When printing objects on an FDM 3D printer (those that extrude melted material through a nozzle), the slicing software will take any solid object in STL format and automatically create an infill pattern according to your settings. This way, you can determine how solid you want the object to be in order to obtain the ideal balance between material usage and object strength.
With an SLA printer (those that use a laser or other light source to cure a photopolymer resin), the process is a little different. If your STL file is a solid 3D object, then the printer will print it solid, using far more resin than necessary.
In order to optimize an STL file for SLA printing, you’ll want to do two things:
- Hollow out the object
- Add draining holes on the bottom of the object (so any resin trapped inside can be drained out after printing, and so the alcohol used for cleaning the part can flow throughout the inside of the object)
First, you’ll want to download the free Autodesk Meshmixer software (available for Windows and Mac). You can download it here.
Open Meshmixer and click on Import to import your STL file.
Rotate your object so you can see the bottom (the part sitting on the print bed).
On the View menu, uncheck “Show Printer Bed” so you can see the object bottom clearly.
Click the Edit button in the left-hand toolbar, then click on Hollow.
Configure the settings as desired. The Offset Distance determine how thick the object’s walls will be. 2mm is a good setting in most cases. I suggest setting “Holes Per Hollow” to 2 (which will create 2 holes for drainage) and “Hole Radius” should be at least 2mm in most cases. Then click on Generate Holes, and you’ll see red spheres that appear on the object to indicate where the holes will be placed. You can click and drag these red spheres to reposition the holes. Place them on the bottom of the object, preferably close to the edges, so it will be easy for the resin trapped inside to drain out.
Your object will now be hollowed out, and you will see holes in the bottom of the object where you placed them.
Now just choose Export from the File menu, give your new file a name, and select STL Binary as the file format. Load that file into your printing software for your SLA printer, and you’re ready to print!
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