It can be seen that the dotted line frame in Fig. 1 shows obvious Z-axis lines caused by the pull-out force, and even the level deviation occurs.And the dotted line position in Fig. 2 also has obvious Z-axis lines, which is still clearly visible after cleaning.
The culprit causing this texture is the drawing force / release force, which are unavoidable in pull-up photocurable 3D printing. this drawing force / release force is unavoidable. Why do you say that? First of all, let's understand the stripping process in pull-down 3D printing again:
Several elements related to the stripping process include: forming platform, trough, resin and release film(As shown in the Fig. 3).This process is not complicated to explain. SLA / DLP / LCD may be slightly different, but they are basically the same:
1. The molding platform and model are lowered and immersed in liquid resin;
2. The light source cures the photosensitive resin, and the cured layer is stuck between the cured layer of the previous layer and the release film;
3. Pull up the molding platform, separate the model and the release film;
4. The molding platform descends, and continues to repeat the action, curing a new layer.
During the separation of the mold and the release film, the pull-out force / release force is generated. Therefore, the viscosity of the resin, the release speed, the radius of the newly formed layer, and the distance between the newly formed layer and the release film height will all affect the drawing force / release force.
After clarifying the cause of the Z-axis texture, it is easy to eliminate this texture. The first thing to know is that the drawing force / release force cannot disappear, so the Z axis can be eliminated in the following two ways:
1.Reduce the pulling force / release force
So replace the resin with lower viscosity, reduce the model or adjust the placement angle to reduce the radius, and reduce the lifting speed. Of course, it is also necessary to regularly check the abrasion and release of the release film and replace the good release film in a timely manner.
If these factors are not easy to adjust, you can use a stable model. In places where the cross section is abruptly changed (where the radius is larger), additional supports are added to stabilize the model. This is also the reason why sometimes the support is added more densely; the Z-axis instability and inching of the machine will also cause the Z-axis texture.
As shown in the Fig. 5, after the model is stabilized, the Z-axis texture is basically eliminated.