Contactless Electrostatic Feeder

The aim of this research work is the design and test of a contactless electrostatic microfeeder, able to orient and transport micro components along straight lines is presented.

The experimental apparatus

The experimental apparatus (Figure 1) consists of a high voltage supply (HVS), a vibrating platform (4), a series of parallel electrodes (6) and a 3-axes micropositioning table, a switching control system (8).

Figure 1- Experimental apparatus

The vibrating platform is used to reduce friction and adhesion forces, so the microcomponents exhibit a random free motion on the working area.

The vibrating system consists of a wave generator (1) which drives a piezoelectric disk (2) that moves the platform is composed by a couple cylinder-hole with limited clearance necessary to eliminate horizontal vibrations that could affect the component motion. 

The electric structure of the device consists of a series of three parallel electrodes (Figure 2) which are repeated several times. The electrodes have a pitch of p and the voltage level repeats at distance 3p. 

Figure 2- The feeding process

In Figure 2 the couple of electrodes a and d, b and e, f and c are connected together to the HVS and their voltage supply sequence is given in Table 1.

Table 1- The supply sequence

The effect of the supply sequence is a travelling high electric voltage corresponding to a moving capacitor. When the component arrives under the electrode, attracted by the higher electrostatic field, the voltage is switched to the next electrode and the electrostatic field is shifted of a pitch.

So the component, after its alignment, moves stepwise under the electrodes from electrode to electrode, following the travelling electric field.

Figure 3 - Steel Cylinder, switching period T=0.5sec

Movies

Sphere

Micro Gear

For more information:

Fantoni, G., Santochi, M., 2004, “A contactless electrostatic device for linear movement of mini and microparts”, Proceedings of the IMG04, Genova, Italy, July 1-2.
IMG04 ISBN 88900426-1-3

http://www.img04.com