Time-controlled insertion and removal of the sanding pad, while the workpiece passes through the machine.

When sanding painted workpieces and thin veneers, there is the risk of the sanding pad to round the front and rear edges when the workpiece enters or leaves the machine or that they are even sanded through (see sanding through). To avoid this, the workpiece is registered at the inlet of the machine and the sanding pad is put onto the workpiece or removed from it controlled by time or way.

For this, the operator changes the default insertion or removal times of the sanding pad using an electronic timer or an electro-mechanical cam control. The cam control is often located at the rear pulley of the conveyor bed, the electronic time control is usually integrated into the control panel, recognizable by the mechanical or electronic timer. For computer-controlled machines, the setting up of the insertion and removal times is integrated into the control software.

Special features

When changing the feed rate of machines with mechanical feed control and electronic time control, the insertion and removal times have to be recalculated.

The company Sandingmaster offers two solutions:

• A machine with two fixed feed rates: For both feed rates, insertion and removal times can be programmed.
• A machine with continuously variable feed rate, insertion control via pulse generator and pulse counter: Insertion and removal are not controlled by time, but via a pulse generator coupled to the conveyor bed. Depending on the selected feed rate, it gives more or fewer pulses. At the pulse counter, the number of pulses until the insertion of the sanding pad and the number of pulses until the removal of the sanding pad are entered.