Manufacturing does not change quickly.
Most joining processes stay in place for years, especially in production environments built around consistency, repeatability, and proven results. Once a process is established, there has to be a good reason to replace it.
That is starting to happen.
Across automotive, aerospace, and other advanced manufacturing sectors, engineers are working with more aluminum and other lightweight materials. That shift supports lower weight, better efficiency, and new design possibilities. It also creates challenges on the production floor, because many traditional sheet metal joining methods were developed around steel.
As the use of aluminum continues to grow, more manufacturers are taking a fresh look at the joining methods already in place.
Are the traditional options still the best fit for the materials now being used?
Why This Conversation Is Growing
Lightweighting is one reason this topic is getting more attention.
In automotive manufacturing, reducing weight can improve fuel economy, extend EV range, and help manufacturers meet emissions requirements. In aerospace, every reduction in weight can have a direct impact on performance and efficiency.
That said, lightweighting is only part of the picture.
Manufacturers are also dealing with greater use of aluminum, more mixed-material assemblies, pressure to improve energy efficiency, and the need to keep production compatible with automated systems. Together, those factors are forcing a closer look at how parts are joined.
The Problem with Relying on Traditional Methods
Aluminum does not behave like steel.
Resistance spot welding has been a standard joining method for years, but aluminum presents challenges because of its thermal conductivity and oxide layer. Those material characteristics can affect process stability, energy demand, and weld consistency.
Self-piercing rivets can solve some of those problems, but they create others. Rivets add hardware, add steps to the assembly process, and can raise corrosion concerns depending on the materials involved.
This gets more complicated when manufacturers are joining dissimilar materials or trying to balance structural performance with production speed.
That is why more engineers are considering solid-state alternatives.
What Refill Friction Stir Spot Welding Actually Does
Refill Friction Stir Spot Welding, or RFSSW, is a solid-state joining process developed for applications where traditional spot joining methods may not be the best answer.
Instead of melting the material, RFSSW uses friction and plastic deformation to create the joint. A rotating tool works at the interface of the sheets, softening and stirring the material below its melting point.
One of the key differences is the refill action.
Material displaced during the weld cycle is returned before the tool retracts, leaving a refilled spot rather than a remaining hole. That is an important distinction from earlier friction stir spot welding approaches.
Because the material is not melted, the process avoids many of the issues commonly associated with fusion-based joining.
Related: Refill Friction Stir Spot Welding (RFSSW) Machines
Why Engineers Are Paying Attention to RFSSW
RFSSW is getting attention for practical reasons.
It can produce strong joints in aluminum without the added hardware of mechanical fastening. It also avoids the keyhole left by FSSW, and the through-hole required by some spot joining methods. Heat input is lower than with fusion-based processes, which helps reduce distortion. It is also well suited for automated production and can be deployed as an end-of-arm robotic tool.
Another factor is energy use. RFSSW can use far less energy than resistance spot welding, which makes it worth considering for manufacturers focused on efficiency as well as performance.
For engineers evaluating process changes, that combination matters. Joint quality is important, but so are integration, throughput, and long-term operating cost.
Not Limited to One Industry
Although lightweight vehicle design is one clear use case, RFSSW is not limited to automotive applications.
The process is also being explored in aerospace and other advanced manufacturing environments that require strong, repeatable joints in aluminum structures. In one NASA-funded project, EWI and Bond Technologies developed and validated an RFSSW process for a solar panel tower intended for lunar use.
That example does not need to be overstated, but it does show the level of interest in the process for demanding structural applications.
Related: Refill Friction Stir Spot Welding (RFSSW) Applications
The Real Question
Resistance spot welding and self-piercing rivets are established processes. They remain effective in many applications.
The question is not whether those methods still have value.
The question is whether they are always the best choice for the materials, production goals, and performance requirements manufacturers are dealing with now.
That is the reason RFSSW is getting a closer look.
Related: Refill Friction Stir Spot Welding (RFSSW) Technology
A Practical Way to Compare the Options
For engineers evaluating joining methods, broad claims are not enough. The useful question is how the options compare on the factors that affect production and part performance.
To help with that evaluation, Bond Technologies engineers created a side-by-side comparison of:
- Refill Friction Stir Spot Welding
- Resistance Spot Welding
- Self-Piercing Rivets
The chart looks at key considerations including joint performance, energy use, material compatibility, production impact, and automation.
Download the comparison chart for a clearer look at how these joining methods differ and where RFSSW may make sense.
