Case Study: Structural Adhesives Increase Productivity for Electric Vehicle Assembly
Clean Motion relies on structural adhesives to provide strength and reduce weight in its Zbee electric vehicle.
The innovative Zbee three-wheeler is an ultra-light, energy-efficient electric vehicle designed by Clean Motion AB, located in Lerum, Sweden, with its manufacturing site in Trollhättan. The Zbee’s final design and build specifications included the use of fiber reinforced plastic (FRP) body panels in combination with two Scott Bader structural adhesives: Crestabond® M1-05 and Crestomer® Advantage 30. These two adhesives were selected because they provide a combination of lightweight adhesive joining, build quality and productivity.
The Zbee electric vehicle is light and compact, with dimensions of 240 cm long by 120 cm wide and 150 cm high. Its ultra-light curb weight of just 230 kg has been achieved by the Clean Motion design team’s rigorous adoption of their “Lean Engineering” development philosophy, which involves reinventing every part of the product through multifunctional design, simplification and a lightweight approach to all aspects from materials selection to methods of assembly.
Its overall design makes the Zbee agile in traffic and easy to park; up to four Zbees can fit in a typical single parking space. Powered by a 4 KW electric motor, it has zero emissions and no engine noise. Clean Motion developed the Zbee as an ideal compact electric city vehicle for short-distance urban transportation for up to three people. It has a maximum speed of 50 km/h and a range of 45 km (approximately 20 miles) on a single charge; the battery recharges in three hours.
On the build quality side, Crestabond M1-05 and Crestomer Advantage 30 were specified by Clean Motion because they are proven structural adhesives with reliable long-term bond strength performance combined with toughness and durability due to their high elongation and impact strength properties. In order to minimize weight, only a bonded joint—with no mechanical fasteners—was specified for joining the FRP body sections together.
According to Scott Bader’s test data, the FRP substrate of a bonded Zbee body panel will always fail before the adhesive joint. All Zbee vehicles are assembled, tested and inspected in Trollhättan by Clean Motion AB.
Shop Floor Productivity
Since the start of the production phase in 2011, both Crestabond M1-05 and Crestomer Advantage 30 have been used for the Zbee fiber glass body panels by HJ Kompositmontering AB, the approved local FRP body parts subcontractor in Sweden for Clean Motion. Crestabond M1-05, which is a grey colored adhesive, is used to bond FRP body sections together, and also for bonding aluminum profiles located in the trunk of the car. High productivity is achieved on the shop floor due to Crestabond being a primer-less adhesive, thus needing little if any surface preparation, combined with its rapid cure and subsequent short fixture time of 12-18 minutes.
Crestomer Advantage 30, which is colored white, is used on all the visible FRP-FRP joints in order to provide the combination of an aesthetically pleasing finish and reliable build quality. Both manual and pneumatic handguns are used by HJ Kompositmontering AB during production of the FRP body parts, depending on the specific bonding application.
To optimize efficiency, flexibility and productivity with minimal waste at current Clean Motion demand levels, 400 ml Crestabond M1-05 and 380 ml Crestomer Advantage 30 co-axial cartridges are used, supplied locally from Scott Bader Scandinavia’s warehouse in Falkenberg. “By using Crestabond M1-05 and Crestomer Advantage 30 cartridges, we get both outstanding performance and shorter lead times,” said Niclas Johansson, co-owner of HJ Kompositmontering AB. “These adhesive products enable us to save time and speed up production times, as minimal surface preparation is needed prior to bonding. We expect orders will continue to increase rapidly in the coming years for this type of vehicle, so it’s important we are using products that meet all parameters for build quality and production efficiency.”
To cost-effectively ramp up production to keep pace with Clean Motion’s rapidly growing order book, HJ Kompositmontering AB is considering switching to using an automated 10:1 dispensing machine, using either 20-liter pails or 200-liter drums of Crestabond M1-05 and Crestomer Advantage 30 adhesives. Clean Motion is expecting to see a significant increase in orders in 2014, especially from Asia, with a forecast for over 350 Zbees and continued growth in the coming years.