Designing a product from scratch is not a difficult task if you know what you want to design and knowledge of the design & manufacturing of parts.
As per my understanding, out of these two knowing what to do is most difficult task. If we know what we need to do we can at least think about the risks and plan for their mitigation.
In this article i will share my knowledge and experience of sheet metal enclosure design. i will try my best to add some value to your knowledge of sheet metal electronics enclosure design from this article.
Steps in sheet metal Electronics Enclosure Design
Step 1 : Understand the Requirements
As discussed earlier first step is to finalize the requirements. Before the start of cad design try to find the answer for following questions:
- Application of the products
- Where and who are going to use this product.
- Size Constraints
- Product Aesthetics
- Details of the parts to be enclosed inside enclosure.
Step 2: Product Industrial & Assembly Architecture Design
Based on the input from step-1 take a decision on following points:
- How the product will look like (Aesthetics) : Industrial Design.
- Assembly Structure of the product
Here google is our best friend. Do a research on google and find a best option of your choice. Below are some of the examples of electronics enclosures. You don’t need to copy, if you like you can choose one of them as well for aesthetics.
Following factors affects sheet metal product industrial design:
- Internal PCB outline
- Position of connectors
- Heat dissipation requirements
- Product IP rating
- Product mounting requirements
- Assembly process
- Manufacturing Process
- Cost Constrains
Assembly Structure for Electronics Enclosure
This is very important part, if we make a mistake at this point we will come to zero.
Following points need to be considered while finalizing product assembly process:
- Product Industrial Design
- Product IP Rating (waterproofing)
- User Interface
- Product functional requirements
- Product disassembly requirements.
After this exercise we will get idea of assembly process, types of fasteners required and total number of parts required for assembly.
Step 3 : Material Selection
After step-1 and step-2, we will get a fair idea of what we need. now its time to start engineers work :Material Selection
Material selection for sheet metal electronics enclosure is not a tough task if you have some knowledge of sheetmetal materials.
Following points need to be considered before selection of material for a defined application.
- Strength Requirements : Stainless steel and CRCA are good options for high strength requirements when compared with aluminium which is relatively softer material.
- Corrosion Resistance : Depending on end use of product we select a material e.g. for costal area we need high corrosion resistance material while for indoor requirements Galvanized iron will work. SS 316 offers very good corrosion resistance while CRCA has least corrosion resistance.
- Electronics Enclosure Weight : If you are making a product for airline industry weight will be a major decision contributor. If the requirement is for a material with less weight, good corrosion resistance and optimum strength, Aluminium is a good choice but if the requirement is for high strength, good corrosion resistance and weight is not a constrain, stainless steel will be a good choice.
- Assembly Process : Steel is easy to weld compared to aluminium, If Design requires decent amount of welding, choosing aluminum can be risky.
- Cost : Lower material cost means more satisfied customers. this factor need to be taken seriously at design stage as well.
- Thermal and Electrical Conductivity : Electrical and thermal conductivity of copper is more than aluminum and steel. For more heat dissipation requirements (heat sink) copper is a good choice.
Step 4 : Detailed sheet metal Part Design
After finalization of requirements and material now cad works start. some friends thinks this is a start of design process. But my understanding is we can not achieve good results if our ground work (work done in previous steps) is not strong.
Most of work done at this step is CAD work. But while working on CAD some of the following points, depending on requirements need to considered:
- Mounting arrangement for PCB : If its a electronics enclosure, PCB will be there. Provision for Mounting arrangement of PCB with housing using Studs, standoff or other required fasteners is done. Position of mounting holes with position of studs in sheetmetal parts need to be verified.
Cutout for Connectors and user interfaces : All electronics enclosure has some kind of user interface. Required cutouts for pcb connectors and all other user interfaces are added & verified in part design.
Cutout for Ventilation and heat Dissipation : With miniaturisation of electronics products, heat dissipation is becoming very important factor. If rate of heat dissipation is very high, thermal simulation can be done for good thermal design.
Selection of assembly fasteners: Pem clinching fasteners, welding fastener, riveting nut, studs & standoff are used for the assembly of pcb with sheet metal parts and one sheet metal part with another.
- Design verification for assembly and manufacturing : After detailed part design designer need to verify the design for manufacturing and assembly. Here you can find sheet metal part design guidelines. for manufacturing.
Step 5 : Define Final Finish Operation
Defining finish operation is a parallel process with material selection and CAD designing. Final finish operation along with material greatly affects the life and quality of a product.
Following are the points that need to considered before selection of type of finish:
- Sheet Metal material
- Corrosion resistance requirement
- Product aesthetics requirements
- Conductivity requirements
Based on above requirements finish operation is finalized. Some of the commonly used finish operations are given below:
Sheet-metal Finish Operations:
- Powder Coating : Powder coating is a type of coating in powder foam that is applied electrostatically and cured under heat to allow it to flow and form a skin. Powder coating is mainly used for coating on metal parts. thermoplastic and thermoset-powder coating are available for sheet metal parts.
Chromate Conversion Coating :Chromate conversion coating is a type of conversion coating used to passivate zinc-plated Steel, aluminium, copper, silver, magnesium and tin alloys parts to provide protection from white rust or red rust.
- Anodizing : Anodizing is an electrolytic process for producing thick oxide coatings, usually on aluminium and its alloys. Magnesium and Titanium also can be 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 6 :Prototype Manufacturing
After the design is ready next step is manufacturing of designed parts. Sheetmetal part manufacturer are available all over the globe. You can select manufacturer near to your location. Selection of a good manufacturer increase the chances of product success.
Before Finalizing the manufacturer find answers for following questions:
- Is your manufacturer has completer setup (in house or outsourced ) to perform all manufacturing operations on your part?
- Is Manufacturer has capability to produce quantities required by you?
- Manufacturer previous experience & Knowledge
- Good DFMEA report from manufacturer for your part.
Step 7: Product Validation Testing
After the parts are manufactured next step is to validate your design with manufactured part. Testing standards are available for different product type and for industries where product is to be used. Mentioning all tests are out of scope of this article. Below are some of the test that are done on sheet metal electronics enclosure.
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 8: Production Ramp-up and Product to Market
After Successful testing of prototype, Part Design is reviewed and required changes are done in design and production order released to vendor.
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