In this blog post, we will be taking a closer look at our Design Guide brochure and the information it includes which has been created to assist designers in the early stages of a product’s development.
Although an effective and high-performance seal is generally considered to be an important part of our customer’s part, it is often one of the last elements a designer considers when developing a new part. Leaving this focus until the end of the design process, or even when the part has gone into production, can cause problems; especially if the part needs to have an Ingress Protection (IP) rating. Despite the flexibility of our foam, parts will often need to be adapted or changed to incorporate the seal, which adds additional time and costs. Therefore, the earlier a designer can consider the way they will seal their part, the easier it is to develop a high-quality seal.
This is where our Design Guide comes into play. It was created for designers to give an overview of Robafoam’s foam, its properties, and how it can be adapted for their companies’ sealing needs. The brochure contains a range of information on how we are able to adapt our foam as well as the impact that can have on the sealing of the parts it is being applied to.
Foam Technology
Our polyurethane foam has a predominantly closed-cell structure. This means that it isn’t reliant on surface skin integrity for it to work and it performs well with water-tight seal requirements.
It is a unique single-part, low-temperature heat-curing foam and so isn’t reliant on any additional chemicals to be added to apply or cure it. The process takes the raw material from a drum, mechanically mixes it with an adjustable amount of air, and then robotically applies it to the part. The amount of air used in this process impacts the foam’s hardness; the more air added the harder the foam will be. Generally, the harder the foam the higher the sealing performance. Other factors which improve the effectiveness of the seal include higher compression levels and wider bead widths.
Obviously, the part itself also plays a role in its sealing performance. Its flexibility, span, wall thickness, and the size of the fixing points all have an impact on the seal. Although most problems can be overcome by adapting the compression, foam hardness, or bead size, it is still crucial for designers to be taking the sealing of a part into consideration early in the designing process.
Joint Design
When looking to include a seal within a joint on a part, the joint design can be an important factor to consider in giving the best possible seal. Robafoam’s foam seals can be used in a range of joint types, working with various levels of compression to provide different sealing abilities. The higher the percentage compression of the foam within the joint, the better the sealing capabilities are. However, some joint designs limit the capability for said compression. The design of the joint can also impact how wide/narrow the foam bead will be which also impacts the seal performance. One way of overcoming difficulties with joint design and compression is by using a tongue and groove joint. Many customers choose this design as there is less surface area needed to provide a higher seal performance.
Adhesion
The adhesion of our foam to a component’s surface is dependent on the surface energy of the material or the surface treatment in question. Different material surfaces exhibit a different level of natural adhesion, as well as potential contamination having an impact.
One way to change the surface energy to ensure the adhesion of the foam is through the application of ‘atmospheric plasma’. All Robafoam’s 6-axis robots are equipped with a plasma system to use with our Contract Gasketing customers. The application of plasma is part of the same process, carried out just before the foam bead is applied.
Another way of increasing adhesion is using liquid surface primers. By increasing the ‘wetting’ of the foam to the surface part, adhesion can be improved, however, this may compromise the height of the bead.
When good surface adhesion already occurs, our foam is also able to be used as an adhesive/bonding agent, both in its liquid foam or unfoamed state. Many customers require us to apply Robafoam’s foam to secure parts together, alongside providing a high-performance seal. This quality means that it can be used in multiple ways, all in the same process, meaning it saves time, space, and investment for our customers.
Heat Curing
Whether requiring Robafoam’s foam for bonding or foam sealing, the material cures rapidly at the temperature on or above 80ᵒC. On its own subjected to these temperatures, it will cure in a matter of seconds. The part itself and its heat sink properties determine the length of time it needs to cure. In most cases, this is 2 to 7 minutes. During the initial enquiry and sample phase of working with a customer, the requirements of the part curing can be adjusted to find the appropriate curing time needed for each part.
Generally, conventional oven systems are used to cure the foam, however, the raw foam will also cure in microwave ovens. The temperature of the part at the time of application can also have an impact on the cure time of the foam. For example, if our foam is applied to a plastic part that has been taken directly from an injection moulding machine (which could be around 60ᵒC), it will require significantly less time in the oven compared to a part being processed at an ambient temperature of 20ᵒC.
The flexibility of Robafoam’s oven systems means that they can be customised to work for any requirement or production environment. Ambient to 220ᵒC, our industrial ovens and thermal systems are suitable for material curing, drying, tempering, preheating, and cooling. Our vertical industrial ovens can help you save space, whilst our wide but flat industrial ovens can fit your current parts exactly.
For any further information about our foam and its properties, feel free to download the full Design Guide from the website. If you have any further questions on how we may be able to help with your company’s sealing needs, please don’t hesitate to get in touch.
