Conceptual design issues are interdisciplinary in nature, and often involve collaboration from customers, designers and engineers. Preliminary design is widely supported at this stage. The concept generated at this stage directly affects the generation and the material selection for the product concerned [4]. Conceptual design begins with a description of requirements and continues with a detailed solution [5]. Here a solution path is laid down through the elaboration of a solution principle and involves formulation of abstract ideas with approximate concrete representations [6]. The early stage of conceptual design is dominated by generation of ideas, which is then evaluated according to the requirements. If required, additional ideas are incor- porated to get the decision [7]. Conceptual design is cru- cial, particularly, when designing new and innovative products, or when generating a completely new design for an existing product [8]. An effective conceptual designed is accompanied by the technical knowhow [9]. If the con- ceptual design activity is team based, then mapping of the activity of the team and full capacity utilization is very important [10, 11].

In the process of conceptual design, the detailed design (geometry, topology, tolerance, dimensions, surface con- dition, materials etc.) is arrived at after the consideration of requirement, function, behavior and  structure.

In this work, CNC lathe attachment has been designed and developed for a CNC machine. After the fabrication, it is installed on the CNC Machine. The CNC machine was designed and developed earlier at M.E, I.I.T-B.H.U along with an attachment of RP (Rapid Prototyping). The CNC machine uses mechatronic controls and a computer inter- face called CAMSOFT for operation. Figure 1 shows the CNC machine installed with RP  attachment.

All the three axes (vertical, horizontal and cross) are controlled by stepper motors (one each for the respective axis). The RP attachment consists of two servo motors (see Fig. 1) and installed on the bed of the horizontal axis and the mounting provision in the vertical axis. The RP machine is FDM based.

Control and Programming

An eight axis Galil Card is used to accommodate the servo controller and the motor and three stepper motors and two servo motors with its own controllers. The control system interface  is  accomplished  with  a  CAMSOFT    package.

Fig. 1  CNC machine installed with RP   attachment

A CNC program is written through the menu (Fig. 2) and the same is used to run the   machine.

The aim of the work is to develop a Lathe attachment for the CNC machine. The components of the RP attachment can be uninstalled from the CNC machine after taking out the attachment from the bed in the horizontal axis and from the mounting provision in the vertical axis. Thus vacating all the three axes and making way for the lathe attachment to get installed on the CNC machine. The entire idea of the work is based on the thought that, the same CNC machine can act as an RP or a lathe, when installed with an appropriate attachment on  it.

After uninstalling the RP attachment, three axes are available (controlled by three stepper motors). Also one separate servo motor is available. So the work aims at the development of the lathe attachment with the help of conceptual design, with respect to the resources   available.

Fig. 2  Screenshot of the CAMSOFT   interface

J. Inst. Eng. India Ser. C (April–June 2013)   94(2):187–195 189

Fig. 3 Procedure followed for the development of the Lathe attachment

Mild Steel is the material selected for fabrication of the components of the lathe  attachment.

Design A: Providing Headstock on the Z axis and Tailstock on the Y axis