The surface quality in 3D printing varies greatly as there are many factors to affect it such as layer thickness, print speed, part orientation and ect. This article discusses how to improve surface quality in 3D printing by optimizing part orientation.
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Step 1: Part Orientation
We put the same model in different positions in ChiTubox which form a certain angle with the vertical plane as 0 degree, 30 degrees, 45 degrees and 90 degrees. Except 90 degrees, the models are positioned in a square and rhombus at each degree angle because those two shape have different cross-sections during the 3D printing process.
Step 2: Number Models
So we get 7 models in total, numbered 1-7 (0°Square Orientation, 0°rhombus Orientation, 30°Square Orientation, 30°rhombus Orientation, 45°Square Orientation, 45°rhombus Orientation, 90°Orientation).
In general, the angle is preferentially 45 degrees. But it still needs to be tested. In the following content, we’ll evaluate the print quality from model integrity, model deformation and surface quality.
Step 3: Model Integrity
Sudden changes of the model structure from a small cross-section to a large cross section area will lead to severe volumetric changes of layers as the volume of 3D resin in each layer highly affects the shrinkage of each cured layer. Uneven quantity of 3D printing material and tumultuous peeling force among layers result in variable shrinkage which is the main cause of misrun and irregularity.
No. 7 (90°Orientation) is positioned horizontally on support structures which is subjected to the largest area changes and biggest peeling forces. So the force directly peel the object away from the support structures which results in misrun.
No. 1 (0°Square Orientation) is positioned vertically on support structures whose cross section areas are also changing largely compared with other orientations. But its area changes are much smaller than No. 7 so the side connected with support structures is just uneven.
The rank of model integrity:
3 > 6 > 2 > 4 > 5 > 1 > 7
Step 4: Model Deformation
According to the principle, those small objects (20*5*20mm) would not encounter model deformation. Due to misrun, No. 7 is certainly more or less deformed. And we found that the rafts of No. 2 and No. 4 are cocking up from the build plate which is caused by the gap between the right side of the build plate and the screen. This may be the reason why No. 2 and No. 4 are aslo deformed.
The rank of model deformation:
3 < 6 < 5 < 1 < 4 < 2 < 7
Step 5: Surface Quality
Sudden changes of the model structure not only affects model integrity, but it will also typically result in visible surface lines. Besides, part orientation impacts surface quality due to the process of slicing and printing the part in increments in the Z direction. And to our surprise, we can see obvious surface lines on 45 degrees. Another superise is that No. 1 (0°Square Orientation) has the best surface quality. But there is no doubt that No. 7 is still the worst.
The rank of surface quality:
1 > 3 > 4 > 2 > 6 > 5 > 7
Step 6: Conclusion
By orientating the part in different directions, there is a significant difference in the print quality as the test above. If we grade the rank with the score 1-7. We give 7 for the best grade, and so on. And we also rule out the rank of model deformation as it has a certain degree of uncertainty. Then the ranking is No. 3 (score 13), No. 6 (score 9), No. 2 (score 9), No. 4(score 9), No. 1 (score 9), No. 5 (score 5), and No. 7 (score 2).
If we divide the group by degree, the ranking is 30°(score 22), 0°(score 18), 45°(score 14), and 90°(score 2). But if we divide the group by shape, square and rhombus did equally well. So we single out the rank of surface quality as it is greatly affected by the shape. Then rhombus team(score 15) will be better than square team(score 12).
As a result, the best orientation in this test is to position the print at 30 degree. Also, you should make sure that cross-sectional area of layers changes as gradually as possible. In addition, the optimal orientation may vary depending on the printed material and the actual situation of the model.