Advertising in MoldMaking Technology offers
Issue link: https://mmt.epubxp.com/i/617955
UNDER THE 28 MoldMaking Technology —— JANUARY 2016 Image courtesy of Toolweld Inc. By Eric Hild A necessary part of mold maintenance and repair is welding. This includes processes such as TIG (tungsten inert gas), micro- TIG and laser welding. Many welding shops have experience in all three processes, while others specialize in only one. Whether you are performing weld repairs in-house or out- sourcing the work to a professional welding house, the success and quality of a repair weld depends on the level of difficulty, welding machine capabilities, welder skill and experience, and most importantly, communication. assume the welder knows what you want. Molds arrive on the welder's bench for many reasons, including engineering chang- es or inoperability due to damage during the molding process. To properly prepare for and ensure optimal mold repair, essen- tial questions must be asked and answered. Questions What am I welding? A welder must understand what the moldmaker requires in order to get the tool running again in a timely fashion. The welder also needs to know what the moldmaker does not want, such as surface areas that do not undergo any welding or experience the effects of welding. Where am I welding? The location of a repair is critical to its success. The welder must know if his or her equipment, whether a TIG-welding torch or a laser-welding head, can suc- cessfully access the area to be welded. To determine this, it is often recommended that the welder position the piece on the worktable and perform a simulation weld to test ease of access. What is the steel type? Each steel has its own guidelines for TIG welding, preheating and post-heating. Each type of steel also has its own welding parameters, which may include matching the steel with the proper filler rod to complement the base steel hardness and chemical composition. For exam- ple, the brittleness of die steels makes them behave quite dif- ferently from mold steels under any welding process. Cracking can occur, so special welding procedures are required. The physical properties of aluminum and copper-based materials limit the effectiveness of TIG or micro-TIG welding on them, as the repair will often require a small weld deposit that is best performed by laser welding. What could go wrong? One problem scenario is when the welder unintentionally damages a mold area by arcing with a TIG-welding torch. This occurs because the arc is unstable upon initial welding startup and causes the arc to wander or hunt, thus producing unintended damages. Another example of welding gone wrong is the beam reflection that can occur when laser welding under certain conditions. Here, the laser beam reflects like a mirror, causing a melted surface opposite the location from which the laser beam originated. This effect can happen when welding highly reflective details, such as a polished finish or an angle. In addition to asking these questions and receiving feedback, it is important for the welder to know if the customer is spe- cifically requesting laser or micro-TIG welding, as well as the reasons behind this request, as there are advantages and disad- vantages to both processes. Considerations for Mold Repair Welding This new series is intended to arm toolmakers and engineers with the necessary knowledge to make better informed decisions during tool repairs, including an understanding of welding terminology, procedures and challenges. Prior to laser welding, such as for the repair seen here, it is important to evaluate potential problems, including laser beam penetration and refection, and ease of access. For example, the welder must fully understand customer expectations, and the customer should be informed of any risks and considerations before welding begins. The golden rule of welding is: "What has been welded cannot be unwelded." Any mistakes need to be machined away to start fresh, so it's essen- tial that all parties involved are on the same page when it comes to project details, process decisions and potential problems. Every repair job is unique to a welder with each one requir- ing a different hand movement and position, and different machine calibration. This means clarity is essential for every- one involved. No one should work on assumptions, so never