Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

Environmental Hazards of Nontraditional

H. El-Hofy and H. Youssef Production Engineering Department Faculty of Engineering, Alexandria University EGYPT [email protected], [email protected]

Abstract: - This paper discusses the environmental impacts generated by some nontraditional machining processes. For each case the mechanism of material removal is explained. Sources of hazards are discussed. Environmental impacts on the workers, machines, air, soil, are discussed. Safety and environmental precautions are also considered

Key-Words: - Nontraditional machining (NTM), chemical, electrochemical machining (ECM) , thermal, ultrasonic machining (USM), laser beam machining (LBM), jet machining (AJM), health hazards

1 Introduction not lead to environmental hazards of a different The increasing sensitivity to environment and nature. Most machining processes uses health issues is reflected in the increasing chemicals and liquids in different as shown in stringent legislations and national and Table 1. Most of machining liquids come from international standards. Scientists and engineers petroleum which is toxic to environment and developed new and alternative manufacturing difficult to dispose. These chemicals can be technologies [1]. Machining processes generate transported by a variety of agents and in a solid, liquid or gaseous by-products that present variety of forms which are defined by Hughes et hazards for workers, machine, and the al [3]. Hazardous substances cause ill health to environment. It is appropriate to understand the people at work. These are classified according environmental hazards created by the NTM to their severity and type of hazard which they processes and analyze their impacts on the may present to the workers. The effect of the environment. These hazards can be considered hazards may be acute of short duration and within acceptable limits through the following appear fairly rapidly, or a chronic one caused by steps: prolonged or repeated exposures to hazardous • Reduction of emissions to air, water, and substances resulting from the machining land. processes. • Compliance with relevant legislations • Pollution prevention. 2 Nontraditional Machining Processes • Efficient use of energy. NTM processes generate solid, liquid or gaseous by-products that cause hazards for the In order to improve the quality of the machining workers, environment, and the equipment [4]. In processes, it is essential to adopt innovative this paper, the sort and level of the hazardous methods that achieve the minimum substances for the NTM methods are discussed. environmental contamination through the Table 2 summarizes the possible hazards of application of near net shape technology that machining processes. reduces machining allowance, volumes of cutting fluids, and provides lower power 2.1 Chemical Machining (CHM) requirements. One of the possibilities for CHM, Figure 1, depends on chemical acids that minimizing environmental contamination is to have severe effects on the surrounding implement dry or machining [2] or replace the environment, difficulties in handling and conventional processes with alternative ones storage, and damaging effect on different (rapid prototyping, laser machining, new cutting materials.. The acidity of an etchant dissolved in tool materials,.. etc). These new technologies do water is commonly measured by the pH

ISSN: 1790-5095 140 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

number. Solutions with pH values of less than 7 contaminated due to alkalinity and at pH 10 to are described as being acidic. Acid deposition 12 it may be classified as heavily contaminated. attacks structures that are made from and Aerosols of solid (Nitrogen and sulfuric oxides) fading paint on machine tools. Chemical acids or liquid corrosive substances are air pollutants, also cause significant corrosion of metals. and so form corrosive gases. These gases may Photochemical machining (PCM) is carried out combine with water to form acids which with aqueous solutions of ferric chloride FeCl3, precipitate with rain. Acid gases and acid used at temperatures over 50 °C. FeCl3 is acidic, fumes damage plants. relatively cheap, and readily available, and versatile. Environmentally, it is attractive as it is 2.2 Electrochemical Machining (ECM) of low toxicity and relatively easy to filter, ECM, Figure 2 is known as an environmental replenish and recycle. During CHM, exposure polluting process. Hazards of ECM include: to hafnium (Hf) occurs through inhalation, ingestion, and eye or skin contact. CHM Hydrogen gas: Explosive hydrogen gas is hazards depend on the properties of the generated during the electrolyzing process - - substance, the concentration, and time of H2O + 2e ==> H2 + 2OH contact with acids and alkalis. The impacts of Fe + 2H2O ==> Fe(OH)2 + H2 CHM include the following: Local exhaust must be provided to prevent the hydrogen gas from reaching its lower Labor: CHM causes health effects on labor flammability limit and remove the mists from which include: the workers breathing zone. • Irritation Electrolyte splash: Electrolytes are aqueous • Corrosive injuries and burns solutions of sodium chloride, sodium nitrate, • Rapid, severe, and often irreversible and other salts that become insoluble damage of the eyes hydroxides that deposit out of the solution as a • Risk of larynx and lung cancer sludge. Skin contact with the electrolyte Machine: Many metals are often affected by contents must be controlled by good work corrosion of many types that include localized practices. The door/cover shall be interlocked attack and uniform corrosion. Traditionally, with the electrolyte supply system and the covering materials (e.g. paints) has been used to machining process should not be started when protect iron and steel from rusting.. Poor surface the interlock of the safeguarding device is preparation is the prime cause of protective opened. coating failure. Chromate: Exposure to trivalent chromium Environment: Improper disposal of CHM compounds occurs through inhalation, etchants changes the level of acidity and ingestion, and eye or skin contact. This affects alkalinity affect the flora and fauna in soil and the skin, liver, and kidneys in humans and water. The change of pH from 7 (neutral water) causes contact dermatitis. has an adverse effect on aquatic life. At pH 6 Nitrate: Nitrates and nitrites are known to cause crustaceans and mollusks start to disappear and several health effects such as: moss increases. At pH 5.5, some fish such as • Reactions with hemoglobin in blood salmon, trout, and whitefish start to and • Decreased functioning of the thyroid salamander eggs fail to hatch. Acidity of pH 4 gland has a lethal effect on crickets and frogs. Some • Shortages of vitamin A alkalis such as ammonia also have an acute • Fashioning of nitrosamines, which a toxic effect on fish. common causes of cancer (nitrates and nitrites) Soil: It is classified as contaminated when, due Methods that is effective in controlling worker to acidity, it has a pH value of 4 to 5 and exposures to nitrogen and trivalent chromium heavily contaminated when the pH is 2 to 4. include the use of process enclosure, local When soil has a pH value of 9 to 10 it is

ISSN: 1790-5095 141 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

exhaust ventilation, general dilution ventilation, nitrous oxide, ozone, and harmful aerosols are and personal protective equipment formed. There is an increasing demand for exploring methods that reduce or eliminate the 2.3 Electrodischarge Machining (EDM) adverse effect of the working fluid dielectric of During EDM the work material is removed by a EDM. series of sparks that occur in the dielectric liquid filling the gap between the tool-electrode Due to erosion of the and tool and workpiece, Figure 3. EDM has several electrodes, inorganic substances such as hazard potentials which are: tungsten carbide, carbide, chromium, • Hazardous smoke, vapors, and aerosols nickel, molybdenum, and barium are released • Decomposition products and heavy and condensate in the air. Emissions of organic metals materials are generated by the vaporization of • Hydrocarbon dielectrics affect the skin. the dielectrics. Additionally, the rising smoke • Sharp-edge metallic particles damages carries organic components from substances in the skin the dielectric liquid. The erosion slurry contains • Possible fire hazard and explosions eroded workpiece and tool material and solid • Electromagnetic radiation decomposition products of the dielectric.

In EDM, the total aerosols and vapor Protective measures: In order to reduce the concentrations exceed the limits of 5 mg/m3 if possible hazards that may arise due machining no protective measures are taken. Fumes, by EDM, the following measures should be vapors, and aerosols depend on the material strictly followed: removal process, the dielectric, and the work • Reduce air pollution to the permissible material. In this regard: extent using suitable filters • Incorporate a dielectric cleaning and • Die sinking generates more fumes and recalculating system aerosols than wire EDM • Keep the temperature of the media at o • Material composition that contain toxic 15 C blow flashing or health attacking substances such as • Reduce the emitted electromagnetic nickel radiation by proper shielding of the • Dielectric type, composition, and machine viscosity influence the fume and vapor. • Reduce the possibility of fire hazard Lower viscosity produces less fumes and • Use level sensors for the dielectric level vapors. • Avoid dielectrics with flashing point of o • The level of the dielectric over the 65 C erosion spot condenses and absorbs a • Apply a suitable disposal of the wastes considerable part of the vapor and fumes • Raise the operator awareness to the risk in the dielectric itself. (80 mm is of high voltage to avoid severe injury or recommended). even death

During EDM using mineral oils or organic 2.4 Laser Beam Machining (LBM) dielectric fluids generates hazardous fumes such During machining by lasers, the material is as polycyclic aromatic hydrocarbons (PAH), heated, partly vaporized, and chemically benzene, vapor of mineral oil, mineral aerosols, transformed, Figure 4. The hazardous materials and other products are generated by dissociation have the consistency of gasses or aerosols. of oil and its additives. Hydrocarbon dielectrics, During laser machining of thermoplastics generate the same vapors and aerosols except Toenshoff et al [5] reported that 99% of the PAH and benzene. Fore water based solvents, particles generated have a diameter less than 10 normally used in wire EDM, carbon monoxide, µm and more than 90% are smaller than 1µm.

ISSN: 1790-5095 142 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

Most particles are in the range of 0.03 µm to 0.5 • Labels and signs that give notice of µm. High alloyed emit 4 to 5 times more lasers operating in a given area. aerosols than carbon steel. Almost all particles Protective equipment: Such as barriers or generated by LBM have a diameter in the range curtains, clothing, or eyewear should be used if of 0.042 µm to 0.35 µm. The hazard potential is the other control measures do not provide influenced by power density, wave length, adequate protection. exposure time of radiation and if LB is visible Administrative and procedural controls: or invisible Consist of a series of rules, regulations that are Skin hazards: Repeated or even a single، designed to minimize the risk of laser beam exposure to certain laser wavelengths causes exposure. One of the most effective skin damage of varying degrees more than other administrative controls is the training. parts of the body. Eye hazards: Eye injuries are caused by thermal 2.5 Ultrasonic Machining (USM) or photochemical mechanisms that occur when USM, Figure 5, is the removal of hard and a laser beam interacts with the eye. If the beam brittle materials using an axially oscillating tool enters the eye, its energy is concentrated by the at ultrasonic frequency (18-20 kHz). During that lens of the eye about 100,000 times at the retina. oscillation, the abrasive slurry of B4C, Al2O3 or Therefore, a small amount of laser light causes SiC (100 – 800 grit) is continuously fed into the damage. Laser beam machining protective machining zone, between a soft tool ( or measures are as follows: steel) and the hard and brittle workpiece. The process finds applications when machining Regulations: The principal American National ceramics, glass, and carbides. However, it has Standards Institute (ANSI), ANSI Z136.1, many environmental and health hazards that provides requirements and recommendations for include the electromagnetic field, ultrasonic the safe use of lasers in typical industrial and wave and abrasive slurry. research environments. Laser hazard zones: This is achieved by Electromagnetic field: The effects of the determining the nominal hazard zone (NHZ), electromagnetic field (EMF) on the health of defined as the space within which the level of individuals are of concern to some people. direct, reflected, or scattered radiation exceeds Individuals are advised to stay away from the the level of the applicable maximum EMF sources, the strength of which drops permissible exposure (MPE). quickly just few feet from the source. Beam path controls: Unless they are totally Ultrasonic noise: Ultrasonic frequencies have enclosed, interlocked, and there is no beam been found to produce sound in the audible access during normal system operation. range from 96-105 dB, although it may not Controlled area: A laser controlled area is appear noisy to older persons and those with required during periods of service a temporary imperfect hearing. Excessive noise levels can be controlled area may be established. reduced usually by enclosures, and thin layers Engineering controls: Engineering controls are of common material that gives adequate features designed into the laser machine to acoustic insulation at upper audible (and minimize the risk of exposure to hazardous ultrasonic) frequencies. Alternatively, ear beams. The most common engineering controls protectors can be provided and used. are: • Protective housings and enclosures that Ultrasound is high-frequency sound that is cover the equipment or the beam path inaudible, or cannot be heard, by the human ear. • Interlocks are often placed on the However, it may still affect hearing and produce protective housings so that if they are other health effects that include noise-induced removed, the beam is shut off. temporary threshold shift, noise-induced • Beam stops that provide safe termination permanent threshold shift, acoustic trauma, and of the beam path. tinnitus. Other communication and performance

ISSN: 1790-5095 143 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

effects may include isolation, annoyance, which are too heavy to be inhaled and captured difficulty concentrating, absenteeism, and by the respiratory system to very small particles accidents. Additionally, it may cause stress, of respirable size. Silica dust is a major hazard muscle tension, ulcers, increased blood in AJM, generated when the abrasive medium pressure, and hypertension. or the cut material contains silica. The major slurry: Slurry fluids are important risk from silica dust is silicosis which causes causes of occupational contact dermatitis, which stiffening and scarring of the lung. Symptoms may involve either irritant or allergic include shortness of breath, coughing and chest mechanisms. Mist is generated by the spray pain. This leads to degeneration in the from the slurry application. Small droplets may individual’s health and an increased risk of lung be suspended in the air for several hours or cancer. Measures to control silica dust several days possibly in the workers breathing generated include using a jet machining zones. Inhaled particles (with aerodynamic medium which does not contain silica, and diameters less than 10 µ m) deposit in the ensuring the process is isolated or appropriate various regions of the respiratory system. One administrative strategies are implemented. acute effect observed is mild and reversible Operators must wear personal protective narrowing of airways during exposure to the equipment and abrasive water jet machining slurry mist causing chronic bronchitis, asthma techniques must be used. AJ equipment must and even laryngeal cancer. The OSHA standard be isolated. Dust must be cleaned and collected for airborne particulate (largely due to fluid in an appropriate manner. Methods of cleaning mist) is 5 mg/cubic meter, and the United Auto include the wetting down of dust prior to clean- Workers (UAW) has proposed a reduction in up. Hazardous impacts associated with AJM the standard to 0.5 mg/cubic meter. Mist can be include: reduced by adding anti misting compounds to the cutting fluids and using mist collector to Worker: In addition to the health hazards, prevent mist from entering plant air. generated by the dusty environment, the Contact hazards: If fingers or hands are put worker's productivity will be decreased, high into a ultrasonic machine, a tickling sensation is physical/mental fatigue, low job satisfaction, instantly experienced on the skin surface and high error rates are possible. Workers are followed 2-3 seconds later by pain in the joints. advised to use suitable wearing and safety tools Other hazards: Effects such as nausea, Product: In the dusty atmosphere, the abrasives dizziness, tiredness and tinnitus can be caused are imbeded in the work surface thus leading to by exposure to sound in the ultrasonic low product quality. frequencies. Workplace: Producing dusty air make problems in other machines in the same station. 2.6 Abrasive Jet Machining (AJM) Workplace condition improvement can be The prime hazard in AJM, Figure 6, is the silica achieved through good ventilation, dust. Particles of other cut toxic materials such implementing air filtration system, and using a as lead, mercury, arsenic, and cadmium, suitable dust collection system. may constitute a significant hazard. Workers are provided with appropriate respiratory protective 3-Conclusions equipment against atmospheres containing Environmental and health hazards are substances which are harmful if breathed. Risk associated with the use of NTM techniques. factors with dust include the type of particulate Such hazards have a direct impact on the involved and its biological effect, concentration workers in the field. Some processes may affect of airborne particulate in the breathing zone of the machines used and product quality. the work, the size of the particles present in the should be aware of the type of each breathing zone, the duration of exposure. hazard, its level, and moreover the necessary Generally the dust contains a wide range of precautions particles of different sizes including particles

ISSN: 1790-5095 144 ISBN: 978-960-474-055-0 Proceedings of the 4th IASME / WSEAS International Conference on ENERGY & ENVIRONMENT (EE'09)

References: [1]G. Byrne and E. Scholta Environmentally Clean Machining Processes- A Strategic Approach, CIRP Annals, V 42/1,1993, 471-474. [2] K. Weinert, I. Inasaki, J. W. Sutherland, and T. Wakabyashi Dry Machining and Minimum Quantity Lubrication, CIRP Annals, V. 53/2, Figure 4 Laser beam machining 2004, 17 p [4] Phil Hughes and Ed. Ferrett Introduction to Health and Safety at Work, Elsevier, 2nd Edition, 2005 [5]Helmi Youssef and Hassan El-Hofy Machining Technology, machine tools and operations, CRC Press, Taylor and Francis Group, USA, 2008 Figure 5 Ultrasonic machining [6] H. K. Toenshoff, R. Egger, and F. Klocke Environmental and safety aspects of Electrophysical and Electrochemical Processes, CIRP Annals, V 45/2, 1996, pp 553-567

Figure 6 Abrasive jet machining

Table 1 Machining liquids Liquid/ medium Application Figure 1 Chemical Machining Etchants Chemical machining Electrolytes Electrochemical machining Dielectric liquids Electrodischarge machining Demonized water EDM wire cutting Abrasive slurry Ultrasonic machining Air + abrasives Abrasive jet machining

Table 2 Hazardous materials of NTM processes Figure 2 Electrochemical machining

Gas Mist Dust

Chips Noise

Liquids Process

Vibrations Vibrations Magnetic field field Magnetic Slurry, Dielectric

Electrolyte, Etchant Etchant Electrolyte, CHM X X X ECM X X X X EDM X X X LBM X X X Figure 3 Electrodischarge machining USM X X X X X X X X AJM X X X WJM X X X X X

ISSN: 1790-5095 145 ISBN: 978-960-474-055-0