There are many items that we use for our daily activities. The items are made from different materials. One of the common materials used for making items is Plastics. The making of items will often require different parts to be joined together.
Various inventions have been made for joining items together. Some of such inventions include screws, nuts, and threads. With threads, it is possible to tie various parts of an item together. Not only are threads used for tying plastics together, but they are also made of plastics.
The refining and perfecting of thread designs were carried out between 1860 and 1950. This led to the development of more reliable threads. The threads were also designed not to affect products aesthetics in a negative way.
In this article, we will discuss threading plastic part manufacturing processes introduction. We will discuss the uses of plastics and why plastic parts are threaded together. We will further highlight why threads fail and common plastic thread profiles. We will conclude with thread location considerations.
The wide usage of plastic across the world is due to its versatility. Most sectors including building and packaging make use of plastic. Other sectors that use plastic include industrial machinery, electrical and electronics as well as transportation and consumer products. Patents for plastics are regularly filed across the world. In the UK, new filings for plastic patents are more than filings for paper, metal, and glass combined. These filings show that there are new innovations with plastic.
In aerospace, weight is vital. There is a need to reduce the weight of planes, vehicles, and goods. This reduction in weight contributes to safe and cost-effective transportation. It also helps with reducing the cost of fuel.
In construction, the excellent ratio of strength compared to weight is vital. It helps with making buildings that are resistant to corrosion and requires low maintenance. It also helps with cost-effectiveness and durability. The result is the wide usage of plastic in various aspects of the construction sector.
In electrical electronics, plastic plays an important role. Everywhere there is electricity, there is plastic. Electricity contributes to our home, lives, work, and play. Plastic contributes much to electricity too. It also contributes to electrical products.
Plastic is a perfect material for packaging goods. Plastics are highly durable and flexible. They are also lightweight, hygienic, and versatile. Considering how much packaging we do, packaging accounts for the most usage of plastics worldwide. Vending packaging, cups, and boxes are some packaging materials we make from plastics. Others are protection packaging, baby products packaging, trays, drums, bottles, and containers.
Plastics are used to make doors, seats, engine parts, dashboards, and bumpers in automobiles. It is used for wave booms, solar panels, and wind turbines in energy generation. The use of plastic applies to household furniture, upholstery, and bedding, it also applies to sails and boat hulls.
In the medical line, plastic is used for wound dressing, artificial limbs, and heart values. It is also used for dialysis machines, tubes, blood bags, and syringes. Communication equipment, aircraft, and warships require the use of plastic. So do tanks, body armor, and helmets.
- Why Plastic Parts Are Threaded Together
Most items we use are made from different parts. The parts are joined together to make the useful item we know. If the parts are not joined or threaded together, they will not be useful.
In some cases, all the parts can be made from plastic. In other cases, they could be a combination of plastic, metal, and wood. There is the need for all the parts to be properly fit together. The finished product can then be gotten.
Hence, plastic parts are threaded together so that they can become a finished product that will be useful to us. It is important for the threading to be perfect. This way, we can have durable and reliable products. When threads fail, it could inconvenience us or even be disastrous.
Many accidents and deaths can be linked to the failure of threads. The parts of an item threaded together fall apart due to thread failure. Depending on the item and its usage during the failure, the valuable substance could be lost or injuries sustained.
A major reason why threads fail is the poor design of parts. Probably metal parts designs were used for creating the plastic parts. We have witnessed many customers asking for the development of a design. On closer use, we notice the design won’t work on plastic.
We explain to our customers they were designed for metal, wood, or other types of materials.
People often trust designs that have worked before. Considering metal was widely used for a long time, its designs have evolved for several years. However, the fact that a design is perfect for metal won’t make it perfect for plastic.
Companies with threading plastic part manufacturing processes introduction and experience now know better. Hence, they now check every plastic design properly to be sure they were developed for plastics. When they observe that it is not, they modify the design so that it will be perfect for plastics. This way, they are able to avoid the cases of threads failing because of plastic parts design.
Another reason why threads fail is because of the quality of the thread. The thread might not be strong enough to hold together the product parts. Also, the stress the product will go through needs to be considered. When it is not considered, a seemingly perfect product could tear apart when exposed to a stress higher than the thread can accommodate.
It is also possible for the thread to be of the wrong size. When a thread is too big or small, it might alter the quality of the product. It might become easier for the thread to tear through the parts leading to thread failure. It might also hinder the flexibility of the parts.
- Common Plastic Thread Profiles
It is possible to mold every size and type of thread with injection. Some profiles are, however, preferred. American Standard 60A buttress threads, tapered thread, and sharp thread are the thread profiles that are most frequently stated.
The machine screw or American Standard is the most popular. However, these threads based on American Standard are made such that their crests and roots have sharp corners. The corners lead to the concentration of stress in a thread of molded plastic.
There is the thread based on British Whitworth that could be better. The crests and roots in this profile have radiuses. The radius helps with stress distribution. Distributing the stress to a wider area makes the threaded part stronger. To avoid interfering with the engagement of the mated strength, the radius should be small.
The metal Acme thread modification is ideal for threads used in molded plastic. It’s shearing off resistance comes in handy. The resistance is due to wider spacing between threads. The thicker thread cross-section also contributes to its resistance. Threaded bottle caps and plastic bottles that are blow-molded have these threads’ profiles.
The metal Acme thread modification cannot be used for many threads turns in a given length. Despite this con, the pros are worth it.
- Thread Location Considerations
Despite the vital nature of threads, they complicate the process of molding. In soft materials, the undercuts can be stripped. There is the need to rotate the core pin. The core pin should also be withdrawn prior to ejecting from the mold.
The rotation of threaded cores is regularly evolving. Hydraulic-cylinder-activated rack and gear are reputed to be the most common mechanism. The mold for the inside thread requires a costlier mold. It would also require more maintenance. The molding cost for the part could increase as well.
Outside threads might not need a mechanism for unscrewing. The need for an unscrewing mechanism diminishes when threading is on the line for parting. Hence, we will save the cost of the unscrewing. However, they might need a mechanism for unscrewing in some instances.
As a result, it is advisable for the threads to be located outside the parting line of the mold. To achieve this, we might carry out some redesigning.
It is important to ensure that more material is used for a thicker section when using outside threads. The thickest threaded projection will need more plastic. A longer cycle for molding will also be required. The projection will require more time to cool and hence, shrink more when compared to other parts. You can core out the thread by creating a hole whose length will be equal to threaded projection.
We discuss the Threading Plastic Part Manufacturing Process introduction to provide some insights. With such insight, you will be able to understand your prototype developer more when talking about what is required to create your plastic prototype.
One of the prototype developers you should patronize is RJC. Over the years, we have attended to various clients and built various categories of prototypes. Our services will go a long way to ensure that you have the perfect prototype for your product. This will save you a lot of cost and time as there will be no need for trials and errors.