Tips to simplify designs
A guiding principle that defines for us all the essence of lightweight component design is:
Always the right material— only the necessary and appropriate material, shaped to its stresses, with care and deep understanding of its end use.
It’s an inescapable fact that, in some ways, lighter really is beautiful, or at least desirable — and highly sought after. And worth paying extra for.
In engineering. In aerospace. In vehicles. In medical applications. In sports. In portable and handheld electronics. In power tools. In weapons. In body armor. In wearable electronics. In the energy sector. In so many critical, high value applications.
Making effective use of light materials is a fundamental driver of good design. Making the necessary careful use of heavy materials is often a required compromise. Minimizing weight without sacrificing strength, stiffness, durability, safety, and resilience is the goal of lightweight design.
A well-executed design can improve various aspects of efficiency, reduce energy consumption, and lower operating costs while meeting the limitless demands of regulatory and environmental pressures.
This guide will take you through the principles, techniques, and considerations essential for designing lightweight parts, including materials selection, structural optimization, manufacturing processes, and practical examples of successful lightweight design strategies
Lightweight part design definition
Lightweight design is not just about reducing mass; it’s about optimizing the entire product structure, material choices, stress distribution, and of course weight, to ensure performance is optimized according to realistic priorities.
A part with much reduced weight that cannot withstand the expected loads is a failure.
In industries that make moving outcomes – aerospace, automotive, and transportation – weight savings translate to energy savings, reduced emissions, and improved commercial and motion performance.
A well-designed lightweight part will typically result in
- Increase operational efficiency: Lower weight will deliver better fuel efficiency and other energy savings, lower stress on elements that carry the product, and generally improved performance.
- Complex effects on production costs: Lighter materials will typically increase material costs and may reduce processing cost or increase it. Reduced usage of less advanced materials may deliver both weight savings AND cost savings. Each case is unique.
- Sustainability: Using less resources/material and more recycled material to deliver lighter components that require less energy for motion reduces net environmental impact variously. A focus on Aluminum alloys, for example, has typically lower net environmental impact than use of Titanium alloys—despite extraction of ores for both being an intrinsic harm to the environment.
Lightweight design has been recognized for its importance since the earliest refined horse-drawn vehicles. The Roman chariot races had minimum weight specifications that had to be met, to even the field as teams vied for lightness. A ‘sporty’ 19th-century carriage had significantly lower mass than a robust and practical, less expensive equivalent.
As industries push for sustainable solutions and better overall performance, designers today operate under the same principles as chariot builders in the Circus Maximus.
How to design lightweight parts
Developing a clear understanding of the underlying design principles is critical to achieving effective lightweight component design. This review introduces the foundational approaches that guide design:
- Material efficiency: Focuses on using the least amount of material while maintaining the application-appropriate strength, durability, and performance of the component.
- Material Selection: It is an early and critical step in achieving material efficiency. Lightweight materials like Aluminum and Magnesium alloys, Titanium, Carbon fiber, and other composites are effective in lightweight design because they offer high strength-to-weight ratios.
- Topology optimization: is a computational, and often AI-driven, design methodology that seeks to remove material from areas of a component that do not bear significant loads.
- Thin-walled structures: are a widely applied technique in lightweight design. By distributing material more effectively and minimally, in response to real and highly regionalized loading expectations, thin-walled sections can be made stiff and strong without the need for the lazy bulk material.
- Multi-material and part aggregation in design: can further improve material efficiency by combining divergent materials to locally tune properties. For example, a product may use lightweight composite materials for less critical parts and tougher metals, composite-integrated materials where extra strength is needed, such as at localized fixing points.
- Additive Manufacturing: has revolutionized material efficiency by allowing the creation of highly complex geometries that would be impossible with traditional methods. It enables precise placement of material only where necessary, often resulting in lighter, more efficient parts.
- Use of Hollow Sections and Ribs: can reduce weight while maintaining or improving structural integrity. Hollow sections remove unnecessary bulk, while ribs add strength and controlled stress dissipation without significantly increasing weight. This approach is used extensively in both metal and plastic components to reduce mass while maintaining rigidity, although it can impose grave complications in manufacture, or rule out some otherwise preferred process options.
Material selection for Lightweight Parts
The material selection process is, in most cases, the most critical aspect of lightweight component design. A high effort in stress distribution and material removal is considerably less effective when applied to an overweight material. Material selection brings diverse opportunities and trade-offs in strength, stiffness, resilience, processability, weight, and cost.
Each class has unique properties that must be matched to the application. For example, carbon fiber is very strong and lightweight but not tolerant of high temperatures.
Material efficiency should also consider recyclability and sustainability in the selection process, aiming to minimize the environmental impact of the materials used.
Lightweight Metals
- Aluminum alloys: Commonly used in aerospace, defense, sporting equipment, energy, and automotive applications, Aluminum alloys offer a good balance between strength-to-weight ratio, processability, cost, and corrosion resistance.
- Magnesium alloys: Lower density than Aluminum alloys and often containing Aluminum, they offer higher strength at increased cost and are used for parts that need greater strength AND lower weight, such as automotive wheels and thin-walled handheld device housings.
- Titanium alloys: Of high strength-to-weight ratio, and superior corrosion resistance, Titanium is considerably more expensive, both as a material and in processing terms, than Aluminum or Magnesium alloys. Titanium is ideal for the most weight-critical applications like aerospace and medical implants, where cost sensitivity is lower. It is particularly useful where corrosion and/or fatigue resilience are as critical as the strength-to-weight performance.
These materials are typically processed by the full range of manufacturing solutions applicable to metal, with some restrictions due to their particular property sub-sets. In particular, Titanium alloys offer considerable challenge and cost in processing, as Titanium is an obdurate and difficult metal to process.
Composites
- Carbon fiber-reinforced polymers (CFRP): Carbon fiber is the most lightweight and high-strength material practically available as an engineering solution, often used in extreme-performance applications such as aerospace, sports equipment, and as a quality-differentiator in luxury vehicles. However, it offers relatively poor temperature resilience due to the thermoset polymer bonding agents that integrate the fibers.
- Glass fiber-reinforced polymers (GFRP): Considerably lower strength than an equivalent section of CFRP, GFRP is a practical choice in industrial applications where weight savings and moderate strength are needed. Its advantage over CFRP is that it offers considerably lower material and processing costs as a trade-off for its lower strength.
These materials are typically processed by a variety of methods, selection of which is typically component size and production volume related;
- Hand layup into molds is common for small-volume and large components. Pressure can be applied by inflated bladders, press tooling, or by vacuum bagging to improve composite integrity by bubble/cavity removal.
- In-mold processing can be used to add a fiber layer or outer skin to an injection-molded part. A preformed shape of fiber roving is laid into the tool, or a sheet is draped, and then the fiber element is integrated and forced to shape by molding material injected from behind.
- Fiber as an additive is integrated with the polymer and injection molded, extruded or cast to final shape.
- Roving pre-preg (pre-impregnated with resin ready to cure when heated) is pulled through a compressing cavity to make pultrusion components of high fiber density and low porosity.
Plastics and Polymers
- High-performance thermoplastics: Materials such as PEEK, polycarbonate, LCP, and nylon offer good mechanical properties and can be used in lightweight designs where environmental and chemical resilience and durability are important. They are commonly reinforced with carbon fiber or glass fiber to deliver higher stiffness, dimensional stability, or toughness.
These materials are typically processed by;
- Injection molding in custom tools
- Machining from cast sold sheet and rod stock.
Materials, Metamaterials, Material Transitions, and Lattice Structures
Recent advances in metamaterials and additive manufacturing processes the use of lattice structures in designs to minimize weight while retaining or improving upon the strength and stiffness of otherwise solid executions.
Metamaterials are engineered materials that deliver properties not found in naturally occurring materials. These properties typically arise from the material’s atomic, crystalline, or composite structure rather than its elemental composition. Metamaterials are often constructed from repeating patterns or structures on nano or micro-scale. These unique formulations/aggregations allow metamaterials to control, direct, and respond to forces in unconventional ways, leading to exceptional strength and resilience properties.
This can be interpreted as entailing multi-material solutions in the most advanced powder-bed metal 3D printing, allowing adaptive solutions by zone to be integrated and fully coupled. These materials/methods are used in the highest value applications in aerospace, propulsion, defense, and medical implants, where minimizing weight while maximizing strength is critical and cost concerns are secondary.
Design techniques for Lightweight Parts
Designers use various strategies to reduce weight while maintaining performance. The following methods focus on optimizing material usage and overall design for lightweight parts.
Material efficiency
The central principle of material efficiency lies in making informed strategic choices regarding materials, design techniques, and manufacturing processes, made from a broad and deep understanding of the degrees of freedom that are open in the design.
It is an intrinsic result of good design as much as it is an extrinsic target of the development of parts/assemblies. It will result from the use of the specific approaches listed below, but it is also a mindset that can be nurtured and stimulated as a free-standing intent.
Topological optimization
Topology optimization uses algorithms to determine the most efficient material layout for a given set of loads and constraints. The process involves systematically removing material from areas that are underutilized in terms of load-bearing capacity. This technique can significantly reduce the weight of components while maintaining structural integrity.
It allows engineers to design structures that are light yet strong by focusing material only where it’s structurally necessary. This results in organic-looking designs with less material, nonetheless aiming at delivering improved performance. To illustrate, in aerospace components, topology optimization can result in parts that are much lighter than typical design will deliver, improving fuel efficiency, and often delivering structures that can withstand equal or greater stress and loads during operation.
Structures should be designed to resist and dissipate loads with minimal material usage, sufficient to address the loading expectations (and applicable factors of safety) and distribute stress with lower strain and component-structural risk.
Using topology optimization, and lattice or shell structures can dramatically reduce part weight without sacrifice of — and often with enhancement — strength or stiffness.
Sharp corners, poorly placed holes, or abrupt steps in sectional thickness typically result in stress localization, requiring reinforcement. Effective and highly organic blending/fileting, progressive chamfering, and linear or spline tapering will dissipate stress concentrations, enabling optimized workload in remaining material, maintaining or improving structure integrity.
Part aggregation and multi-material components
This method seeks approaches to apply the right material for each zone/function, balancing weight and localized property needs by changing materials on a task/zone basis to create pockets of property adjustment adapted to highly localized needs.
Wherever possible, parts should be designed to integrate multiple purposes, such as; structural support AND housing enclosure/protection of workings; or structure AND mechanical function; or flexibility AND hardpoints gif mounting.
A classic broad-scope example is the integration of the engine as a frame element that set Britten motorcycles apart in their early designs. In a race context, weight is key, small savings have big impacts.
A narrower perspective illustration is the integration of load distribution and threaded metal inserts in composites, to provide rigid hard point attachment zones in flexible structures to progressively dissipate the local stresses that result.
This reduces the component and fasteners count, thus reducing net-weight.
Thin-wall design
Reducing the wall thickness of parts can contribute to significant weight savings. However, the trade-off is the potential for reduced strength and stability under small deformations and adverse loading, which must be accounted for by optimizing material distribution and adding structural features where necessary.
This is another case where the improved processability and reduced geometric and handling limits of additive manufacture can offer significant design benefits by increasing the scope of design decision making beyond what is typically considered practical/executable.
Lattice structures
Lattice structures consist of a repeating pattern of cells or nodes designed to distribute stress smoothly and without concentration, while simply removing all or most of the material that isn’t working hard.
This method applies the least material possible in a given zone, while ensuring that strength and stability are not compromised. At its best, this approach uses no default repeating pattern of material but modifies the lattice structure in a dynamic 3D flow that always meets the stress requirements and minimizes the material.
This can be seen as a functionally detailed method in the topological optimization toolkit. It relies increasingly on advances in 3D printing, which have made such fractally complex lattice structures feasible for low-volume, high-value production. Increasingly cost effective additive manufacturing processes are slowly disseminating this technique into middle value applications, as equipment and methods proliferate.
Shell structures
Shell structures are a highly efficient form of load distribution, in which material is concentrated along the outer surface and minimized in internal and less hard-working areas, reducing internal mass by as much as 90% with essentially no loss of performance.
Examples include aircraft fuselages, car chassis components, and housing for consumer electronics.
Depending on the manufacturing process, these shell structures can be of variable intensity of wall thickness, with organic topology that facilitates greatly reduced risk of stress concentration and highly regionalized properties/topography.
Additive manufacturing
One of the tools that serves to facilitate many of the above techniques is additive manufacturing, or 3D printing. This family of processing methods can free the designer from the feasibility restrictions of most production methods—with some consequent issues and costs to consider.
This group of methods allows for greater design freedom and can reduce the amount of waste material compared to subtractive manufacturing methods like machining. Only the required material is supplied, only where it is needed, with fewer restrictions in wall section, curvature complexity, hollow section integration, lattices, variable density, transition smoothing, and the intricate integration of two (and potentially more) materials into closely coupled and even material-transition, regions.
At the same time, since materials available for additive execution are limited and the properties that result from the process can be less controllable, additive manufacture is not a magic bullet. For example, forging can deliver highly selected crystalline structure, whereas 3D printing commonly results in isotropic and somewhat porous structures, depending on the process used. This can negate the benefits of the method, if it is carelessly applied.
Lightweight Parts Design examples
Automotive industry
In the automotive industry, reducing vehicle weight directly leads to better fuel efficiency and lower emissions. Automakers have adopted aluminum, magnesium alloys, and high-strength steel to reduce the weight of structural components like the chassis, engine, and suspension.
By careful control of grain size development and distribution, high strength low alloy (HSLA) steels have allowed a 30% reduction in body panel thickness over the past 40 years, for no loss in overall strength.
Aerospace
In aerospace, every gram saved translates to lower fuel consumption and extended range. Boeing and Airbus have fully adopted lightweight CFRP composite construction for structural and aerofoil surfaces. This is steadily reducing the weight of commercial aircraft, resulting in significant fuel efficiency gains.
Spacecraft are exponentially more sensitive to takeoff weight and much less cost-sensitive than commercial aircraft, which has a serious impact in the selection of lightweight materials to reduce component and overall system weights to benefit fuel efficiency, thrust to weight ratio, maneuverability and net mission-endurance.
Consumer electronics
Companies like Apple and Samsung focus on minimizing the weight of their devices without compromising strength or performance. Thin-walled enclosures made of magnesium alloys or aluminum, combined with the strategic placement of internal components, lead to lightweight yet durable products.
What are the challenges in designing lightweight parts?
While the benefits of lightweight design are evident, several challenges must be addressed. No toolset is ever as capable as we hope, but the key to good design is the realistic integration of approaches and toolsets that overlap, exploiting their individual strengths and compensating for their shortcomings.
Cost and availability of materials
High-performance and extreme-lightweight materials, such as CFRP and Titanium, are costly by weight and additionally costly in processing. Their use implies design methodological adaptations that must be fully understood, to make beneficial use of their capabilities and avoid the often significant pitfalls in their shortcomings. Designers must balance performance requirements with the economic feasibility of materials in making the selection and look past the material choice to processing conditions and difficulties, because materials that are often interchangeable in their end use are entirely incompatible in processing terms.
Manufacturing complexity
Commonly, pushing the boundaries in lightweight component design requires advanced and harder-to-access manufacturing techniques, such as hot forging, vacuum bagging, pultrusion, 3D printing, any of which will introduce new complexities, property difficulties/opportunities, and costs. Traditional methods like casting, forging, or machining are typically not suitable for complex geometries that require lightweight optimization.
Strength and durability
In lower-experience design exercises involving extreme materials and design techniques, reducing weight too often comes at the expense of strength and/or durability. While materials like carbon fiber offer high strength-to-weight ratios, they are prone to fail under certain conditions, such as impact or fatigue. Deep understanding of property benefits and shortcomings of the extreme material options is not widespread, and avoiding assumptions about properties and processing techniques is critical to delivering on the potential these materials represent.
Factors such as fatigue behavior, response to adverse chemical conditions, stress/strain characteristics, loss or gain in ductility/malleability, and response to adverse temperature environments can all render the benefits of a change to lightweight materials null, or deleterious.
Manufacturing techniques for Lightweight parts
Leading-edge manufacturing techniques offer significant design opportunities and benefits. These included improved efficiency, reduced waste, enhanced product quality, and the ability to tackle complex optimizations in designs with increased precision and reduced geometrical restrictions.
They can lower or increase production costs, they can often speed up time to market, and typically they serve to enable more sustainable practices by minimizing resource usage.
However, these advanced methods also present challenges such as high capital expenditure CAPEX, steep design, and operational learning curves, and property benefits and degradations that must be accommodated. Integration into existing processes can be challenging, and there are often issues as to scalability as companies adopt newer, less-established technologies.
Additive manufacturing
As already discussed, additive manufacturing is a paradigm-reset in lightweight component design, enabling the production of complex and apparently abstract AI-generated geometries, lattice structures, and hollow components that weigh considerably less, without compromising strength, when the capabilities they represent are carefully applied.
Injection molding
Injection molding is widely used for producing lightweight plastic parts with thin walls and complex geometries. High-performance thermoplastics like PEEK and nylon are often used in lightweight applications, and the leading edge of additive-modified and new polymers is expanding rapidly in both cost and performance terms.
It’s important to keep in mind that injection molding is no longer restricted to thermoplastic materials. The molding of metal powders that are carried in thermoplastic binding agents is an expanding field, as the capabilities this offers can have profound impact. Thin sections, complex geometries, and diverse metals can be processed in this way, with a sintering stage that burns out the binder and renders the powder into low-to-zero porosity solids.
The design considerations/implications of the sintering stage can be significant, so care must be taken in cheating art geometries in which the shrinkage implicit in the sintering stage is accommodated without creating distortions or other component faults. However, this tool can be applied to form complex net-shape and precise parts with very simple processing.
Casting and forging
For metals, advanced casting and forging techniques allow for the production of lightweight parts with optimized material distribution. Vacuum casting, for example, can be used to produce hollow metal components with reduced weight.
The spectrum of precisions and capabilities represented in the various casting processes requires a clear understanding in the mind of the designer, in order to fully exploit the benefits and shortcomings of the various processes and minimize costs while optimizing precision/quality/strength or other variables as required.
The microstructural benefits of forging can be very significant in amplifying the intrinsic material properties by creating ‘grain’ and geometrical flow of material, by mixing hot and cold working in work-hardenable materials, and by creating complex net shapes with high precision and repeatability.
Advanced machining
Machining techniques, like multi-axis CNC machining, allow for the production of lightweight metal parts with intricate geometries. Parts can be machined with internal cavities or optimized profiles to reduce material usage.
Not all geometries are possible, but the restrictions represented by cutter access can be minimized by selecting internal geometries that lend themselves to the process and equipment.
Simulation, prototyping and testing for Lightweight Design
Advanced simulation tools can help in predicting how lightweight parts will perform under various load conditions. Finite element analysis (FEA) is often used to simulate structural behavior, enabling the identification of weak points and areas where material can be removed. Prototypes are critical in the evaluation process, but the making of prototypes that are fully representative of final production parts can be challenging.
Finite Element Analysis (FEA)
FEA and simulations are tools that should be trusted with great care, as the methods are highly very susceptible to error based on incorrect assumptions and executions (GIGO – garbage in, garbage out). The most experienced FEA and simulation analysts can give fairly high confidence—but those services are very costly. FEA is best used as an indicative tool in strength terms, to be backed up with real material testing—particularly in life critical and high cost-of-failure applications.
FEA is used to simulate the mechanical behavior of parts under load, allowing designers to optimize material usage by visualizing the flow of stress and the concentrations that occur at pinch-points and load applications. Such simulation methods help to identify areas that are material-rich and can tolerate reductions that can greatly influence final weight.
Fatigue testing
Fatigue testing ensures that lightweight components can withstand repeated loading cycles without failing. This is particularly important for parts in aerospace, automotive, and industrial applications.
When that testing is applied to prototype components, it is critically important that the analysis of test results reflects the material and processing differences between the prototype part and the real production components, which can be profound. For example, the strength differentials between a CNC-machined prototype and a cold forged component in identical materials can be very large.
Impact testing
Lightweight parts, especially those made from composite materials, may be prone to failure under impact. Localized collapse/fracture under adverse loading can present profound failure risks that will not be reflected in ‘normal’ loading scenarios.
The weight benefits of thin sections can be very large, but the analysis of the likely and feasible usage scenarios should account for divergent conditions of use and abuse. Impact testing helps ensure that lightweight designs can withstand the expected unexpected loads or impacts of real-world interactions, without compromising performance.
Sustainability in Lightweight Design
Lightweight design is a critical component of sustainability in many areas of power-consuming and power-generating engineering. By reducing material usage, the energy efficiency in operation and the raw materials/energy usage in first creating products is improved. By this means, designers and manufacturers can impact the environmental consequences of their products.
Lighter parts contribute to better energy efficiency, whether in vehicles, aerospace, or industrial equipment. This translates to lower energy consumption and reduced resource exploitation.
The selection of materials that can be more easily and effectively recycled is an increasing consideration in lightweight design. Aluminum and magnesium, for example, are highly recyclable and can be reused in future products.
Notable exceptions that resolve the recyclable/resource consumption balance can create apparently conflicted outcomes. As an example, European regulation in the area of HVAC fans regulates materials for high efficiency, where efficiency includes the implications of recyclability—and this exudes the composite and light-weight options in the blades of fans in this sector, shifting the market towards heavier, less power efficient, but more recyclable metal fan constructions.
Another example where recyclability is prioritized over component weight is in the shift towards organic source materials for the seat padding in European cars. The petrochemical foams that are typical in this application are giving way to heavier, but more recyclable organic source substitutes.
Near term trends in Lightweight Design
The future of lightweight design is a direct result of advances in materials, manufacturing processes, AI design tools, and simulation tools. New materials such as metamaterials, nanocomposites, and bio-based composites are increasingly playing roles in the next generation of lightweight components.
As industries strive to enhance both performance AND sustainability, the demand for lightweight solutions will only increase. The integration of artificial intelligence and machine learning in design optimization are triggering a revolution in the ability to create lightweight parts that meet the rigors of extreme engineering applications.
Developing an understanding of the principles, techniques, and materials involved in lightweight design equips engineers to create components that exceed former performance expectations and look to contribute to a more sustainable and environmentally secure future.
