THICKNESS LOSS WHEN GLUING VENEER SHEETS INTO BOARDS IN THE HOT PRESSOR BY HIGH-FREQUENCY

An investigation was carried out on the influence of a number of relev ant factors which, in the case of hot press gluing i.e. conduction glu ing (CG) and high-frequency (HF) gluing of peeled beech veneer (Fagus silvatica L.) to produce veneer boards, result in a permanent thicknes s loss of the boards. Using both types of gluing, four different thick nesses of veneer, four different veneer humidities, and four different gluing pressures were varied to make a large number of different comb inations. Gluing of a total of 384 test boards 500 x 200 mm, with a th ickness of approximately 15 mm, was carried out using urea-formaldehyd e glue at a temperature of 120 degrees C. The gluing lasted for 8 minu tes for hot press gluing, and 5 minutes for the HF method. The results of the tests showed that the interdependencies noted between the effe cts of the studied factors were similar for both methods of gluing. In fluence of humidity on thickness loss was greater in the case of HF gl uing and premanent thickness loss was greater for high frequency gluin g.