Cadno Roll Inspection System

Sophisticated high precision electronic roll gauging

The CADNO Roll Inspection and Management System is the latest in a range of instruments developed in Wales as a result of University / Industry collaboration. Mechanically, the CADNO system consists of a pre-adjustable calliper similar to the well known "trotter" or "vine". The best features of the well established scanning micrometer have been combined with electronics and bespoke software. The instrument is modular in design to allow for easy maintenance and a number of features have been incorporated to make the system rugged and reliable. In addition to the carriage and calliper there are three modules: gauging module, encoder module and on-board microcomputer module.

Precision Gauging Module

The variation in diameter is measured using a Linear Variable Displacement Transducer (LVDT) where the movement of the gauging tip is converted to an electrical signal by the change in the coupling between primary and secondary coils produced by the co-axial movement of a ferrite slug. The LVDT used has a stroke of 2 mm and a linearity of better than 0.3%. Repeatability is better than 0.1 micron. The design allows for fine radial adjustment and clamping whilst offering protection against damage and over-travel.

Encoder Module

Distance along the barrel is measured by means of an optical encoder (which generates 100 pulses per revolution) mechanically coupled to a polyurethane tyred wheel of 100 mm circumference. The design permits measurement right to the edge of the barrel.

Electronic Control Module

The on-board signal processing, display and recording is achieved by a fast analogue to digital converter. The operator interface has deliberately been kept simple and robust and consists of a sealed membrane keypad and a liquid crystal display. On first switching on the electronics, the output from the LVDT is displayed digitally. This allows the probe to be positioned near its mid stroke and also facilitates calibration. When the start button is depressed the displays record zero electronically and thereafter the distance traversed across the barrel and the change in diameter are displayed digitally.

PC Software Module

The electronic calliper, as described, may be used as a self-contained inspection tool. However, the scope for improved quality control and analysis of roll profile data is greatly enhanced if such a calliper is used in conjunction with a PC based software package , the data being transferred from the calliper to the station using a plug-in CMOS SRAM memory card.