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moldmakingtechnology.com 21 Using a coordinate measuring machine (CMM), an operator can acquire data, perform a CAD-to-model comparison and relate those fndings to the mold's nominal values. the CAD model. However, during this pressing, the panel gives a certain amount of spring-back that results in a slightly different shape. The solution is to adjust the tool so the spring- back is accounted for in the finished product. The metal is overbent in the pressing process and springs back to conform to its CAD nominal. When the tool fails, the process is repeated. Precious time and resources are wasted to make the "perfect" tool, mount and press the part, analyze the spring–back, and remake the tool. By adding laser scanning technology mounted to a portable CMM, 3D data can be collected for surface modifications and uploaded to the master model. The master model then can be used to manufacture the tool. Reduced Material and Tooling Costs Another benefit in producing highly accurate molds is reduced overall material costs. In certain industries, a micron knocked off the thickness of a container's side equates to a million dollars per year in savings for that plant. Controlling the amount of material used to produce a part is becoming an art form in the moldmak- ing industry. Moldmakers are continually searching for the differ- ence between a "thin" container and a "too-thin" container. Using advanced metrology tools helps to find that boundary. Tooling costs also drop as advanced metrology equipment comes into play. Multi-cavity molds can be engineered so each cavity is identical and mates perfectly with its counterpart. If one tool cracks, both tools do not become scrap. A new top or bot- tom can be easily reproduced and fitted to the remaining tool. Images courtesy of Hexagon Metrology. Probing Technologies for Data Acquisition There are three main probing technologies available for portable-arm and bridge CMMs: discrete-point probing, analog scanning and laser scanning. Using discrete-point probing, the operator can measure individual points on a mold or part. While this method may yield as many as 100+ points of data, it is likely that some surface features will not be inspected. An analog scanning probe, which moves along the surface of the part, collects more points in less time. Using this method, the number of points gathered during a typical work session could jump to 10,000+. Yet, all relevant features still may not be in- spected. The fnal option is laser scanning. With the ability to capture millions of points on a component, the possibility of a critical point being missed decreases substantially with this method. However, ac- curacy is the tradeoff, as laser scanning is traditionally less accurate than touch-probing or analog scanning. To address these limitations, multi-sensor CMMs are available that feature both an analog probe and a laser scanner. Depending on the application and the required tolerances, the laser scanner could be used to measure the general shape of a mold, which may have a lower tolerance. However, the CMM could switch to the analog scan- ner to measure the fash edges of the mold, where more accuracy is required. Using a multi-sensor CMM enables a single setup with mea- surement results populated into a single part program. For example, if the allowable tolerance of a finished part is ±1 mm, and the mold meets specification to within ±1 mm, there is no room for error down the line. Typically, the mold should be accurate to approximately 10 percent of the final product's value. So, in the given example, the mold should be accurate to within ±0.1 mm, providing the manufacturer a sliver of room for error for the tool and allowing the remaining processes to take up the rest. Time Saved Moving to an automated inspection solution saves time, which translates into saving money. To illustrate this point, consider the inspection of a motorcycle gearbox housing component. It would take more than a week to validate the component on a CMM using a touch-trigger probe. At the end of the process, if errors were found on the part, an adjustment would be made on the tool. After a few iterations, the component would eventually meet specifications. This process can be dramatically expedited after installing a laser scanner on the CMM. The same component could be scanned and the results achieved within approximately three hours. Another example of time savings comes with the ability to reverse engineer tooling and warehouse the data electronical- ly. Consider an automotive door panel built by an OEM. This panel is pressed into a shape that should line up perfectly with LEARN MORE Visit our Inspection/Measurement Zone for more information on coordinate measurement machines and software, pr obes, vision systems, balance machines, calibrators and scanners. Go t o moldmakingtechnology.com/zones for a complete list.