Considerations in Mechanical design

A list of important considerations for any new mechanical design project for product design or systems design

Initiating a new project of mechanical design whether it be a simple mechanism or a complex system, the design engineer needs to account for various factors.

Function:

It is the primary purpose(s) of a system. A scissor has a primary function to cut whereas a bicycle has the primary function to transport. Similarly, each design has a primary function and can have many secondary functions. Knowing and understanding the function clearly is first important step which includes.

Specifying primary and secondary functions
Clear definition of requirements.
Functional decomposition – breaking down the functional elements to the lowest denominator.
Repeatability and reproducibility of functions

Space and size:

Space and size considerations in mechanical design are fundamental which influence the functionality, efficiency and overall performance or the system

Spatial constraints : Evaluating whether the available physical space is sufficient for a mechanism or a structure
What are the limits of motion
Form factor considerations.
Weight distribution considerations

Cost & weight

Every project is driven by constraints on its economic viability and maximum weight for which the system needs to be designed.

Material selection plays a very important role in both cost and weight considerations .
Manufacturing processes are also a major chunk of the cost. Reducing processing cost and overheads related to manufacturing to keep the overall cost in check .
Lightweight design for functional performance : Many times having lightweight design aides the functional performance. For example fuel efficiency in a car is higher for a light weight design.
Using advanced materials , optimizing structures especially crucial in aerospace and automotive industries
Minimizing wastes in manufacturing
Lifecycle costs analysis : considering not only upfront costs but also cost to maintain and dispose of.
Performing VAVE (value analysis and Value engineering ) . Increasing value and reducing cost.

Manufacturing and assembly:

Considerations of how the design will be manufactured and assembled is of prime importance to develop practical design. Also these considerations play a pivotal role in efficiency , cost effectiveness and quality of product.

Designing geometry with process in mind pro-actively. For example, when designing for sheet metal , the geometry is designed considering the sheet metal design constraints and guidelines.
Using cost effective manufacturing processes
Accounting for tolerances closely and performing tolerance stack up analyses wherever required to ensure assembly takes place or there is no interference between parts
Assigning Fits whether clearance or interference to assemblies of components
Sequencing assembly in design and ensuring simplicity of the assembly sequence
Making use of self-locating features for easy assembly
Designing for automated assembly vs manual assembly

Safety :

Considerations for safety include making fail proof designs. Incorporating mechanisms which avoid injury in case of failure. Designing with the worst case in mind.

Materials : Making use of materials which indicate impending failure or donot failure catastrophically . For example, ductile materials generally yield before fracture as opposed to brittle materials
Fail safe designs : Designing systems such that if failure occurs it defaults to a safe state. Very commonly used in electronic systems in which fail safe design involves shutting down faulty component to avoid further damage.
Overload protection : designing for overload . For example, pickup trucks which carry load are designed to withstand more load than specified
Isolation systems : When failure occurs a certain section of system isolates itself and consequential failure is avoided
Assessing and documenting risks through DFMEA and having counter measures associated with them

Durability and environmental degradation:

Durability indicates the overall life of a product. A durable system is one which can perform the function for a long period of time without deterioration. Environmental effects, wear and tear effects reduce the functional life of the product Key factors include :

Material selection: Long lasting materials require resistance to environmental elements, ability to take constant wear and tear and simultaneously handle dynamic loads with out failing. For example , High strength stainless steels used in critical applications .
Structural integrity and stability : Apart from materials, the structural design configuration itself plays a huge role to maintain the durability. A poorly designed structure with good materials would still fail or deteriorate in function with time
Product lifecycle : Considering durability aspect of the product through the lifecycle from the concept of the design to manufacturing process and also how it is handled in maintenance and service. Faulty service practices may compromise durability of a well designed system
Corrosion and chemical resistance . Tied into the material selection . Understanding and accounting for corrosive effects in operation is key
Accounting for level of wear and tear and ways to reduce it to improve life. Any mechanical system with wear and tear will eventually deteriorate. Using lubrication in bearings enhances their lives . similarly using lubrication and low wear and tear designs improves life

Reliability:

While durability is the life of the product within which it performs the function, Reliability is the consistency of functional performance of the system or product . For example, a machine which operates for many years but its performance output is not constant with variable output . Then the machine might be durable but not reliable.

Ensuring a product consistently performs its intended function without failure over its life .

Conducting Risk assessment of the design with a comprehensive DFMEA (Design failure Mode Effect analysis) to identify potential causes for unreliable behavior.

Aiming for Robust design. Meaning designing in such a way that design tolerates variations and unexpected conditions

Maintenance and service:

Integral aspects of mechanical design ensuring ease of dealing with issues in components , replacement and re-work .

Also ensuring longevity and consistent and optimal performance of a product by timely issue resolution .

Key aspects include

Accessibility of components in assembly. Allowing easy assembly and disassembly in service
Interchangeability of parts and Modularity: Chunks of assemblies designed in the form of modules which can be interchanged.
Design with predictive maintenance in mind
Standardization of part : Using parts off the shelf or standard parts so that m they are available in service and easy to replace.

Regulatory compliance:

Adherence of the product or system to established standard and regulations set by relevant authorities

Safety standards
Regulatory standards
Quality management systems
Risk and Liability legal requirements

Usability and ergonomics

Usability refers to the ease with which users interact with the product or system

How quickly users can understand and become proficient in using it.
How efficiently can users perform tasks.
Ability to minimize errors and wrong operation
Ergonomics, or human factors engineering, involves designing products and systems to fit the capabilities, limitations, and preferences of the human body
Designing physical interfaces to accommodate human anatomy and reduce strain or discomfort to user.
Considering mental workload , reasoning , decision making processes and information processing associated to each task for user .
User centered Design for consumer products is the approach to product design with a primary focus on usability and ergonomics

Aesthetics

Aesthetics in mechanical design involves the deliberate consideration of visual and sensory elements to enhance the overall appeal and user experience of a product. Beyond functionality, the aesthetic aspects contribute to consumer perception, brand identity, and market competitiveness.

Visual appeal -Aesthetics play a crucial role in determining the visual attractiveness of a product. Well-designed shapes, proportions, and finishes contribute to a visually pleasing and harmonious appearance.
Form and Function integration- Aesthetics should complement and enhance the functionality of the product. Striking the right balance between form and function results in a design that is both visually appealing and practical.
Material selection - The choice of materials can significantly impact the aesthetic qualities of a product. Considerations such as texture, colour, and surface finish contribute to the overall visual and tactile experience.

Sustainability

Sustainability in mechanical design involves the integration of environmentally conscious practices to minimize the ecological impact of products and systems

Material Selection: Choosing materials with a lower environmental footprint, considering factors such as recyclability, biodegradability, and the energy required for production. Sustainable materials contribute to a reduced impact on natural resources and ecosystems.
Lifecycle impact and Energy Efficient processes- Evaluating the environmental impact of a product from raw material extraction to end-of-life disposal. This comprehensive analysis informs design decisions and identifies areas for improvement in terms of sustainability. Striving for Energy efficient processes are used to convert the design from raw material to final product .
Renewable Energy Sources: Considering using renewable energy sources in manufacturing processes. This reduces the carbon footprint associated with energy consumption during production and aligns with sustainable energy practices.
End-of-Life Considerations: Planning for the end-of-life phase by designing products for easy disassembly and recycling. Considering the potential for repurposing or refurbishing components, contributing to a more sustainable product lifecycle.
Minimization of Waste: Minimizing waste generation during manufacturing by optimizing material usage, reducing scrap, and promoting recycling. Design components with an emphasis on easy disassembly and recycling at the end of the product's life.

Packaging & Handling

Packaging and handling considerations in mechanical design are aspects that influence the safety, transportation of a product
Protection during Transportation: Packaging should be designed to protect the product during transportation from manufacturing facilities to end-users. This includes safeguarding against impacts, vibrations, and environmental factors.
Ease of Handling: Design packaging with user-friendly features to facilitate easy handling. This includes considerations for ergonomics, such as comfortable grips or handles, and clear instructions for unpacking.

Categories: Design process