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Tree supports

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SL1
CW1
SL1S SPEED
CW1S
PrusaSlicer
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Unlike FDM supports, which are usually lattice or grid-like, SLA supports are scaffolding tree-like structures with thin tips. When removed, they’re easy to remove and leave little to no traces on the printed object’s surface. This also means that an insufficient number of supports can lead to unwanted effects – e.g., heavy objects can detach during the print.

Starting from PrusaSlicer version 2.9.1, the automatic supports are generated based on the size and type of supported part:

  • Small islands are supported by a single point placed at their center of mass.
  • Medium islands use the Voronoi diagram to optimally place two or more supports.
  • Large islands are divided into thin and thick sections, where supports are placed either along the central axis or around the perimeter for greater stability.
  • For detected overhangs, PrusaSlicer adjusts the support density based on Z height and overhang angle, minimizing unnecessary supports and ensuring even distribution.

The supports are identified by colour, distinguishing islands in blue, manual edits in orange, and overhang supports in white.

To generate the supports, select the model, click on the SLA support points icon, and click on Auto-Generate points. The two top icons will allow you to switch the view between showing the tree supports and only showing the support points. The sliding bar will adjust the support points density, which will automatically show in the preview when changed. The standard value should be good for most cases.

Also, remember that removing the supports can leave tiny marks on the surface, so if your object has areas that should be completely flawless (an ornament on a piece of jewelry, the face of an action figure), try to keep the supports away from them.

Manual support editing

If you wish to edit the supports, click on the Manual editing button. This will allow you to add new points by clicking the left mouse button and remove points, including automatically generated ones, by clicking the right mouse button. Selecting a point and dragging it will move the point.

If you have manually added points, the automatic support generator will consider them and adjust the surrounding support density accordingly.

The option "Lock supports under new islands" will lock the blue points, making only the overhangs and added points possible to be edited.

You can tweak the support thickness in manual editing mode by using the Head diameter slider, or you can go to Print settings -> Supports and modify the following parameters to increase the thickness of supports:

  • Support head front diameter: 0.6 mm
  • Support head penetration: 0.6 mm
  • Support pillar diameter: 1.3 mm

Comparison of automatically generated supports and manually edited supports

Useful shortcuts

Left click   Add point

Right click   Remove point

Drag   Move point

Shift + left click   Add point to the selection

Alt + left click   Remove point from selection

Shift + Drag   Select by rectangle

ALT + Drag   Deselect by rectangle

CTRL + A   Select all points

Delete    Remove selected points

CTRL + Mouse wheel    Move clipping plane

R    Reset clipping plane

Enter    Apply changes

Esc    Discard changes

M   Switch to editing mode

A    Auto generate points

Orientation

Supports go hand in hand with object orientation – by rotating the object to an optimal position, you can minimize the need for supports. You can also go to the left side menu and click on the rotate tool. This will show you the option to turn the object to the angle with the least amount of overhangs.

Pad

Another thing you should consider using is the pad. The pad (enabled by default) is a large structure at the base of the print, which serves as the foundation for the supports. While it’s possible to have supports printed directly on the aluminum printing platform, the pad will ensure much better stability.
If you're printing your model solid, it can be quite heavy. Consider Hollowing the model or add more supports and/or make them thicker so they can support the object’s weight.
 

5 comments

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HQPP
Tree support in PrusaSlicer: In this video Jeff will show you how to get tree support in PrusaSlicer for FDM prints. https://www.youtube.com/watch?v=2qNvszl2foU&t=366s
JayFabra
Can you please add tree support for FDM printers? They are much better for printing art models than the grid support. I know there are workarounds, but that's annoying
William H. - Official Prusa

Probably not. Does not make sense for Print speeds etc with FFF printing. Just looks cool.

raew
That's plain wrong, unfortunately. Just one example:
The very same object (a simple post cap) sliced in latest CURA 4.13.1 with tree support takes 7h52m and 125g of filament, while the latest PrusaSlicer 2.4.1 requires 11h16m and 200.5g of filament with its "standard" supports.
Same (default) settings, same printer (MK3), original Prusa printer profiles. Sure there may be differences in detail (e.g. the PrusaSlicer uses 4 top layers as default, where Cura with original Prusa profile uses only 3), but those only make a difference of a few minutes and a gram or two in filament consumption and don't change the overall picture. 
Supports are not the forte of PrusaSlicer (never have been) and you should better acknowledge that and try to improve, rather than dismissing this topic.
 
Dan B
Been trying to figure out for a little while, does Prusa slicer support multiple-sized supports in 1 file?  Eg having "thin" support for delicate detail pieces (sword, arms on a miniature) and "thick" supports for larger parts like the main body/back?  I haven't been able to get it to work, but there's still a lot I have to learn about using the slicer.  Thanks!
Mikolas Zuza

The support head diameter (when manually editing tree supports) can vary. When you click on the model, the current head diameter is used, so you can have tiny connection to the model, thick and extra thick one all at once. However the rest of the support settings can only be changed either globally or for individual objects. You cannot have different support base diameter on the same model at the moment.

DavidUnboxed
Currently, I am using the SL1 profile to generate tree supports, then export it with supports, then import into the MK3S+MMU2S profile so that I can print it with the preferred tree supports. However, this leaves me unable to easily choose to have only the supports or the interface layer be PVA. Please consider adding 'tree supports' to MK3S+MMU22S profile in the slicer - with the option to use soluble supports and the option for soluble interface layer.
97marno
+1 on that
William H. - Official Prusa

I think we will eventually, but there are other considerations with FFF than SLA printing. Even more so when you want to use the MMU2S. We always try to cover most edge-cases as well as general use before releasing a new feature. You can also use another program, like Meshmixer, to generate the tree supports.

ilja
Hi, I have a MK3s, so how can I create supports that start from the object, like in the picture ?
Does it involve meshmixer ?
Giuliano - Official Prusa CS
Hi. This article is about the SL1. However you can also have supports starting from the object on the MK3S, if there are some parts that requires it, like the jaw of the t-rex in the picture.