Ultrasonic monitoring of resin curing in a press for the production of

Abstract

The technology used in the present invention is acousto-ultrasonics (AU), in which a transmitted signal, at a controlled frequency is injected into a specimen with one transducer and received at another location by another transducer, permitting evaluation of the condition of the material in the signal path. In the experiments that were made using the present invention, the material within the press was a particleboard mat having the signal injected into the edge of one platen and received at the edge of the second platen. The AU signal received at the second platen is initially in response to pressure changes in the mat and subsequently follows the progression of internal bonding of the material. Since the propagated wave through the mat reacts to resin curing during the last phase of pressing, changes in material or press variables are reflected directly in shifts of the curve received at the second platen. By monitoring the AU response curve, the press can be manually or automatically controlled to open within a specific range of board properties, such as IB. Not only does the technology of the present invention permit the shortest possible press cycle, it also permits control over the desired internal bond of the boards. The technology can be used in many types of presses and can serve as a supervisory system for press performance to determine if any openings are degrading in heat transfer. Additionally, shifts in the AU response curve can alert the press operator to both trends and abrupt changes as they occur.