transportation

Higher productivity with flexible manufacturing

Pump and compressor manufacturer CVS invested in a flexible manufacturing system with two horizontal machining centres HEC 630 Athletic from Heckert and a Schuler pallet system. The success of this investment is reflected in significantly reduced setup and processing times when machining cast iron components in small batch sizes. Furthermore, the quality of the components has also improved.

“We are investing in the future ...“

CVS Engineering GmbH develops, produces and distributes vacuum pumps for suction vehicles as used, for example, in sewer cleaning. Their product range also includes compressors for silo vehicles, with which media such as plastic granules or building materials can be discharged. Compressors for tanker trucks, and pneumatic systems for trams, commuter and local trains also belong to the business segments of the company from Rheinfelden, Germany.

Since it was established in 2006, when CVS started with 30 employees, the company has developed very successfully, as General Manager and Head of Production Uwe Schröter reports: “Today we have 57 employees and an annual turnover of around 14 million euros. Our success is primarily due to our employees, who already brought a wealth of experience in the compressor and vacuum pump-world with them when the company was founded.”

This enabled CVS to capture about 70 % of the German market for vacuumsuction vehicles within just a few years, making it the clear market leader. As a supplier of oil-free screw compressors for silo vehicles, the company is now the number two in Germany. The Rheinfelden pump and compressor manufacturers also have a strong international presence.

The early days were anything but easy, despite all the experienced staff. The available capital had to be used to the very best effect. For manufacturing, this meant falling back on tried and trusted used machines to begin with. Head of Production Schröter explains: “We manufacture the main components of the pumps and compressors ourselves. For this we need high-performance machining centres, but also machines for processing small parts and for special machining, such as for honing. Our machine park has enabled us to produce at a high quality, while still being able to respond to special customer requests. “This demands high flexibility, particularly when considering the delivery times. According to Uwe Schröter, the range of delivery dates requested by suction vehicles customers is between one day and four weeks. For silo vehicles, the time span is a maximum of just two weeks, then the compressors – usually between five and ten per order – need to be ready for delivery.

Flexible manufacturing system for higher productivity

In recent years, economic conditions have deteriorated. New product developments have also made modernised production, that can act more quickly and flexibly, a must at CVS. At the beginning of 2011, a team of employees headed by Andreas Marterer, who is primarily responsible for work preparation, took over the task of rethinking the entire manufacturing and assembly process and re-planning it according to modern criteria – including investing in innovative machines and automation equipment.

Two machining centres linked via a linear pallet system were to form the core element of the new flexible manufacturing. At the EMO 2011, the responsible CVS team visited a variety of machine tool manufacturers and obtained detailed information on relevant cutting solutions. Head of Production Schröter was surprised by the result: “Most manufacturers back then, especially suppliers from the Far East, had focused on fast, light machining, as required particularly in the automotive industry. For a medium-sized company like ours that conducts heavy-duty cutting in small batches, the range of offers was rather small, so we only shortlisted two suppliers.”

Andreas Marterer defines the necessary cutting operations more closely: “We machine housings for compressors, valves and gearboxes, their corresponding covers and flanges, oil containers and the like - usually in batches of less than 30 units. 75 % of the parts are made of cast iron and 20% of aluminium. The remaining ones are made of other materials.” For cast iron processing in particular, the machining centres require maximum performance. “In our company, drill-finishing pump housings is the core operation. We use this type of machining for all bearings and housing bores, starting at a diameter of 30 mm up to 520 mm. For this we need a strong spindle that has to provide a torque of at least 900 Nm.” Another key requirement was a tool magazine with more than 200 pockets and a changer that can also cope with large tools weighing up to 30 kg and more than 450 mm in length.

Rigid machine design and generous work space

CVS decided to invest in two identically constructed HEC 630 Athletic horizontal machining centres from Heckert. “The 630 model pallet size corresponds to our preceding machines. While that is a bit tight, the available space in the production hall doesn’t permit any larger machines.” The comfortable working environment of the Heckert HEC 630 Athletic was all the more decisive. It enables a workpiece swing diameter of 1,550 mm, and a maximum workpiece height of 1,250 mm. “We have enough space for retracting and for table rotation, even with our large parts. What’s more, enough leeway remains for larger work pieces, which addresses the general trend with pumps”, says Uwe Schröter.

The casting bed and thermo-symmetrical machine construction with its high rigidity also scored points for the Heckert horizontal machining centre. These factors are a fundamental requirement for progressive cutting performance and high precision. Profile rail guides in all linear axes, pre-clamped guide carriages and ball screws with counter bearing ensure accuracy is maintained over a long period. The steep workspace cover and the wide, centrally arranged chip conveyor contribute to the safe and rapid removal of even large quantities of chips – as well as the associated heat.

Modular system enables optimal machine configuration

50 % lower setup times

As the HEC centres have a modular design, CVS was able to choose an optimal solution with respect to the work spindle and tool magazine. “We decided on the powerful 78 kW gear spindle”, Andreas Marterer explains. “It provides up to 1,500 Nm of torque at 25% c.d.f. and covers a speed range of 20-7,500 rpm. This gives us a buffer for even more intensive processing power.”

The tools and their handling were an important part of the specifications: In order to achieve high flexibility andreduce setup requirements, the magazine should provide space for all the necessary tools, including the particularly large and heavy ones.

CVS, therefore, decided on a tower magazine with a total of 240 pockets. It can even accommodate tools of up to 800 mm in length and 340 mm in diameter (bridge tools up to 520 mm), weighing up to 50 kg individual weight. This also poses no problem for the tool changer. The user-friendly magazine can be retooled during running time and saves space with its slim, tall design.

“The alternative machine tool we looked at from another supplier would have required various special modifications in respect of tool handling, whereas the HEC 630 Athletic already fulfilled all our needs in the standard version”, says the delighted Team Leader Marterer.

In addition to the two Heckert HEC 630 Athletics, the Schuler LoadMaster Compact 1,400 pallet system with two setup facilities and 33 shelf positions on three levels is an important component of the new production concept. “After all, we are investing in the future, and this includes flexible manufacturing with some degree of automation”, says Uwe Schröter about their investment. “The Schuler system offered us optimum use of the space available and flexible design of the setup facilities, which are loaded by crane.”

Bottom line:Time savings and improved quality

10 % lower processing times

The restructuring took place in 2014 without disrupting production. This was achieved by first exchanging one machine and taking the pallet system into operation. Six months later, the second machine followed. Andreas Marterer is full of praise: “The scheduling and indeed the entire cooperation with Heckert and Schuler worked perfectly.” Their experience so far with the new production plant has also been very positive, as production manager Schröter confirms. “We are currently using them in operator-controlled two-shift operation. If necessary, we will introduce an unmanned third shift. But first it is still necessary to optimise downstream processes right through to the assembly.”

As far as machining is concerned, the goals have been met. Setup times have decreased by 50% and the processing times on the HEC 630 Athletic are around 10% lower than before. Planning Engineer Marterer is particularly pleased that he was largely able to take over the existing tools and programs as they stood.

In addition to the time saving, the new production plant also resulted in improved processing quality. For example, with the HEC 630 Athletic, CVS effortlessly achieves the position tolerances of 0.04 mm required for screw compressors. Bore tolerances in the range of IT6 are also complied with, as is the necessary surface roughness of Rz = 6 μm. Uwe Schröter explains: “We subject our components to regular quality control. We inspect the critical dimensions of every fifth screw compressor, for example. Here we observed a trend towards a significant improvement compared to our previous production.”

We use cookies to ensure the proper functioning of our website. For an improved visit experience we use analysis products. These are used when you agree with 'Statistics'. Privacy statement