Modern Machine Shop and MoldMaking Technology present ADDITIVE MANUFACTURING, a quarterly supplement reporting on the use of additive processes to manufacture functional parts. More at additivemanufacturinginsight.com.
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14 — AM Supplement F E A T U R E to optimize form, ft and function. Kieffer also stresses the importance of part orientation in re- ducing print time. A part oriented one way might take two hours to print, but the build could take signifcantly longer in another orientation. Currier has also learned to allow for some trial and error in the process to optimize a product's design, including pushing the limits of wall and part thickness. "For example, we learned that with our amenity bottles we have a wall thick- ness threshold of 0.040 inch. If we go any thinner, things start to get too fimsy. Then just holding the part while you're trying to clean it in the cleanup tank, you run the risk of snapping the part or dropping and cracking it," Sieber says. An often overlooked aspect of 3D printing is material inventory control, in terms of both main- taining suffcient supply and ensuring that the material on hand has not expired. "When we purchased the printer, we were unaware of the speed at which we'd use the material, so when building an inventory, we over-invested," Sieber says. "We did not use the material as fast as anticipated, which resulted in expired material on our shelves." Every material has a shelf life and should in- clude an expiration date stamp. Today's machines are smart. They can read the date code on the material container and will not accept expired material. "So if you buy new material with a noted two-year shelf life, make sure it didn't sit on the supplier's shelf for a year before purchasing," Sieber advises. To help determine an appropriate material inventory, he suggests tracking its usage. "You want to have enough material on hand to get you through your jobs and avoid anxiety about getting more," he explains. Lead time for receiving mate- rial can be a short as two days, he adds. In addition to planning for effective inventory management, there are a number of other vari- ables that can impact a shop's ability to maximize use of a 3D system, and they should be consid- ered prior to the purchase of a machine. These variables include space constraints relevant to machine size, secondary fnishing requirements, options for hazardous material disposal and fume Do's and Don'ts of 3D Printing Don't allow a volume check to be performed on a 3D-printed part. The volume of a printed bottle, for example, will not be the same as that of an injection- blown bottle of the same size. Don't expect that a 3D-printed part's function will be exactly the same as a molded part's. Educate your customers that functionality is subject to the materials available for 3D printing and their respec- tive properties. Don't accept every job. Currier employs a "value times velocity" formula for evaluating whether it can take on a particular job in-house. To continue offering a value-added service, the company might contract work to an outside service bureau that specializes in what it is unable to do. Do use the printer frequently. Some 3D printers cannot sit idle for long periods of time without requiring material purging. Currier says if its printer sits for more than a couple of weeks, it must be purged to get the chemicals and materials out of the piping; otherwise, they set up and get "gooey." Non-usage is timed, so the machine should indicate when it needs to be purged. Do push the printed part's limits. Materials can be surprisingly more durable and stable than expected. Some are so durable, they can be drilled, tapped or machined. Don't be afraid to test a part's limits. If you break one, try again. Do trust the part's accuracy. Accuracy is a strength of 3D printing. Currier says it has been successful in printing units that are suitable for geometric dimen- sioning and tolerancing (GD&T;) fxturing. You can actually hold the part very accurately on datum, which can be unexpected.