Mold Maintenance & Repair

OCT 2013

Mold Maintenance & Repair

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F e at U R e Photo courtesy of Precision Laser Technology. teristics of the steel in diferent ways at diferent places along the temperature scale. The real problem is that due to these changes the repair may be signifcantly diferent than the base metal, and consequently may not take a polish the same as the surrounding steel. The diference can be enough to show on a molded part. i've seen expert polishers who can make an acceptable match, but i've also seen repairs that need periodic attention to maintain the match. There are special handling procedures that can mitigate the efects of Tig welding. Full process color match welding entails pre-heating (that can be problematic when you have a 30,000-pound cut-in-the-solid cavity block), fller material matching and post weld- Advancing a sidewall of a 420 SS mold insert by 0.015" using laser welding technology. ing tempering. This process can dramatically reduce the efects of heat on the repaired mold, but takes time and expertise. color match welding is probably best left to a professional with experience. Micro Welding Micro welding is a sub-set of Tig welding, with the added beneft of small scale repairs using fller wire as small as 0.003, amperage settings 16 Mold Maintenance & Repair under 10 amps and on the level of requiring magnifcation. needless to say with repairs, the less material added, the less machine or hand work required to take it back to net shape, the less time involved in the repair. due to the small size of weld—for the purposes of mold repair—micro welding is a signifcant enhancement of the Tig welding process, but comes with some increase in initial investment. Further, it is a continuous arc process that builds up heat in the workpiece and results in the attendant HAZ though on a smaller scale. Another permutation of Tig welding is pulsed Tig welding. The advantage of pulsed welding is that the build-up of heat is minimized, and so the efect on the surrounding steel. These units give micro sized spot welds that can be overlapped, but unlike resistance welds, are in fact homogenous welds done with a shielding gas to enhance cleanliness and uniformity of the weld. due to their ubiquitous nature, straightforward Tig welders are inexpensive. on the other hand, micro Tig welding setups are more expensive. Laser Welding Without considering all relevant factors, laser welding is the closest thing to a perfect weld; at least when it comes to mold cavity repair. Microscopic welds can be performed with total control of the size and location of the weld. From flling in small voids to repairing parting line fash, there is probably not a more accurate option. due to the fact that so much of the process is equipment controlled, the learning curve is short. You won't be an expert the day you unpack the welder, but you will be making

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