Reliability of the Butt-Fusing Welding (BFW) joint of High-Density Polyethylene (HDPE) pipes is highly affected by the given parameters of Fusion Procedure Specification (FPS). Due to the operational effect, machine process capability and the impact of environment & climate, the required FPS may not be accurately applied to the joint and may vary largely during the welding process. The methods to assess the mechanical property and life expectation of the welding joint are very complicated. The best performance of welding joint is guaranteed by a capable machine which can execute an approved FPS correctly. The machine innovated and presented here is highly automatic and intelligent. It eliminates operational mistakes and delivers the consistence for joint quality. This machine reacts to the environmental influence, and thus, eliminates or compensates their effect. With the creative calibration system, it can self-detect the faults of those critical parameters. Therefore, welding process reliability is reached. Melted material geometry is used as the criteria to judge the quality of joint, which is a method of non-destructive inspection. In addition, this machine is reliable to be used to assess and define a best FPS to improve joint quality.