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Hammer mill – the name says it all!

From agriculture to process technology: Tietjen mills have taken their market by storm. Key to this success is their high level of vertical integration: every hammer mill is individually optimized for its own specific purpose and the company's know-how is deployed to systematically address the application ...

Sinumerik in the mill production of Tietjen Verfahrenstechnik GmbH

At velocities of up to 132 m/s, the rotating hammers in Tietjen mills crush a very wide range of materials: raw materials for animal feed, plastic, organic waste, wood and many more. Controlling the high forces involved takes many years of mill expertise and precisely dimensioned components.

Modern mills are high-tech precision products

The small company's site, nestled in the tranquility of Hemdingen, Germany, (northwest of Hamburg), looks more like an agricultural enterprise than the headquarter of a manufacturer of industrial mills for producing animal feed which is known throughout the world. The original idea for the first mill patent for a pneumatically controlled turbo mill really came from the agricultural history of the Tietjen family in hog feeding. "The founder realized at an early stage that when it comes to animal feed, the grain size is also important for how well animals absorb the nutrients, in addition to the recipe and ingredients. This led to the founding of the Tietjen machinery construction company in 1959. Today, we are process engineers who operate within the scope of a complex project business to supply industrial mills with feeders, control systems and explosion protection for a vast range of applications around the globe", explained Thomas Runde, one of the three CEOs in the family-run business employs 60 people. 

Material-dependent design

Tietjen mills are impact crushers with different power ratings and chamber sizes. However, the design not only varies regarding power rating and size, but also depending on the material. Each mill is precisely adapted to the material to be crushed or milled: capacity, humidity, intended granularity, starting sizes, material hardness, surface attributes – and the list goes on. This is why seven employees work on 3D design.

Impact crushers

All variants have the same fundamental design: arranged in segments, a large number of hammers are attached to a rotor, which rotates in the chamber at over 3,000 rpm. The material, introduced from the top into the mill chamber, hits the hammers which crush it as a result of the massive force of the high-speed impact.

 

The company's core expertise focuses on the arrangement of the hammers, their segmentation, and in particular the rotor design. Tietjen guarantees the performance and grain sizes after crushing, and this is verified by customers when they accept the mill at the factory. 

Flexible component manufacture as a success factor

"We use different steel grades for our hammers. Stainless steel is frequently used, as the materials are acidic or else relatively hard. However, the core component is the rotor that must be manufactured with great precision due to its rotational speed," said Peter Wagner, Tietjen's General Manager and Head of Production. "The components were produced semi-automatically for many years. The continuous growth and the restricted space on the traditional factory site of this family-run business made us think about purchasing a CNC machining center. Such a capital investment would allow us to produce more flexibly, faster and with a higher degree of precision." 

High level of vertical integration and flexibility for replacement parts

Another argument was the spare parts business. Tietjen is still producing replacement parts for mills that customers have had in operation since the beginning of the 1960s. These individual parts can be more efficiently produced with a higher repeat accuracy when using a CNC machine.

The 3-axis machining center was not supplied with Sinumerik. But we made it possible for the customer ...
Michael Schaaf, Technical Manager of the STAHLWERK KNUTH brand

Sometimes fate points in the right direction

Fate not only plays a role in crime thrillers, but also when it comes to making investment decisions. 

 

The Tietjen team quickly reached agreement with machine supplier Knuth about the selection of a modular, configurable 3-axis machining center with a tool changer.

 

"One of the last demonstrations involved a tool change, its influence on the programs and how it is mapped in the control system. As the whole thing appeared to be complicated and was taking somewhat longer, some of us wandered around the Knuth demonstration center. And as luck would have it, we bumped into Mr. Bartsch from Siemens, who was setting up a Sinumerik control system with ShopMill at another machine. Right from the outset, operation was smoother, and appeared more user-friendly and easier. This aroused our interest. We asked if we could see more, and then made a quick decision: We would be equipping our new machining center with a Sinumerik control system", recalled Peter Wagner, Head of Production. 

SINUMERIK 828D as customized control system 

BuHowever, this turned out to be easier said than done. Michael Schaaf, Technical Manager of the STAHLWERK Knuth brand: "The 3-axis machining center was not supplied with Sinumerik . However, we then made it possible for the customer, and thanks to the support from Siemens, the machining center was installed with a Sinumerik 828D and ShopMill. For the typical batch sizes of between 3 and 5 up to maximum of 50 parts, Tietjen really does benefit from the flexible programming options and the significantly easier operation of Sinumerik."

Installing the machining center in the narrow factory hall presented another challenge. Machines had to be moved around, the floor of the hall opened up and a solid foundation poured – and all of this in record time and with high factory utilization levels. The machining center was installed and able to go into productive operation early 2018. 

Right from the outset, it was clear that Sinumerik operation was smoother, more user-friendly and easier.
Peter Wagner, Tietjen

Offline programming with SinuTrain saves time

In the meantime, Tietjen is enjoying higher factory utilization levels, and this bold investment decision has met with much praise internally. With the new machining center, key workflow steps which had previously been outsourced for capacity reasons were re-integrated into the company, increasing the level of vertical integration. "This further improved our flexibility and supply capabilities. This gives us an important competitive edge in the project business, where milestones and completion dates are crucial," explained CEO Thomas Runde.

 

The Sinumerik control system also again played its part in achieving this flexibility: using SinuTrain, CNC programs are now also generated offline so that the machine can remain in productive operation for longer. "Another extremely helpful option, which would not have been available with the original machine configuration. The Knuth machining center equipped with Sinumerik and SinuTrain, as well as the excellent collaboration between Knuth and Siemens, provide us with the best possible solution – packed with features and offering a high degree of flexibility."

Industrial history as shown by Tietjen

The development of Tietjen serves to illustrate core developments in agriculture and animal feed production. 

 

What was originally an agricultural company transformed itself into a machinery construction company. In the 1950s, the first mills were sold to agricultural businesses, small farm cooperatives and suppliers in the region. Just a few standard models were sold. Back then, the mills had capacities of about 2 tonnes of animal feed per hour

 

With the industrialization of agriculture, large domestic and international companies took over feed production. Mill specialist Tietjen responded to this. Today, Tietjen's hammer mills are on average significantly larger, with capacities seldom below 70-80 tonnes/hour. The state-of-the-art, electronically controlled mills and Tietjen's entire global sales and service network is geared up for 24/7 mill operation. 

 

Today, more than 50 % of Tietjen's mills are installed outside Germany. The range of applications has also widened. In addition to fodder for pigs, cows and chickens, products in the pet food and fish food domains are playing an increasingly important role. Not only that, many Tietjen mills are used for material recycling and special tasks. The manufacturing process and the mills themselves have comprehensive certification: ISO standards, explosion protection, energy efficiency etc. In some of the models, materials are crushed down to particle sizes of less than 500 µm. The range of mills available today is correspondingly wide. 

 

Feed and discharge systems, as well as upstream material preparation processes are playing a bigger and bigger role in the actual crushing process in the mills, in addition to their efficiency and output. Tietjen has responded well to this trend, and turned into a process technology specialist. For several years now, this has also been evident in the company name: Tietjen Verfahrenstechnik GmbH - which means Tietjen Process Technology. 

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