Developing a Method for Ultrasonic Quality Control of Plastic Products Obtained by Rotary Moulding Method

Rotational moulding of plastics is rapidly developing in the world today. However, with this method of processing, "microbubbles" can occur in the walls of products, considerably impairing their quality. In this paper, the method of ultrasonic testing (UST) is applied to assess the quality of plastic products. With the help of an echo method at a working frequency of 2.5 MHz, samples of various degrees of quality were analyzed. It has been revealed that the propagation speed of an ultrasonic signal does not depend on the degree of product quality and is $$2330 \pm 10$$ m/s. It has been found that the larger the surface roughness parameter Rz of the products (from 2.5 to 20 μm), the smaller the amplitude of the bottom signal $$Aa$$ becomes. An underheated sample is determined by the values of parameter $$Aa$$ from –6.0 to –15.0 MHz. A reference sample was established ( $$\rho = 0.942~$$ g/cm3) for calibrating the flaw detector; for this sample $$Aa = 0$$ dB at an operating frequency of 2.5 MHz. The relationship between the density/heating of products and the amplitude of the bottom signal has been revealed. The possibility of detecting internal defects of products by ultrasonic inspection has been proven. A new method is proposed for identifying suitable articles in production using which it is possible to determine the degree of product quality.