Call Us: (419) 678-4877
Call Us: (419) 678-4877

Solid-State Spot Friction Welding Systems

Our SpotMeld™ system is a Refill Friction Stir Spot Weld (RFSSW) solution for aluminum and magnesium that provides an alternative to single-point joining processes like resistance spot welding, laser welding and riveting. SpotMeld is an easier process to fixture and its automated tool change capability saves significant time as compared to self-piercing rivet changeover. Additionally, a variety of weld recipes can be used on demand by the robot controller, which results in a very flexible production system. Coldwater Machine Company’s robot mounted SpotMeld head can be integrated with a variety of robots, such as Yaskawa Motoman, Fanuc, Kuka, ABB and others.

About Friction Welding

Friction Welding, a type of solid state joining, creates mechanical friction between workpieces in relative motion to one another, heating the materials until they reach a plastic state (non-melting) at the joint interface. The materials are then forged together by force, creating a joint. It offers numerous benefits over other joining techniques including elimination of filler metal or flux, higher quality joints, a very small heat affected area, and no coarse grain formation.

A proven joining methodology, friction welding can be applied as friction spin (or rotary) welding, linear friction stir welding (LFSW or FSW) or refill friction stir spot welding (RFSSW), as well as multiple variants of each approach. While most rotary friction welding is used on round, symmetrical parts, linear friction stir welding and RFFSW allow solid state welds on a wider range of part geometries.

A major advantage of friction welding is that it allows dissimilar materials to be joined. In fact, nearly half of the welds made through friction welding are for joining of dissimilar materials. Normally the wide difference in melting points of the two materials would make it impossible to weld using traditional techniques and would require some sort of mechanical connection. Friction welding provides a “full strength” bond with no additional weight.


  • Joins 1000 – 7000 series aluminum, magnesium sheet
  • Flexible sheet thickness combinations in one operation
  • Can replace other single point joining processes for less weight
  • Weld near original material strength
  • Non-corrosive bonding
  • No flux, filler or other consumables
  • High energy efficiency
  • Environmentally friendly

Joining Aluminum with Refill Friction Stir Spot Welding – SpotMeld

As a variant of friction stir welding, RFSSW has become a focus as a solution for spot welding aluminum and dissimilar materials. It shows great potential to be a replacement of single-point joining processes like resistance spot welding and riveting – creating stronger joints.

Refill friction stir spot joining is similar in principal to Linear Friction Stir Welding (LFSW), although generally applied as a joining technology for overlapping or stacked sheet material. Both techniques use a rotating tool with a specially designed pin and shoulder. However, with LFSW the tool travels along a seam between two metal plates versus the tool staying in one spot in friction spot joining.

In 2014, Coldwater announced its SpotMeld RFSSW solution, based upon technology developed and patented by Helmholtz-Zentrum Geesthacht, Germany. For integration of the technology into high production environments, Coldwater continues to partner with the Helmholtz Institute and weld-head provider Harms & Wende.

SpotMeld uses a three-piece tool to join two or more faying surfaces. Heat generated between the tool and materials creates a soft, plastic-like region that is then forged into a nugget. Coldwater has had success in spot welding aluminum (1000 – 7000 series), magnesium, non-ferrous and dissimilar sheet materials, making SpotMeld a viable alternative to single-point joining processes like resistance spot welding, laser welding and riveting especially for the future EV market.

SpotMeld Application

Compared to laser welding and other aluminum-joining techniques, SpotMeld is an easier process to fixture and it’s more tolerant of imperfections. It is also designed to have the same basic footprint and work envelope as a resistance spot-weld robot, putting it in a familiar context for OEMs. Additionally, the electricity cost is much lower than that of resistance welding since there is no need for the huge current. The only utility cables are the servo lines that connect to the servo motor and some water cooling for the tools.

A major advantage of the Coldwater approach is that the tool doesn’t fully penetrate through the bottom sheet, leaving a smooth surface with potential for use on exterior body panels. Alternative friction spot welding techniques typically use a solid pin that does not retract, so the pin advances partially into the sheet, a little more than halfway through the joint, leaving a surface that has some material off-set on it. Additionally, this creates a 3-4 mm hole on the center in the center of the weld.

Currently, Coldwater can join a stack-up of materials from 0.8 mm to 8 mm, weld dissimilar aluminums in one stack and join multiple sheets across the edge of a panel.

We’re Joining the Future

with New Technologies for Lightweighting

Coldwater Machine is a leader in the development and manufacture of solid-state welding solutions that specifically address lightweight, we have deep experience with traditional MIG and resistance welding technologies that is a greatly expanded capability with access to the global resources of the Lincoln Electric Company. We have designed and produced automated weld cells using fiber lasers, CO2 lasers, MIG (GMAW) and friction solutions.

Research & Development

Our Solid-State Joining Center is focused on furthering the development of processes that enable the joining of materials at temperatures below their melting point and without the addition of filler metal or shielding gases. We are partners with the Edison Welding Institute, LIFT (Lightweight Innovations for Tomorrow), as well as other research institutions helping to commercialize new joining technologies for the production environment.

Testing & Validation

The Solid-State Joining Center also houses a Materials Evaluation and Testing (MET) lab that provides microstructural evaluation in addition to mechanical testing for weld tensile and hardness verification. This on-site service provides prompt verification of weld integrity, enabling Coldwater Machine to shorten the development time for laser, solid state and arc welding customers.

Prototype Project Requests

We accept applications for prototype project requests. Please submit your initial request for parts joining prototype work. We can work to produce custom parts that make use of advanced joining technology as well as apply a joining to your existing parts. Provide some of the information below and we’ll contact you for more details and state the process with your team.