As an advanced surface treatment technology, abrasive flow technology has demonstrated excellent results in 3D printing application. It can remove surface burrs and improve accuracy and surface quality, with environmental protection and energy saving advantages. However, during the processing of complex internal flow channel surfaces, uneven processing phenomena can occur. Therefore, the work aims to address the issue of excessive wear on the exterior of the elbow runner at right angles, which is caused by variations in the gradient of abrasive inertia force during abrasive flow polishing, and enhance the uniformity of processing in elbow components. To achieve this, three innovative structural designs for elbows were proposed by modifying the geometry of the flow channel. The effects of various point pressures and flow channel shapes on material removal and surface quality were studied through numerical simulation and experimental analysis. A 3D-printed aluminum alloy bend pipe was used as the test object. The process parameters were determined through tests, and the abrasive flow processing was simulated with the Carreau-Yasuda equation for non-Newtonian fluids. The simulation parameters of the outer pressure in the bend pipe were obtained and divided into two groups for comparison. The pipe bending was modeled with SolidWorks software, and the model was then imported into Fluent for simulation. The simulation results showed that the pressure of the non-uniform thickening type was larger than that of the ordinary type, and the pressure trend of the bar type and the half ball type was almost the same. During the machining test, the removal amount on the outer side of the bend was measured, and the sample points where the cutting amount changed were analyzed. Finally, the shape accuracy of the bend pipe was analyzed by 3D scanner. Under a processing pressure of 10 MPa and after 100 processing cycles, the removal amount for both ordinary and uneven thickened bend pipes initially increased and then decreased. The uneven thickened bend exhibited the greatest removal at the chamfer and the bend section, increasing by 20.7% compared to the ordinary bend. Due to the increased processing allowance of the uneven thickened protection structure, the overall surface consistency of the inner wall of the bend was better. The cutting amount for strip and hemispherical bend pipes increased sharply at the protruding structures, with increase of 67.2% and 47.5% respectively compared to ordinary bend pipes. The protruding part deformed after processing, which affected the practical use. The inner removal for strip and hemispherical bend pipes was significantly improved compared to ordinary bend pipes, increasing by 172% and 151% respectively. The process parameters of machining pressure and machining times are determined by experiments, and the surface quality after bending with three optimized structure designs is explored. It is found that the surface quality of the bend pipe with the uneven thickening design is superior, offering theoretical guidance for further optimization of bend pipe structures and abrasive flow machining experiments.