The reasonable assembly process is the key to produce uPVC doors and windows with excellent performance. The connection of uPVC window frame and mullion adopts soldering and bolting in European bulidings. It is widely used by many manufacturers of uPVC Windows because of its lower cost , convenient operation and firm installation. uPVC windows adopt screw joint, thus feeding fast, assembly easily. There is no need to cut the V-shaped mouth. It's very convenient and easy. It can use the four- angle welding machine with high work efficiency .The strength of uPVC window is much higher than that of welded structure, especially in the cross connection between the transom profile. The high performance of screw structure is more prominent. UPVC profiles with screw joint are not easy to deform when making large windows.