Success Story

Higher profitability per square metre

New HEC machining centres from Starrag Group modernise demanding cast processing

The GEA Refrigeration Germany GmbH in Berlin has replaced three somewhat ageing machining centres with the new HEC 630 Athletic and HEC 800 Athletic CNC machining centres. In doing so, they have been able to reduce processing times by around 40% while generating additional manufacturing capacity in the same space.

What do a wind tunnel in Vienna, an indoor ski resort in Dubai and the Stuttgart trade fairs have in common? They all contain cooling equipment from GEA. The international technology group also supplies refrigeration and air-conditioning solutions suitable for many other industrial applications, such as for engine test benches and spray booths, warehouses and cold chains for food products like yoghurt or ice cream.

At the heart of these units is the GEA screw compressor, manufactured at the company's Berlin site. In 2016, a total of around 1,500 compressors left the factory, in 28 different models ranging from 280 m3 to 11,500 m3 in flow volume. Their special features: high efficiency and long service life.

Such a screw compressor essentially consists of rotors and housings. Each manufacturer keeps the rotor profile a particularly closely-guarded secret, as it lays the foundation stone for efficiency. But suction, pressure and rotor housings also have a marked effect on quality. Tight shape and position tolerances have to be adhered to, from the flange faces up to the mating holes for the rotor bearings. Production Manager Hanno Heim explains: "Axis parallelism is particularly important to guarantee years of trouble-free service from the rotors. We are therefore moving in areas of higher than 20 µm accuracy for position, and higher than 10 µm in terms of concentricity and angularity."

Pressure to modernise machining

Processing housing units places high demands on the machines. As well as the aforementioned precision, high levels of reliability and large travel paths are required. Not least for the extra-large screw compressors, whose housings have a volume of around a cubic metre and a weight of roughly 1.5 tonnes.

In order ensure economic housing machining for the entire product range, GEA took the decision to make their facility in Berlin state of the art. Since numbers have grown so much recently that part of the production had to be moved out, returning to entirely in-house production should create additional capacity. 

The plan was to replace two ageing horizontal machining centres from the beginning of 2015. This came with the need to dramatically reduce machining times (especially downtimes), to increase machining accuracy and to devote particular attention to high-precision depth machining of holes. A high level of machine availability was also in the list of requirements along with the most up-to-date Siemens 840 D sl controller and a switch to HSK-100 tool holders. "We considered every detail in terms of optimising the machining process", stresses Production Manager Hanno Heim. "Then we thoroughly compared the relevant machines from various manufacturers. This included time studies for a reference component, involving all the necessary machining processes."


Reduction of machining times

HEC 630 Athletic collects the most plus points

After evaluation using a sophisticated points system, GEA managers decided to make their purchase from Starrag Group, a global technological leader in the manufacturing of precision machine tools. A horizontal machining centre HEC 630 Athletic was ordered first, to be followed a few months later by an HEC 800 Athletic for the machining of large parts.

Several factors swayed this decision. For one, the HEC 630 promises a calculated time saving of 36% over their previous machining process. As a comparison, the closest competitors only offered between 30% and 32%. The Heckert machining centre came out on top in the technical machine evaluation, and what's more, previous good experiences made a new partnership with the Starrag Group very appealing.

From a technical point of view, the HEC 630 triumphed with its overall design. Its axle configuration makes it extremely stable: X and Y-axes in the tool, with the Z-axis in the machining table. This is supported by the rigid and thermo-symmetrically designed main components. Together with the digital AC feed drives, the profile rail guides and ball screw spindles (which are mounted with the highest precision in all linear axes) these provide a solid basis for process-safe machining.

Burghardt Krüger, a process engineer involved in machining housing for many years at GEA, was involved in the decision. He emphasises a strength which other manufacturers aren't able to provide: "Starrag Group offers a quill even on its mid-sized 630 and 800 HEC machining centres. For our deep bore holes, this is an enormous advantage. Because it enables us to use short, compact tools which bring high precision and process reliability." The alternative to a quill (125 mm in diameter and 500 mm extension length) is to use long, heavy tools. These are more expensive and also tend to vibrate and bend, increasing the likelihood of machining inaccuracies.

Large working area and convenient swarf collection

Burghardt Krüger also mentioned the working area, another important detail: "With the HEC series, Starrag Group has been successful in significantly increasing the interference range and traversing paths compared to previous models. This means we can go one machine smaller than in the past, which really helps when installation space is limited."

The working area is also designed in such a way that the chips fall freely into the centrally-positioned swarf conveyor. This prevents chips piling up in the work area and endangering process reliability. Krüger also rates the use of fixed plates instead of telescopic covers positively, as this provides optimal protection to the function elements from swarf and coolant. This enables higher accelerations and rapid traverses while reducing maintenance costs.

After the successful benchmark of the HEC 630, GEA decided on a second machine in the same range: an HEC 800 Athletic, which is equipped specially for processing large housings with its extended Z-axis and machining table capable of supporting up to 2.5 tons.


A faster start to series production

The HEC 630 began operating in February 2015, and the HEC 800 in July. Startup went smoothly for both machines. Series production was able to start just days after handover, as the horizontal machining centre specialists from Chemnitz also provided technical support. Part of this was the preparation of the work step sequence for different housings, checking the tools in use, starting the program and finally achieving a good part.

Ronny Kolbe works particularly intensively with the new HEC machining centres. The specialist in production planning and control works together with Burghardt Krüger to create and optimise the CNC programmes run on it. He also mentions another plus point which has already been proven in practice – the tool magazine with 240 slots that can automatically accommodate tools of up to 340 mm in diameter and up to 800 mm in length: "This capacity makes us very flexible and means we don't have to constantly re-tool, even for the smallest series runs. We were also able to reduce clamping operations per housing from three to two." Despite its large tool wealth, the tower magazine requires only a small footprint in comparison to other solutions, which is an important argument in cramped conditions. In addition, tools can be loaded and unloaded during machining time.

The new Siemens 840 D sl controller has gone down well with machining staff. Although a Siemens CNC 840 D was installed in the previous machines, the latest generation allows a much more relaxed way of working, as Ronny Kolbe explains: "The control panel has been redesigned. A large screen and the implemented operating software make work easier and simple to understand with numerous pictograms. The simulation options have also improved significantly. The operators can use Help and service routines for quick fault diagnosis."


Savings of over 40%

The results of the modernisation measures are pleasing: In practice, processing times for housings in the GEA Grasso M series have been reduced by around 45% on the HEC 630. The savings for the XL screw compressors in the GEA Grasso LT range, machined on the HEC 800, are of a similar size. It was proven practical successes such as these which convinced management to replace another machine sooner than planned. In December 2016, the Heckert CWK 1000 made way for a further HEC 800 in the Berlin GEA factory. The shorter processing times not only reduce manufacturing costs. They increase production capacity to such an extent that housing machining previously done externally can now be brought back into their own factory.

The new investment also prepares the Berlin GEA plant well for the future and Industry 4.0. This is why Head of Maintenance, Manuel Marks, is delighted to be looking after the three new machines: "These machines can be monitored remotely with Starrag Connect. This means I can find out about current operating parameters like parts programme, spindle speed, NC block, tool etc. at any time from anywhere with a tablet and an internet connection. If GEA later decides to enhance its manufacturing with further machines from the Starrag Group, these can be integrated easily into the Starrag Connect system. Preventive maintenance is replaced by situation-dependent maintenance, because I can monitor the condition of the machine constantly by means of temperature and vibration sensors. The software detects increasing wear or failing lubrication so that I can respond at exactly the right time." The software also reports faults and error messages, as well as offering direct access to the machine documentation when required. 

GEA company profile

Refrigeration and air-conditioning technology in the GEA Group
GEA is an international technology group specialising in process technology and components for demanding production processes in various end markets. The group employed around 17,000 people globally in 2016, turnover was around 4.5 billion euro, of which more than 70% came from long-term growth in the food industry.
In the field of industrial refrigeration and air conditioning technology, GEA is number 1 in Europe and number 3 worldwide. In many ways, GEA Refrigeration Germany GmbH in Berlin is the centre of excellence for solutions of this type. Screw compressors are primarily manufactured there, then expanded into service-ready units in GEA's German, American and Asian plants, before finally being deployed in the food and chemical industries, in office and storage buildings, or in shipping.

I have been informed that I can withdraw my consent to the processing of my personal data at any time. Withdrawal shall not affect the legality of any data processing already carried out before withdrawing my consent. By providing my consent, I confirm that I am aged 16 years or older. I hereby consent to the processing of my data. I give my consent voluntarily. I know that this declaration of consent will be saved.