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Resistance Welding Cable Guide

Unplanned downtime in production can be expensive for a business when it comes to overlooked maintenance issues on resistance welders, spot welders.   Following some simple guidelines on a routine basis will save valuable dollars in the long run and help to keep production lines up and running when it comes to proper planning.  Welding cables and shunts are often called out as an MRO item when purchasing agents procure parts for resistance welders, spot welders, robotic welders.  These are often referred to as secondary cables or leaf shunts.   While a number of items fall into this category, including electrodes, transformers, and control cables, this guide will help to address secondary cables and shunts. What are secondary cables?  Secondary cables or resistance welding cables are typically air cooled cables, water cooled cables or dual polarity kickless cables.  These cables are made of bare copper stranded rope at a specific gauge appropriate for all resistance welding equipment in the industry.  Bare copper stranded rope is typically either 30 gauge, 34 gauge or 36 gauge (rigid, somewhat flexible, extremely flexible).  A spot welder that has excessive repetitive motion may achieve peak performance when utilizing a 36 gauge rope due to it's extreme flexibility.  All cables consist of copper terminals utilizing 110 copper and/or Tellurium (Te).  The primary use of Tellurium is in alloys including copper to improve machinability.  Tellurium is a semi-conductor that shows greater electrical conductivity.  Just as it is important to select the most appropriate gauge in bare copper stranded rope, it is important to choose the correct cable cover.  Hose covering/flat lay should be nonconductive and have properties that best match the needs of the equipment as far as rigid, flexible or extra-flexible. Determining which secondary cable to select? Air cooled cables are easily identified as the nonconductive cover simply lays "flat" on the braided copper stranded rope and is not clamped or banded onto each end.  By nature, therefore, the copper terminal ends are exposed to movement, the specific climate of the facility (i.e., humidity, heat) and will reveal oxidization, which is inherent to copper and Tellurium.  This reaction can be slowed or hastened by the use of silver plating not just to the contact surface of the terminal, but also on the inside.   Silver (Ag) has the highest conductivity of all metals, even higher than copper.  At high frequencies, the current tends to flow on the surface of the conductors and therefore improves conductivity, lowers resistance levels and less heat build-up, which means less fraying of the cable.  Utilizing a cable that has excessive fraying and oxidation will eventually lead to substandard welds. Water cooled cables are identified by the outer hose being clamped or banded on both ends, which is necessary to contain the water that flows through the cable for cooling.  For this reason, water cooled cables are not exposed to as much oxidization like air cooled cables because the copper braided rope is not exposed to air; however, their terminal ends can be silver plated to hasten oxidization of the Copper/Tellurium extruded terminal ends of cast copper terminal ends.  Terminal ends are either soldered or pressed into the copper braided rope to not only facilitate the connection, but to facilitate conductivity throughout the cable.  The most important factor in prolonging the life of a water cooled cable is appropriate water flow.  Water pressure, well water, city water are all external factors that are independent to each facility and should be acknowledged.  Inadequate water flow to a water cooled cable will cause the cable to fail or hasten it's effectiveness and will eventually result in failure or substandard welds. Water cooled cables are called single conductors.  Dual conductor water cooled cables (alternate polarity i.e., a positive end and a negative end) are also utilized.  Dual conductor cables are often called "kickless" cables due to the fact that they are constructed to withstand welding equipment that has excessive "kicking, pulsing or vibrational" repetitive movement.  Scheduled Maintenance of Welding Cables for Best Planning: While performing scheduled maintenance of the more popular aspects of the resistance welding equipment, reviewing secondary cables and external factors will go a long way toward hastening or eliminating expensive down production lines. Visual Inspection:  As mentioned, the signs of "wear" on a welding cable will eventually hasten expected life and result in substandard welds.  Visually inspect cables, particularly air cooled cables where the flay lay can be pulled back to review fraying or "pilling" of the copper braided rope where it rubs against the inside of the flat lay.  Check oxidization of the contact surface where the cable is bolted to the equipment.  Visually inspect water cooled cables for signs of water leaking at the bands, check for damage to the hose, and make note of any "wear" points or sign of "thermal" overheating. External Variables:  Every facility has it's own independent climate particularly if located in a state or country where it is hot or humid.  Every facility has it's own source of water such as well water or city water.  Most cable manufacturers recommend 2 gallons of water per minute for single conductor water cooled cables and 2 1/2 gallons of water per minute with dual conductor water cooled cables (anything more than that is simply a benefit).  When the water and temperature can be controlled the life of the single or dual conductor water cooled cable will be prolonged. Review Connections:  Reviewing the connections of the secondary cables periodically is important as over time, dust, dirt, debris, lubricant can slightly loosen connections.  Periodically tightening connections is beneficial.  A joint compound such as Noalox ™ applied when the connection is initially bolted to the equipment may be helpful.  Stainless steel bolts are recommended. Cable Sizing and Placement:  Ensuring the correct cable size is being utilized is an important factor to achieving excellent welds.  Substandard welds may be the result of an incorrect cable or incorrect placement/bend radius.  Most cable manufacturers will provide their own recommendations relative to minimum and maximum bend radii for air cooled cables as well as water cooled/dual conductor water cooled cables.  For example, a water cooled single conductor with a tight bend radius could result in restriction of recommended water flow, thus, impedance of the cable.  Longer water cooled cables typically add resistance, therefore, often the shorter cable is recommended. Determining proper cable size is necessary to achieve their maximum potential and minimize down production time.  Most cable manufacturers have a guide to assist in ascertaining the correct cable for the welding equipment.   Determining Correct Cable:  You will need to know the continuous duty cycle, current to be used and length of the cable (measured bolt hole center to bolt hole center).  This information will guide you through obtaining the correct Thousandths Circular Mill (MCM) of the cable. Understanding these factors will determine the proper "Thousandths Circular Mill (MCM)" needed for cables. Cable suppliers are good sources for determining the correct size required for a resistance welding application. Need More Information?  Most cable manufacturers are a good source for information on secondary welding cables/resistance welding cables.  Additionally, when a cable manufacturer understands the type of welding equipment, solutions to achieve peak performance can be made.  Running through the checklist during routine maintenance is an excellent opportunity to take stock in the state of the current secondary welding cables and it is often recommended to keep at least one extra cable on the inventory shelf to avoid expensive down production time.