Maintenance avoids welding machine failures
By Bill Butler, Sales/Application Engineer, Miller Electric Mfg. Co., Appleton, WI, Mark Jacklin, Interstate Welding Sales Corp., Marinette,WI
Welding machines in poor repair waste money
Outsourcing provides expert maintenance
Because of their durability and long life, welding machines sometimes don’t get routine maintenance. For some companies, a broken welding machine is a minor interference. For those who rely heavily on welding, a broken machine can cause major headaches. It typically means expensive lost production. Welding machines with erratic arcs also waste energy. Welds that fail to pass x-ray, ultrasonic, or other tests are costly to repair.
Hard failures, such as blown PC boards or electrically “fried” components, are unpredictable. However, owners of welding equipment can directly control “soft failures” by repairing worn items, such as cables, connections, internal wiring, drive roll systems, guns, torches, and consumables. Preventing soft failures also includes removing corrosion and air-borne contaminates from the machine that lead to over-heating and circuit board failure.
Pressing deadlines and other priorities often cause delays in maintenance until it’s too late. If this is the case, strongly consider outsourcing maintenance to a qualified source.
Preventable cost efficiency
The premise behind outsourcing maintenance is that manufacturers may not have the internal resources to perform maintenance, or their internal resources are already over-burdened with more pressing maintenance issues.
While some people may hesitate to outsource work because they perceive it costs more, calculating Preventable Cost Efficiency (PCE) can put actual numbers to the problem. PCE is a factor of the cost of production downtime per hour and the cost of service per hour. The following calculation illustrates the potential savings:
PCE = Cost of Maintenance/Hour
If a service provider charges $75/hour for service and downtime costs $500/hour, then the PCE is 15%. In other words, spend $15 for preventative maintenance now or pay $85 dollars to fix it later. Service experts believe that preventative maintenance generally reduces the chance of hard failures by up to 50%.
Before servicing equipment, unplug it; this includes all 115 V plugs from feeders and water coolers. Always follow established lock-out/tag-out procedures and follow the safety information in the operator’s manual. Contact the manufacturer when in doubt.
The following is a basic list of service actions for most welding systems. For a complete, detailed list, consult the owner’s manual or an authorized service provider.
Fig. 1. Welding machines must be blown out regularly to maintain reliable performance.
Power sources. Approximately every six months use clean, dry air to blow out the inside of the machine. In heavy service conditions, cleaning monthly or weekly may be necessary (Fig. 1). For inverter-type machines, leave the cover on and direct the airflow through the front of the machine. Failing to blow out the machine can lead to overheating, erratic arc performance, board or electrical failure, and premature wear.
Load bank testing. Load test each machine to ensure the welding output is accurate, it is required for ISO compliance.
Cable connections, cables and electrode holders. Poor weld circuit connections can yield any number of problems. This includes excessive resistance in the weld circuit, which in turn leads to arc wandering, an arc that won’t start or an arc that is difficult to start.
Fig. 2. Inspect cables to ensure they are not damaged.
Frequently inspect all parts of the circuit. Tighten loose connections and inspect cables, electrode holders and ground leads for wear, cracks, and damage (Fig. 2). Immediately replace those with excessive wear or damage. Note that excess cable length and coiling cables around ferrous metal, such as a table leg or pipe, also causes erratic arcs and drifting weld parameters. Use quick disconnects to add or subtract cable as needed to avoid these problems.
Guns. A gun is not a hammer, but operators often use it as one. Banging may loosen connections inside the gun and lead to erratic arcs. Inspect guns every six months, tighten loose connections, and blow out any particles.
Cables and liners. Clean the cable assembly after finishing a spool of wire, or about twice a week. Disconnect the cable from the feeder and check for a secure connection. Blow out the cable, directing air into the contact tube end. Tap the cable every few feet to loosen any residue trapped in the liner and blow it out again.
Without regular cleaning, the liner will eventually clog and seize the wire. This causes feeding problems, typically slipping, that can cause the wire to burn back to the contact tube. This may cause a bird’s nest at the drive rolls. If the liner is cleaned and still there still are wire feed problems, the liner is likely worn and needs replacing.
Drive rolls. Inspect the drive rolls when the cable is cleaned. If dirty, remove and clean them with a wire brush. If deformed, replace them. In addition, check the inlet and outlet guides and replace them if they are deformed from wire wear. More pronounced wear on the inlet guide may indicate the need to realign the wire spool hub assembly.
Water coolers. Maintain proper coolant levels. Rather than water, use a blended coolant from the manufacturer. It solves problems related to sludge build-up and foaming.
Gas hoses. Porosity in the weld bead and poor bead color can result from insufficient shielding gas coverage. Examine hoses regularly for leaks, wear, and loose connections. Immerse pressured hose in water to check for leaks. Repair a leaky or worn hose by cutting out the damaged area and splicing. Do not use tape.
Regulators. Remove a faulty regulator from service for repair after closing the cylinder valve. External gas leaks, excessive creep (when delivery pressure continues to rise with the downstream valve closed) and faulty gauges (pointer does not move off the stop pin when pressurized, nor returns to the stop pin after pressure release) indicate a faulty regulator. Do not attempt to repair a faulty regulator; send it to the manufacturer’s designated repair center.
Engines on welding generators. Basic maintenance includes changing the oil, oil filter, air cleaner, and fuel filter. Check the owner’s manual for service intervals, as this varies greatly between gas and diesel engines.
Edited by Joseph L. Foszcz , Senior Editor, 630-320-7135
For additional information on welding equipment maintenance, visit the company’s web site, millerwelds.com.