29 July 2021
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An Intertronics guide to adhesive specification

Two vital parts of adhesive specification are introduced by Matthew Baseley, technical sales executive and Kevin Cook, technical manager, Intertronics. First is assessing the return on investment of a potential adhesive; second is validating its real-world performance.

If you’ve ever tried to source an adhesive for your application, you probably realised quickly that there is no universally-perfect adhesive. Everything from the substrates you’re bonding, operating temperature and humidity, to the exposure of the assembly to solvents, weather and mechanical stress, will influence your choice of adhesive.

It is worth understanding that the adhesive choice will only be one component of the full bonding process – which includes surface preparation, adhesive mixing, application and dispensing, curing and quality assurance – and that it is in this entire process that you are investing. It is important to take a holistic view; for example, application and curing equipment costs, and efficiency of method, are factors that will affect an ROI calculation and so allow comparison to other options.

We think of ROI as a measure of how fast we get our money back after making an investment. For a bonding process, an investment in equipment can be justified by improvements in the method, or savings in resources like labour, energy or space. However, there are many hidden, intangible benefits that come with suitable investment – ones that go beyond the headline ROI figure.

There is always a compromise to be made in adhesive choice, and that is often between ultimate functionality and optimal bonding process. The very best bond strength may come from an adhesive with a complicated preparation requirement and an extensive cure time; but that may not be suitable for the proposed production volumes or speed of manufacture. Sometimes this dilemma stems from over-specifying the adhesive requirements, which limits material choice and so can add cost. Factoring in adhesive ‘processability’ can ultimately deliver a faster ROI, without compromising on quality.

For example, while the up-front cost of UV light-curing equipment may be higher than a process using an adhesive that cures at room temperature over time, the increased throughput achieved with on-demand curing – seconds, rather than minutes or hours – may well offer a much shorter payback period. In fact, when a UV light cure systems technology is looked at as an integral part of a full production process – across inventory, dispensing, curing and quality assurance – it can lead to an average of 30% savings in overall process costs.

Turning to dispensing, while it is not necessary for small-batch adhesive assembly operations where manual mixing and application are deemed sufficient, the accuracy and repeatability possible using robotic dispensing or automated adhesive mixing lowers process variability and can be compelling even in moderate volume applications. By reducing human error and increasing precision, you can decrease scrappage rates and material waste. The labour cost element is often reduced, as operators are reallocated to more productive work (possibly with upskilling). Adhesive dispensing robots (pictured, right) are available for surprisingly modest costs, and factoring all the advantages of automation usually results in a quick ROI.

It’s important to note that the collective improvement in all these areas, from throughput and standardisation, to quality and yield, has an impact on the business that goes well beyond tangible measures. It is ultimately the imperceptible improvement in your brand and reputation that leaves a lasting impact on your customer.

Thinking about the return on investment for a new bonding application or improvement of an existing one involves a comprehensive consideration of the entire process. A higher initial investment can lead to a faster ROI. In addition, investing in a robust, reliable and repeatable process can have a lasting, intangible impact on your brand.

TESTING

Having made a business case, customers also need to verify the adhesives’ expected benefits. Though the adhesive or equipment manufacturer will have done extensive testing to determine the basic datasheet parameters, it is vital to evaluate products in a real-world application, ideally on production parts, so manufacturers can be sure that they function adequately on their unique assemblies.

While product data sheets are a useful way of shortlisting adhesives and other materials to test, Intertronics does not recommend selection based on the datasheet alone. Published product parameters are usually determined from laboratory testing or under ideal circumstances. It is important to verify that the expected performance is achievable on the intended parts – with their particular surfaces and geometries – as well as in the proposed use environment.

The datasheet will not answer every question the user has; for example, the list of which substrates it can bond may not be exhaustive. An experienced adhesives supplier will have a wealth of knowledge from real-world applications to help understand the datasheet in practical terms. Nevertheless, this is still no substitute for testing. The evaluation process translates the datasheet on to a real-life application.

The evaluation should take a holistic approach, with an understanding of which selection factors are set in stone, and which can have their tolerances widened in order to arrive at a dependable product that can be used efficiently and at an appropriate cost.

Practical testing can establish that the assembled part can withstand whatever environmental conditions in which it will be operating. Environmental testing assesses the performance of the finished product when exposed to the relevant humidity and temperature extremes and changes that it will likely face in its lifetime.

Testing will confirm that the chosen bonding methodology will meet the requirements of the assembly and production in terms of accuracy and repeatability, meeting quality and productivity needs. Examples include measuring a number of deposited shot sizes from proposed equipment; using statistical analysis to confirm the required precision; assessing a UV curing function to ensure that it complies with the overall takt time; or determining the minimum and maximum adhesive quantities in a bond that still produce the required strength.

It is quite common that a material selected early in the process does not suit an application in real life, and an adhesives partner can work through this with you to help you select an alternative.

To support customers through their testing and evaluation process, Intertronics operates a technology centre in Kidlington, Oxfordshire (pictured), where customers can either send their parts for our team to bond together as a prototype for customer testing. It also provides laboratory reports with supporting images and videos to give insight into the process choices.

Intertronics finds that many customers benefit from developing their adhesives process in a knowledgeable environment, and that the technology and materials available on site can open their eyes to alternative ways of doing things, inspiring them to forget their preconceptions and be inspired by new options. It believes in collaborating with customers throughout process development to give confidence that their process is the best possible option, with minimal compromise.

Author
Matthew Baseley and Kevin Cook

Related Companies

Intertronics

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