Guha Manogharan

Additive manufacturing–integrated hybrid manufacturing and subtractive processes: economic model and analysis

This article presents economic models for a new hybrid method where additive manufacturing (AM) and subtractive methods (SMs) are integrated through composite process planning. Although AM and SM offer several unique advantages, there are technological limitations such as tolerance and surface finish requirements; tooling and fixturing, etc. that cannot be met by a single type of manufacturing. The intent of this article is not to show a new manufacturing method, but rather to provide economic context to additive and subtractive methods as the best practice provides, and look at the corresponding economics of each of those methods as a function of production batch size, machinability, cost of the material, part geometry and tolerance requirements. Basic models of fixed and variable costs associated with additive, subtractive and hybrid methods to produce parts are also presented. An experimental design is used to study the influence of production volume, material and operating cost, batch size, machinability of the material and impact of reducing AM processing time. A composite response model for the unit cost is computed for the various levels associated with such engineering requirements. The developed models provide insight into how these variables affect the costs associated with engineering a mechanical product that will be produced using AM and SM methods. From the results, it appears that batch size, AM processing time and AM processing cost were the major cost factors. It was shown that the cost of producing ‘near-net’ shape through SM and AM was the decision criteria; which will be critical for tough-to-machine alloys and at multi-batch size.

Quantifying the Role of Part Design Complexity in Using 3D Sand Printing for Molds and Cores

Abstract3D sand printing provides a means to fabricate molds and cores without the need to fabricate patterns and core boxes. It is desirable to understand when to use this evolving advanced technology versus conventional pattern making. This analysis evaluates this question by examining the cost of molds and cores as a function of part design complexity quantified by a complexity factor. Two case studies are presented where the complexity of the castings is systematically varied by changing the geometry and number of cores. Tooling costs and fabrication costs are estimated for both 3D sand printing and conventional pattern making. The breakeven points are identified, and it is shown that 3D sand printing is cost-effective for castings with complexity factor values greater than that of the breakeven points. For low volume production of these castings, 3D sand printing is shown to be cost-effective for low quantities (<45 parts) of castings with lower complexity. However, it can also be very cost-effective for casting with higher complexity even at quantities of 1000 units. Since breakeven point is sensitive to the cost of 3D sand printing, lowering the materials and operations costs can significantly improve the cost-effectiveness of 3D sand printing for varied production volume and part design complexity.

An assessment of implementation of entry-level 3D printers from the perspective of small businesses

Purpose – The purpose of this paper is to examine the implementation of entry-level printers in small businesses and education to identify corresponding benefits, implications and challenges. Design/methodology/approach – Data were collected from four small businesses in northeast Ohio through survey- and interview-based feedback to develop an understanding of their use of entry-level 3D printing. Three businesses are representative of typical manufacturing-related small companies (final part fabrication-, tooling- and system-level suppliers) and the fourth company provides manufacturing-related educational tools. Corresponding learning from implementation and outcomes are assessed. Findings – Adoption of 3D printing technology was enabled through hands-on experience with entry-level 3D printers, even with their shortcomings. Entry-level 3D printing provided a workforce development opportunity to prepare small businesses to eventually work with production grade systems. Originality/value – This paper deta...

Current state and potential of additive – hybrid manufacturing for metal parts

Purpose This paper aims to investigate the extent to which traditional manufacturers are equipped and interested in participating in a hybrid manufacturing system which integrates traditional processes such as machining and grinding with additive manufacturing (AM) processes. Design/methodology/approach A survey was conducted among traditional metal manufacturers to collect data and evaluate the ability of these manufacturers to provide hybrid – AM post-processing services in addition to their standard product offering (e.g. mass production). Findings The original equipment manufacturers (OEMs) surveyed have machine availability and an interest in adopting hybrid manufacturing to additionally offer post-processing services. Low volume parts which would be suitable for hybrid manufacturing are generally more profitable. Access to metal AM, process engineering time, tooling requirements and the need for quality control tools were equally identified as the major challenges for OEM participation in this evolving supply chain. Practical implications OEMs can use this research to determine if hybrid manufacturing is a possible fit for their industry using existing machine tools. Originality/value Survey data offer an unique insight into the readiness of metal manufacturers who play an integral role in the evolving hybrid supply chain ecosystem required for post-processing of AM metal parts. This study also suggests that establishing metal AM centers around OEMs as a shared resource to produce near-net AM parts would be beneficial.

Additive Manufacturing of Orthopedic Implants

Additive Manufacturing (AM) is the process of selectively joining materials to fabricate objects in a layer-by-layer approach using digital part information, i.e. 3D CAD models. This definition highlights the fundamental difference between AM process and traditional manufacturing methods such as subtractive processes (e.g. machining), forming processes (e.g. forging) and bulk solidification processes (e.g. casting). AM is often also called 3D printing, additive processes, freeform fabrication and layered manufacturing. When compared to traditional processes, AM offers unique advantages to economically produce low volume batches (one to a few) of highly complex products. Since AM does not require design and/or material dependent tooling (e.g. jigs and fixtures), AM is an ideal candidate for the next generation design and manufacturing of orthopedic implants. Although “customization” of product specifications implants has been around long before the introduction of AM technology to the medical field, the lack of tooling requirement for each design in AM makes it economically viable for patient-specific orthopedic implant production. Finally, design freedom that can be easily achieved through AM technology enables introduction of porous structures for bone ingrowth and biological implant fixation. The motivation for this chapter is to understand the current state of orthopedic applications of AM which have been shown to economically produce highly customized and highly complex design features in low volumes.

Re-Thinking Design Methodology for Castings: 3D Sand-Printing and Topology Optimization

AbstractAdditive manufacturing of sand molds and cores for metal castings, often called 3D sand-printing (3DSP), is an efficient “freeform” fabrication process that enables rapid production of sand metal castings. The ability to create highly complex molds and cores for advanced metal casting geometries via 3DSP provides unparalleled design freedom, particularly for low-volume production. However, there is a need to thoroughly understand the opportunities and restrictions of 3DSP in a systematic approach similar to well-established design guidelines for traditional sand casting. This study presents a knowledge-based design framework for 3DSP with the goal of developing new part design guidelines under such 3DSP framework. In particular, constrained topology optimization approach for the part redesign is developed for 3DSP. The presented design framework is compared with traditional sand-casting rules and validated through a case study on an existing metal component. Advantages of the developed 3DSP design framework are illustrated and validated through a case study where a 30% improvement in factor of safety and a 50% reduction in weight of a mechanical part is achieved. Other advantages, such as reduced lead time and production cost, are also observed. This research provides the first known investigation into systematic implementation of simultaneous constraints of 3DSP sand-casting rules mechanical strength through the integration of topology optimization and novel design rules to castings via 3D-printed molds. 3DSP also eliminates multiple design constraints in conventional mold-making and core-box fabrication. Findings from this study can be applied for a wide range of alloy systems, part geometries and loading conditions for sand castings in industrial applications.