Two-point Incremental Sheet Metal Forming

Introduction

Metal forming is one of the most important industry, which gives 15-20% Gross Domestic Product (GDP) and plays a significant role in manufacturing process. The conventional manufacturing processes like drawing, deep drawing, stamping, stretch forming allows mass production with high level of automation but low flexibility. But when it comes to meet customer needs, the batch becomes smaller and smaller. Because of the complex part shape the tool complexity and cost increases in conventional sheet forming processes.

In recent years the research was made to find new methods to meet customer demands for small batch products. The Incremental sheet forming is mostly used to meet customer demands. This is a die-less process and also need low costs to develop new products. It is mainly used in prototype production.

In the incremental sheet metal forming process, a simple hemispherical or ball end tool is used to produce a local plastic deformation thereby forming the complex shapes. The forming tool follows a two-dimensional contour. The final shape of the product is obtained by repeating the step layer by layer. So, depend on the new shape of product only the CNC program has to be changed and the forming tool if necessary. The main elements used in the ISF process are sheet metal, blank holder with or without backing plate, clamping plate, forming tool and a three axis CNC machine. The tool have three degrees of freedom in x, y and z axis and rotation around its own axis. Depend on the contact between the tool and blank ISF is classified into Single point Incremental Forming, Incremental sheet forming with counter tools (another tool support from other side of the blank), Two-point Incremental forming (deformation takes place in more than point with help of partial die or full die support). In first two types only the tool moves along the programmed path and the blank holder is stationary. But in third type the blank holder is also moving along with forming tool direction to ensure die support. In most cases CNC milling machines are mostly preferred because they allow high speed, large working volumes and good stiffness. Special machines were also developed for ISF process. Using Industrial robots have benefits like large working volume, high flexibility than milling machine. The disadvantages with robots are low stiffness and low capacity to apply big forces. Unlike machining processes, the tools used for ISF process are not yet standardized. The tools used in CNC milling machine can be straight and hemisphere at the end. The tools used in CNC lathe are bend. The tool diameter varies from 6mm to 100mm for manufacturing of large parts. The materials selection in ISF process is done based on strength needed, weight and corrosion resistance. The material that mostly used in ISF process is aluminium and its alloys. Brass and Copper also used because of the formability properties and light weight. Titanium is used for its corrosion resistance property and magnesium is used for its light weight in many industries.

Problem Definition

The formability, geometrical accuracy, low cost and instantaneous product development makes Incremental sheet forming (ISF) more suitable over conventional forming methods. Even though the process has remarkable advantages, there are restrictions in forming complex shapes which makes the process inapplicable for industrial applications. The process parameters like tool diameter, tool velocity, step depth, spindle speed and tool path have considerable effect on the formability on the material. By controlling these input parameters, the complex shapes can be achieved.

Scope

To focus on the formation of complex shapes which is used in various fields such as aerospace, biomedical, prototyping and architectural aesthetic and decorative works.

To provide high accuracy than the traditional sheet forming process by controlling various process parameters.

To achieve good surface finish

That’s the reason many industries doesn’t implement this process. So this paper focus on that area. ISF is used in manufacturing industries for producing complex parts in automobile, aerospace, defence, missile and satellite components and in biomedical. In automobile industries craft production of luxury cars, customization in sheet metal works; in aerospace industries, high weight sheet panels, excellent fabrication; in defence, highly variable sheet metal works for minimum material cost and energy consumption. These are the areas where ISF is used. There are various process parameters such as tool diameter, tool velocity, step depth, spindle speed which influence the part accuracy and formability of the work piece which has to be focussed and many industry peoples are researching in this area. By our research of work we can implement ISF in industry to produce complex shapes with suitable method and process parameters. Future research can be done on formability and dimensional accuracy which are more important area influenced by process parameters.

Objective

To design and fabricate the setup to do Incremental sheet forming in the CNC machine tool for the applications of the aerospace industry.

To find the optimum parameters for the titanium material to achieve complex shaped parts.