Support structures are always needed in SLA/DLP/LCD 3D Printing which are one of the most important safeguard for successfully producing 3D printed parts. Support structures are used for avoiding deformation and crumbling. As the support structures are produced as an inseparable part of the whole print, post-processing is necessary to remove the visual marks left on the part.
Support Structures in Top-down & Bottom-up 3D Printing
Support structures in top-down and bottom-up 3D printing are not the same:
In top-down 3D printing, support structures are similar to FDM. They are needed for producing accurately overhangs and bridges. As they are no peel force/separation force (Click here to know more about peel force/separation force: How to Eliminate Z-axis Lines Caused by Peel Force/Separation Force?) during the 3D print process, the part can be oriented in any position. In top-down 3D printing, the most crucial factors to consider is to minimize the amount of support to avoid damaging part surface & reduce post-processing and decrease the total number of layers to reduce printing time.
While in bottom-up 3D printing, the situation is much more complicated due to peel force/separation force as the most crucial criterion is to fight with peel force/separation force. There are many factors to affect the peel force/separation force like resin viscosity, lifting speed, radius of new cured layer, and height between new cured layer and FEP film. Among them, the cross-sectional area of each layer is related to the support structures. So in bottom-up 3D printing, parts should be oriented in a certain angle to minimize the cross-sectional area of each layer. And the reduction of support structures isn’t a priority.
In the followting guide, we’ll be focused on support structures in bottom-up 3D printing.
Part Orientation Determines the Location and Amount of Support
Part orientation plays a crucial role on where support is located for SLA/DLP/LCD 3D Printing. By reorienting a part, the amount of support can be drastically reduced and the cross-sectional area of each layer can be minimized. Besides, reorienting a part can also be beneficial for the improvement of surface quality as mentioned above.
In CHITUBOX, there are two ways to reorient a part. Click the orientation button, gradually increase/decrease XYZ angle by 0.5°each time or directly enter the value in the input box.
Also you can also directly double click the mouse to activate the rotation indicator line and reorient the part by moving the mouse in X (red rotation indicator line) /Y (green rotation indicator line) / Z (blue rotation indicator line) direction.
Where is support needed in bottom-up SLA/DLP/LCD 3D printing?
Overhangs and Bridges
Overhangs and bridges are usually illustrated with the help of the letters Y, H, and T in many articles.
If an overhang tilts at an angle less than 45 degrees from the vertical, then you may be able to print that overhang without support structures. Letter Y have an angle of 30 degrees with the vertical which can be printed without support structures. The overhangs in the letter T have an angle of 90 degrees with the vertical. So you must use 3D printing support structures to print the letter T. In general, if a bridge is less than 5mm in length, the printer may be able to print it without support structures.
In fact, those critical points may be limited by the actual situation of your 3D printer, printing material, and parameters. So it will be helpful to print those overhang (https://www.thingiverse.com/thing:40382) and bridge (https://www.thingiverse.com/thing:3931816) test models to verify your 3D printer.
Here is an easier way to judge where is support needed in bottom-up SLA/DLP/LCD 3D printing. Under CHITUBOX slicing preview, we can easily detect those positions.
Take the above parts as examples. We focus on the following positions of the base where the overhangs begin to appear and seperate. We can see that this layer is connected with the previously cured layer, and can be superimposed layer by layer without support structures.
Then the overhangs begin to extend to both sides, and the whole layer separate into two parts. Even during the separation process, the new layer is still connected to the previously cured layer, until the whole structure of the overhang is printed.
As for the “mouse” part, all the suspendings under CHITUBOX slicing preview need to be shored up with support structures.
Weaker Structures
The peel force/separation force in bottom-up 3D printing may cause deformation, visible lines and even breakage on weaker structures. Though they may not need support structures for successfully generated, support strutures are still needed for stabilize its structure during 3D print process.
Shapes of Support Structures in SLA/DLP/LCD 3D Printing
Ribs
The most common support structures in SLA/DLP/LCD 3D printing look like thin ribs, with only small tips actually touching the model to save material. The advantage of using rib support structures is that it can satisfy most applications and does not damage the surface quality too much.
Flakes
Flakes are thin wall-like structures that add support and rigidity to the parts. They are thinner than the parts and are used to support them by running perpendicular to these structures. Flake support structures provide enough stability for flat overhangs than ribs. But they leave more remarkable structures on the parts which need tedious post-process.
Nets
Net support structures are like the intertwinement of shin flakes which provide stable base for the parts. The bottom of the parts are nearly wrapped up by those nets. They are easier to be removed than flakes as they are much thinner. At the same time, the contact points of the net support structures are more compact.
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