Compressed Air in the Machine Engineering Industry

Respiratory Air

Many production areas include tasks executed in the area of dust, paints and other - much more dangerous - substances. In such cases it is applicable that the employee executing the task is protected against aerosols and fine dust and corresponding health hazards. The people will be supplied with breathing gas via a respiratory protective device or must even, like astronauts, wear totally sealed protective suits. In order to save space, compressed air is often stored in bottles - utilising respiratory air compressors. The compressed air must comply with high purity criteria for use as respiratory gas. The individual limiting values with regard to residual oil content and degree of drying are specified in DIN EN 12021.

Cooling and heating air

Cooling and heating with compressed air is executed by utilising a so-called vortex tube, in which gases are separated through rotation in hot and cold air flows. The gases then subsequently exit according to their temperature condition through different sized holes.

If compressed air is also available in the works, then it is advisable to use it for this application since it is a very cost-effective solution. Compressed air is, for example, therefore advisable within the framework of metal cutting for the cooling of a drilling or turning machine, since the otherwise necessary cleaning of the adhering liquid refrigerant is no longer necessary.

Sealing gas / Inert gas

Compressed air can be utilised for contact-free sealing of plants, systems and jigs: The cavity will be sealed without friction and wear by utilising compressed air. Particularly in mechanical engineering, especially sensitive components and surfaces must be protected against dust, dirt, humidity or moisture. This is performed by creating a so-called air curtain above the surfaces.

Compressed air can also be utilised for inspecting seals and leaks.

Surface treatment: Compressed air blasting and painting

Compressed air can be utilised for applying abrasives and atomising colours within the context of surface treatments:

Compressed air blasting and/or grit blasting is the description for the surface treatment of a material or workpiece (blast quality) due to the effects of an abrasive agent. Sand is used as an abrasive agent against rust, dirt, colour, scale and other contamination or for surface design via matting.

Care must be taken when painting with compressed air to guarantee a high level of purity class and the limiting values with regard to particles, oil aerosol and oil vapour, silicone containing materials as well as condensate are complied with. Furthermore, no paint-wetting impairment substances (PWIS) may occur.

3D printing

Additive manufacturing and 3D printing are becoming more and more important in mechanical engineering – not only for the preparation of prototypes but also as a serious, supplementary manufacturing technology. There are fields of application for 3D printing or additive manufacturing in many other industries, too, such as in plastic and metal production.

There are different methods and approaches used in the field of 3D printing to manufacture three-dimensioning objects. However, compressed air is not required for all of these. Compressed air is used for the laser methods (SLS and SLM) for example. With these processes, compressed air is routed through a generator to produce nitrogen at low cost. The inert gas gained in this way is pressed into the work chamber to protect the printed material from oxidation.

In addition, almost all 3D printers require a certain amount of post-processing, with considerable deviations possible between the respective procedure and the effort involved. Sometimes, it is enough just to remove residual powder using compressed air and to submerse the component in water; in other cases more complex procedures such as the separation of polymer support structures is necessary.

An important aspect that is often overlooked is the influence of compressed air on product quality and as a reason for downtimes. Because particles, humidity and oil vapour in the compressed air can interfere with the printing process and influence product quality.