The use of glue thread (thermoplastic yarn) in the production of plywood and veneer
Hot melt glue thread is widely used in the production of plywood at the stage of splicing veneer into sheets of a certain format, from which the thickness of the finished plywood sheet is then drawn.
There are several types of ribbed gluing equipment of various capacities and purposes. Each of them uses its own type of thread.
Large and medium-format semi-automatic lines for veneer cross-splicing such as Kuper DMF/H 1800/2800 (Germany), Cremona (Italy) use thick hot melt glue thread NPI-131and NPI-135 in combination with the RN-28 lubricant, which prevents the heated glue thread from sticking to the stitching roller. The supply of glue thread from 5-8 bobbins to the spliced veneer is carried out through the yarn guides, which heat the thermal thread to the required temperature immediately before applying it to the sheet surface.
Large and medium-format semi-automatic lines for veneer cross-splicing, such as the Raute type (Finland), have a similar method of edge gluing, however, unlike Kuper DMF/H, adhesive tape is used in this process. The adhesive tape has a large contact area with the surface in comparison with the NPI-131 and NPI-135 hot melt thread, which ensures better adhesion of the thread to the veneer.
Small-format machines for longitudinal veneer splicing, such as Kuper FW920 / 1150/1200, RS-9 use the "zig-zag" splicing method applying NPI-181 glue thread.
When gluing veneer longitudinally, the glue thread is applied to the two surfaces to be joined with a "zig-zag" stitch. This method ensures reliable and high-quality splicing of veneer sheets. The glue thread is fed to the sheet from 1-2 bobbins through an electric or electro-air yarn heating pipe..
Kuper's KHL-1, KHL-2, HFZ-4 hand gluers for veneer are designed for splicing small veneer pieces using the NPI-191 and NPI-192 hot melt glue thread. These machines are used to "set" veneer sheets in the production of veneered doors, as well as in the furniture industry in the manufacture of veneered elements.