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Graphic element Research > Growth > Research projects > Products & processes projects > Smaller jets for cleaner cuts at lower cost
Graphic element Smaller jets for cleaner cuts at lower cost
    04/02/2002
 

High-pressure water jets containing grit have long been used for heavy duty cleaning and cutting in applications such as descaling large oil pipes and decommissioning offshore platforms. The abrasive water injection jetting (AWIJ) technique has been further developed to much smaller cutting tasks in a CRAFT project under the BRITE-EURAM Industrial and Materials Technologies programme. The project was based at Böhler Hochdrucktechnik and the Institut für Werkstoffkunde (IW) at the University of Hanover. SME partners in the two-year project developed a smaller abrasive water jet, through careful examination of the parameters of the cutting head, and opened up a wide range of new applications.

Instead of just smashing through concrete and heavy grade steel, abrasive cutting can now be applied to finer materials such as ceramics, composites and thin magnetic steel. The key to this improvement was the redesign of the cutting head, which mixes water and fine sand and ejects it in a high-velocity stream.

Developing the cutting head
 

If the focussing tube in the abrasive system is miniaturised, the cutting head has to be completely redesigned. The project at IW began by investigating the essential parameters that determined the cutting dimensions of the head. The abrasive material had to have a small grain size for a finer cut, but this gives a 'stickier' mixture with greater adhesive forces. To overcome this problem, the teams developed a special dosing unit for the abrasive and a forced feeding mechanism. Following studies on optimising the geometric parameters, a prototype small abrasive cutting head was developed.

One important requirement was to keep the cost of the new unit as low as possible to give it a competitive market position. The solution was a pre-aligned cutting head that was easier to put on stream and to manufacture than the conventional manually adjustable type. The prototype head was qualified in terms of efficiency and quality of cut, and then tested for precision in a complete cutting system. This included a new multi-axis handling system, designed to make the smaller system easier to use.

 
Accurate and versatile cutting
 

The different partners in the project produced various tasks for the new cutting heads to accomplish. The reference material was 10 mm of aluminium, which was used to evaluate the field conditions. But they found that the heads could also make fine cuts in composite materials, thin magnetic metal sheets, thick plastics and ceramics. The quality of the cutting was impressive. The width of the cut could be reduced to less than 0.3 mm, whereas 0.6 mm was the best previously achievable. These results mean that it is safe to cut more expensive and sensitive materials with the new heads.

Moreover, the surface of the cut was much smoother that the one normally obtained by abrasive cutting. The redesign meant that the cutting was also speeded up with reference to the use of hydraulic power and abrasive material, so that small AWIJs have much higher productivity than their predecessors. Small heads use less water and energy - about a quarter of the amount - and only 8% of the amount of abrasive material, compared with the conventional kind. There is a resultant rise in efficiency of 36%.

 
Competitive efficiency
 

Small AWIJs also compare well with different methods of making fine cuts in more expensive materials. The competing methods are laser cutting and wire electric discharge machining (EDM). Abrasive jets have a higher cutting performance than wire EDM and are more powerful than Excimer lasers, the only ones that can deliver a cut of 0.3 mm or less.

Additionally they allow the processing of advanced non-metallic materials of high strength or wear resistance, such as reinforced plastics and ceramic materials. Cutting the thin magnetic steel sheets used in transformers and electric motors is a unique application, as abrasive jetting is the only method that does not affect the magnetic properties of the steel. This saves a further stage in the manufacturing process.

Water jetting is also environmentally benign in comparison with other cutting methods. It uses natural materials, water and sand, that do not have to be manufactured and can be recycled or disposed of without risk. It is relatively quiet, and produces no gaseous pollutants, harmful aerosols or greenhouse gases.

 
Exceptionally good results
 

The exceptionally good results of the test programme give the new head great promise of success. The results of the project will significantly strengthen the competitiveness of the participating European companies, manufacturers and users.

The lead industrial contractor in the two-year project, Böhler Hochdrucktechnik of Kapfenberg, Austria, is already putting the miniature abrasive water injection jet head on the market. And the various SME members of the project - manufacturers of components for abrasive water jet technology, such as cutting heads, nozzles or ceramic products, and users of abrasive water jets - are developing further novel applications for the new head.

 
Developing the cutting head
Accurate and versatile cutting
Competitive efficiency
Exceptionally good results
   

Key data

Improving efficiency of production technologies is an important element of the Innovative products, processes and organisation key action. This CRAFT project aimed at extend the range of the non-polluting cutting method, abrasive water jetting, by miniaturising its components.

Projects

Small abrasive water jets open new applications (BRST985492)

     

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