Rapid tooling route selection and evaluation for sand and investment casting

Abstract

Today, a number of direct routes using rapid prototyping (RP) processes (fused deposition modelling (FDM), laminated object manufacturing (LOM), stereolithography apparatus (SLA), selective laser sintering (SLS), etc.), as well as indirect routes (RP coupled with secondary or soft-tooling processes like RTV vacuum casting) are available for rapid fabrication of tooling for sand and investment casting processes. Each route is unique in terms of geometric, material, quality and cost characteristics; no comprehensive database of their capabilities has been reported, especially for metal casting applications. The problem of selecting the optimal rapid tooling (RT) route is a complex multi-criteria decision-making problem. This paper describes a systematic approach for RT route selection and planning. A database of RT process capabilities was generated through benchmarking experiments, covering 20 different widely used RT routes (both direct and indirect: two-and three-step processes) involving an impeller pattern. In this approach, RT process route selection involves translating the tooling requirements specified by the casting engineer into weighted tooling attributes using quality function deployment and analytic network process (QFD-ANP), which along with part specifications is used for RT route selection by calculating the overall process compatibility indices. The routes are ranked as per the value of the overall compatibility index. Once the optimal route is selected, process planning is carried out by retrieving a similar process plan using casebased reasoning (CBR). The methodology has been implemented in a software program using Visual C' ' programming language in a Windows environment. The methodology is demonstrated and validated with an industrial example of a separator body casting. It has proved to be a robust evaluation and decision-making tool for selecting appropriate tooling route for a given casting based on customer requirements.

Digital Manufacturing Process Chain for One-Off Replacement Parts: A Precision Casting Case Study

“…It was found to be very useful in that it enables elimination of feeding system designs that are obviously useless as well as focus on promising values of casting parameters. Among all papers, mainly case studies, that were found in literature dealing with rapid casting of parts based on an original to be replicated [1,2,[5][6][7]11,13,16,17,19,25,26,29], all but three tacitly admit that a right-first-time casting can be achieved, obviously by selecting casting feeding and process parameters according to experience. The three exceptions [16,19,29] used simulation to check that the single envisaged casting system design was suitable, i.e., without trying out alternatives.…”

The role and impact of 3D printing technologies in casting

“…SLA parts can be used as patterns to prepare moulds for injection moulding (Direct AIM) [22] . SLA was used for indirect RT to create master patterns for moulding and casting processes [23] . LOM was also used to create patterns for silicone moulding and wax injection moulds for investment casting [24] .…”

“…This can be overcome by adopting indirect routes, such as silicone rubber moulding, polyurethane/epoxy casting, and investment casting, which can be used to convert RP master patterns into moulds (or vice-versa) [9,[21][22][23][24][25][26] . These secondary processes aim to comprehensively optimize the development time, cost, quality, and lifespan.…”

“…Examples of 3D printed pattern, shell, wax pattern, core and mould are shown in Fig. 2. (a) SLS made polyamide-based models of heat exchanger for a Pratt & Whitney PW6000 engine [13] (b) Resin shell + slurry filling for wax making die [26] (c) Patterns fabricated by direct and indirect RT routes for sand and investment casting [23] : R-resin, W-wax, PU-polyurethane, RTV-a rubber, S-solid, VCvacuum casting, WIM-wax injection moulding (d) Assembled core and mould fabricated by 3DP [35] 2.1 Rapid tooling-3D printing of prototype, pattern, core box and wax injection mould A number of direct routes using 3D printing methods such as FDM, LOM, SLA, SLS, etc., as well as indirect routes (3D printing methods coupled with secondary or soft-tooling processes like vacuum casting), are available for rapid fabrication of a prototype, pattern, core box, etc. for the first step in the casting process [8][9][10][11][12][13][14][15][16][17][18][19][20] .…”

A high-efficiency automatic de-bubbling system for liquid silicone rubber

“…RT is divided into direct tooling and indirect tooling. 3 Direct tooling means fabricating mold inserts directly from an RP machine, such as selective laser sintering. 4,5 Indirect tooling means fabricating the mold insert by a master pattern fabricated using various RP technologies.…”