spot welding advantages and disadvantages

Spot welding has high compatibility with efficiency and uniformity. It has the advantage of producing a high volume of work at high speeds and does not require filler materials.

Said another way, pressure is applied to the two overlapping sheets being joined. However, due to its low resistance, very high levels of current need to be used when welding aluminium (in the order of two to three times higher than for steel of equivalent thickness). Weldability is controlled by three factors: Metals with high resistance to current flow and with low thermal conductivity and a relatively low melting temperature would be easily weldable. Difficulties may be encountered when welding certain metals in thicker sections. This welding process is used primarily for welding two or more metal sheets together by applying pressure and heat from an electric current to the weld area. In the welding of particular types of wire mesh, welded wire mesh, or sheet metal, a process called spot welding is used.

Lastly, the metal and the end-result may come out less resistant to corrosion. When spot welding zinc coated steels, electrodes must either be frequently exchanged or the electrode tip surface should be dressed, where a cutter removes contaminated material to expose a clean copper surface and reshapes the electrode. What is It Used For? The welding heat is generated by the electric current, which is transferred to the workpiece through copper alloy electrodes. This formula is: If weldability (W) is below 0.25, it is a poor rating. It has been shown to be adaptable to some degree of feedback control. Heat is generated by the passage of electrical current through a resistance circuit. Heliarc Welding Explained: What Is It? Also, the resistance welding process is limited to overlapping joints, which requires more material than a butt joint. Galvanised steel (zinc coated) requires slightly higher welding currents to weld than uncoated steels. Copper and its alloys can also be joined by resistance spot welding, although spot welding copper cannot be easily achieved with conventional copper alloy spot welding electrodes, as heat generation in the electrodes and work piece are very similar. KPTCL, BESCOM, MESCOM, CESC, GESCOM, HESCOM etc are just some of the clients we are proud to be associated with.

Changes in power supply leads to weak welding. The resistance welding processes differ from many of the other more popular welding processes such asMIG,StickandTIG. Resistance welding equipment is more expensive than arc welding equipment. Welds are reproducible and high-quality welds are normal. Only thin metals can be welded accurately and efficiently. The metals in the zone of pressure gets heated up to their melting temperature and the joint so made gets cooled under pressure. But since the resistance of Aluminum is lower, therefore excessive levels of the current need to be used when welding Aluminum. Depending on this frequency and the speed with which the material is being welded, the weld will be either a continuous seam weld, an overlapping seam weld, or a roll spot weld.

Also, with zinc alloys, the copper electrodes rapidly degrade the surface and lead to a loss of weld quality. Parts to be joined are limited to a thickness of less than 1/4 of an inch due to current requirements. To produce higher levels of resistance dissimilar parts are used. Certification is recommended for professionals in the fabrication or production of products that utilize resistance welding. The certification will confirm an understanding of the fundamentals of each of the resistance welding processes including: There is an education and experience requirement. With this very short time of energy delivery, overheating of adjacent parts of the sheet can be completely prevented. The pressure is applied by mechanical, hydraulic, or pneumatic systems. It doesnt make use of dangerous open flame. The materials used to construct the electrode has to sustain high loads at high temperatures while maintaining adequate electrical and thermal conductivity. The process involves applying pressure and heat to the weld area using shaped alloy copper electrodes which convey an electrical current through the weld pieces.

Welding heat is proportional to the square of the welding current. Professional spot welders generally take into consideration the types of electrodes, properties of materials, and the thickness of the sheets when determining the amount of heat to be applied to the targeted spot. In resistance spot welding, the metal surface pointsusually sheets of 0.5 to 3 mm thicknessare pieced together under tremendous pressure exerted by the electrodes. This includes light metals, aluminum and magnesium. Resistance welding operations are automatic. In resizing of metal molar bands, we can find the use of spot welding equipment, which is small in scale. It is not easy to achieve spot welding with conventional electrodes from copper alloy spot welding, as workpiece and heat generation is the electrodes are alike. The time the current flows through the work. Save my name, email, and website in this browser for the next time I comment. Spot welding may produce weak and insufficient weld if the current applied is not strong enough or the heat produced is not hot enough. However, spot welding machines can only hold metals with certain thickness limitation, and this range of thickness is from 5 to 50 inches. Construction, Working and Applications, What is an Incandescent Lamp? High current at a low voltage flows through the circuit and is in accordance with Ohms law. The main factors affecting the quality of the spot weld are , The main advantages of spot welding are as follows .

Spot welding can also be easily performed to weld together multiple sheets, and sheets as thin as .25 inch. Big problem resistance spot welding 017 -017 -033 inco no penetration in to thin out side sheet any clues. National Structural Integrity Research Centre, Granta Park, Great Abington, Cambridge, CB21 6AL, UK. Spot welding is made more accessible by using steel, as the electrical resistivity is higher and thermal conductivity is lower when we compare it to copper electrodes. Electrode wear acts to increase the diameter of the electrode face. Resistance spot welding is used extensively because it is a simple, inexpensive, versatile, and forgiving process. A typical spot welding machine consists of a transformer to produce high current at low voltage and the electrodes are connected to the ends of the secondary winding for leading the current to the work. Therefore, in the industry, only specialist applications of spot welding can be found. The strength and size of the weld are dependent on the shape and size of the electrodes. The process of spot welding, however, entails three specific stages, namely: The preparation process wherein electrodes that are seated on the weld head are positioned towards the spots of the materials to be joined. For this reason, only specialist applications of aluminium spot welding are currently found in industry. Ferrous metals all fall into this category. The lack of a simple, in-process nondestructive testing technique for resistance spot and seam welding is also a limitation. Painting is the other key application for industrial robots. Spot welding has applications in a number of industries, including automotive, aerospace, rail, white goods, metal furniture, electronics, medical building and construction. In this type of welding the base metal does not undergo to large heat affected area. Within each group, the Resistance Welding Manufacturers Association (RWMA) sorts electrode materials into classes. Metals that have a lower resistivity but a higher thermal conductivity will be slightly more difficult to weld. Process, Advantages, Disadvantages and Applications, What is a Metadyne? Spot welding requires a large working area. The Zinc can blend with steel during the weld and lower its resistivity, so to weld galvanized steel, a higher level of current is required. Although the electrodes are movable, the electrode holders, however, are only capable of the limited amount of mobility. Spot welding can also be applied to all types of boxes, cores and enclosing cases, etc. Resistance spot welding, the most popular, is shown in figure 10-77 below. Because resistance welds are produced between overlapping sheets, there can be no visual examination if the finished weld. Sai Shankar Rudra By pushing a large amount of current onto the target points, the targeted spots are melted and eventually form welds. Required fields are marked *. Overlapping or Continuous Seam welds are typically used to produce continuous gas- or water-tight joints in sheet assemblies, such as automotive gasoline tanks. Steel coated with Zinc to prevent corrosion, also known as Galvanized Steel follows a different approach than uncoated steel. This amount of heat generated is lower since the resistance between high conductivity electrode material and the normally employed mild steel is less than that between two pieces of mild steel. During production, current values must slowly rise to compensate for the decreased current density, else nugget size drops. Although individual spot welding guns may have limited movement on the assembly line, the power source is fixed. The cells are linked to battery terminals by spot welding thin nickel straps. Welding programs for resistance welding can become quite complex. However, high carbon content steels (Carbon equivalence > 0.4wt%) are prone to poor fracture toughness or cracking in the welds as they tend to form hard and brittle microstructures. If you have any questions or need help, email us to get expert advice: A form of resistance welding, spot welding is one of the oldest welding processes whereby two or more sheets of metal are welded together without the use of any filler material. Resistance welding equipment utilizes programmers for controlling current, time cycles, pressure, and movement. To figure out whether it is spot welding process that you need, it would be good for you to understand the advantages and disadvantages concomitant with spot welding. Pressure is required throughout the entire welding cycle to assure a continuous electrical circuit through the work. It is a subtype of electric resistance welding wherein the welding process happens via the application of pressure exerted by electrodes and the electric current on the workpieces. By following resistance spot welding, Copper and its alloys can also join. In view of this, quality welds do not depend on welding operator skill but more on the proper set up and adjustment of the equipment and adherence to weld schedules. Learn more, What is Seam Welding? Other materials commonly spot welded include stainless steels (in particular austenitic and ferritic grades), nickel alloys and titanium. Process, Advantages, Disadvantages and Applications, What is Flash Welding? The Resistance Welding Manufacturing Alliance and the American Welding Society are offering in beta testing a Resistance Welding Certification. Working Principle, Construction and Applications. Several disadvantages are associated with this process. The current flows across the electrodes and metal, causing the formation of the weld nugget. The position of making resistance welds is not a factor, particularly in the welding of thinner material. Working and Applications, What is Projection Welding? He has always been interested in welding from an early age and has the cuts and bruises to prove it as he set out to work with a variety of metals. The precious metals comprise the third group. to ensure that welds are of the highest quality. It is not difficult to identify spot welding on many sheet metal goods, for example, metal buckets. disadvantages seam Your email address will not be published. Aluminum has a weldability factor of from 1 to 2 depending on the alloy and these are considered having a good weldability rating. The welding electrodes are motor-driven wheels rather than stationary caps. By using this website, you agree with our Cookies Policy. Given the ease with which spot welding can be automated when combined with robots and manipulation systems, it is the most common joining process in high volume manufacturing lines and has in particular been the main joining process in the construction of steel cars for over 100 years. First, spot welding is easy and quick to perform.

Resistance welding is used by many industries manufacturing a variety of products made of thinner gauge metals. In the spot welding process, the materials to be welded are overlapped and pressed between two water-cooled electrodes and a high electric current is passed through the assembly. Resistance seam welding is a variation on resistance spot welding. UNI POWER TRANSMISSION is an ISO 9001 : 2008 certified company and one of the leading organisation in the field of manufacture and supply of ACSR conductors. Copper is used for the electrodes as it has a high thermal conductivity and low electrical resistance compared to most other metals, ensuring that the heat is generated preferentially in the work pieces rather than the electrodes. Electrode materials typically used for spot welding copper include molybdenum and tungsten. Spot welding is not suitable for the thicker materials. Spot welding may produce weak welds if the metal sheets to be joined are not properly held together.

Additionally, the correct timingwhen applying current and heat to the spot to be weldedwould surely play a critical role in producing optimal results. (a) I is the current in amperes, E is the voltage in volts, and R is the resistance of the material in ohms. In general, higher levels of resistance occurs when the power supply overcomes the level of resistance. Mechanical pressure which forces the parts together helps refine the grain structure of the weld. As the cross-sectional area increases rapidly with distance from the workpiece, thereby providing a good heat sink. Motion, when it is involved, is applied mechanically. The solution to welding copper is to use an electrode made of an alloy with a high electrical resistance and a melting temperature far in excess of the melting point of copper (much greater than 1080C). Heat is also generated at the contact between the welding electrodes and the work. It is excellent for the sheet metals used in automotive construction, and because no filler metal is needed, the complex wire feed systems in many arc welding processes are avoided. 2006 - 2022 WeldGuru.com - All rights reserved, Base Metals Weldable by the Resistance Welding Process, Advantages & Disadvantages of Resistance Welding, Resistance Welding Manufacturing Alliance, Duty Cycle in Welding Explained (with Chart). A range of copper-based or refractory-based electrode materials is used based on the application. The process is also adaptable to robotic manipulation so the speed is extremely fast.

Due to its lower thermal conductivity and higher electrical resistance, steel is comparatively easy to spot weld, with low carbon steel being most suited to spot welding. The welding process which is used for welding two or more metal sheets together by applying pressure and heat from an electric current to the weld area is known as spot welding. There is a possible to weld multiple metals at a time. Resistance welding is a group of thermo-electric processes in which coalescence is produced by the heat obtained from resistance of the work to electric current in a circuit of which the work is a part and by the application of pressure. We specialize in the manufacture of ACSR Rabbit, ACSR Weasel, Coyote, Lynx, Drake and other products. Short time, high power demands can cause lights to dim and computers to reset if the electrical system in a factory is not properly prepared for the introduction of resistance welding equipment. In fact, automated machines in many factories usually can perform 200 spot welds within a very short time of six seconds. The process is also used to weld longitudinal seams in structural tubular sections that do not require leak-tight seams. The first advantage is speed. The heat losses should be held to a minimum. Spot welding is economical, i.e., it is relatively cheap to operate.

As the heat flows into the surrounding metal more effortlessly, so it is not easy to spot-weld a thicker stock. Sign up and join 10,000+ other learners and get free welding articles and tips sent straight to your inbox. (adsbygoogle = window.adsbygoogle || []).push({}); thank you for the information. Various new technology developments are emerging to help enable stable high quality spot welding in aluminium. A highly experienced and efficient professional team is in charge of our state-of-the-art equipped manufacturing unit located at Belavadi, Mysore. With more than a decade of experience and expertise in the field of power transmission, we have been successfully rendering our services to meet the various needs of our customers. Welding is performed with operators who normally load and unload the welding machine and operate the switch for initiating the weld operation. The amount of heat depends on the thermal conductivity and electrical resistance of the metal as well as the amount of time the current is applied.

The disadvantages of spot welding are as follows .

After the contact point has been melted, current is then removed, although the electrodes are left in place to let the material solidify and cool afterward. Spot welding is a type of resistance welding process, which is why it is also known as the resistance spot welding. When the welding current is turned off, the weld cools causing the welding nugget to become solid while joining the two pieces of metal. The welding gun used in the spot welding is heavy and require great strength when using it. These are difficult to weld because of very high thermal conductivity. Current control is completely automatic once the welding operator initiates the weld. When compared with the steel of equivalent thickness, it is two or three times higher. seam disadvantages Spot welding is used in high volume production applications. It does not require more skilled persons at operation. Spot welding is used in various industries such as automotive, aerospace, metal furniture, electronics, building construction, etc. Customer Delight has always been our top priority and driving force. Although aluminium has a thermal conductivity and electrical resistance close to that of copper, the melting point for aluminium is lower, which means welding is possible. The material melts, fusing the parts together at which point the current is turned off, pressure from the electrodes is maintained and the molten nugget solidifies to form the joint. It is vital to keep connecting surfaces free of contaminants such as oil, dirt, scale, etc. There are three independent parameters in configuring seam welding machines: sheet configuration, welding wheel configuration and the power supply. This type of welding is also used in the steel industry for manufacturing pipe, tubing, and smaller structural sections. This article is one of a series of TWI frequently asked questions (FAQs). When over 5000 welds need to be made in a typical car, a process where each weld takes less than a second is of great importance.

By using an electrode made of an alloy with high electrical resistance and having a melting temperature greater than the melting point of Copper (higher than 1080C) copper can then be welded.