Currently only 3 file formats are supported. .STL, .OBJ, .3MF
The main difference between these 3 file formats is the way they handle the scale of your object.
.STL or Stereo Lithographic data format will only save the 3D model information, nothing else with no scale. Lychee Slicer will suppose that 1 unit = 1mm in Lychee Slicer.
Note: Make sure you set up the program used to create/modify the file to export with this in mind.
Refer to the program documentation if needed.
.OBJ will have the 3D model information and some extra Lychee will ignore like color. For the unit, you can set up the program used to export the model to use mm.
Lychee will always assume that 1unit = 1mm during the import.
.3MF is a more recent file format, specifically created for the needs of the manufacturing processes.
It stores the 3D model data and more information. Most importantly it will allow you to work with any units. Lychee Slicer will convert the model during the import to have the same scale.
Note: 3MF is the only file format to support the inches if you require it in your workflow.
TIPS: During the import process of a .STL or a .OBJ file, Lychee Slicer will create a new object center based on the bounding box of the model and place the model based on it in the scene.
The 3MF file will keep its own center and be placed in the center of the scene.
See the import 3d file article for more details.