Automating New Joining Technologies for Lightweight Materials

Ongoing efforts to reduce vehicle weight by OEMs (original equipment manufacturers) create the requirement for new and innovative methods of joining in body-in-white (BIW) assembly systems. This article will discuss some of the challenges of integrating advanced joining processes into an automated production system based on our experience with such work at Comau, a member of the FCA Group. Comau is a company devoted to continuously developing, testing and deploying cutting-edge manufacturing and assembly solutions that are able to address these dynamic changes in today’s market. As a means of meeting these changes, Comau developed the ComauFlex assembly system. This high-speed vehicle manufacturing line optimizes operating flexibility and floor space, and has the ability to assemble high volume BIW structures which incorporate new materials and joint types. Comau’s offices and innovation centers around the world support the needs of its customers from process optimization to production simulation in order to deliver high-speed automated production solutions.

Since the early 1900s, the automotive industry has incorporated lightweight and multi-materials into body structures. During this time, the areas in which this material was used represented a small percentage of the vehicles’ structure. In the past 8-10 years, there has been additional emphasis on incorporating lightweight, stronger materials into the majority of the automobiles’ composition. This has led to the need for adapting new joining technologies into automated production systems.

To meet this need, Comau works with many companies to help develop new joining technologies, including: self-pierce rivets (SPR), flow screws, RIVTACs by Boellhof, clinching, adhesives, and lasers that can work within the same manufacturing environments as traditional joining technologies such as resistance spot welding. Traditional BIW joining methods have revolved around resistance spot welding and gas metal arc welding (GMAW). Since the use of mixed materials has continued to increase in order to reduce vehicle body weight, system integrators like Comau have been tasked with changing the traditional body shop manufacturing methods and adapting them to handle these new joining processes. One of the major challenges is introducing the new joining technologies into a high volume production environment (40+ JPH) and ensuring the new processes operate as efficiently as the methods that have been tried, tested, and optimized for decades.

Comau works with manufacturers to test and validate the latest advancements in joining technology. This allows both the integrator and manufacturer to have a complete understanding of the new joining process. When a new process is introduced, there is much to consider prior to installation: PLC communication, robot communication, maintenance intervals, mean time between failure (MTBF), mean time to recover (MTTR), robot dressing, fault recovery, and packaging. Therefore, it is critical to understand all of these items so that the new process is robust and ready to be implemented into a demanding production environment.

The footprint of the newer joining technologies has also created unique challenges. For example, now that there are several joining technologies to choose from, there are also multiple suppliers. Each supplier has their own way of packaging their equipment, which can drive the creation of custom layouts for every project. To address this issue, Comau has designed a technology tray, which incorporates all of the equipment that these joining systems require into a single package (electrical panel, feeder, HMI, etc.). Comau is able to fit joining technologies such as self-piercing rivet systems (SPR) and flow drill screw systems on the same technology tray, which then easily connects to Comau’s Basic Robotic Integrated Configuration (BRIC) system to keep the large electrical panels, feeders, and controllers off of the production floor and on a standard size tray. The tray allows for the BRIC system to quickly change between processes in the event in which there is a product change that creates the need for assembly line reconfiguration to a different joining process. This flexible concept also allows for the replacement of the tray if there is an equipment failure, and can be easily replaced by removing the old one and installing a new, preconfigured one.

Some joining technology manufacturers have completed the majority of their own product validation testing and in-house development, which can provide most of the data and information needed; however, they may not have tested their equipment to the level they would experience while in an actual high-volume production environment. The need for increased thorough and applicable testing has created a demand for a partner to complete the testing and validation of the new process for production.

Comau answered this industry need by building a research and development facility in its Innovation Center at its Southfield, Michigan campus. The Innovation Center has the capability to test multiple types of joining technologies on advanced materials including flow drill screwing, self-piercing rivets (SPR), laser welding, brazing and etching, RIVTAC, and more. Comau also houses a fully capable metallurgy lab that has the ability to destructively examine these new materials and joining processes. This lab is located in the same building as the process equipment to ensure that the time between process testing and process validation is minimized.

The company has received excellent customer feedback on the ability to demonstrate the joining process capabilities in real-time. Most of the new joining processes require initial destructive tests to determine if the joint quality will be acceptable for the customers’ product requirements. This destructive testing is completed by sectioning test coupons or dismantling subassembly components into small specimens that can be mounted, ground, polished and measured under a microscope (up to 1000X magnification) in Comau’s metallurgy lab. Once the joint meets the customers’ specifications, more joints are run without the need to perform further destructive tests.

The 21st century is the age of process monitoring. The new joining technology that is being created and developed to meet the customers’ requirements requires more sensor monitoring of the actions/motions that take place during the process to ensure a strong and robust joint is created. This capability is built into the PLC program, and creates profile data for the insertion of the fastener that can be monitored in real-time and can provide failure analysis. Utilizing this known data with an acceptable specimen as a process benchmark helps ensure the process is within the acceptable software monitoring windows.

Comau’s Southfield Innovation Center has the capability to use in-house robotic automation to test the longevity of the entire joining process. This includes all cable management, as well as any additional attachments that are key functional items for many of the new joining processes. This data is then thoroughly analyzed for uptime performance, strength of each process item, and mean time between failure (MTBF) data. The acquired data is used to improve any areas of the process with the lowest performance. All of the capability studies that have been completed are then shared with the customer.

Comau works to provide solutions that are capable of withstanding the harsh production environment that a system will endure during manufacturing. From concept design to full-line integration, the company specializes in helping their customers compete in fast-paced markets with emerging demands. As a worldwide leader in the industrial automation technology market, Comau’s solutions are flexible, scalable, incorporate lean manufacturing concepts, and are designed to help their customers improve their competitiveness in terms of quality, cost, and service.

Written by Brandon Reinhold

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