Electroerosion

The main characteristics of EDM machining are:

• – Possibility to work very hard metals (special steels, fast steels, hard metals, etc …), or hardened with thermal or chemical treatments (hardened, carburized, etc …). In fact, the hardness of the material to be processed slows down the erosion speed for the same energy used, but unlike conventional techniques, it does not require that the tool (negative or wire) have a greater hardness and mechanical strength than the processed material.
• – Possibility of making cuts and cavities, impossible for conventional techniques.
• – Lower processing speed compared to other chip removal technologies.
• – High relative tool wear. A typical value can be 1-5%; i.e. the wear of 1-5 mm3 of tool per 100 mm3 of material removed.
• – More or less pronounced roughness, depending on finishing degree, of the worked surfaces. This is due to the creation of micro-craters due to the electro-erosive action.

The removal therefore takes place by electrical discharges and there are mainly two subsets of EDM techniques.

1) Plunge spark erosion EDM
In this application, the processing has as main purpose to work the piece making it assume a complementary shape compared  to electrode.
The processing cycle is divided in two phases:
– creation of an electrode with a ‘negative’ shape with respect to the needed shape;
– EDM of the piece with the electrode previously created, obtaining the needed shape in ‘positive’.

2) Wire EDM
In this application, a tight conductor wire is used as electrode to cut or profile the working piece.
The wire (stored in a reel) is continuously changed during the processing, since, being subjected to the wear of the discharges and to the stress of expansion, it would break frequently, interrupting the processing.

Depending on the type of production and processing required, it is presumed that particular types of pollutants will arise during the processing of the EDM and consequently a suitable AR Filtrazioni air purifier has to be used.

The air pollutant that all EDM techniques have in common is fume.
The main causes are however attributable to the sum of these factors: the evaporation/combustion of the liquid coolant  with production of fumes and odours in the workshop.

The problem of fume exhalation and smells not treated.

The volatility of polluting particles such as fumes,exhalations and odors entails and creates various problems in the workshops, to operators and machine tools.

Firstly they negatively affect the health of the air and the health and hygiene conditions of the operators, in particular at the respiratory level, since the particles smaller than 0.3 microns can reach the pulmonary alveoli, compromising the respiratory tract. Not only that, in contact with the epidermis they create skin irritations, dermatitis and redness.

From production point, pollution in the workshop considerably reduces the productivity of the plant and in particular the efficiency of the machine tools, since the stratification of pollutants invalidates the precision and tolerance of the measuring instruments, with the onerous consequence of having to increase maintenance on the most delicate components.

Without forgetting any possible fines deriving from current regulations, which impose a concentration limit for oily mists in the workplace.

The best system for the abatement of fumes, exhalations and odors is an active carbon stage preceded by a very high efficiency pre-filtration H13 / 14.