Digital Manufacturing of Patterns for Casting through Rapid Prototyping (RP) Technologies

Abstract

Sand Casting is very old technique for casting metal parts. In this process a pattern is made which is a replica of the desired part. The pattern is placed in a box and curing sand is poured around it. After curing of sand, pattern is detached so that replica is imprinted in the sand. Then metal in molten form is added into the hollow portion and desired part is obtained after cooling. The process is cheap and incorporates all kinds of metals, however, the correctness of the final part is primarily dependent on the correctness of the pattern itself. Rapid Prototyping (RP) is a collection of contemporary manufacturing methods which create the part straight from Computer Aided Design (CAD) model using layer-by-layer deposition technique. The CAD model is first sliced and each cross section of the CAD model is used as a guide to deposit material at the desired location. The RP process varies with the technology being used. Additive Manufacturing (AM) has been of significance importance because of its precision and overall time reduction in product development process. Moreover, a prototype can be developed to know the functioning of the actual part which gives flexibility to designers to vary the design to eliminate the inaccuracies. A case study was undertaken in this research work in collaboration with KSB Pumps Hassan Abdal, Pakistan. KSB pumps are a well renowned manufacturers of pumps for variety of applications. The company was facing problem in one of their pumps named ‘Sewatec 250-401’ whose performance (efficiency) was not up to the desired standards. The impeller of the pump was being manufactured through manual pattern making and sand casting techniques. After detailed study of the manufacturing process of the said pump, it was observed that the vane of said impeller was manufactured in a crude way leading to doubts in its accuracy. Therefore, it was decided that the vane of this pump will be manufactured replacing existing manual pattern making with RP patterns and performance of the new and old pumps will be compared. The pump manufactured using RP technique showed higher efficiency (83.6% efficiency) as compared to the one manufactured using manual patterns (74% efficiency) and met all performance standards (82% efficiency). The manufacturing through RP reduced the overall cost of the manufacturing by 1/8th and considerably reduced the time to manufacture (by 11 weeks).