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Consistently Building Better Vehicles; The Four Pillars of Successful Bonding in Vehicle Manufacturing

Thomas Besley | 7 min. read

Bond failures or issues relating to adhesive issues are affecting the quality of your vehicles. This in turn is damaging your reputation, creating warranty issues and ultimately eroding your profits.

So you want to eliminate those issues. Or you certainly want to reduce them. But the question arises. How can you reduce bonding issues and consistently build better vehicles?

That’s the question that often comes across us here at Forgway. And it’s one that we’ve been helping industrial vehicle manufacturers answer for over 25 years.

There is never just a single answer. Every time, the answer is ‘It Depends’. Although that’s an answer no vehicle manufacturer wants to hear, it’s the truth. The answer will depend on your specific application.

To help manufacturers find the answer, we guide them through the Four Key Pillars of Bonding Success. Design, Materials, Adhesives, and Operators. These four pillars will determine whether your bonding process will produce high-quality bonds consistently.

By the end of the article, you’ll understand why consistent bonding quality will depend on these four pillars. You’ll also understand the pillars and what you can do to implement the four pillars of bonding success.

Why Bonding Consistentcy Depends on Four Key Pillars

Before we dive into the four pillars, we should perhaps explain why bonding consistency is dependent on four key pillars. The real reason lies in the word ‘consistent’.

That’s because scholars and academics fiercely debate the topic of success. They rarely arrive at a conclusion as to the key drivers for ‘success’. However, many will agree that consistency is the fundamental indicator of success.

Motivation, skill and resources will only get you so far but consistency will be the main driver of success. For industrial manufacturers, consistency is also one of the most difficult things to accomplish; especially when it comes to bonding.

You need to remove as much complexity as possible when it comes to bonding. That’s no mean feat.
Speed up production with faster curing adhesives?

Interestingly, manufacturers often blame the adhesive when things go wrong. They believe a poor-quality adhesive is causing bond failure.

What they don’t realise is that adhesives are rarely to blame. Operator error is responsible for over 90% of bond failures. It’s not always their fault. Improper joint design and poor material selection are two key factors responsible for tripping up operators when bonding.

So, after decades of experience in the industry, we’ve established that consistently successful bonding is dependent on four key pillars; Joint Design, Materials, Adhesives, and Operators.

When vehicle manufacturers come to us with a bonding issue, they will often start by focusing on the adhesive. After a while, their attention starts to focus on the design, the materials, and mainly the operators.

Vehicle manufacturers realise that the quality of their bonds depends on all four pillars. Not just one.

The next few chapters of this article will focus on explaining each of these four pillars in more detail.

Pillar 1: Joint Design – The Blueprint for Success

Joint design is often a point of contention amongst adhesive manufacturers. Each manufacturer will have their specific way of designing a strong and durable joint.

However, two underlying factors will determine the success of a bond:

  • Maximising surface area
  • Minimising peel/cleavage force
adhesive joint design for bonding composites.

Without considering these two factors, the bonded joint isn’t optimised for success.

Firstly, an increase in surface area will increase the amount of interaction between the adhesive and the substrates. This then helps increase the amount of strength in the joint.

Secondly, adhesive experts will often describe peel and cleavage forces as an adhesive’s ‘nightmare’. And whilst some adhesives can withstand these forces, most can’t. Designing the joint to reduce these types of forces will increase the likelihood of success.

Different types of forces subjected on an adhesive bonded joint
Try and eliminate Peel and Cleavage Forces where possible

These two factors are the two key elements of a strong and durable bond in vehicle design.

But it doesn’t stop there. There are other important factors to consider such as bondline thickness, exposure to elements, and impact resistance.

A poorly designed bonded joint will increase the chances of failure. This will particularly put the adhesive and operator under much more pressure to perform perfectly.

When trying to achieve consistent bonding quality, the number one pillar of a good design will form the plans to then build the foundations of a strong bond.

Pillar 2: Materials – The Foundation of a Strong Bond

Once manufacturers have analysed the design of the joint, it’s time to look at the materials. Materials are an underrated part of a strong bond. The materials ultimately create the foundation of a strong bond.

So how can you make sure you have the right materials for the job?

The first thing you can do is make sure you don’t have the wrong materials. And yes, there’s a difference between having the right materials and not having the wrong ones.

Let’s explain.

Not all materials bond equally. Some types of plastics and metals will have surfaces that don’t interact well with most adhesives. They will cause adhesive failure.

Polypropylene, polyethene and coated metals (like galv. steel) are all typical examples of problematic materials.

These materials will often require specialist adhesives or surface treatment to form a strong bond. Both of these increase cost and complexity.

Where possible, you should try and keep away from these materials.

The right materials will not only interact well with the adhesive and form a strong bond, but they will also be strong and durable themselves. This increases the strength and durability of the vehicle as a whole.

As adhesive experts, we can offer guidance on the right materials. But finding the right material for your application is your job. Our job is to make the bonds, and vehicles, as strong as possible.
To help you do that, we often recommend using a bonding matrix. This analyses the materials and the application to produce a risk rating. A bonding matrix will expose any high-risk bonds in your vehicles.

Forgeway Bonding Matrix

Pillar 3: Adhesives – Binding the Parts to Form a Whole

When you arrive at pillar 3, you need to evaluate the adhesive you’re using. Adhesives literally hold all the different parts in place. It’s an essential part of the process.

However, most people think it’s the most important pillar. This article should prove that the other four pillars are equally as important.

So what do you need to consider at this stage?

That’s the question that hundreds of vehicle manufacturers ask us each year. It’s the million-dollar question that never has the same answer. As we have already explained, each application is very different.

But there are always fundamental adhesive characteristics that are essential to consider. Then, some characteristics often fly under the radar but play a pivotal role in helping ensure consistent quality bonds.

It's essential to get the right adhesive when bonding vehicles

Let’s start by evaluating the basics for a strong and durable bond:

  • Adhesion to all materials – As we mentioned in Pillar 2, materials play a key role in a successful bond. You must make sure the adhesive can stick to the materials in the bond. This isn’t always a simple task if you don’t have specialist help. It’s crucial nonetheless.
  • Adhesive Strength – When you know the adhesive will stick, you need to start making sure it’s strong enough for the job. You can determine the adhesive strength required by working out the surface area available to bond and the weight of the materials to calculate the strength required.
  • Adhesive Flexibility – Most vehicle manufacturers focus on strength more than flexibility. Whilst this makes sense, strength isn’t the most important characteristic. As we have explained in separate articles, flexibility can be more important than strength for adhesives in vehicle applications.
  • Service life conditions – A strong and durable bond doesn’t stop with strength and flexibility. Durability is also very important. Evaluating the service life conditions of the vehicle will help you determine the conditions it will face exposure to. Temperature, humidity, chemicals, and UV exposure can all affect the durability of a bond. Make sure the adhesive can withstand the different types of exposure.
Different climatic conditions can cause adhesives to degrade

These are the main characteristics you will need to consider when selecting an adhesive. However, some other characteristics are less well known which can significantly help increase the consistent quality of your bonds:

  • A reasonable cure time – If the adhesive cures too fast, it can start to cure before the materials are put in place. This will affect the quality of the bond. If it cures too slowly, this can hold up production.
  • Concise and understandable packaging – Some operators don’t have the time (or willingness) to search around an assortment of similar glue tubes trying to find the right number combination. Save their time. Purchase colour-coded adhesives.
  • Minimal surface preparation – Some adhesives (like acrylics or hybrid polymers) do not require extensive surface preparation. They will form a strong bond with most surfaces without primers or abrasion.
  • Arrive pre-mixed – Single component (1K) adhesives arrive pre-mixed. This removes the need to mix two parts. 1K adhesives significantly reduce the likelihood of incorrect mixing and producing a weak bond.
Single Component adhesives do not require mixing
1K adhesives with clear packaging are easier for operators to use

Evaluating all of these characteristics will help you ensure the adhesive is the best product for the job. Once you have the right adhesive, the focus on the operators’ skills will only increase.

Pillar 4: Operators – The Driving Force Behind Successful Bonding

You can have an immaculate design, flawless materials, and a perfect adhesive, but operators are responsible for putting the different parts together. If you don’t train the operators, you risk derailing the whole project.

But why are operators such an important pillar?

The answer lies in an interesting statistic. Operator error is responsible for more than 90% of bond failures in the field.

When an adhesive is too brittle it can cause substrate failure

This stat highlights exactly why effective training is so important. It ensures all the other pillars come together to form the final product; a strong and durable bond.

Training operators is one thing. Training all levels of adhesive users will take that 90% right down to a more reasonable figure.

Supervisors play an important role in spotting errors as they happen on the line. This means they can remediate the bonding error before the vehicle leaves production.

Engineers and designers also play a critical role in creating a process that is simple and repeatable. Eliminating complex steps in the bonding process will make the operators’ lives easier.

As a result, less bonding errors. Fewer quality issues. More profitable vehicles.

It’s not always easy to portray just how important operators are to the bonding process. Nonetheless, they are one of the most important pillars of a successful and durable bond.

Don’t take them for granted.

Applying primers before bonding to improve adhesion
Make sure operators have recieved the correct training

Have you Implemented the Four Pillars of Bonding Success?

Now that you know what each of these four pillars is about, you’re likely wondering what next? What can you do as a vehicle manufacturer to make sure your bonding process has these four pillars?

These questions often arise when we explain the four pillars to vehicle manufacturers. They often come to us with a bond issue and think they know what’s causing the issue.

However, after analysing the four pillars, they often realise that they were initially wrong. What they first thought was an adhesive issue turned out to be a material inconsistency, for example.

That’s why you need to first analyse your bonding process. Even if you have no glaring issues at the moment, have you made sure none of these pillars are neglected?

Before you start implementing the pillars, you first need to identify the gaps. Will a new adhesive really reduce the bond issues? Or will operator training turn the needle on these bonding inconsistencies?

These are all questions you should ask yourself as a vehicle manufacturer to ensure an optimum bonding process can help you maximise profits.
If you’re stuck on where to start, you can speak to an adhesive expert by clicking the button below. Or, if you would prefer to research this topic in more detail, you can download the Fundamentals of Adhesives eBook.

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Thomas Besley

Thomas is the Content Manager here at Forgeway. Thomas' job is to translate the technical jargon from the ivory tower of academia into easy-to-read content that everyone can understand. Forgeway's mission is to answer every question our customers and prospective clients ask, or are apprehensive to ask.