I would like to know the advantages and dis advantages of Resistance welding and Ultrasonic welding process.

-- Srinivasan Rajesh (srajesh@indiainfo.com), June 16, 2001

Answers

Resistance welding is basically a process for conductive materials only. Ultrasonic has been used for conductive as well as non conductive materials but as far as i know this has been done on thin metal jobs only.

Resistance welding can be used for thicker sheets, machined components etc. It is also used in applications wherein load requirements are large.

Capital investment in ultrasonic machines is very high compared to resistance welding.

Subhash Patwardhan www.artechengg.com

-- Subhash Patwardhan (artech1@vsnl.com), June 16, 2001.

Dear Srinivasan Rajesh

Ultrasonic Welding is where mechanical vibrations at ultrasonic frequencies are transmitted by a resonating horn into the work pieces. The intense vibration between surfaces causes sufficient friction to heat and melt the surfaces to produce a molecular bond. Ultrasonic welding is most often associated with welding of plastics or insertion of metallic fasteners into plastics.

Resistance welds are molecular bonds made from the heat produced by resistance to electrical current flow for a specific amount of time under a controlled pressure. The materials joined must allow current to flow in the secondary path (welding circuit). This produces heat due to the resistively of the material interfaces and basic material resistance. This method is rarely used for radiating heat into plastic type materials due to the large demand on the primary power supply as well as the difficulty in directing the heat to a specific location by way of radiation.

-- Bob Balla (bobballa@tjsnow.com), June 18, 2001.

It depends on the application. For instance, in the wire joining industry, ultrasonic metal welding is commonly used. A previous post suggested ultrasonic was used for non conductive metals, this is wrong, ultrasonic is most commonly used for non-plated conductive materials (copper). Resistance welding can be used for conductive, or non-conductive materials, again, depending on the application. The maintenance costs for Resistance welding are generally lower. In ultrasonic welding, the horn and anvil must be periodically replaced, at a significant cost. More information on plastic and metal joining may be found at the non-profit Edison Welding Institute, www.ewi.org

-- Kurt Tolliver (kurt@unitekequipment.com), June 18, 2001.

Dear Srinivasan Rajesh

I stand corrected if the previous posting lead to the conclusion that Ultrasonic Welding was used for only non-conductive materials. Ultrasonic welding of aluminum, copper and other high thermal conductive materials require less energy than resistance welding. I agree with Kurt’s input that “It depends on the application.” Depending on the exact application, there are many joining methods available. It is best to get a good understanding of all the processes which can be used to for your metal joining project. Then choose the best solution.

Ultrasonic Welding is used for joining both monometallic and bimetallic materials. A sound metallurgical bond is made without melting the base material. The process is presently use for production in the semiconductor, microcircuit, and electrical contact industries. It is beginning to receive acceptance as a structural joining method in the automotive and aerospace industries. It is used for producing hermetic seals where high temperature joining methods cannot be used, such as encapsulating explosives, pyrotechnics, etc.

Advantage over resistance welding is that little heat is required during welding and the base metal is not melted. Since there is no molecular change in the base metal, there are no cast nuggets or brittle intermetallics formed. Presently one disadvantage, to Resistance welding is the thickness of the material adjacent to the energy inducing device is limited, due to power limitations. Ultrasonic welding is also presently limited to lap joints, except in some polymer systems.

-- Bob Balla (bobballa@tjsnow.com), June 18, 2001.