As shown in Fig. 4, the design will eliminate the require- ment for a guide way to the tailstock, as the work piece of any size will be accommodated by varying the position of headstock on Z axis. The major drawback of this design is the rigid connection between Y axis and Z axis. Also the positioning of the tool post will be problematic. The deflection of the vertical column (containing Z axis) will also be possible due to a relative larger weight on    it.

Design B: Providing Headstock and Tailstock on the Z axis and Tool post on the Y  axis

As shown in Fig. 5, the design will eliminate the rigid connection  between  the  Z  and  Y  axis.  Provision  of the

The development procedure followed and the relevance of conceptual design is shown in Fig. 3. The procedure begins with problem identification and the aim is to develop the lathe attachment which can be mounted to the CNC machine. On thorough analysis the requirements for the attachment are identified, like positioning of different components of the lathe attachment on different axes. Now design of different assemblies and subassemblies (head- stock, tailstock, tool post) is done with the help of con- ceptual design. Conceptual design generates design concepts and uses solid modeling and yields the preliminary design, based on which further possibilities of different designs are explored to refine the preliminary design. The crucial aspects of different designs are considered and are used to get the detailed design. On fulfillment of all the desired requirements, the particular design is finalized for the desired components. Now production planning is done accordingly to realize the finalized design and the compo- nents are manufactured. The assembly of different com- ponents accordingly leads to the desired lathe  attachment.

Conceptual Design for the Lathe  Attachment

Of the three axes in the CNC machine, the cross axis is designated as X axis, the horizontal axis is designated as Y axis and the vertical axis is designated as Z axis. These Axes can be seen in Fig.  1.

The major components in any lathe machine is head- stock, tailstock and tool post. Three basic designs (A, B and

C) are developed with respect to the available axes of the CNC machine. CATIA V5 and AUTOCAD 2007 have been used for solid  modeling.

Fig. 4 Design A, Headstock on Z axis (Vertical) and Tailstock on Y axis (Horizontal)

Fig. 5 Design B, Headstock and Tailstock on the Z axis (Vertical) and Tool post on the Y axis   (Horizontal)

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

Fig. 6 Design C, Headstock and Tailstock on the Y axis (Horizon- tal), Tool post on the Z axis   (Vertical)

headstock and the tailstock on the Z axis will require a slide way. Tool post is will be provided on Y axis. But the height of the tool post will be limited, thus restricting the reach of the tool on the work   piece.

Also supporting a large mass on a vertical plane in a cantilever condition is not considered as a good design; to eliminate this defect, heavy stiffener will have to be pro- vided at the back of the vertical   column.

Design C: Providing Headstock and Tailstock on the Y axis and Tool post on the Z  axis

As shown in Fig. 6, in this design both the headstock and the tailstock will be on Y axis. The design provides the maximum extent of freedom for movement of all the axes of the machine tool. The design will require a slide way. As the work piece will have a very little weight as compared to combined weight of headstock and tailstock, so proper balancing could be achieved. It is quite evident from the model that rigidity of Y axis is quite high as compared to Z axis. Tool post will to be mounted on the Z axis, thus it will enable the machining of the entire length of the work piece.