What are some examples of asymmetrical designs that enhance assembly performance and aesthetics?

Asymmetrical designs are not only appealing to the eye, but they can also improve the assembly process of products and components. Design for assembly (DFA) is a skill that aims to reduce the complexity, cost, and time of assembling parts by applying certain principles and guidelines. One of these principles is to use asymmetry and orientation features to facilitate alignment, positioning, and insertion of parts. In this article, we will explore some examples of asymmetrical designs that enhance assembly performance and aesthetics.

1 USB plugs and ports

You probably use USB devices every day, but have you ever wondered why the plugs and ports have an asymmetrical shape? The reason is to prevent incorrect insertion and ensure proper connection. The USB plug has a trapezoidal cross-section with one side longer than the other, while the port has a matching slot. This asymmetry makes it easy to orient and insert the plug without damaging the pins or the port. The USB logo on the plug also serves as a visual cue for the correct orientation.

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Paul Paris Coker

Complex Mechanical Design Engineer
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Asymmetry of the connector itself is not the only way to ensure good connection of hoses/cables. Note that similar principles can be used when connecting gas and liquid conduits as are used when connecting cables. By having an asymmetric run for the cables or hoses you can ensure that some cables/hoses won't reach the incorrect connection point. Remember the assembly personnel may not understand what is going on. If they can't make the parts fit (different connector/fitting or won't reach) they may think the parts were built or designed wrong. Many people assume things should be symmetric, even when they are intentionally asymmetrical. So constant training and reminders should be used. "If it won't connect, don't force it."

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Paul Paris Coker

Complex Mechanical Design Engineer
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The human element should always be considered. Always try to tell the assembler or end user that the asymmetry is intentional and important. Where there isn't room or opportunity to explain, use a few words (5 or fewer) combined with graphic depiction of the issue. On pressure cylinders, oxygen will have a right hand thread while hydrogen will have a LH thread. That is because connecting one of these gases to the wrong pipe could cause a terrible explosion. But I have seen a hydrogen cylinder that was connected to an oxygen pipe by a poorly trained delivery driver. He was very strong and had to use all his strength to screw that LH thread onto that RH fitting. Perhaps a graphic depicting an explosion would have been useful.

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2 Lego bricks

Lego bricks are one of the most popular and versatile toys in the world, but they are also a great example of asymmetrical design for assembly. Lego bricks have studs on the top and tubes on the bottom that interlock with each other. The studs and tubes have different diameters and shapes, creating an asymmetrical fit that ensures a strong and stable connection. The asymmetry also allows for different orientations and combinations of bricks, enabling endless creativity and fun.

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3 Puzzle pieces

Puzzle pieces are another example of asymmetrical design for assembly that combines functionality and aesthetics. Puzzle pieces have unique shapes and patterns that fit together in a specific way, creating a coherent image. The asymmetry of the puzzle pieces makes it easier to identify and match them, as well as to prevent incorrect assembly. The asymmetry also adds to the visual appeal and challenge of the puzzle, making it more enjoyable and satisfying to complete.

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4 Furniture joints

Furniture joints are the connections between different parts of a furniture piece, such as legs, frames, shelves, and drawers. Furniture joints can be symmetrical or asymmetrical, depending on the design and function of the furniture. Asymmetrical joints are often used to increase the strength, stability, and durability of the furniture, as well as to create a distinctive style and appearance. For example, dovetail joints are asymmetrical joints that consist of wedge-shaped pins and tails that interlock with each other. Dovetail joints are commonly used for drawers, cabinets, and boxes, as they provide a tight and secure fit that resists pulling apart.

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Paul Paris Coker

Complex Mechanical Design Engineer
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Where the look/shape of the item of furniture is asymmetric for functional or aesthetic reasons, that asymmetry can be mirrored in the connecting interfaces between the major sub-components of the item, thus making it impossible to assemble those components in the wrong orientation.

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5 Bottle caps

Bottle caps are the closures that seal the opening of a bottle, preventing spillage and contamination. Bottle caps can have different designs and mechanisms, such as screw caps, flip caps, or pop caps. Some bottle caps have asymmetrical features that enhance the assembly and usability of the bottle. For example, some screw caps have a tamper-evident ring that breaks off when the cap is opened for the first time, indicating that the bottle has not been tampered with. Some flip caps have a hinge that allows the cap to stay attached to the bottle when opened, preventing loss or littering. Some pop caps have a dent or a ridge that helps to open the cap with a lever or a bottle opener.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Roland Schwarz

Senior Product Design Engineer
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Star Wars stormtrooper helmets First batches were crudely made. Later films had time and budget to mold professionally. Early helmets had slight asymmetry, while later ones were much more symmetric. While the difference seems imperceptible, it is enough to make the later, more perfect helmets seem more sinister.

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Paul Paris Coker

Complex Mechanical Design Engineer
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This Star Wars example illustrates that symmetry and asymmetry have psychological impacts on the viewer. This can be used to subtly shape the flow of foot traffic through a garden.or indoor space.

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What are some examples of asymmetrical designs that enhance assembly performance and aesthetics?

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1 USB plugs and ports

2 Lego bricks

3 Puzzle pieces

4 Furniture joints

5 Bottle caps

6 Here’s what else to consider

Design for Assembly

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