Change-over time reduction and stock organisation in a truck cooler assembly line

Abstract: Valeo Engine Cooling in Mjällby mainly produces truck coolers. At the production site, there is on-going work to phase out the automobile cooler manufacturing and concentrate the production to one facility. At the same time the main production flow needs to be improved. The purpose of this Master's Thesis is to analyze the flow of coolers from the brazing furnaces through the different crimping and welding assembly stations, to find problem areas and implement changes to improve the situation. The analysis has pointed out three different areas:

• The need to increase throughput of the brazing furnaces and lower the work in progress levels by reducing change-over times
• The necessity to organize the crimping stock in FIFO and improve the layout
• The importance of having a separate stock area assigned for manual welding assembly

Currently, the brazing furnaces are operated 24 hours a day and this is still not sufficient to meet customer demands. Therefore, every extra hour of production that can be gained is valuable. The work with the change-overs in the brazing furnaces has resulted in a step-by-step guide to shorten the change-over time. It is based on the SMED methodology (Single Digit Minute Exchange of Die) and an analysis of shift reports from the furnaces. The yearly extra profit that would be made by implementing each step has been calculated to be between 2 and approximately 15 million SEK. The work is supposed to point out the importance of working on reducing the change-over times and show which actions are the most profitable. The actions include: reducing the number of belt speeds in the furnaces, having an end of line stock for all products, optimizing change-overs on the same belt speed and shorten the time used for changing belt speeds. Today, the crimping storage is very unorganized and difficult to overview. The plan is to store the cores in rows of wagons, instead of pallets, and to use the FIFO (First In First Out) principle. The stock levels fluctuate heavily over the week. To be able to dimension the new storage area the variations have been carefully analyzed. Two layout suggestions were created and compared. Both alternatives have advantages, but one of them was found to be superior due to higher safety and better stock organisation. The layout of a nearby water leak test station had to be changed in order to have the cell working as efficiently as today. The final layout alternative made this possible using a smaller area than today. The analysis of the main process flow showed that today there is no separate storage area for manual welding. Instead, these products are mixed within the robot welding assembly stock, and thereby complicating the work for the operators. A new storage area was needed with an area able to store 15 pallets. From the decision factors two layout alternatives were created. The chosen alternative is located closer to the manual welding cells and requires less extensive layout changes. To have everything working on the least possible area, the supply of tanks to a nearby crimping station had to be done with supply trains. These wagons were designed and built. They were also tested in a supply loop and at the crimping press with good results. Unfortunately, the wagons could not be added to the train loop since there was no room for the tanks in the service area. Still, it served as a good example of how much space is made available in a work cell by using small boxes and supply trains.