Fig 1.
(a) Creality Ender 3 V2 3D printer. (b) 3D printed TPU test specimens.
Fig 2.
The cross-section of the test specimen corresponds to a rectangle of base b and height h; the length of the specimen is l. The extremes of the test specimen are used for clamping to the testing machine and maintain the exact dimensions a and b across all test specimens.
Table 1.
Process parameters.
Table 2.
Parameters and their levels.
Fig 3.
The test specimen marked in blue is fixed to the hub marked in green that applies the combination flexural and torsional load, the other end is fixed to the six-axis force torque sensor attached at the free end of the robot arm marked in red. The force torque sensor is marked on red, the test specimen is marked on blue and the hub is marked on green.
Fig 4.
The torsional and flexural loads applied to the test specimen are described by the variables τ, F, and the resulting angular deformations defined by , and Ψ, depending on the direction of deformation.
Table 3.
Experimental data.
Table 4.
Multivariate analysis of variance for x coefficients.
Fig 5.
Effect of the independent variables on the damping coefficient for linear deformations.
The effect of each independent variable on the damping coefficients are shown for the linear deformations X, and Y, the medians are marked by red lines and show the increase in stiffness at a raster angle, layer thickness increases the damping, influence of the geometric variables is associated with the capacity of the test specimen to bend, the printing density of the specimen has the most influence on the damping.
Fig 6.
Effect of the independent variables on the spring coefficient for linear deformations.
The effect of each independent variable on the spring coefficients are shown for the linear deformations X, and Y, the medians are marked by red lines, the geometric variables width, height, and length have an inverse effect on the spring where the thinner the test specimen, the less effect, the spring coefficient increases with the layer thickness.
Fig 7.
Effect of the independent variables on the damping coefficient for linear deformation Z.
The effect of each independent variable on the damping coefficients are shown for the linear deformation Z, the medians are marked by red lines and show the increase in damping at a raster angle, and a low sensibility to the other variables given the medians are similar.
Fig 8.
Effect of the independent variables on the spring coefficient for linear deformation Z.
The effect of each independent variable on the spring coefficients are shown for the linear deformation Z, the medians are marked by red lines, the geometric variables width, and height have the most effect on the spring coefficient.
Fig 9.
Effect of the independent variables on the damping coefficient for angular deformations.
The effect of each independent variable on the damping coefficients are shown for the angular deformations and ϕ, the medians are marked by red lines, has higher medians as the width and height values increase.
Fig 10.
Effect of the independent variables on the spring coefficient for angular deformations.
The effect of each independent variable on the spring coefficients are shown for the angular deformations and
, the medians are marked by red lines, the spring coefficient at
raster angle is higher and has less variability, has lower medians as the width, length, and height increase.
Fig 11.
Effect of the independent variables on the damping coefficient for angular deformations.
The effect of each independent variable on the damping coefficients are shown for the angular deformation Ψ, the medians are marked by red lines, the spring coefficient at raster angle is higher.
Fig 12.
Effect of the independent variables on the spring coefficient for angular deformations.
The effect of each independent variable on the spring coefficients are shown for the angular deformation Ψ, the medians are marked by red lines, the spring coefficient is affected by the raster angle being higher at and at
has less variability, the geometric variables with, height, and length have the most influence on the spring coefficient.
Fig 13.
Correlation heat-map between input and output variables.
The correlation between variables are represented by values from –1 to 1 where close to 1 shows strong positive correlation, values close to –1 show strong negative correlation, and values close to 0 show little or no linear correlation.
Fig 14.
The test specimen is fixed and a load is applied at the other end where a marker is placed.