Part Buyers Authority Issue #1

Surface Roughness Surface roughness was measured on each of the castings as shown in the table below. The casting from the additive manufactured pattern had a rougher surface but remained within limits for the casting application, and well below the typical surface roughness of a no bake casting (150-600 in Ra) or green sand (250-900 in Ra) Surface Quality Surface quality refers to the absence of surface imperfections that detract from the appearance and functional performance of the component and may require repair. Such imperfections can include negatives to the surface such as pitting or cracks, or positives to the surface that could result from shell imperfections. The casting made from the SLA pattern exhibited an increase in negative areas on the casting, however, the severity of the surface defects did not impact casting performance. COMPARING THE PROCESS As outlined earlier, the basic casting process remains the same if the foundry is using a traditional wax pattern compared to a 3D printed pattern - however the cost and time savings are realized through additive manufacturing not requiring tooling to be built. A comparison of the respective timelines is shown below. • Machining due to the combination of improved surface finish and the processes ability to hold tighter tolerance, in many cases parts can be produced without the need for additional machining operations, which may be required if using traditional green sand or no bake casting methods. • Applications – Direct manufacturing SLA patterns reduce the total costs of finished casting for limited runs or low volumes without significant sacrifice to casting quality. – Repair Parts No investment of injection tooling for one-off repair or legacy items. – Concurrent Designs An additive manufactured pattern ordered simultaneous with wax tooling allows the foundry to prove out processing during tool construction. – Research & Development Multiple variations may be tested at the same time without incurring tool alteration costs. As this technology continues to be developed, we can expect to see a further reduction in lead times, equipment costs, raw material pricing, and improved efficiencies as the foundry becomes more familiar with the process. Companies such as Tech Cast are there to help our customers not only just produce parts, but to educate design and purchasing teams on these new technologies and how they can be applied to each customers unique need. 10 PART BUYERS A U T H R I T Y Contact: ANDY BOMBERGER [email protected] ANDY MILLER [email protected] Table 4: Process Comparison Step Description Wax Pattern SLA a CAD Modeling Pattern Foundry Processing Time to First Casting Cash Expenditure 0-1 Week 7-9 weeks 1-2 weeks 1 -2 weeks 9-12 weeks 2-5 weeks $40,000 $3,150 Incorporate pattern shrink, solidification modeling and gating into the casting design Obtain soluble core and pattern tooling or SLA pattern Process the pattern through the foundry and clean the casting Time from receipt of order to shipment of first casting (Casting complexity and value added services may affect this time) Purchases required to obtain first casting CONCLUSIONS • Casting Quality While not quite as good as a casting made from a wax pattern, thequality of a casting made from an additive manufactured/SLA pattern is good enough for all but the most demanding applications. • Cost of the First Casting The foundry must invest $40,000 into tooling before obtaining the first casting when using wax patterns. If they choose to use SLA patterns, they need only invest $3,150, less than 10% of that required for molded wax patterns. • Labor Content of Castings Casting a SLA pattern requires similar labor compared to a wax pattern. • Time to First Casting Additive manufactured patterns allows the foundry to deliver the first casting 6-8 weeks faster than wax patterns.