A New Approach for Handling of Micro Parts in Bulk Metal Forming

During last 10 years a lot of research has been done in micro forming processes. In spite of the challenges micro forming has in process, material properties, tooling technology and machines, micro forming technology yields remarkable accuracy and good mechanical properties with high rate of production [1].

This can fulfill the demands for mass production and miniaturization in industries and academic communities. According to the recent studies, topics related to materials, process and simulation have been investigated intensively and well documented. Machines, forming tools and handling systems are critical elements to complete micro forming technology for transferring knowledge to industries and toward miniature manufacturing systems (micro factory) [2].

Since most metal forming processes are multi stage, making a new handling system with high reliability on accuracy and speed is required. The handling system for micro parts should provide good precision and reproducibility with high speed and acceleration for gripping and positioning micro parts in the right place within few micron tolerances.

Nowadays, many handling systems have been developed; either the conventional systems have been optimized or handling systems based on new concepts for gripping and releasing micro parts have been proposed. Making a handling system for micro parts made by sheet metals or foils is easier than those in bulk metal forming because parts are attached to the sheet during the forming process.

Geiger made a prototype with vacuum gripper which enables transport of 260 parts per minute; with the length of 25 mm and the part diameter 0.85 mm and the accuracy of 5μm in positioning [3]. Wafios AG built up a multi station former with output rate of 400 strokes per minute and parts with diameter down to 5mm [4].

In addition IPU made a manipulator for micro parts for a multi stage bulk metal forming process [5]. This handling system works based on tension forces of viscous lubricant. Generally, conventional systems do not meet the requirements for accuracy in the micro domain, not only sticking forces are predominant compared to the weight of parts, but also small surfaces make gripping more difficult.

Moreover, they have to position micro parts above forming dies in high acceleration within few microns. Backlashes and clearances which are not so important in the conventional handling systems must be considered in the manipulators for micro parts. So currently the trend for the design of micro manipulators is to reduce the size of them, simplify their design and make them more flexible to be able to include a wide range of products.

This paper presents an approach for making a linear transportation system for bulk micro parts in a multi station bulk metal former. The system is analyzed with respect to accuracy and repeatability.