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A short guide to finding high-quality plastic components

clock 4 minutes | 24 Jul 2019

Getting the process right is key to quality products

Whether you’re designing or assembling a new product, ensuring that your plastic components are made of the best materials and to the closest tolerances is essential.

As well as affecting the quality of the final product, selecting an inaccurate part can cause faults in its function and lead to increased costs and customer dissatisfaction.

Plastic injection moulding is one of the most popular manufacturing methods for producing plastic components across the UK and wider world. Its ability to mass produce high-quality parts to an accuracy of within 0.005 inches makes it clear why the British Plastics Federation estimated the UK turnover of the process to be in the region of £3.5 billion.

However, to guarantee a consistent level of quality, manufacturers have to consider and control a range of parameters within the process, such as temperature, mould design and machine efficiency. For engineers and assemblers to ensure they have the highest quality parts possible, they need to choose a manufacturer who’ll offer expertise at each stage of the process.

How to choose the right manufacturer

Customers seeking a plastic parts manufacturer should be aware of what’s involved in the injection moulding process and what level of input to expect from a components provider at each stage.

Our Global Process Development Manager, Chris Butler, also offers assemblers and engineers advice on the types of questions to ask manufacturers before ordering parts from them:

  • Does the supplier have a good history and background in manufacturing the type of products that the customer requires?
  • What are the manufacturing capabilities of the company?
  • What manufacturing and quality systems are in place to ensure delivery of good quality parts at the correct costs?
  • Have you addressed considerations around their manufacturing capabilities, tooling, machinery and process control?
  • Do you have a full picture of their capacity, quality control measures and staff competences?
  • What are their OTIF measurements and on-time-in-full delivery performance like?

By focusing both on the process and the service the manufacturer provides, designers and assemblers can ensure their parts will be both high-quality and produced efficiently.

Creating an accurate mould

Finding out about the expertise a manufacturer will provide at each stage of the process will help to ensure you have a full picture of how their components are created.

At the centre of the injection moulding process is the mould that’s used to shape the part. The development of this mould requires expertise and experience to ensure it’s accurate enough to avoid faults in the final part, such as flash, warpage or an excessive parting line.

During mould development, good manufacturers should offer the opportunity to try out prototypes, particularly if you’re creating a custom part. This will ensure that the mould is producing a consistent, high-quality part, as well as the design characteristics you’re looking for.

Choosing the right plastic

Making sure your part has the material characteristics you need is essential to both the tensile and aesthetic quality of your final product. For example, whether you’re looking for custom colours, textures or qualities (such as the need to be washable or strong).

Some of the most common thermoplastics used in injection moulding are:

  • Acrylonitrile-Butadiene-Styrene (ABS)
  • Nylon (PA)
  • Polycarbonate (PC)
  • Polypropylene (PP)

Although all of these can be heated and used for parts, they all have individual characteristics which suit certain types of components best.

For example, ABS is strong and chemically resistant but isn’t suitable to be used outdoors, making it a popular choice for automotive interiors and computer equipment. Alternatively, PC is resistant to heat, transparent and can be used for outdoor components, making it suitable for eyewear, greenhouses or test tubes.

If they’re compatible with each other, plastics can be mixed to combine different characteristics into one material. Different colour resins can also be added to the plastics to get a desirable aesthetic finish. This means that with advice from an experienced manufacturer, assemblers and engineers should be able to find a material that combines the material and aesthetic qualities they need.

Efficiency of the injection moulding process

As well as delivering high-quality parts, a manufacturer’s injection moulding process should be efficient enough to produce a high number of components quickly with as minimum waste as possible.

Reduce and recycle waste

Experienced manufacturers will work to reduce waste from the mould development stage by ensuring the right amount of plastic is injected at the correct pressure and the tool is tight enough to prevent material from escaping. In addition, some manufacturers recycle their flash waste material by reheating it and mixing it with virgin plastic ready to be used to create new parts.

Also, the hot runner systems in certain machines keep the plastic liquid between injections. This saves energy because the plastic doesn’t need to be reheated and reduces the amount of plastic that’s wasted. This helps to reduce the costs passed onto customers, as well as lower the environmental impact of the process.

Machinery maintenance

In addition to using materials efficiently, maintaining machinery is essential to minimising downtime and delayed delivery times. By selecting the right type of machinery and harnessing predictive maintenance technology, manufacturers can ensure they maximise efficiency.

OEE

By asking for a manufacturer’s Original Equipment Effectiveness (OEE) score, you can quickly discover how efficient their machinery is. Our injection moulding machinery has a score of around 90%, with the majority of our factories using Sumitomo Demags, which enable us to achieve quicker cycle times and a stable process.

As Chris explains, the machines also bring advantages with maintenance: “On average against our older machines we see savings of around 1 second just on movement and open-close profiles. The equipment manufacturers can also dial in remotely and actually see how well our machines are running, if they’re in calibration, and advise on a routine maintenance programme.”

Choosing a manufacturer with the right machinery

Although the basic process each machine completes is the same, there are many variations in the types and specifications of injection moulding machines. Machines can be run by either electric, hydraulic or hybrid (a combination of the two) power, providing manufacturers different mechanisms and levels of efficiency.

Choosing a manufacturer with efficient machinery is important, but making sure the machines are the right specification for the parts you need is also essential, as Chris explains: “It’s so important to choose the correct specification when purchasing new injection moulding machines. Purchase the wrong one and it can have a catastrophic impact on manufacturing - you won’t be efficient, you won’t hit your costed cycle times and you can end up making out-of-spec parts.”

By selecting the right machinery, we ensure that the complex, high-quality components we’re known for producing are of a consistent quality and can be efficiently delivered.

Using Industry 4.0 to maintain quality

Using Industry 4.0 to maintain quality

Our machinery is also Industry 4.0 enabled. By harnessing these advances, we’re not only able to maintain our machinery for maximum efficiency and uptime, but ensure that our components are of a consistent level of quality.

At our Kidlington site, we use 3D printers to help develop prototypes for custom parts. Using this technology helps both to reduce cost and increase the efficiency of the design process, as we don’t have to create an injection moulding tool to test out a component’s design and can quickly produce a number of prototypes for testing. Installing robotics and monitoring technologies, such as predictive maintenance in our machinery, also helps us to maintain efficiency during the production phase.

Chris explains that this move towards smart factory technologies is essential for future-proofing our production: “Pace, the ability to get products to market and across the line quickly, is where smart factories really strike out. 3D printing means you can have prototypes on your desk the same day rather than waiting a week for the parts to come back.”

Look for great service with efficient process

Although part quality is important, which is why we ensure we consistently meet international quality standards, finding a manufacturer that can produce the amount of components you need and deliver them quickly is also essential.

Not only will this save you headaches in the long run, but ensure there are no delays in your production schedules and the resultant wasted cost. Chris explains: “At Essentra, we completely control every aspect of the process from order intake through to manufacture and dispatch to the customer; and with the wide range of tooling and machinery we have on our sites we can produce good quality parts in a short space of time.”

“For example, the size ranges of our PVC grommets and standard LD/PE protection caps are vast and, likewise, the number of different industries they are supplied to is equally broad. We manufacture millions of these types of products on a huge scale to an extremely high standard.”

To get the process right, there are many parameters to control