Meshmixer
Meshmixer is a tool for easy 3D mashups and remixes with specialised tools for 3D printing and repair.
Meshmixer is a fantastic free software for creating and manipulating 3D files for 3D printing. Whether you need to clean up a 3D scan, do some 3D printing or combine multiple 3D models to create a remixed design, Meshmixer can help.
Supported filetypes
STL (best for 3D printing), OBJ, PLY, AMF, MIX
Minimum system requirements
At least 4GB of RAM. At least 700 MB of available hard-disk space. Intel HD or similar graphics card with at least 512 MB video memory