Success Story

Process reliability in line with purity requirements

In customers' hands: Dörries VCE 1600/140 SM So vertical turning lathe from the Starrag Group

What important factor do a cruise ship in the Mediterranean, a brewery in Asia and a dairy in Bavaria have in common? They are all equipped with GEA centrifugal technology, produced in Oelde. Centrifuges are used to process and clean all types of liquid or to separate liquids and solids. Example applications of this technology include in the treatment of drinking water and waste water, the production of beer and milk, the cleaning of ballast water and the treatment of diesel fuels. GEA, a company based in East Westphalia in Germany, meets the extremely high demands of its customers in the food and process industries using reliable production technology from the Starrag Group. 

"If you open your fridge at home, you will definitely find at least three food products that were produced using technology from GEA", says Lilian Schmalenstroer, who is responsible for Corporate Media & Press at GEA Group AG based in Dusseldorf and is Public Relations Manager for the East Westphalian subsidiary. GEA has evolved from a manufacturer of individual components, such as separators and decanters, into a supplier of systems that operate at a high level of vertical integration, including complete dairies, breweries or special facilities for ships (preparation and cleaning of fluids). 

"With its innovative system solutions for the constantly growing global population, GEA is making its contribution to the field of food processing and the use of scarce energy resources", says Antonius Mußhoff, Project Manager at GEA at the site in Oelde. The production facility in Oelde is equally complex. Among the products manufactured at this site are some of the company's key components (e.g. around 800 separators a year, generally in batch size 1 to 3). "We fulfil all manner of unique customer requirements at this site", the expert mechanical engineer notes. "Nothing comes ready-made: We go to the customer with a view to creating an individual system following intense discussions".

In this respect, the Swiss Starrag Group is a perfect fit with GEA, as Starrag also primarily focuses on creating customer-specific production solutions. "We have been manufacturing separators that can process ever-increasing throughput quantities for over 120 years now", says the project manager. "Requirements in terms of accuracy have also increased; we currently offer accuracy of at least 20 µm at certain points." For these exact points on the component, the production process must be designed so that it is extremely reliable and machining can take place with a high level of repeating accuracy. This requirement stems from the typical operating conditions in which separators work, namely with a speed of up to 12,000 rpm. Despite this high speed, smooth running is nevertheless required and can only be achieved using drive technology that delivers low imbalance and precise running properties. Antonius Mußhoff: "We have reduced the imbalance of a 1.5-tonne drum to 300 to 400 grams. Once all components have been mounted and fine-balancing has taken place, the residual imbalance is only five grams". 

To meet these requirements, as well as the extremely strict regulations that apply in the food industry for example, the typical main components of products must be precisely coordinated with one another and offer a precision fit. All components are made exclusively from modified duplex steel. As production technology for processing food must be cleaned with water and chemicals due to the strict hygiene regulations, non-rusting stainless steel and a highly effective sealant are used. Lilian Schmalenstroer: "We are able to supply all our customers around the world with centrifuges that meet the requirements set out in the strict hygiene regulations from the European Hygienic Equipment Design Group (EHEDG) and/or the 3-A Sanitary Standards that apply in the USA." 

To achieve this, once fully machined, the most important components are now finished on a Dörries CONTUMAT (VCE 1600/140 SM So) vertical turning lathe supplied by Dörries Scharmann, a company based in Mönchengladbach, Germany, and a subsidiary of the Swiss Starrag Group. Antonius Mußhoff: "This important finish achieved on the CONTUMAT significantly increases productivity. At this point in the production process, accuracy is tremendously important." 


However, it is not only a high level of precision that is required; products must also demonstrate a good surface quality. Regulation 3-A from the USA stipulates that surfaces in contact with food must have an arithmetic mean roughness value of Ra ≤ 0.8. All in all, the success of products ultimately hinges on a high level of process reliability being achieved — a factor that is monitored on an ongoing basis. When looking at the production process, specialist visitors will immediately see that process reliability is not just achieved here, but actively ensured. This reliability is checked and safeguarded by the use of 3D coordinate measuring technology.

GEA manufactures with coolants that flow out of the round, closed components during machining in order to ensure a reliable production process. "In the final phase of the machining process, we change to a vertical finishing process that runs without tension to ensure quality", the project manager explains. "We centre the components so that all the diameters have the same tolerance as each other." GEA already has considerable experience with this kind of machinery that it has gained operating two Dörries CONTUMAT vertical turning lathes since 1970. When replacing these machines, the company ultimately switched to a competitor for cost reasons. However, as Antonius Mußhoff notes, because GEA could not manufacture all of the components using that system, they soon learned that cheaper does not necessarily mean better. 

For this reason, GEA purchased a new Dörries CONTUMAT machine for handling important components weighing up to a tonne. Thanks to its solid cast construction (designed for a maximum workpiece weight of 9 tonnes), significant drive power (feed force of 35,000 N) and hydrostatic guide, the Contumat is able to machine heavy duty components with a high level of repeating accuracy, in a quiet and reliable process with very little vibration. For the application at GEA, it is particularly important that no vibrations occur: With the CONTUMAT, the hydrostatic guides and solid cast machine bed ensure quiet processing. "Flexibility is another key strength offered by the Starrag Group", Antonius Mußhoff goes on to say. "This flexibility enabled us to seamlessly integrate an additional measuring axis that we worked together to develop in several stages. This sort of collaboration only works if there are specialists on both sides who can exchange ideas. We are therefore very satisfied with the machines built as a result of this process." 

The vertical turning lathe has proven its worth in particular handling drum bases, one of the most complex components seen to date: As this component is used as a supporting element for all the other components of a separator, a great deal hinges on the level of quality and precision it offers. The drum base offers the highest level of quality with the IT6 tolerance grade, which requires parts to demonstrate a position and form tolerance of 20 µm in relation to one another", explains Mußhoff. "This quality can only be achieved with a reliable process." 

However, it was not only process reliability that played an important role in the decision to purchase: As a great deal hinges on the machining process using the Contumat, GEA places considerable value on receiving a reliable service. "We do have our own maintenance team that covers a lot of the work", says the project manager. "However, for special operations, an expert from the Starrag Group can be on hand within three hours. This is important in a process flow where there is no room for breakdowns. We also expect our machine suppliers to work over the weekend in emergency circumstances thanks to a 24/7 round-the-clock service." 


The products and services of the Starrag Group are developed in line with the slogan "Engineering precisely what you value", meaning that customers only get precisely what they need and what is important to them. But what is important for GEA as a customer? According to Antonius Mußhoff: "For us, the added value is in the high level of process reliability. With this level of reliability, we can produce all components on the Dörries CONTUMAT to a consistently high level of quality. Thanks to the highly reliable, production-level turning process employed on the Contumat, there are practically no instances where rework is required. What's more, we are on our way to achieving 0% wastage with a great deal of success."

VCE 1600/140 SM So

Machining diameter 1,600 mm
Turning height  1,200 mm
Table diameter 1,400 mm
Workpiece weight  9,000 kg (max.)
Machine table drive Liquid-cooled 60-kW drive with a torque of 13,400 Nm
Right-hand crossbeam support  
X-axis, horizontal  ±950 mm
Z-axis, vertical   1,100 mm
Cutting force during turning 50,000 N
Feed force  35,000 N
Rotating holder Fixed base holder with HSK A 100 retainer
Tool magazine Disc magazine for 30 HSK A 100 lathe tools
Plunge diameter of tappet 300 mm
Further details Workpiece measurement with integrated measuring sleeve, tool measurement and coding (Balluff system), collision monitoring, minimal-volume lubrication, completely closed work space, suction unit

GEA Group profile

GEA Group AG based in Dusseldorf, Germany, is one of the largest system providers for the food-processing industry and many companies in the process industry (group turnover in 2015: around EUR 4.6 billion, with more than 17,000 employees worldwide). The international technology group focuses on process technology and components for complex production processes in various end markets. Over 70 percent of the company's turnover is generated in the food industry. The GEA site in Oelde plays an important part in this, as this is where separators (centrifuges designed to separate liquids or solids and liquids) have been manufactured since 1893. From its origins in this form of production, GEA has since evolved together with all subsidiaries into a provider of systems such as complete dairies or breweries that feature a separator at their heart.

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