Laser Sheet Metal Formation - Literature review Example

 Laser sheet metal formation Introduction This report intends to investigate the technology behind laser forming of sheet metals. Based on examination of magazine articles, published journals, published books and internet sites on this topic, this report focuses on creating an understanding of the very critical attributes of laser forming of sheet metal. These attributes include the scientific principles behind this technology, evaluation of the applications within the process including environmental, manufacturing health, ethical and safety regulation. The impacts of this technology to different market sectors are also reviewed. Laser forming of sheet metal is an extremely flexible rapid modeling and low –volume constructing process. This process uses thermal distortion induced by laser rays to shape sheet metal into the required shape without the use of other tools or need for an external force. Use of laser is very effective and efficient owing to excellent energy efficiency, ease of control, no need for tools and its wide range of applications. This process is also very flexible in the sense that very many other applications such as brazing, soldering and hardening can be performed through the same apparatus. Laser technologies in application and comparison There are several types of lasers including but not limited to carbon (iv) oxide lasers, Nd:YAG lasers and diode lasers. Carbon (iv) oxide and “neodymium-dopedyttrium aluminium garnet” (Nd:YAG) lasers are technologies that are well developed. Research on these types of lasers use a power ranging between 100 kilowatt level watts to kilo watt level. The amount of power used depends on the forming conditions and the thickness of the material. However, Diode lasers have become the most preferred lasers in industrial applications due to their higher efficiency and lower cost in terms of energy consumption. Diode lasers are also easier to integrate within production lines owing to their reduced sizes. Though there has been application of diode lasers in industrial applications, it still remains within a lesser magnitude since its application to High-power level is still low. Scientific principles in laser applications Basic principle: Laser metal sheet formation applies the scientific principle of plastic metal deformation to produce bending on metal sheet. A metal sheet is irradiated with a high-power laser radiation with intent of producing a temperature gradient in between the metal area under the laser irradiation and the other area of the material in the neighborhood. This continuous change in temperature gradient brings about expansion followed by contraction but in a non-uniform manner (Draper, 2013). No-uniform contraction and relaxation usually gives rise to thermal stress leading to plastic deformation. Rapid localized heating combined with gradual more even cooling is so important in laser metal sheet forming process. Other principles: The effectiveness and outcome of metal forming through the use of laser is dependent on a number of factors (scientific principles). These include relation between bending angle and material thickness, relationship between bending angle and laser scan speed, and relation between bending angle and laser scan passes. The fore mentioned principles/laws in relation of the bending angle and the mentioned factors are very critical in making decisions on the type of laser, power of the laser and industrial application of lasers. Material thickness: Experimental evidence obtained from an experiment where a “Rofin-sinar Lx16 160 W diode laser in a UW200” was used on varying material thickness showed that the laser produced stable test results on 0.51 and 0.79 mm material. Two out of six specimens had irregular results when 0.25 mm material was used. This indicated that the thickness of a material is a factor to be considered when using different powers of laser beams(Draper, 2013). A power of 200 watts is good enough to bed low-carbon steel to a thickness of 0.79mm. Compared to former carbon (iv) oxide laser there is no need for further coating of the surface since the surface of the metal has a higher laser absorption coefficient for shorter wavelength laser(940 Nm). Holding the thickness of a material constant, the bending angle arising from a laser increases with increase in laser power up to a certain level where any further increase reduces the bending angle. Width of the laser beam: An experiment performed on the relationship between the bending angles of sheet metal to the beam width of a laser indicated that regardless of a maximum bending angle, the surface quality and the thickness of a material. If a relationship is drawn then for two beams of laser of a given intensity distribution and a given sheet thickness range the maximum angle of bending depends on the thickness of the material rather than the thickness of the laser beam(Draper, 2013). However, given metal thickness ratio, the maximum angle of bending increases linearly with increase in width of the laser beam. This principle brings about the understanding that a wider more evenly distributed beam is more preferred over a sharp laser beam. This however holds in a case where the desired angle is the same and there is little variation in the properties of the material or its surface appearance. The graph below shows the relationship between the thickness of a metal and the angle of bend Laser scan speed: Another very important aspect or principle is the relation of laser scan speed to metal formation. Research indicates that lower energy was required to produce the same angle of bending if a higher laser scanning speed was used as opposed to energy needed when a low scan speed laser was used. This arises because in a situation where there is a high speed laser scanning, there is accumulation of light energy at any point where the laser beam passes. Light energy is converted to heat energy consequently creating a huge temperature gradient between the area in contact with the laser and other region of the metal. There is also a remarkable relation between the number of passes of a laser beam over a surface and the bending angle produced after every respective pass. The bending angle obtained decreases gradually with the increase of the number of times a beam passes over the surface of the metal. Laser bending is therefore more effective within an initial number of passes. Use of multi path bending reduces morphology on the surface as compared to scan passes over the same line. The graph below shows the relationship between laser scan passes and the angle of bend Applications of laser forming of sheet metal Soldering: Laser forming of sheet metal has become very important in today’s world. Very many applications have immerged to utilize the heating effect of laser beams. The first application is the use of laser metal in soldering (Edgar, 2005). Metal soldering refers to the process of joining two or even more metal items through melting and flowing of a filler metal referred to as a solder into the joint. Soldering is applied in plumbing, metalwork such as jewelry and electronics(Edgar, 2005).. In this process the laser beam is used as the source of the heat used to melt the solder. The laser beams used in this process are highly regulated to ensure the right temperature. For this reason use of laser becomes very important since it’s possible to control the properties of the laser beam. Hardening of metal: The second application of laser sheet metal formation is hardening of metal. In this process metal is dynamically heated by means of laser beam scanning (George1984). In most experimental cases incrementally formed metal sheets have been used to study the localized laser hardening. When a laser power of 202 watts, a beam of diameter of 6 millimeters and a scanning velocity of 600mm/min was used to test hardening effect that arises reviewed that laser beams lend to generation of selectively hardened band of material. This process of transformational hardening takes place as a result of heating of the metal sheet to a temperature that reach the austenization temperature which results to subsequent self-quenching to form a hard martensitic metal structure(George1984).. Developing prototypes: Another application of laser metal formation is in developing prototypes for different metallic structures. Prototype refers to a model of a structure that is usually created in order to test and verify the functionality of the structure as well as observe whether the proposed or intended system will meet the requirements necessary to attain the goal of the application. Prototypes enable an organization to invest in an application that the organization is sure that it will perfume the desired functions. In the process of making prototypes a lot of designing and developing of the system components is necessary. This therefore calls for laser sheet metal formation to develop these parts. It is the most cost effective means since there is no need of many other tools to perfume this role. Ship building: Laser sheet metal formation is also very important in ship building. This process is applied in three areas within the ship building sector (George, 2008). First area is in hall section fabrication. In this section 2D and 3 Dimension laser formation is used to replace former mechanical methods such as steel plate bending. 2D laser forming is applied to form part-cylinder shapes towards welding together of hull skin panels. Considerations are underway to the use of 3D laser forming to develop primitive 3D shapes(George, 2008). The second application of laser metal formation in ship industry is in correction of distortions. Since welding is a major operation in ship making, very many distortions arise from the process. Manual re-working of the distortions arising from welding is very expensive and can take up to 30% of the total cost of building the ship(George, 2008). A less expensive means of correcting these distortions is the use of laser metal formation. The third use of laser metal formation is shaft alignment. Laser can be used for straightening cylindrical tubes and rods at smaller scales. When a laser beam is glanced upon the surface of these metal shafts then straightening occurs. Health, safety and ethical consideration in use of laser in laser sheet metal formation Laser use in metal formation is becoming more common by the day and consequently making it necessary to consider safety, healthy and ethical issues arising from the use of laser in the various applications (Lawrence, 2010). Laser beams with a radiant power exceeding 0.5 watts may cause injury to the eyes and also pose a risk of skin burns. It is therefore necessary that workers and employees working within areas that expose them to these beams are provided with safety equipment(Lawrence, 2010).. Ethics also imply that equipment’s that use these beams should have a guide that directs the user on the best practices in handling the equipment to avoid harm. The manuals should be available to every user of the equipment and should be use a clear explanation. It is also very crucial and ethical that the manufactures of these equipment’s provide technical assistance and guidance on the installation and use of these equipment. Manufactures should also offer training opportunities for users of these applications to learn how to use the facilities(Lawrence, 2010).. The greatest safety issue arises in a situation of faulty equipment. Faulty equipment can cause a disaster if the condition is not quickly contained. Laser beams are very harmful as a result of the energy they emit(Lawrence, 2010).. A faulty application may lead to destruction of properties worth a lot of money or even death of the user of the application. For safety the manufactures always should put in place a containment plan for a faulty application. There should be development of beam enclosure, stops and masks. The government has also put in place laws that govern the safety of the workers in the working stations. Ethics call for observance of the conditions set by the authorities of the land to address these issues(Lawrence, 2010).. Conclusion In conclusion laser sheet metal formation is a form of recent technology that has developed rapidly. This technology involves the use of laser beam of light to illuminate the surface of a metal with the intent of inducing plastic deformation of the metal. Illumination of light on the surface of a metal leads to absorption of energy inform of heating hence causing a temperature gradient between the illuminated region and the other area of the metal. This causes expansion and uneven contraction leading to bending of the metal. The most significant phenomenon of this process is the bending angle produced by the laser beam. There are a number of principles that govern the results of this process. Careful consideration of principles behind the relation of laser beams to bending angle of metals aid in the choice of a suitable laser application for a given situation. Laser formation of sheet metals has a lot of applications in ship construction, prototyping, soldering, and hardening of metals among others. Though the great importance, there are ethical, safety and health issues associated with use of these applications. Use of these beams may cause harm to those users, and even properties. For safety the manufactures of these applications must observe ethical conditions such us provision of manuals, training and technical support to the users. Reference Draper C. (2013) Laser Surface Treatment of Metals, Mexico: Springer Edgar, C. (2005) Laser Soldering Applications for RF Shield Rework: By using one-piece RF shields and lasers for rework, throughput, Singapore: HarperCollins. George, G. (1984) Hardening, Tempering and Heat Treatment: Workshop Practice, New Jersey: Trans-Atlantic Publications. George, J. (2008) Ship Construction, London. Butterworth-Heinemann Henderson, R. (2010) Laser Safety, New Jersey: John Wiley & Sons. Lawrence, O. (2010) Public Health Law and Ethics: California, University of California Press Menéndez, A. (2012) Metal nanoparticle formation by laser ablation in liquids, Twickenham : Tredition. Read More