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"Teach programming for one exchanger required the full use of a robot for a week. That would amount to tying up 25 weeks of robot time in the Charmes plant. It was deemed as too costly and led to offline programming."
“Teach programming was not an option for robotized cutting, and without Alma's software, the project probably would not even have been considered.”

At Trane, offline programming boosts robotized welding and plasma cutting

Trane, world leader in air conditioning systems and refrigeration, adopted robotized welding in 2004, wagering on Alma's offline programming software to maximize the robot efficiency. Trane wanted to cover two goals: improve the productivity of its tubular exchangers production line in the Charmes plant in France and solve a triple-sided issue of workload fluctuations, personnel qualification and production quality. Drawing on this blooming integration, a robotized plasma cutting installation, also driven by alma's solutions is successfully commissioned two years later.

With more than 26 000 employees and a turnover larger than 6 billion dollars, Trane is the world leader in air conditioning systems and refrigeration . The product range of its air conditioning appliances covers residential, commercial, and industrial applications. Trane has a worldwide presence through its sales offices, its joint-ventures and its 29 production sites. Both French plants, located in Charmes and Golbey since the end of the 60es, manufacture liquid chillers and fan coil units. The Charmes plant, with about 500 persons, produces high power models, 60% of which are destined to the European market. Each Trane plant is autonomous and pursues a triple objective: to manufacture, in the shortest time, high quality products while respecting security issues.

All the products are manufactured on command. About 5 days are needed to perform the assembly. The Charmes plant has two assembly lines, one for air cooled systems, the other for water cooled systems. Both assembly lines are supplied by the tubular exchanger manufacturing unit. For productivity, quality and security issues, reducing assembly times to the bare minimum is of the essence. One way to reach this goal is to set up the task as well as possible beforehand. That is the context in which Trane began considering using robots for the tubular exchangers welding. The goal there was to reduce manufacturing costs and improve the assembly lines synchronization.

 

Robots: improving welding productivity and answering a triple-sided issue

Other constraints explain Trane interest in robotization. Seasonal fluctuations have a very strong impact on air conditioning and refrigeration appliances production. This requires to be able to call on, preferably highly qualified, welders at the right time. Furthermore, the welding quality required to adhere to the demands of pressure vessels design codification calls for the welders to follow a three-month formation cycle. Seasonal load fluctuations, hard-to-find and costly-to-train manpower, quality issues related to manual welding... Faced with this triple sided problematic, welding robotization appears to be the right choice.

This of course calls for the robot to be able to weld the products, but the exchangers conception led to an uncontrolled looseness in the shell positioning in regard to the plates located at its ends. This could be up to 20 mm on a 4 m long shell. In 2002, the design office began working on modifying the products conception to guarantee the parts positioning, precondition to any robotized welding. At the same time, the welding strategy was updated.

Benchmarking was initiated with an American sister plant, already using several welding robots. Different robots manufacturers were contacted. The chosen installation, consisting of a cell equipped with a robot hanging from a longitudinal translation axis frame, fit quite nicely with Trane configuration. Two parts-bearing rotating positioners enable loading/unloading the assemblies in masked time.

 

Offline programming was comprised from the beginning of the project

The American plant experience indicates that teach programming for one exchanger required the full use of a robot for a week. That would amount to tying up 25 weeks of robot time in the Charmes plant. It was deemed as too costly and led to offline programming being considered from the start of the project. act/weld, alma's welding offline programming software was assessed in 2003. It seemed more efficient than the manufacturers solutions, a simulation software not specific enough or a “virtual” teaching tool deemed too rigid and imprecise. Alma's deep knowledge of the controller and the existing relationship between Trane and Alma won over the project's managers. As a matter of fact, alma's 2D cutting/punching CAM software had been used in production in the Charmes and Golbey plants for several years already. The project's managers first objective was that the programs must not be modified on the robot, that all the settings and tunings had to be performed directly through the software. “The whole programs must be repeatable and usable on a computer” indicated Vincent Guerbeur, quality manager of the Charmes plant, who was then welding manager for permanent assemblies responsible for the robotization project.

The robot cell and the act/weld software became operational in April 2004. Alma then performed the cell software calibration (update of the virtual cell to correspondence with the actual cell), an essential service which conditions the programs quality. Even if nothing was left to chance, robotized welding was a complete unknown in the plant and everything remained to be learned. Fortunately, Trane fully assigned Vincent Guerbeur, welder engineer, and two robot operator to this task. “ At the end of the training given by Alma, we had to master the offline programming tool, familiarize with the parameters, establish a programming method, find out the correct configurations and test them on the actual robot.” remembers Vincent Guerbeur, aware that he bore a huge responsibility on a fascinating assignment. It took about two months to harness act/weld and define the necessary parameters. Four more months were required to reach the productivity and quality objectives set at the beginning of the project. Around thirty programs are created in these six months, encompassing the whole product range.

 

The same technology to cut the shells in 3D

By the end of 2004, Trane management started thinking of robotizing the shells manufacturing, outsourced until then. “Following the successful integration of robotized welding, we wondered whether we could not produce better and cheaper shells, by cutting them ourselves, with a robot.” said Stéphane Hacquard, process and development manager of the Charmes plant. Technologically, robotized plasma cutting consistently ensures theperfect quality of the chamfers and, as a consequence, ensures minimum looseness during welding. From an economic point of view, a cost benefit analysis easily confirms the relevance of this new project by showing cost reduction of more than 35% over outsourced manufacturing.

Having assessed the feasibility of such 3D cutting, Trane and their partners only had to define the particulars of both the virtual and actual installations. The cell contains a robot fixed on a ground rail with a translation axis, a positioner with a rotation axis and an ELS laser sensor. Drawing on Trane experience in robotized welding, implementing robotized cutting was much faster and the installation became operational as early as 2005. A module was added to the act/weld installation to manage the 3D cutting technology, so that a single workstation can feed programs to both robots.

As the welding parts, the cutting parts are imported in Alma's software from the 3D CAD (Inventor / Mechanical Desktop), using the STEP format. They are then automatically positioned in the virtual cell by a macro developed by Alma. The software also programs the ELS laser sensor. “Teach programming was not an option for robotized cutting, and without Alma's software, the project probably would not even have been considered”, remarks Stéphane Hacquard in hindsight. Furthermore, the offline programming software simulation capacities allowed a high productivity gain on shells cutting. Romain Gotti, a young engineer, inhouse trained a few months ago on the offline programming software, quickly devised a new cutting method to host the parts welded to the shell. That greatly simplified the positioning operations prior to the welding.

 

Improvements all over…

As for the welding two years before, robotized cutting has found its cruising speed and Trane management has a very positive return from the integration of both these robotized processes. Trane has reached its objectives, from an economic point of view as well as from a quality and production organization point of view. Productivity has increased by 45% and production capacity by 50%.

The high quality of the software calibration and Alma's encompassing knowledge of the controller have enabled Trane to generate programs offline, without any correction on the actual robot.

New products entering production by the end of 2008, Alma's software will again be strongly called on for the welding. This illustrate another decisive advantage of offline programming; “Thanks to act/weld, we can now anticipate new products development, provided we plan carefully.” emphasizes Vincent Guerbeur.

When asked to define the main components of the successful integration of offline programming in the manufacturing process, Trane management emphasizes the importance of the collaboration between the robot manufacturer and Alma. Alma's technical expertise quality and steadfastness all along the project development are also deemed as crucial. For the customer to take enough time for the robot integration with sufficient personnel is a sine qua non condition for the project to be successful. This is even more important if the robot and the offline programming software are brought in simultaneously. The project will be all the more successful as the person in charge of the offline programming software will have been trained correctly about the robotized process. More proof that robots need men to reach their full potential…

 

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