Manufacturers are constantly fighting against adhesion problems. Surfaces not sticking and adhesives not working is the daily reality facing manufacturers looking to make high quality, reliable products. The daunting nature of the task to eliminate adhesion failure seems insurmountable and never-ending.
Changes to equipment or processes are made, and yet, failure still occurs in the form of bonds not holding, coatings not uniformly covering a surface, paint or ink not adhering and in dozens more ways that every manufacturer is all too familiar with. These failures redound to costly scrap rates, recalls, unhappy customers, expensive rework and major stalls in getting a product to production or to market.
So, what are manufacturers to do? Luckily there are some steps that can be implemented quickly and relatively easily to move towards eliminating adhesion failure and increase productivity.
By looking at common mistakes made by manufacturers we can identify exactly how those steps can be used to combat the everyday scourge of adhesion failure.
Common Mistake 1: Not knowing your materials in the surface preparation process
This is a common error made by manufacturers across every industry and discipline. A lack of understanding of the properties of a material that directly relate to how it will bond to another material is all too common. Often this is because of an intrinsic trust of suppliers who may not tell manufacturers everything they need to know about the material. Sometimes subtle changes can be made to a material that the supplier believes will not affect their clients but can end up having catastrophic consequences downstream.
To remedy this mistake, manufacturers need to gain knowledge of the state of every material surface that comes into the production facility and seek expertise about what properties of a material have the highest impact on adhesion.
Common Mistake 2: Using the wrong surface prep process for a material
This mistake goes back to the first one. It is imperative that manufacturers have awareness of the material properties that relate to adhesion and understand how to utilize this knowledge to create a surface most amenable to successful adhesion. If this awareness and understanding is lacking, it is likely a surface preparation process may be implemented that is, at best, not helping and, at worst, making the surfaces impossible to adhere to.
This can be avoided by overcoming the first common mistake - gaining the proper knowledge of the material properties – but then taking the next step to apply the best preparation method for that material and application.
Common Mistake 3: Over or under-treating a surface
No matter what method for surface preparation is used by a manufacturer it is possible to insufficiently prepare the surface as well as degrade the surface by overtreating. This mistake often looks like abrading too much or too little, the duration of plasma treatment is too long or too short to create the most adhesion-friendly surface, using a parts washer that is only removing large particulate but not oils, or sometimes not having a treatment or cleaning step at all.
To make sure you’re not making this all-too-common mistake there needs to be a verification step associated with any treatment, cleaning and preparation step in a manufacturing process. There needs to be a step implemented that validates that the surface has reached the exact level of preparation necessary for adhesion. Without this it is impossible to know if you’re doing too much or not enough.
Common Mistake 4: Letting the surface age
Surfaces, like everything else, are subject to the forces of entropy. Surfaces degrade over time and because of the manufacturing environment, it often doesn’t take long at all. This aging can take place when materials come in from a supplier and are immediately put into storage, or if they are stored at a later point before bonding, coating or printing. Similarly, if an adhesive or coating isn’t applied as quickly as it should be after treatment or cleaning, that surface could have changed enough to create problems for adhesion.
Determining the most optimum time to apply an adhesive or coating after treatment is crucial to getting tripped up by this mistake. It is also critical to inspect every surface once it is taken out of storage so the preparation steps can compensate for any changes that might have occurred.
Common Mistake 5: Using abrasion incorrectly
This is a mistake more common to manufacturers with applications involving composites and metals and usually is due to over-abrading or under-abrading a surface. However, for manufacturers with applications involving polymers, using abrasion at all may be a mistake.
Be certain the material you are abrading is a material that requires abrasion for adhesion. Also, know the exact amount of abrasion necessary and implement a verification step to ensure this specification has been reached and not exceeded.
Common Mistake 6: Not cleaning before abrading
When abrasion is the proper preparation method for the material, it is often used without first ensuring the surface is clean before abrading.
It seems logical that abrading would remove any gunk on the surface since it is essentially removing the top of the surface, however, the gunk that is most detrimental to adhesion is not visible to the human eye and is not always removed by abrading. Sometimes the molecular contamination is merely spread around or ground into the surface by the abrading step.
Always cleaning a surface with a parts washer or an IPA wipe prior to abrasion is necessary to not fall prey to this classic blunder. It is also very important to verify that the cleaning was sufficient to remove contamination, so inspecting the surface before abrading is a must.
Common Mistake 7: Reusing cleaning materials
When cleaning supplies are overused they increase the risk of spreading contamination from one material to another. For instance, when a wipe is reused it can remove contaminate from one surface and apply it directly to the next surface even if that wipe appears to be clean. Similarly, not changing out the water or solution in a parts washer as often as needed means you might as well be giving materials a contamination bath.
Never reuse a wipe once it has come into contact with a surface and regularly inspect parts after any cleaning step so you can track when it is time to change the cleaning elements.
Common Mistake 8: Not using the proper wiping technique
Yes, there is a proper wiping technique.
It seems to be human nature to want to wipe a surface by moving the wipe or cloth in a circle. This method does next to nothing when it comes to truly cleaning a surface.
The proper technique is to use a lint free cloth with an ample amount of cleaning solution, usually isopropyl alcohol, more pressure than is typically applied, and then wipe in one direction – typically towards your body so the pressure can remain consistent. After each pass the cloth needs to be folded so an unused surface of the cloth touches the material with each wipe. This alone will give you astonishing results.
Common Mistake 9: Using improper personal protective equipment
There are protocols for safety and cleanliness in every manufacturing environment, however if not implemented with the effect on adhesion in mind, these may not be sufficient for keeping contamination off the production line.
Always make sure anyone handling materials or adhesives are wearing gloves and that those gloves are changed frequently. People often handle contaminated materials without thinking about them as being contaminated because it is not visibly compromised. The chemical components that can create adhesion failure are not able to be seen and therefore are not often considered when using personal protective equipment.
Common Mistake 10: Not restricting materials allowed in a facility and not knowing where contaminants can come from
Much like mistake number 9, there are almost certainly procedures in place to keep facilities clean and therefore some items and activities are banned from production areas. But if the origin of some contaminants is not known or understood, some could be flying under the radar of manufacturers. For instance, it is common to not allow the popular silicon wristbands in a facility, but scent-masking sprays and frostbite prevention substances often used by hunters are silicon-based and if even a trace amount is brought into a production line it can spell disaster for adhesion.
Ensure all policies about cleanliness currently in place are being followed by everyone and begin thinking outside the box when it comes to determining ways that contamination can be introduced to a facility.
So, What Now?
Avoiding these common mistakes may seem like a massive undertaking. Mostly, each comes down to increasing awareness of what is occurring at a surface preparation step, awareness of the surface state of your materials before and after those steps, awareness of treatment best practices and awareness of contamination origins. Taking a systemic view of adhesion failure goes a long way to preventing it. Implementing several small changes can have an enormous impact on the manufacturing process as a whole.
Have the solutions to your adhesion problems in your manufacturing operation eluded you?
Contact BTG Labs’ Process Experts about how to locate and validate the Critical Control Points in your manufacturing process. A free Production Line Process Walk is available to start the gaining insight into where adhesion failure is originating. You don’t need to tackle the problem alone. To learn more about eliminating adhesion issues, please download the free eBook titled "Manufacturer's Roadmap to Eliminating Adhesion Issues in Production."