What You Need to Know About Fastening & Joining Technology
Product design depends on joining. Before you can achieve a successful end product, fastening and joining technology must be considered. And the earlier, the better. A product that works well but makes noise based on a poorly fastened component is not going to do well.
Miranda Marcus, applications engineer, ultrasonics at EWI, says that joint design is more important than it may seem. “People may not be aware that it’s not the entire joint design, it’s the entire product design. The weld will affect the entire product.”
Perhaps you can relate to this scenario. “This happens quite a lot,” says Marcus. “A customer or a company will have prior experience working with a particular joining process that didn’t work out. For the entire future of that company, that process is basically forbidden.” Maybe it didn’t work 20 years ago on a project because the process was not suited to the application, or perhaps the company was not using best practices for the process, Marcus explains. “But often, once you get that bad taste in your mouth, you’re never going down that path again,” she says. “People will say, ‘We tried ultrasonics once, and it didn’t work.’”
Trends in fastening and joining technology mirror changes going on in other applications. “Products keep getting smaller and more complex. The joining processes need to be more precise and also we need to be able to provide better predictive capabilities.”
Marcus works with more than a dozen different plastic joining processes, and says that most people probably aren’t even aware this many options are available.
Often engineers will work on the design and development without thinking about how to join the product. Or, conversely, they may think of a method to use and even build parts, targeting a particular joining process. But once they try to weld it they run into difficulties. At that point they may consult a joining expert, only to find out that a simple design change in the beginning could have made the process work better.
Later in the product development cycle, Marcus says common questions are: “What’s the cycle time going to be? How much does this cost? How do we test it? Once the weld process is working, how do we evaluate it?”
Sometimes taking risks can pay off. Marcus says sometimes people will want to use a certain process for their product that might not seem well-suited for the application. In one situation like this, Marcus told the client: “‘Well, here’s a lot of reasons why X is unlikely to work. If you do decide to use it, here’s what I would recommend.’ It actually ended up being more successful than either I or they thought it would be,” she says.
Liquid sealants, more flexible than o-rings, are often used for appliances. Source: DELO
Four Trends to Watch
Paul Gregory, senior applications engineering specialist, industrial adhesives and tapes division at 3M, notes that there are four major trends affecting fastening and joining technology. “The first trend, and maybe the most significant, falls into what 3M calls sustainability,” Gregory says. “In the long term, this is your environmental impact, and compliance with environmental regulations. In the area of sustainability, there are two areas of concern: electricity usage is an area of great concern for appliance design, which affects our area as designers are doing things to reduce electricity usage of appliances. Secondly, using advanced software to control the electric motors, and some of the heaters as well so that they are smoothing out the power usage.”
There are a number of ways to go about this, whether it be reducing electricity usage in refrigerators or reducing the amount of water used for dishwashers and washing machines, he says. A front load washer calls for very different tape and adhesive solutions so the way an appliance is designed has immediate consequences for suppliers.
The next trend, Gregory says, is the human machine interface (HMI) or how the homeowner interacts with the appliance. Today’s appliances have bigger and bigger displays, which is intended to provide useful information about the device’s operation as well as connectivity.
“The third trend, which we see the most of at 3M, is the use of new materials,” Gregory says. “Not necessarily new materials that are new to the world, but designers are shifting from different grades of steel, or one plastic to another plastic.” This means that the adhesives have to be compatible with and bond well to these new surfaces. Whenever a material change is made, the manufacturer would need to work with the supplier to make sure the adhesive will work.
The fourth trend is noise, Gregory says, noting that the quieter a refrigerator is, the better it will sell. Today there is more and more concern over the noise in an appliance, particularly dishwashers and refrigerators. The noise level difference from a 15-year-old dishwasher vs. a new one is dramatic, he says. Some of these trends can overlap. For example, designing a dishwasher to use less water may create a stronger and faster water spray. This could lead to noisier operation, and thus may call for new materials to dampen the sound.
Combination of screwing and bonding can also be used as a bolt. For appliances, they can be used if you need a visually appealing design where you don’t want to see the welding spots. Source: Böllhoff
Jeff Frantz, director of North America business development for Branson at Emerson, notes that the style of an appliance can affect the joining processes used. “When it comes to appliances, the industry is looking for a sleek, slim, trim type of design, which can make the fastening and joining a little bit more challenging,” Frantz says. “We try to work very closely with the design teams as early as possible into the development of the process. We can give input into the design aspects that make our processes more effective and efficient.” He noted that both the supplier and manufacturer want the same thing: to meet the customers’ needs and create a cost-effective assembly.
“Every technology or process that is used in the assembly of appliances, they all have their limitations and advantages,” Frantz says. “The key is getting that information to the design teams in the early stages, what works well and what doesn’t in certain technologies, and leverage the right approach and right technology.”
“Before you get too deep into the project, engage with the technology people that you’re going to use to assemble this to get their input,” Frantz says. “What we try to do is put the right technology to the right application that brings them the best value.” In other words, the priority is the least amount of capital expense for the greatest amount of performance.
Torsten Uske, president of DELO Industrial Adhesives, says that the electronics have affected the joining technologies. “A lot of electronics are going to be built into these devices, which raises the demand for new joining technologies and displays that are going to be integrated.”
With touch panels being added to refrigerators, ovens, and dishwashers, new adhesive technologies are needed. Clients want a well-rounded adhesive that cures quickly, has high strength, and is also affordable, and ideally, they want everything in one adhesive, he says. The next questions deal with manufacturability. Designers would like to know: how reliable the adhesive is, how long it will last, and how they can create every single assembly exactly the same. From there, he also hears a lot of process-related questions. He’s also heard some seemingly contradictory questions. Sometimes customers ask for adhesives of the highest strength, but then also ask how they can de-bond it.
As an adhesive manufacturer, they prefer to be involved in the very early stage of the process. But the company has also worked on applications that need to be solved within a month or two, because everything else has failed, he says.
Many appliances have different switches. For example, a washing machine has a very important one that detects whether the door is open. Source: DELO
“Most of the time it comes down to cost,” says Uske, although having a reliable process and fast cycle time are also considered. In addition, manufacturers are always looking at innovating with new materials and formulations, Uske says, and regulations will also continue to play a role in the future of the industry. Green materials continue to be a concern, as manufacturers often want to look into the recyclable aspect of the adhesives.
Automation and Examples
Rachel Nashett, an application engineer at Henkel, says, “Automation is essential to large device manufacturers to stay competitive.” North American manufacturers are looking for ways to automate the current assembly of what they are building now, she notes.
What should design engineers consider when selecting a fastening or joining method? Nashett notes that designers should consider the items being joined, as well as the forces and temperatures that the joining method has to withstand during transportation, production and end use. Other key criteria are: “How quickly do your parts need to be joined? What duration do your parts start seeing stresses?”
“The most common misconception is that adhesives are always slow, which isn’t the case,” Nashett says. “It’s really optimizing the right adhesive technology with the right application technique to meet the criteria of design and criteria of manufacturing. This is where many manufacturers see their disconnect. The design engineers are not always working with the manufacturing engineers. In those cases, production and design engineers need to work hand in hand to determine the best case for production and end use.”
Customers often want to see proof that this has worked for someone else in a similar environment, especially with automation, Nashett says. Another chemical fastening example in an automated assembly line helps the customer know that their application is viable.
Since Henkel works with a wide variety of customers, she said they typically can find someone else using this product. They would be able to work with both customers to set up a tour in the other plant. This isn’t always possible, she notes, and only works when companies have a range of customers in different industries.
Some trends have not panned out as expected. Weight reduction for appliances, for example, has not lived up to the hype. Nashett notes that it was previously thought to be important, but today it seems to have reversed for appliances, and manufacturers are not as concerned with this. In fact, for safety reasons, some appliances may have weight added to make sure they don’t fall over.
Sustainability and Cost
When considering adhesive trends, David S Woodcock, marketing manager, coatings, construction & adhesives at Huntsman Advanced Materials, says sustainability and cost are two larger trends. “It all depends on the application,” he says. “The mega trend of sustainability and the green movement is always driving the consumer attitudes toward things that are compliant.”
And of course cost is always a factor. He often hears questions regarding cost per pound as well as the affixing time and return to service. When selecting an adhesive, Woodcock says design engineers should consider factors such as the type of application, service temperatures, and the exposure to UV, heat, or the type of chemicals. He notes that there is always a solution, it may just depend on price. “For us, as a supplier of these things, we have pretty exotic materials, adhesives that are going into space vs. a homeowner bonding broken glass together. It always come down to, we have a solution, but what cost are you willing to incur in this project?”
In addition to cost, he said engineers should consider the processing conditions involved, and the equipment that might be used, although these are just a few of the variables involved in making the right recommendation. After deciding on an adhesive, the testing involved could be a lengthy process, particularly in more conservative industries. He notes that in the aerospace industry the selling cycles could be several years long.
Performance testing depends on how severe the application is and the liability involved, he notes. It is necessary for the engineers to know the required tensile, modulus, required operating temperatures, and to specify all those things in a product design or product definition, which greatly helps suppliers make appropriate product recommendations. It’s important to know “what are the critical elements that must be adhered to, no pun intended,” Woodcock says.
“The design of a product can greatly affect how an adhesive will work,” he says. For example, joining two different materials with a flange can help or hinder the adhesive working. A supplier would be able to guide the engineer in how to get a more successful design. If this is done earlier in the design process, the supplier could tell you if it will work or not in that design.
With more lightweighting and more composites being used today, Woodcock sees more unusual applications. As new materials are adopted, such as perhaps carbon fiber reinforced plastics to aluminum, the design may become more complicated as well.
“I think the future will ultimately involve dissimilar bonding of substrates,” Woodcock says. “With the amount of choice of materials out there, it’s getting more and more.