When working with 3D models in Maya, it is often necessary to export the models into different file formats for use in other software or for sharing with collaborators. One commonly used file format for 3D models is OBJ, which is compatible with many other 3D software applications. Here's a step-by-step guide on how to export a 3D model from Maya as an OBJ file:

1. Open your Maya project and make sure the 3D model you want to export is ready for export. Ensure that the model is properly UV mapped and has all the necessary materials and textures applied.

2. Select the 3D model in the Maya viewport by clicking on it. If you have multiple objects in the scene, make sure to select all the objects you want to export as a single OBJ file.

3. With the 3D model selected, go to the 'File' menu at the top of the Maya interface and choose 'Export Selection...' from the dropdown menu.

4. In the Export Selection window, choose 'OBJexport' from the 'Files of Type' dropdown menu. This will ensure that you save the selected 3D model as an OBJ file.

5. Specify the file name and location where you want to save the OBJ file. You can also choose additional export options such as the OBJ export settings, but the default settings should work for most cases.

6. Click the 'Export' button to save the 3D model as an OBJ file. Maya will then export the selected model as an OBJ file, along with any associated materials and textures.

7. Once the export process is complete, you can open the exported OBJ file in another 3D software application to verify that the model was exported correctly.

By following these steps, you can easily export a 3D model from Maya as an OBJ file for use in other software or for sharing with collaborators. Remember to check the OBJ export settings to ensure that the exported file meets your specific requirements. With this knowledge, you can seamlessly integrate your Maya 3D models into various 3D pipelines and workflows.