VOL. 14 November ISSUE YEAR 2013
in Vol. 14 - November Issue - Year 2013
Success Is In The Air
Machine design checking phase
Compressed air shot peening machine
Nozzle setup simulation and study
Shot peening as a method to enhance the fatigue-resistance characteristics of materials has become a well-established trend for years. The specialisation of such a treatment is in continuous evolution: just think of how different prosthetic components that are typical of the biomedical sector are from aerospace components or from cogwheels, typical of the automotive sector, or even from moulds for light alloy die-casting.
The above-mentioned are just a few examples, far from being exhaustive, to describe what must be now considered right and proper "surface engineering". It is moreover clear that speaking of quality in such an ambit is a matter of primary importance. The attention that the market has been showing for quite some time about quality is constantly growing.
It is a trend that came to life many years ago and in some markets, it developed in a particular way, so much so that specific approaches to specific sectors have been developed. Two typical cases, with profound different approaches are for example, the aerospace sector and the automotive one. The former, characterized by relatively small production volumes, focused complete attention on products, to such an extent as to get to the serialization of the parts and total control of every single production piece.
It is quite evident that even the single failure, in the aerospace ambit, could bring about catastrophic consequences involving the loss of human lives. The economic cost deriving from research of the maximum possible quality is perfectly compatible with the level of risk and the entity of the associated risk. On the opposite end is the automotive sector. In this sector, the recall of defective components can become financially unsustainable for the manufacturers.
The massive production volumes that characterize this sector leave significant space for control of statistical areas only; hence, the problem passes from the product to the process. In fact, statistical controls on products are effective exclusively if the processes are perfectly under control. The control on a limited number of parts of a production lot takes on real statistical meaning only if the lot is reasonably homogeneous or at least with similar characteristics.
Machine tools and production plants must hence generate always better and repetitive processes in order to get higher and higher reliability. Shot peening, being a "special process" that enhances the characteristics of fatigue resistance of the metallic components, is surely one of the first that must follow such a trend. Nonetheless, the massive production volumes require, in addition, maintenance of very high attention on the production costs, and for this reason, it is quite usual to see, in such a sector, shot peening lines made of wheel machines.
In the aerospace field, as already underlined, research of performance and reliability inevitably lead to the only possible direction: compressed air machines. On the other hand, lower energy and plant costs of wheel machines have become widespread in the automotive sector, so much so that until a few years ago, the two positions were almost irreconcilable: high volume by wheel machines and high quality by compressed air ones.
Today, compressed air technology has evolved, becoming much more competitive from an economic point of view than it was in the past, while maintaining at the same time the highest possible quality characteristics. The modern compressed air plant can be equipped with high efficiency nozzles that significantly reduce noise emissions and energetic costs; furthermore, nozzles have negligible wear and costs of maintenance and consumables are extremely reduced. The set-up of a compressed air machine, traditionally considered very complex, can be incredibly simplified by means of studies and computer simulations that allow the grouping of similar components by "families" that can be thus treated under the same working conditions.
Compressed air machines are extremely flexible and can easily be set or converted to production processes even very different from the one(s) for which it was initially prepared. Flexibility of a production plant is a very high value characteristic, especially in an extremely fickle market like the current one.
Norblast was established in 1977 as a manufacturer of compressed air-peening and sandblasting machines. In those years, surface finishing was considered just little more than a "make-up" treatment. Potentialities of surface treatments were not yet understood. The Company firmly believed that finishing could become a real technological treatment and decided to invest in research.
In the following years, research expanded and investigated shot-peening treatment as well, which has developed through a dedicated company branch. Today, that company branch has become Peen Service, a real centre of research and development in shot peening. With over 35 years of experience and 6000 plants sold worldwide, Norblast has covered the major part of the industrial sectors. The Company offers a wide range of solutions, from the ones designed through a modular logic that are able to adapt to specific technological needs, up to the most particular cases, entirely designed ad-hoc.
The most renowned market leaders in fields such as Automotive, Aeronautics, Energy and Biomedical to name just a few, have adopted totally customized technological solutions that start from the analysis of the single specific product up to the definition of the plant placement layout inside the customers' factories. The control software can be totally customized as well, from the operator interface to the control of every single working parameter.
Norblast's plants adopt compressed air technology. This allows the rigorous control of all the process characteristics such as working pressure, hot-spot localization, impingement angle, media-size and shape, transverse and rotation speed of the several motions, etc. Norblast's machines are the result of the collaboration with Peen Service, the shot-peening job shop subsidiary, and of its direct in-field experience. They are designed according to the most modern criteria of ergonomics, energy saving, strength, and lasting ability. Low-energy consumption components and special wear-resistant materials, specifically studied for such applications, are used.
One Customized Solution
One of the last carried-out projects has seen, as a protagonist, a company leader in transmissions and gears in the naval field - a very sensitive sector, and extremely focused on the reliability of its products. A company that is traditionally linked to the world of shot-peening wheel machines will understand and appreciate the added value brought in by compressed air technology: a not-at-all simple task carried out with success bearing in mind all the requirements, from the obvious technical and quality items to the production and environmental ones.
These requirements posit a totally robotic plant that enables the operator to have every working parameter under control with great flexibility and ease of use, whether it is a single piece, many lots with a few pieces, or large production runs. The autoloader, specifically designed to totally eliminate the need to setup with standard piece-handle "shuttles", perfectly matches ergonomic and energy requirements ensuring working autonomies up to several tens of minutes without need of intervention of the operator.
A concrete aid to programming allows binding of the position of the shot-peening nozzles to the dimension of the piece to be treated through a dedicated algorithm. All this is aimed at achieving the maximum possible simplification of the machine set-up, whilst ensuring the uniformity of the intensity of shot peening disengaged from the particular geometry of the parts to be treated.
The real strength of this type of plant is the repeatability of the process that, in the interests of quality control, allows knowing the exact technological history of every single part. The software is designed entirely ad-hoc and enables the operator to manage the technical system in a global manner: from the total control of the nozzles to the shot intensity, from the control of status on every single piece up to advanced reporting.
Easy and immediate maintenance is a feature thanks to the use of high-resistance materials: pneumatic hoses, seals and wear-resistant coatings. As always, also in this plant, much attention has been paid to ergonomics and safety in all its forms: ease of programming and care in detail; ample spaces reserved to the operator in order to load and unload pieces, and main working cycle start commands located in a convenient and intuitive position. The main control panel has been "remoted" in order to facilitate the operation during the generation of the work program, so that it can be followed by the technician during all programming operations. Great attention has also been paid to acoustic compatibility with the work environment. The modern sound-absorbing materials allow the reaching of extremely high intensity of shot peening, even over 20 Almen A, with very low noise emissions.
Barriers that used to divide the two worlds of wheel and compressed air machines have become just cultural barriers today. Success is in the air.