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5 Hacks In Designing Easy-Assembly Plastic Parts

Adriaan Brits



Designing plastic parts for assembly is not an easy job, there are several aspects that need to be considered. But the most important thing is to have a goal, an objective in mind before designing these parts. Plastic making done by injection molding has come a long way since making different injection molds for every single component. 

It has been a hassle and a time-consuming process for each resulting piece to be assembled. Nowadays, the plastic injection process has become more efficient because plastic parts are designed specifically for an assembly process. 

When designing a product, you want to avoid too many parts which require assembly. This way you can save costs and produce a cost-effective product that performs well. To start off in designing, take notes on the following hacks below!

Consider Material Usage

Whatever design you are making, you must first consider what type of material you’re gonna use. In making plastic parts, the material you’re gonna use is, of course, plastic! It may seem obvious, however, there are a lot of plastic materials to choose from. Each material may work well in contact with chemicals and environmental factors when exposed, and others may not. 

It is crucial to pick out the material that operationally works because it can prevent product failure. You can research or ask experts in the industry how your material will expand and contract, and react to load, compressions and tension. 

It’s also important to consider what materials might be present in your product’s final assembly. This includes metal fasteners, screws, and such. After consulting with your injection molding partner and designer, take a moment to plan out how each of these parts could affect the overall performance and strength of your product’s overall build.

Cross Sections 

When designing parts, the thinner and more uniform they are the better because this allows you to use polymers with higher possible temperatures. Not only is a perfectly thin cross-section important, but it must be smooth as well in order to ensure proper oxygen release during polymerization. Ribs can be used on some parts to compensate for thick or thin lines depending on how they’re formed and whether they’re integral or layered into the product. Temperature changes and dimensional stability problems can occur if these are used so keep that in mind!

Plan Proper Compensation for Part Warpage

Materials shrink at different rates, which can affect the integrity of parts. For example, thermoplastics are heated at high temperatures and injected into the mold cavity. Naturally, your material shrinks as it cools down. The thick sections cool at a slower pace than thin sections, which results in reduced press cycle time. This means that you’re able to reduce the production of your plastic part, upping up your production costs. 

Also, the difference in cooling rate between thick and thin cross-sections can cause distortion of the plastic’s integrity after removing it from the mold.  

Don’t Go Overboard with Your Hardware

When building a product, it’s helpful to design around commonly-used hardware. This can simplify your manufacturing process and reduce the total cost. For instance, let’s say you’re building a plastic case for a smartphone. Instead of using rare hardware, you can use a common hinge, plastic casing, and screws for your design. This can drastically reduce production costs and make your product easier to build.

Plan Initial Assembly Process

In order to guide your designing process, you must also put in mind the assembly process by simply writing it down. Writing down each step can reveal forgotten or overlooked steps from the initial process. Also, by writing down the steps in the assembly process, you can review what is required, what can be simplified, and can the step be redesigned to reduce potential mistakes.

Choose the Best Assembly Method

Most often, the best choice would also be the easiest one. However, in plastic assembly, there are a lot of ways for assembly. They fall into three major categories: Mechanical, Adhesives, Friction, and Heat methods. 

The mechanical method is recommended for products that have to be manually disassembled such as battery packs, plastic cases, etc. These methods are generally used for low-volume and low-cost applications. 

The adhesive methods are used when certain materials are not compatible. This is because these methods permanently hold the components firmly while adding a protective layer in-between. 

The friction and heat methods are used when you need a permanent, tamper-proof assembly. Examples of these methods are ultrasonic and vibration welding.

Additionally, the UV (ultraviolet) bonding method has the advantage of bonding plastics to non-plastic materials such as glass or metal. However, this method costs more because of the equipment. 

Key Takeaway

Plastic making might seem difficult to make. But with the right approach and keep in mind the tips you read, you can design and make a plastic part that is easy to produce and assemble. 

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