Transparency for the purchase of a WATERJET CUTTING SYSTEM
STM Stein-Moser GmbH, Wasserstrahl Schneidsysteme
Transparency for the purchase of a WATERJET CUTTING SYSTEM
To avoid losing your bearings in the jungle of the waterjet market it is necessary to familiarize yourself with the critical parameters which determine quality
The need for education in the technology of waterjet cutting is as great as the level of innovation of the technology itself. The production technology as innovative as it is economical has been burgeoning for years and continuing to expand into more and more industrial sectors. However this rapid development has resulted in transparency falling by the wayside: Many entrepreneurs are prepared to invest in a waterjet cutting system but give up in the face of the multitude of solutions on offer. The Austrian specialists and waterjet pioneers STM now help first-time users to focus their attention on the essentials. Irrespective of manufacturer and industrial sector, with the 10 most-important criteria the long-established company provides a solid basis for taking decisions which will ensure that an introduction of waterjet cutting is successful.
As far as the execution is concerned it is imperative that the machine is an easy to load, compact and strong construction. It makes sense to have
a wear-resistant cutting tank in aluminium or stainless steel with stainless-steel screws. Care should be taken to select the highest available quality of materials since even stainless steel can corrode. The side walls should be flat and the linear guides concealed. The best choice is for a system without bellows which become porous over time by contact with the abrasive sand. Ideally the high-pressure pipe should be fed through the axles to save space, a principle of design which simplifies loading and unloading for transportation. In addition the complete system should be designed for maximum process reliability and energy efficiency. On the whole portal systems are easy to maintain, uncomplicated to move and are distinguished by a good cost/performance ratio.
As far as control is concerned an all-digital drive train with controllers and AC servo motors is an absolute essential. It should be capable of processing cutting data in downloading mode to enable even very large CNC files to be sent to the control without problems. Equally important is a simultaneous plain-text error log. Furthermore care should be taken to ensure that the
Z-axis has sufficient lift and that an integral positioning laser as well as an automatic height sensor with intermediate stroke and collision protection are provided. This is the only basis which provides equal levels of precision and process reliability.
A user-friendly MS Windows-based program is an absolute must. The software must provide a functional and easily manageable graphics module as well as a comprehensive cutting program. Important parameters of the cutting program are the continuously variable setting of cutting pressure and abrasives quantity from zero to maximum, various approach strategies, an extensive list of materials with preset cutting pressures and abrasives quantities as well as an automatic tool adjustment. Care should be taken to ensure that retrofit extras such as a drill spindle can be fully integrated into the software and also operated by it. The software should provide fully automatic operation of the system with a minimum expenditure for training and installation. The pre-installation of remote maintenance software on the system computer is also an important criterion.
4. High pressure pump
The high pressure pump is the heart of the waterjet system and not only has to fulfil the highest demands on quality but must also provide economical operation. A high pressure pump for waterjet cutting usually provides
a performance of 3.8 l per minute at 3800 bars. Thus either one 0.35 mm water nozzle or two 0.25 mm water nozzles can be operated. The connected load should be as low as possible at approx. 37 kW for this capability. In addition the high pressure pump should be equipped with a certified pressure tank of 2.5 litres capacity to ensure a constant high pressure. A pre-boosting pump makes sense to ensure that a constant input water pressure of at least 3 bars is maintained. The pressure must be reducible to 150 bars for drilling starting holes. Furthermore remote activation via the cutting software should be possible and automatic switching off after cutting or in case of defects. Finally a good high pressure pump should also be fitted with a pressure relief valve to relieve the high pressure system when the machine is shut down, a noise protection hood and an oil/air blast cooler as well as the necessary assembly tools. It is also important that the high pressure pump be easy to maintain and that no complicated assembly tools are required. In addition, wear resistant seals are of fundamental importance for economical operation.
Savings are often made on the components. It is therefore worthwhile to "take a look behind the scenes". To ensure defect-free operation all components should be from approved manufacturers with suitable guarantee provisions. Above all reacquisition of spare parts using branded components is simple and reliable. Furthermore it must also be possible to retroactively improve or convert the system. Examples in this respect are an automatic abrasives flushing system, a drill spindle or a swivel head.
6. Energy efficiency
Waterjet cutting can be extremely economical as long as attention is given to the crucial parameters when a system is purchased. In particular the connected load and the capacity of the high pressure pump must be in an optimum relationship to each other. The connected load should be as low as possible in relation to the capacity. The high pressure pump should switch off automatically in idle mode. Other components such as the abrasives metering system as well as cooling and control and in fact the design of the complete system itself should be tuned for energy efficiency. The best way is to have the manufacturer work out the operating costs for one's own requirements then more often than not this is what separates the wheat from the chaff.
7. Spare parts
The appropriate tools for changing wear parts on the pump and cutting head should also be included as part of a waterjet cutting system. Spares packages for the cutting head, abrasives head as well as seals and spare parts for pressure intensifier and non-return valve should be included within the scope of supply. An operating resources starter kit for the first hours of cutting and consisting of focussing tubes, water jets and last but not least abrasive sand should also be included in the purchase price. All wear parts should be readily available and easily obtainable from the manufacturer at reasonable prices. Worldwide there are only 2 reputable manufacturers of high quality focussing tubes and only approx. 4 producers of water nozzles. By using operating resources of proven quality operating costs are reduced in the long term. Furthermore reacquisition of standard spare parts is straightforward.
A machine only functions perfectly when it is operated properly. Even if operating is on the whole simple one should insist on intensive training for the designated operators. As well as instruction in operating the machine this includes essential maintenance work and the replacement of wear and spare parts on the waterjet system as well as on the high pressure pump. The training is best scheduled to take place immediately before the machine is supplied. A few weeks after supply and installation of the waterjet cutting machine the supplier should commence after sales support in the form of
a short meeting for debriefing and if necessary refresher training on site.
As always good teamwork and close contact with the manufacturer are decisive for economic success. One should make certain that all documentation for the machine is supplied in the relevant national language and that the after sales service is of an acceptable standard. Should technical defects occur factory engineers must be available within the shortest possible time and at fair conditions in the event that the defect cannot be rectified via the remote maintenance system. The hourly rate for engineers should be made clear as part of the quotation. Shipping, installation and commissioning by the manufacturer should be included in the purchase price.
The manufacturer should be able to guarantee the quality of its systems and be happy to do so. A guarantee is therefore a reliable indicator of good quality. One can expect a guarantee of a maximum of two years or 4000 hours. In addition it is important that individual components are also covered by a guarantee. That is usually only the case for branded products. Furthermore, serial products are usually better developed than bespoke manufactured products and also a guarantee for reliable operation.
It is self-evident that the Austrian waterjet specialists STM have been consistent in matching their complete range to meet these ten decisive parameters. The individual advantages for prospective customers can be demonstrated at any time without obligation at the company's headquarters in Bischofshofen. Not only are cost-benefit analyses created here but free test cutting or test equipment for a customer's own manufacturing location are part of the company's service. Visitors to the trade fair "Schweissen & Schneiden" can experience the technology in action from 14/09 - 19/09/2009 in Essen, Germany. So if you want to be absolutely certain about your decision you should not be content with less transparency concerning performance.
STM is a leading provider of waterjet cutting systems with its head office in Bischofshofen, Austria. For more than 20 years, the traditional company has developed future-proof production solutions, primarily for the steel, aluminium, metal, plastic, stone and glass industries, which are most notable for their efficiency, ease of use and resistance to wear. Alongside future-proof technology and quality as standard, STM places great emphasis on innovative full service. In so doing, the brand name manufacturer ensures that its individual manufacturing processes are continually matched to the current requirements of its customers. STM cooperates with the German, Schweinfurt-based company, Maximator JET GmbH, in the fields of development and sales. Maximator Jet chooses STM systems for their reliability and quality.
Stein-Moser GmbH I Salzburger Straße 77 I 5500 Bischofshofen I Austria I Phone +43. (0) 6462. 30 30 0 I Fax +43. (0) 6462. 30 30 5 I email@example.com I www.stm.at
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