To be a PVC window manufacturer you need an appropriate PVC - U window welding machine to weld your window corners and to produce Aluminum Window you should have a corner crimping machine. PVC - U welding machine can be single corner welding machine, double corner welding machine; four corners welding machine or CNC Welding and cleaning center . This stage is one of the most important steps in PVC window production process and you should pay enough attention in selecting PVC window Welding machines.