By Paul Uglum, president, Uglum Consulting, LLC
One question that is asked far too infrequently in manufacturing, and especially with plastic decorating, is “Why?” The purpose of the question
is to reach an understanding of just how things are made and the science that both limits and enables successful plastic decoration.
A good first question is, “Why are plastic parts decorated?” This probably is the easiest question to answer: Plastic is decorated to add value. That value can be in the form of increasing desirability, improving appearance, improving performance in the application or enabling communication with the customer (labels, for example). Understanding why a particular appearance or performance is expected allows the best option to be chosen. Understanding why specific technologies produce the desired results allows choices that meet or exceed expectations.
The central question is: What level of understanding, by those who are making decisions, is needed for success? The answer depends upon the complexity of the design and the expected life in its use environment. Understanding the underlying principles of how the environment, materials, processes and expectations limit and enable the best choices is of utmost importance.
This understanding also needs to include the economic aspects as well. What is the investment required for one option over another, and what is the payback? The financial risks can include make-vs.-buy decisions and the degree of internal control needed to ensure quality parts. Other risks include the stability of the supply chain and the maturity of the selected processes. Also consider future plans for the product. Is there some level of mass customization expected, and will it have a facelift that consists of changing from one technology to another (for example, from a painted to a plated part) during the planned production life?
Understanding fundamentals goes to the root of processing requirements and their drivers. It goes to the core of why one design choice is better than another and gives tools to choose from among them.
“Why” in Design
In the design phase, the project is taken from concept to manufacturable plan. It’s also where the program is set up for excellence or disaster, as these decisions have the greatest impact on the cost of the part and quality of the decorated part (Figure 1). Although the purpose of the design phase does not change with the product, the range of design freedom varies greatly. In-house products designed for consumers have a high degree of design freedom. Very highly constrained designs, like those for automotive interiors, have less freedom. Regardless of the degree of design freedom, all designs are limited by the laws of physics, by the capabilities of the materials and processes, and by the laws of economics.
Early in the process, there should be a design review – or, as possibly better described, a design intent review. Too many design reviews are held after most of the work is done and opinions are set in stone. This is a good time for teams with various skill sets to take a look at what is planned.
Since internal and external customer expectations are not always realistic, it is important to understand how best to meet these expectations and/or resolve issues. Some product designs are constrained not only by the limits of the chosen technology and materials but also by extensive regulation and validation specifications. In large organizations, where the original author of the specifications may have long ago moved to a new position, it is useful to try to understand the testing requirements’ purpose and origin. Do the tests still add value? The question is, “Why is this testing required, and what information does it actually offer about the performance of the finished product?”
Checklists and design standards provide useful guidance, but without understanding why they exist, there is a risk of unintended consequences. The world is dynamic, and the underlying limits can change as the use environment evolves and technologies and materials improve. Care should be taken any time a design is reused or when there is a substantial amount of cut-and-paste documentation. If the design is reused and the technologies change, what impact does that have on manufacturability, and why?
For example, it is important to understand why issues, such as sharp corners and small radii, are a problem with some processes. For coated surfaces, sharp radii cause paint to pull away and form picture framing during curing, due to changes in the surface energy as coatings dry. In the case of plating, sharp radii result in thicker plating due to the higher current density. Understanding the why behind each technology’s limits allows for better designs; when using multiple technologies, it allows for seamless integration.
The design process is more than one activity, and a range of skill sets is needed to produce manufacturable products. Implementing new or leading-edge technologies always involves some level of risk. This should be clearly understood and communicated as the process moves from design to execution. Buy-in from the manufacturing plant is important early in the process. Identifying any invention or technology introduction is needed so that risks can be mitigated.
The bottom line is that the best decisions are made by designers, engineers and teams that understand the limits and advantages of each technology, as well as the reasons these limits and advantages exist.
“Why” in Manufacturing
When a decorated plastic part reaches the manufacturing stage, the materials have been selected and validated, the equipment has been installed, the process has been studied and the operators have been trained. In production, written quality plans, work instructions and visual standards serve as guidance on just how to make a part.
What can go wrong? Probably a lot of things. This is why it is important for manufacturing supervisors and operators to understand not just what to do, but why they are doing it. If they understand the “why” behind the process they control, then they will be able to respond correctly when issues arise.
Why are cure temperature and time important? Also, why is it important that the cure cycle be carefully controlled and not interrupted? Some cure systems can be quenched if the cure cycle is interrupted and, as a result, never achieve the full crosslinking required for acceptable field performance. If an even oven temperature is not maintained, some parts can have more or less cure. It is not just a matter of setting parameters but understanding what actually is happening when those parameters are met, and why that is important.
Similarly, it is important to understand that chemicals have risks, both to line operators and to the applications themselves. Isocyanates are a good example. Isocyanates are used as cross-linkers in the thermal curing of both inks and paints. For safe handling, it is important to understand that inhaled exposure can lead to occupational asthma. Personal protective gear, training and process design all act to protect the operator. On the chemistry side, exposure of the isocyanate to the environment also can cause process issues. If exposed to moisture, isocyanates can react over time with moisture and, therefore, are less capable of acting as a cross-linking agent. As a result, materials may not be fully cured.
Constructive employee engagement is important, but employee engagement with understanding is so much more important. Those tasked with making the parts need to understand not just what to do, but why they are doing it.
“Why” in Innovation and Invention
Innovation and invention are important in all industries. Equipment manufacturers and material developers continually work on improving their products to enhance capabilities and meet an ever-increasing demand for unique and functional surfaces. Higher Q-switch frequencies in lasers and the use of nanomaterials in formulations are just two of the many improvements leading to capabilities that previously were impossible.
Invention comes in many forms. Often, it is the result of incremental improvements needed to fabricate parts in new geometries or with improved yields. Dramatic improvements and innovations can come from asking “Why?” when experimentation results in an unexpected result.
Some discoveries result from studying nature and asking why. Biomimicry has been used to create a variety of appearances and functional surfaces. For example, why are the colors in Morpho butterfly wings so vividly blue? The answer was found in the spacing of nanosized structures in the wings. The next question is, “Can this condition be mimicked with the technologies available now?” It was found that not only can it be duplicated, but it also can be tuned to provide a rainbow of colors. Although not yet commercial, this demonstrates the importance of understanding not only the chemistry but also the optics and physics of what one sees.
Constant awareness of how technologies are advancing and when it is best to start implementing them is a starting point. But, turning innovative decorating concepts into successful products requires more than great ideas. It takes technical expertise and a clear understanding of what is needed to bring a concept into production. This includes a business case and a committed supply chain that supports commercializing the technology. When implementing a new technology, make sure there is a process and a plan that transitions innovations from concept to serial production (Figure 2).
Asking why, and also why not, can lead to innovative solutions. Smart materials, including self-healing, structural color, soft feel, anti-fog and many others, are the result of the relentless questioning of what can be done.
“Why” in Problem Solving
One of many useful tools in identifying a root cause for a problem is the “Five Why” method. Five Why analysis is an interrogative technique used to explore the underlying causes of a specific problem. This method is most useful for problems with a single root cause and is good for beginner-level problem solving. It does not replace other methods but illustrates the importance of asking why and not being satisfied with the first answer (Figure 3).
The first step in this process is to clearly define the problem. This should involve looking at physical parts and visiting the manufacturing site. Without this clear understanding of the problem, all problem-solving techniques fail. Once the problem is defined, ask why the problem occurred. Then, ask why the situation described in the explanation occurred. This should be repeated until the root cause is identified. Five is not a hard-and-fast rule. It can take as few as three or as many as seven repeats. The method is iterative and intended to counter the tendency to stop short of the actual root cause. The method works well for both field and production problems. As with other methods, it is important to verify the cause with each step. Also, since it is a fairly simple method, results can vary.
The method can be used as a three-legged Five Why, where the first series of questions works to identify the physical cause of the problem. The second series of questions focus on why the problem was not detected (this protects the customer if the problem escaped the manufacturing plant). It can be a failure to look for the problem, issues that are invisible to testing or an entirely new problem caused by environmental concerns. The final set of questions looks at the process. Why was this issue not prevented? This can be the most useful as it looks at how the business is run.
Conclusion
Regardless of the stage of the decorating process, success relies on understanding just how things work and why. In an age of cut-and-paste and quick answers from AI, taking actions without understanding has significant risks. (Remember that AI is known to make things up and is no better than the too-often incomplete or incorrect data sets it learns from.) Even well-established tests and processes can cause issues if they are misapplied or the technology changes. Take the time to learn not only how to use technology but also the reasons behind why it works.
Paul Uglum has 43 years of experience in aspects of plastic materials, plastic decoration, joining and failure analysis. For more information, email paul.a.uglum@gmail.com.