hello every one. i have problem with stl model, after editing when i iexport the file iam not getting require size how can i set the size of model (width x height x thickness) plz help me.?
Hello @ramu
It would first be useful to understand how ZBrush manages scale, and that the units contained within some common export formats are generic. The file doesn’t store whether a mesh is inches, or mm, or cm. It only knows that the mesh is 10 something wide. If a file says that a mesh is 10 units wide, and it is imported into a program with an internal space measurement set to mm, then that file will be 10mm wide when imported into the program. If the program is set to CM, then it will be 10cm wide on import, etc.
Scale Master and 3D Print Hub can both help you export to specific dimensions (again, assuming your target program is set to receive those dimensions accurately). There is no export setting for “thickness”–this is something that would be established when creating your mesh.
Keep in mind, however, that ZBrush requires a mesh to have Tool > Geometry> Size >XYZ size of approximately 2 for best results when working in the program. A mesh should not be drastically larger or smaller than this value when working, or unexpected things may happen.
This is why, when importing a mesh by default, or into a tool with Tool> Export> Scale factor of zero (like the default poly star), Zbrush will auto-scale the mesh to fit this size, and record the values required to restore the tool to its original size upon export in that menu. This all happens seamlessly without requiring user input. Many scale mismatch issues are the result of users importing improperly, or manually trying to change the scale because they don’t understand the auto-scaling aspect of the import/export process.
Hope that helps! 
thank u my frnd. can u explain plz when i importing the stl file how can i set the xyz?
You don’t have to do anything to set the XYZ on import. If you import your tool properly (select Tool> Import, and don’t have a tool with a non-zero export scale factor selected), zbrush will scale it to optimal size for working in zbrush automatically. Then, if you you want to export your mesh at the original size, simply export it as normal. ZBrush will scale it back to the original size on export.
If that original file was 10mm tall in an application set to an internal scale of mm, it will still be 10mm tall in that application unless you changed the actual dimensions of the mesh through sculpting or otherwise, in which case those changes will still be proportional to the original size.
If you want to export the mesh at a different size than the original file–for instance if the mesh is only 10 units tall in the original file, but you want to export it to be 20mm tall in your target application–then the target application will need to be set to mm as the internal scale, and the mesh will need to be changed to 20 units tall in ZBrush prior to export.
Both Scale Master and 3d Print Hub have tools that let you easily specify the dimensions you want to export your model at, which are then exported directly from that plugin’s menu. Please refer to the documentation linked above on the use of these plugins.
thank u so much my frnd. i will try according to ur suggestions and feed back to u