The production of micro tablets entails a whole range of special requirements. In addition to consistently high product quality, the main focus is on operator protection. Compression of the explosive powder mixtures, for example, requires strict segregation of individual zones: “For us, the powder must never escape from the compression chamber into other parts of the machine – such as the upper part of the housing or the drive chamber. There are often electronic components that are warm or do not have sufficient protection for direct contact with explosives. Tool breakage can also theoretically lead to ignition,” says Michael Wendtland, Foreman of Fuel Production at ZF Airbag Germany, describing the working situation on the machines.
For this reason, the tablet presses are equipped with spark-extinguishing systems that use small water nozzles to prevent possible ignition of the fuel. Another requirement is the minimal use of plastics that could become electrostatically charged. “The machines from Fette Compacting meet our safety criteria. Their components are mostly made of stainless steel, offer space for safety attachments, and can be connected ex works with the additional control system we need. We were also always able to find a solution for all other special requests with our colleagues,” says Wendtland.
Small tablets, big forces
The compression process produces tablets with dimensions within the range of a few millimeters. “Due to the requisite compression forces and the sensitivity of the product, high-precision operation of the machines is of enormous importance,” explains Detlef Oetken, who is responsible for fuel production technology at ZF Airbag Germany. “In addition, we need as few extras as possible on the machine at the factory. For us, it is rather the programming options that are decisive, such as the start relief and punch-saving.”
The programming options referred to above ensure optimum pressure conditions during compression: start relief reduces compression forces and friction, especially when the machine is started up several times. Punchsaving detects unusually high compression forces at the pre-compression station, such as those that can result from double compression. The tablet press then stops in time and allows the corresponding pair of punches to pass the main compression station before restarting.
Running like clockwork
The company uses a number of tablet presses of different types from Fette Compacting. These not only meet the safety requirements, but also enable a high throughput with high precision: “As everywhere, there is little room for delays in our production. At the same time, the tiny tablets allow only infinitesimal tolerances. Therefore, it is important that the tablet presses run like clockwork,” is how Wendtland sums up the requirements. With the appropriate tools using EU19 punches, a very high output is possible despite the small dimensions involved. This ensures the necessary supply at the airbag production sites from Aschau via Xian in China to Mesa in the USA. The production capacity is more than 1,000 tons of fuel and 40 million gas generators, which are installed in vehicles all over the world.
Flexibility is the trump card
Wendtland cites the standardization of components at Fette Compacting as another criterion for the tablet presses. This reduces stock-keeping and increases flexibility, since, for example, an adjusting gear can be used on any machine. Added to this are the intuitive operation of the machines and the low effort required for maintenance and cleaning. Finally, this overall picture rounds off the high level of satisfaction with the support: “The service has always been reliable and fast, so that production could run smoothly,” Oetken emphasizes.