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“It was great, because normally it


takes three to five weeks to develop a new pattern,” Garza said. “With this method we lowered the leadtime to no more than 1.5 weeks.” Acuity designers draw the part, whether it is adding a logo to an exist- ing design or creating a completely different style, in 3D and scale it in the model based off pattern shrink- age, which is an allowance made on patterns to compensate for the change in dimensions as the solidified casting cools in the mold. “I consult with the factory in Mat-


amoros because shrink is not linear,” Davis said. “I rely on their knowledge and expertise to guide us.” Acuity scales the model for two


shrink sizes since the plastic pattern will be used to cast the tool, which will then cast the part. “Te first aluminum part we get off the plastic tool is one shrink big, and that becomes the tool for production,” Davis said. “We take the ABS


These finished finial and roof frame castings were produced using Acuity Brands’ rapid tooling method. They are components to a street lamp.


plastic pattern and label it master.” When a new tool is needed for an existing product, the casting facil- ity makes it from the master ABS plastic pattern. “We go to the shelf, use the master and an hour later, we have a brand new tool,” Davis said. “Tere is no downtime.”


If the required pattern is too big


for the printer envelope, the model may be produced in sections and assembled together to make the finished pattern. Davis used this method to produce a custom scroll measuring 3 x 5 ft. Since the first 3D printer, Acuity also has added a


February 2013 MODERN CASTING | 33


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