validation tests can be done on prototypes as well.
Following are a list of some of major mechanical tests done on sheet metal enclosures. Tests are not limited to this list.
List of Tests
- Salt Spray Test
- Scratch Test
- Drop Test
- High temperature test
- low temperature test
- Temperature cycling test
- Wire Pull Test e.t.c
Step-6: Production Ramp-up and Product to Market
After Successful prototype development, verification and validation. Enclosure is released for production with quality plan, Testing jigs and fixtures. Read this article to know in detail about Ingress Protection Rating for sheet metal enclosures.
To sum up, Sheet metal enclosures offers an advantage of low manufacturing cost and low turnaround time. Manufacturer can deliver sheet metal parts within one week time.
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