K.P. Karunakaran

Weld bead modeling and process optimization in Hybrid Layered Manufacturing

Hybrid Layered Manufacturing is a Rapid Manufacturing process in which the metallic object is built in layers using weld deposition. Each layer built through overlapping beads is face milled to remove the scales and scallops and ensure Z-accuracy. The formations of single beads and overlapping multiple beads are modeled in this paper. While the individual beads geometry is influenced by the size of the filler wire and the speeds of the wire and torch, the step over increment between the consecutive beads additionally comes into the picture for the multiple bead deposition. These models were validated experimentally. They are useful not only to predict the beads shape but also to optimize the three process parameters.

Rapid manufacturing of metallic objects

Purpose – The purpose of this paper is to review additive and/or subtractive manufacturing methods for metallic objects and their gradual evolution from prototyping tools to rapid manufacture of actual parts.Design/methodology/approach – Various existing rapid manufacturing (RM) methods have been classified into six groups, namely, CNC machining laminated manufacturing, powder‐bed technologies, deposition technologies, hybrid technologies and rapid casting technologies and discussed in detail. The RM methods have been further classified, based on criteria such as material, raw material form, energy source, etc. The process capabilities springing from these classifications are captured in the form of a table, which acts as a database.Findings – Due to the approximation in RM in exchange for total automation, a variety of multi‐faceted and hybrid approaches has to be adopted. This study helps in choosing the appropriate RM process among these myriad technologies.Originality/value – This review facilitates i...

Optimal part orientation in layered manufacturing using evolutionary stickers-based DNA algorithm

Over recent years, layered manufacturing (LM) has been one of the most important emerging research areas, as well as practice perspective, owing to its capability to reduce the product development time, and therefore time-to-market. In LM, owing to the significant role played by the part orientation in the successful and efficient reduction of the staircase effect, the determination of optimal part orientation is a matter of paramount importance. In this research, the dual parameters problem has been modelled, taking into consideration the constraints pertaining to the rotation of the computer aided design (CAD) model about two axes, while aiming to optimize the objective function that involves layered process error as well as build time. The current paper presents an advanced stickers-based DNA algorithm (SDNA) inspired by the characteristics of deoxyribonucleic acid (DNA) as a tool to achieve the optimal orientation during fabrication of a part. The salient feature of the proposed algorithm is the use of stickers along with DNA memory strand, which are responsible for the representation of information. Moreover, fundamental operations are applied to manipulate the positions of the stickers in essentially all the possible ways. The performance of SDNA has been tested on two standard case studies and the comparisons are made with results obtained from genetic algorithm (GA). The results clearly demonstrate the efficacy of proposed algorithm over GA when applied to the underlying problems.

Evolutions of rapid product development with rapid manufacturing: concepts and applications

This paper relates to the recent evolutions of rapid product development and mainly on technological point of view. Critical issues are of several nature, methodologies, product-process knowledge-based approaches, new technologies and applications. The idea is to take into account the knowledge related to the additive manufacturing technologies when defining the main characteristics of the products. The evolution of the capacities of the actual rapid manufacturing technologies enlarges the scope of new product design and manufacturing. The final goal is to increase the efficiency of the rapid product development processes by the use of new technologies and new methodologies.

Techno-economic analysis of hybrid layered manufacturing

Subtractive manufacturing (CNC machining) has high quality of geometric and material properties but is slow, costly and infeasible in some cases; additive manufacturing Rapid Prototyping (RP) is just the opposite. Total automation and hence speed is achieved in RP by compromising on quality. Hybrid Layered Manufacturing (HLM) developed at IIT Bombay combines the best features of both these approaches. It uses arc welding for building near-net shapes which are finish machined to final dimensions. High speed of HLM surpasses all other processes for tool making by eliminating NC programming and rough machining. The techno-economic viability of HLM process has been proved through a real life case study. Time and cost of tool making using HLM promises to be substantially lower than that of CNC machining and other RP methods. Interestingly, the material cost in HLM was also found to be lower. Synchronisation of this two-step process offers a new accelerated way of building metal tools and dies. HLM can also be used as a cheaper retrofitment to any three or five axis CNC milling machine or machining centre.

Build strategies for rapid manufacturing of components of varying complexity

Purpose – This paper aims to develop build strategies for rapid manufacturing of components of varying complexity with the help of illustration. Design/methodology/approach – The build strategies are developed using a hybrid layered manufacturing (HLM) setup. HLM, an automatic layered manufacturing process for metallic objects, combines the best features of two well-known and economical processes, viz., arc weld-deposition and milling. Depending on the geometric complexity of the object, the deposition and/or finish machining may involve fixed (3-axis) or variable axis (5-axis) kinematics. Findings – Fixed axis (3-axis) kinematics is sufficient to produce components free of undercuts and overhanging features. Manufacture of components with undercuts can be categorized into three methods, viz., those that exploit the inherent overhanging ability, those that involve blinding of the undercuts in the material deposition stage and those that involve variable axis kinematics for aligning the overhang with the d...

Statistical process design for hybrid adaptive layer manufacturing

Purpose – This paper discusses the optimization of the process parameters for the hybrid‐layered manufacturing (HLM) process during its weld layer deposition with subsequent surface machining in attaining the desired accuracy and contour profile of the deposited weld layer thickness.Design/methodology/approach – The HLM process integrates the synergic metal inert gas (MIG) – metal active gas (MAG) welding process for depositing the metal layer of a desired slice thickness and perform the computer numerical control (CNC) machining process on the deposited layer to enhance both the surface quality and dimensional accuracy of the deposited layer. For the HLM process the weld bead geometry plays a vital role in determination of the layer thickness, surface quality, build time, heat input into the deposited layer and the hardness attained by the prototype. A feasible weld bead width and heights are to be formulated for the exterior contour weld path deposition and for the interior weld cladding. Thus, Taguchi ...

Geometric Modeling of Manufacturing Processes Using Symbolic and Computational Conjugate Geometry

The present paper describes a unified symbolic model of conjugate geometry. This model can be used to study the geometry of a cutting tool and the surface generated by it on a blank along with the kinematic relationships between the tool and the blank. A symbolic algorithm for modeling a variety of shape generating processes has been developed. It has been shown that using this algorithm one can develop geometric models for conventional machining processes such as milling, turning, etc. as well as unconventional or advanced machining techniques such as Electric Discharge Machining (EDM), Laser Beam Machining (LBM) etc. The proposed symbolic algorithm has been implemented using the symbolic manipulation software, MACSYMA. The algorithm is based on the concepts of envelope theory and conjugate geometry of a pair of mutually enveloping surfaces. A case study on the manufacture of a helicoidal surface and an illustrative example are given at the end of the paper.

Hybrid rapid manufacturing of metallic objects

While CNC machining, the subtractive method, is the only option when it comes to high quality components, the need for human intervention to generate the CNC programs makes it a slow and costly route. On the other hand, rapid prototyping (RP), the additive method, is able to convert the design into the physical objects without any human intervention but its total automation comes with compromises in the qualities of geometry and material. A balance between these two extremes is hybrid rapid manufacturing (HRM). In HRM, the near-net shape of the component is built in layers (additive method) and the same is finish-machined (subtractive method). While the priority during material addition is material integrity, the same is on geometric quality during material subtraction. As the focuses in both these steps are different, they are very fast. The existing HRM processes for metallic objects are reviewed in this paper followed by a brief description of ArcHLM under development at IIT Bombay. The generic ArcHLM facility or Hybrid FMS will be able to demonstrate its various applications of for fresh manufacture and repair of tools and components.

Swept volume of a generic cutter

Abstract Calculation of the swept volume of a cutter is the heart of any numerical controlled (NC) simulation system. In NC machining, a wide variety of cutter shapes are used such as flat end mills, dome end mills, ball nose end mills, angle cutters, face mills and side-and-face cutters. There are also many types of cutter paths along which the cutter is guided by the NC controller: rapid motion, linear motion and circular motion are the most commonly used cutter paths among them. Furthermore, the kinematics of the NC machines also differ leading to 2.5-axis, 3-axis and a variety of 5-axis configurations. The swept volume algorithms have to take into account all these variations of cutter shapes, motion types and machine kinematics. In this paper, first the parametric definition of a generic cutter is presented that can emulate all types of cutter shapes. Subsequently, the motions are classified into six types considering the cutter path and kinematic variations for ease of swept volume calculations. Finally, the swept volume algorithms for each of these six motion types are presented. These algorithms are used in a volumetric NC simulation system for which applications are envisaged in (a) NC verification and (b) optimization of the feed rate.