Research On WAAM Variable Width Path Planning And Process Parameters Matching

The traditional path planning algorithm and process parameter matching usually use offset and constant process parameters to deposit metal parts.This method limits the additive manufacturing ability of WAAM on metal parts with variable width section shape to a certain extent.In order to solve this problem,this paper takes the cam structure with variable width characteristics as verification part,and proposes a variable width path planning algorithm based on straight skeleton extraction and a matching strategy of process parameters based on response surface methodology.The experimental platform of arc additive manufacturing was established,including MOTOMAN arc welding robot,PANASONIC YD-500FR welding power supply and software control system.Based on this platform,125 groups of sample data were obtained by using the comprehensive test method to carry out the basic experiment of single cladding channel between the process parameters and the deposition forming size.The forward model of BP neural network is established with walking speed(V),deposition current(I)and deposition voltage(U)as input parameters and width(W)and height(H)as output parameters.The verification set was used to verify the prediction ability.The results show that the forward model has very high prediction accuracy,the R2 value of fusion width is 0.993,and the R2 value of fusion height is 0.983.In the actual deposition process,it is necessary to predict the appropriate process parameters according to the planned forming size of the deposition channel.Therefore,the neural network model is used to reverse predict and establish the deposition size process parameters database with the input of the width and height and the output of the process parameters.In order to study the shortcomings of the traditional path planning algorithm in cladding cam structure,the parallel line path planning algorithm,contour offset path planning algorithm and compound path planning algorithm are compiled based on CGAL computational geometry library.After the analysis of the cladding,it can be concluded that the traditional algorithm will appear ladder effect,contour offset self intersecting,contour offset self intersecting on the variable width parts along the axis can not be deposited and the phenomenon of holes,deposition efficiency is low.Therefore,a variable width path planning algorithm based on straight skeleton extraction is proposed.Through straight skeleton extraction and radius function division,the path trajectory is generated.The results show that the path trajectory generated by the variable width path planning algorithm can adapt to the geometry with variable width characteristics.In order to solve the problem of process parameter matching under variable width path,a process parameter matching strategy based on response surface method is proposed with the constraint of constant height,which aims to realize continuous change of weld width by adjusting walking speed and deposition current.Firstly,based on the central composite design(CCD),the response surface equation with process parameters as input variables and weld width and weld height as response variables is established.Through statistical analysis,it can be concluded that I,V,U,I~2 and V~2 have significant influence on the deposit size,and P values are less than 0.05.Then,the sensitivity analysis method of process parameters is introduced to discuss the influence of small changes of deposition process parameters on the change of bead size.Combined with response surface and contour map,the coupling analysis of walking speed and deposition current is carried out,and it is found that the corresponding adjustment methods of region I(I and V increase with the decrease of W)and region III(I and V decrease with the decrease of W)are feasible.Secondly,combined with the design expert response optimizer,the initialization and continuous optimization of process parameters are proposed.By limiting the width,height and range of process parameters,the walking speed and deposition current combination satisfying the conditions are solved.Finally,the single pass multi-layer variable width verification test was carried out by using the proposed variable width path process parameter matching strategy.The results show that the forming size of the cladding channel changed from 5.5mm to 8mm,the deposition current increased from 165a to 196a,the walking speed increased from 5.0mmgs to 10.9mm/s,and the average error rate of the weld height was 3%;The results show that the forming dimension of the cladding channel is changed from 5.0 mm to 7.5 mm,the deposition current is reduced from 165 A to 100 a,the walking speed is reduced from 5.0 mm/s to3.5 mm/s,and the average error rate of the weld height is 1.9%,which is within the error requirement range.Therefore,the proposed process parameter matching strategy can give the optimal combination of walking speed and deposition current under the constraint of constant weld height,the continuous change of melting width is realized.In order to further verify the variable width path planning algorithm and process parameter matching strategy,a multi-channel multi-layer cam stacking test was carried out on a flat plate,with a total of 8 layers and a height of 20 mm.The 3D scanner is used to scan the surface of the formed part.Through the best fit analysis and error analysis,due to the lack of support and welding spatter,the error of the inner and outer contour boundary can reach 2～3mm,while the error of the inner contour area is about 1mm.By making sections A-A,B-B and C-C on the surface of the cam,it can be seen that the accuracy of the cam forming parts is good,which verifies the effectiveness of the variable width path planning algorithm and the process parameter matching strategy in the additive manufacturing of metal parts with variable width section.