014 bathroom fitting
Technical Report
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Plant retrofitting allows greater flexibility
and efficiency during grinding

This is a common problem: The production plant purchased years go still works well, yet maintenance and repair costs are increasing, lexibility is inadequate, and even the capacities are no longer ufficient. Today, alternative solutions to this problem often involve oving production overseas, which seems to get cheaper and heaper, or investing in new equipment. However, as the following ractical example demonstrates, plant retrofitting should also be onsidered an option.

Grohe AG calls itself a world leader as well as Europe’s largest manufacturer of sanitary fittings, and substantiates this claim with a market share of around 80%. The company, based in Hemer, Germany, employs a total of 5,200 employees in six production plants who generate a yearly turnover of a good 939 million Euros. Three production plants are located in Germany, and one each in Portugal, Thailand and Canada. At the head office in Hemer, about 650 people are employed to manufacture as many as 550,000 units of washbasin and bidet casings for the bestselling Eurodisc product line as well as for the upcoming Europlus product line. Due to the high and increasing number of workpieces, the fitting casings have been produced fully automatically since 1996 by SHL Automatisierungstechnik AG, Böttingen, Germany, on a robot production line that fully integrates SHL grinding and polishing machines. The high level of automation and consistent reduction of manual work to a minimum ensured, until recently, that the production costs were the lowest among all other competitors and that they could not be undercut by either other Grohe production plants or by the sub-contract manufacturers employed from time to time. However, over time, frequent wear and tear and higher maintenance costs came about due to the high utilization ratio, demonstrated, for instance, in over 50,000 robot operating hours. The demanded output, or piece production, was then no longer achieved, and the costs of repairs and standstills added up so that a sustainable solution had to be considered. Matters were complicated further by the fact that since the beginning of 2006 the new generation of Eurodisc was to be ground and polished on this production line together with the previously mentioned addition of Europlus WBcasings (washbasin casings), starting in 2007. It quickly became apparent that due to the larger product dimensions that the labor costs would be still higher. Yet demand was just the beginning. The exacting grinding and polishing work of the more complex contours with tight curves and design lines would possibly have to be done by hand. Analyses and calculations revealed that the yearly demand of ca 547,000 washbasin and bidet casing units of both the Eurodisc and Europlus product lines would certainly no longer be able to be manufactured on the “old” plant.

A difficult decision: whether to make “new” from “old” or relocate to a new location?

Consequently, various new designs were drawn up, and how to combine the following requirements was taken into consideration: processing time, product variants, flexibility of utilization, efficiency, machining quality, maintenance costs and, above all else, productivity and cost effectiveness. Graduate engineer Hartmut Holzmüller – Production Planning of Surface Technology at Grohe AG – commented on this as follows: “First and foremost, it was obvious that we wanted to maintain our plant at Hemer. For this reason we chose, together with our established plant partner SHL Automatisierungstechnik AG, Böttingen, a new and rather unconventional way to do this that equally took account of our demands and wishes as well as our investment.The outcome was a comprehensive retrofitting project; to be exact, the partial utilization of existing components from the old plant and the integration of new, additional robot systems.” The new design envisioned the replacement of what was known as a polishing rotary table by four robot grinding cells, and to link it to the existing workpiece transfer system. Furthermore, four existing 16 kg industrial robots (grinding operations) and four existing 30 kg industrial robots (polishing operations) were each either partially or completely replaced by larger robots, so that instead of the 30 kg robots, new 60 kg robots came into operation. In the end, it was necessary to install yet another robot polishing cell for the operation “Finishing”. The automatic surface monitoring, done by a camera system, remained unaffected by the retrofitting and extension, and it performed its inspection function as before.Yet, Hartmut Holzmüller and graduate engineer Jörg Tengler – Production Planning and Joining Technology at Grohe AG – went a step further and even incorporated mechanical manufacturing into the automated production process through drilling and milling on double spindle machining centers.

The solution: Retrofitting plus an additional investment for expanding capacity and productivity.

Jörg Tengler said in reference to the above: “After die casting, the fitting casings arrive in bulk in pallet cages to the area for mechanical processing. The workpieces were earlier fed by hand into the chuck of the processing unit and then removed after processing. In the meantime, the pieces had to be degreased in a washing machine. Today, by contrast, we have placed two new automated machining centers at the beginning of the production line for cutting the casings, and we see the whole production process completed entirely automatically. Linking these processes was first made possible through the development and implementation of dry processing, particularly since degreasing was able to be omitted. For parts transportation, a workpiece circulation system was developed in close collaboration with the application engineers at SHL. The system begins with the automated positioning of unprocessed slabs at the beginning of mechanical processing and ends with the manual removal of the emptied workpiece pallets, or it goes back to the beginning.The automated production process includes the loading and unloading of both machining centers by two industrial robots. Workpieces are not put onto the pallets until after drill machining and milling. After the pallet is filled, the workpiece transport system carries it to “Pregrinding,” where henceforth four robot cells carry out the entire grinding process. The pallet, which is assigned a “free” robot cell by the control system, remains in the cell until it is completely processed. After pre-grinding, the pallets go to finish grinding and polishing. There are a total of 8 active robot cells in this area. The finish grinding and polishing takes place in another robot cell, indicated as “final polishing,” before the pallet or the completed parts on the pallet are finally checked per camera monitoring. Each pallet has a specific code that allows a status and information check for machining progression at all times. After the final polish and the final check, the finished workpieces go on an electroplating rack, and the empty pallets go into a transport cart. The rejected parts, on the other hand, go to manual refinishing and then back to the transfer circuit again through a bypass. The same goes for rejected parts from electroplating, which are moved in this same way after dechroming

Application and utilization flexibility paired with high productivity and reproducible quality.

The carts with the empty pallets are manually taken back to the beginning of the plant, and the pallets are then automatically placed by robots in a loading station, known as a setup station, in the transfer system. SHL Automatisierungstechnik AG, as a main contractor, delivered not only 16 robots total, including gripper systems and control systems, etc., but also new grinding units, polishing units, pallet loading units, pallet unstacking units, flexible workpiece pallets with various workpiece slots, the expanded pallet transporter and positioning system, the safety installations and the total control technology including software. The entire system is controlled by means of a superior industrial PC as well as surface visualization for a quick overview. Every day, about 2,500 casings pass through the plant, which has also already been prepared for the upcoming Europlus product line. The cycle time is 30 seconds. Production runs continuously in an 18 shift model (4 shifts per 24 hour day) from Monday morning 6 am until Sunday morning 6 am. Just one plant supervisor and 3 operators are in charge of service for the entire plant, including the loading of workpiece carriers for the processing plants. The offered process reliability during clamping and machining of the workpieces is ensured by integrated swarf blowout units on the gripper jaws. Both machining centers are equipped with tool monitoring systems. The exchange takes place on the grinding belts according to figures based on experience. With pride, Hartmut Holzmüller explains in conclusion: “With the retrofitting project, we were able to clearly win the competition against other locations, and to that effect we were successful in keeping a product of significant volume in Hemer. With the high automation level and the marked increase in capacity, we managed to reduce the total processing time for fitting casings from 3 days to now just 10 hours. 70 workpiece pallets run in the system, and this is something that allows us a certain autonomy; we, with only four people, are able to run the entire plant and still have time for other things. We have technically and economically found a very good solution, in close collaboration with the specialists from SHL Automatisierungstechnik, which, in the end, has cost only a fraction of a new plant. For this reason, we got the go-ahead for the investment despite stiff internal competition.”