Besides manufacturing cutting tools, since 1948 Fette GmbH has also been involved in development and production of tablet-press machines. Today the enterprise, which belongs to the Leitz company group, ranks among the leading manufacturers of tablet-presses world-wide. Under the international term "Compacting" Fette is moving into new markets, besides the pharmaceutical industry, in which powder or granule materials are also used. Thus on Fette machines for example semi-manufactured products for ceramics and electrical industries are produced and also metal, environmental and animal food industries use their services.
The Fette tablet-presses are equipped with rotary tables, assembled on a modular basis and available in different sizes and versions on demand. Effective forces reach up to 15 t per press process. A double version can press up to 79 tablets per revolution with attainable RPMs of over 100 per minute. The Fette P 3090i can for example achieve an output of 1.1 million tablets per hour. Each finished tablet is examined via the press itself. If pressure deviates by more than a freely programmable percentage from the default value, the tablet is rejected and an air jet blows it out of the process.
Tablet-presses require high quality parts
A basic requirement for the market success of the highly accurate, fast machines is their quality, which is subject to strict control procedures. Mangnus Schumacher is in charge of quality assurance for tablet-presses at Fette and is responsible for checking quality of all parts and machines, from incoming goods and their own manufactured goods up to and including machine acceptance and start-up at customers: "Here in our plant in Schwarzenbek we have a very strong in-house production depth, we even manufacture our own adjustment mechanisms and guides. In addition we have our own sheet metal department, which takes care of housings and control cabinets. Our electronics and software requirements are also taken care of in house." So the eight staff members in our Quality Control Department have to deal with various tasks ranging from purchased goods inspection to measuring complex components and checking sheet metal parts.
Mangnus Schumacher explains: "For series production parts, which are manufactured in large batches, we use in-process-inspection. That means we check the parts when production starts and during production we carry out spot checks, which are statistically evaluated. Thus we secure a qualitatively high-class process. A different process is in place for parts where we are responsible for the quality of end products. Nest plates for example are measured 100 per cent according to customer requirement and the results are recorded."
The tablet-presses and associated parts to be measured have become larger and more numerous, Mangnus Schumacher and his team have had to re-equip the measuring room accordingly. In 2006 Fette invested in a Leitz coordinate measuring machine, which is able to cover the immense measuring volume of 3000 mm x 2000 mm x 1000 mm. "We selected this machine among other things, because we can divide the measuring volume very well", commented Mangnus Schumacher. "The reason for that is we wanted to automate a share of the measuring jobs, so we can use it at night with a minimum of staff. To do that automatic loading and unloading of the machine were necessary. But at the same time the measuring machine had to be able to measure our largest components with dimensions up to 1800 x 1800 x 600 mm."
Alufix pallets for fast measurement setup
While the front area of the measuring machine is used for such large and heavy items or for programming measuring sequences for test purposes or even for "in between measuring", the rear area is available for automatic loading. To do that Fette invested in a Kardex rack system, which is loaded with components mounted on Alufix pallets by Witte, Bleckede. Grid clamping systems from Witte have been in use for many years at Fette, because the low weight of the aluminium pallets enables easy handling - and for measuring setup no particularly hard surfaces are necessary. Mangnus Schumacher particularly emphasized above all co-operation with the Witte company and their high commitment: "Both the grid plates in the front measuring area, and the pallets for the shuttle are specially designed for us acc. to our dimensions and tolerances. It was especially convenient for us that Witte also took over the installation of the Kardex shuttle." Since almost one year the CMM and Kardex shuttle have been in use. During the day QC staff members mount components onto the Alufix pallets and transfer them to the shuttle. The system checks for the highest part and looks for a suitable rack in the shuttle. Depending upon component size the shuttle can store up to 20 pallets, which are transferred automatically during the night to the CMM, measured and returned back to their rack. Fette created their own user interface, with which measuring jobs are easily entered and sequences pre-determined. Mangnus Schumacher points out a speciality: "The components to be measured are generally cleaned before mounting. This process takes place in a 60°C environment, and the part is still warm and cannot be measured because of thermal expansion. That’s why we created the possibility via the user interface to measure such components only late at night."
Before storing the parts in the shuttle they have to be fixed onto the pallets. "We talk about clamping systems, but ‘clamping’ is the wrong word", mentions Mangnus Schumacher. "Any tension would deform the parts at least minimally, which affects the measuring results. For this reason our aim was to obtain a fast, simple connecting system, which allows secure fixation of the parts with as little effort by hand as possible. Because even when they are not clamped, the parts must neither slip strongly nor change their position in any way."
Customized bolts and positioning pins from Witte as modular fixing accessories
For fixation issues Witte is also partner for Fette’s measuring technicians and was heavily involved in developing their solution. Witte offers bolts and positioning pins as well as other modular fixturing accessories, which are especially suitable with a view to fast preparation. With a current range of 200 to 300 parts, which have to be measured on Fette’s CMM the modularity of the clamping system gains particular importance. Mangnus Schumacher describes: "We do not want to spend time and money building a special fixture for each set up. The Witte system allows us to do it quickly and flexibly."
It is important to recognize the requirements fast. Therefore the quality team takes digital photos of the individual set ups, which are stored in the software and displayed via user interface. "In co-operation with Witte an idea developed, which we have adapted and extended to suit our purpose," reports Mangnus Schumacher. "we use the grid system to document important fixation points. That works like playing battleships; for example when the operator wants to mount a part, which the system already knows, a photo automatically appears on screen with the instruction ‘Clamp on G3 and C7’. The operator can immediately see how and where to set up fixturing. This makes it very easy to build repeatable fixtures fast.
With the Alufix system from Witte and corresponding fixturing accessories the quality team at Fette is in a position to fix even free-form parts fast to prepare them for measuring. They are highly satisfied with their choice: "On the one hand we did not find anything similar at a comparable price and on the other the modularity of Witte parts is unmatched by any other system. Here each element fits to all the others and the precision is impressive. We particularly appreciate the high quality of the elements. We are still using Witte items today, which we purchased 20 years ago." That doesn’t mean time has stood still. Witte has developed many new elements during the last years, which are especially useful to speed up fixturing. Quick connectors which accelerate fixture building considerably have almost completely replaced screw connections. But compatibility to earlier components has always been retained when new items have been developed.
B01_Alufix_Fette_0394.jpg Fette’s newly equipped measuring room for tablet-press production: A Leitz coordinate measuring machine with a measuring volume of 3 m x 2 m x 1 m dominates it. The CMM can be equipped directly or be loaded automatically from a Kardex rack system. Pictures: Witte/Fette
B02_Alufix_Fette_0369.jpg The components to be measured are mounted on Witte Alufix pallets.
B03_Alufix_Fette_0364.jpg B03_Alufix_Fette_3803.jpg Mangnus Schumacher: "The Witte system allows us to deal with our clamping requirements quickly and with flexibility."
B04_Alufix_Fette_3784.jpg The grid fixturing system makes fast measurement setup possible.
B05_Alufix_Fette_3812.jpg Alufix pallets are mounted with parts during the day and then stored in the Kardex rack system. They are measured automatically during the night shift.
B06_Alufix_Fette_3771.jpg Up to 20 pallets can be stored randomly.
B07_Alufix_Fette_3796.jpg B07_Alufix_Fette_3821.jpg Their own special user interface simplifies fixture setup. It shows digital photos of fixtures, which have already been built and shows the Alufix components and grid points to be used.
B08_Alufix_Fette_3090i.jpg The Fette tablet-presses are equipped with rotary tables on a modular basis, which are available in different sizes and configurations acc. to customer requirements. The Fette P 3090i shown here) for example reaches an output of approximately one million tablets per hour.
B09_Alufix_Fette_Tabletten_in_ein_Fass.jpg B09_Alufix_Fette_Tabletten_diverseFormate02.jpg However different tablets may look, to fulfil their function exact dosage, and highly accurate machines are pre-requisite. Each tablet is checked via press force before it falls into the container.