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A functional machined casting for a rear housing in a dual clutch transmis- sion was produced in three weeks using 3-D printed sand technology. This enabled the customer to evaluate several designs quickly and achieve short time-to-market.
complexity factor of 45 or higher.—Connor Marrying Additive to Production
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thread slot allows lifting with straps by crane. Handholds reduce mold weight, allowing easier removal and allow for easier placement.—Shah
15 28 | MODERN CASTING January 2017
Remember that when prototyp- ing for production, there is more freedom in additive manufacturing than in standard production tech- niques.—Weiss.
The design process must account for additive manufacturing all the way from concept to pouring, including the removal and handling of cores and molds. Cores greater than 80 lbs. require attachment points for crane removal. Dual purpose all
For some highly complex parts, 3-D sand printing may be cost eff ective even if tooling exists already or part quantities are high, especially in situa- tions where cores can be consolidated. With 20% fabrication cost reduction, sand printing is eff ective for parts with a
produce your sand casting. Machined sand might need draft. T e tooling will limit
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fi llet sizes. You must be able to see what needs machined. Normally this method is not suitable for a core. On the plus side, there is no need for tooling, it’s fast, any sand with or without additive can be used, and large molds normally are cheaper than printed sand. In conventional tooling, draft is needed. T e more com-
plexity or tooling needed, the longer the lead times will be, but any sand—with or without an additive—can be used and it may be the most economical route depending on complex- ity, quantity and size. 3-D printed sand carries the need to be able to remove unbound sand, and consumables are limited. But no draft is needed, you are able to combine multiple cores into a single core and print complex geometry, and lead times are short.—Rittmeyer
T e tips shared in this article were taken from presentations given at the AFS Additive Manufacturing for Metal Casting Conference held October 3-6, 2016, in Novi, Michigan.
It’s time to unlearn standard fl ask sizes, common height copes and drags. Don’t be a square. 3-D printed molds can be contoured around the shape of the casting, saving printing time and mold material.—Lamoncha
But still use common sense. You must have a parting line to clean internal cavities. T e entire mold or mold pieces must fi t in the printer. Safe handling practices must be consid- ered.—Lamoncha
—Dave Rittmeyer, Hoosier Pattern. Closing Note
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So which process is best? All of them: conventional tooling, printed sand, or machined sand. In order to opti- mize printed mold designs, you need to learn how to apply each option or combination of options for the most cost eff ective and/or fastest way to
Printed sand’s strongest advantage is reduced lead time. T ere is no need to manufacture tooling, part development can be at infancy stage, package designs (partings) are unconstrained, and there is more freedom in gating strategy.
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