Positive displacement motor is a widely used downhole power drilling tool. In order to solve the problems of short life of conventional positive displacement motors and difficulty in processing micro-sized positive displacement motors with equal wall thickness, this paper proposes to use the liquid filling and external extrusion composite forming process to process the tiny size spiral tube with equal wall thickness. Based on the tensile test of 304 stainless steel and the liquid-filled and external extrusion composite forming process, a finite element model of the 5LZ54 type equal-wall spiral tube by liquid-filled and external extrusion composite forming was established. We use the finite element method to study the composite forming of liquid-filled and externally extruded metal spiral pipes with equal wall thickness. The reasonable process parameters are that the outer diameter of the tube is 51 mm, the wall thickness of the tube is 5.5 mm, the friction coefficient is 0.125, the hydraulic pressure is 700 MPa, the extrusion speed of die is 0.167 m/s, and the hydraulic pressure loading path is path 5. The spiral tube completely fits the die. The variance of the wall thickness is 0.00846, and the wall thickness is more concentrated. The minimum wall thickness is 4.948 mm, the design wall thickness is 5 mm, the maximum wall thickness is 5.353 mm, and the average wall thickness is 5.15 mm. The maximum wall thickness error of the spiral section is 0.275 mm. The wall thickness at the convex arc is larger, and the wall thickness at the concave arc is smaller. Studies have shown that it is feasible to form a spiral tube with a small size and equal wall thickness by liquid filling and external extrusion forming process.

容积式马达是一种广泛使用的井下动力钻井工具。为解决传统容积式电机寿命短、等壁厚微型容积式电机加工困难等问题，提出采用充液外挤压复合成型工艺加工微型螺旋管。壁厚相等。基于304不锈钢拉伸试验和充液外挤压复合成形工艺，建立了5LZ54型等壁螺旋管充液外挤压复合成形有限元模型。我们采用有限元方法研究了充液和外挤压等壁厚金属螺旋管的复合成形。合理的工艺参数为管外径51mm，管壁厚5.5mm，摩擦系数0.125，液压700MPa，模具挤出速度0.167m/s，液压加载路径为路径5。螺旋管完全贴合模具。壁厚方差为0.00846，壁厚更集中。最小壁厚4.948mm，设计壁厚5mm，最大壁厚5.353mm，平均壁厚5.15mm。螺旋截面最大壁厚误差为0.275mm。凸弧处壁厚较大，凹弧处壁厚较小。