Meshmixer Basics
Posted by John Sullivan, Last modified by John Sullivan on 01 February 2019 12:37 PM

Meshmixer Utilities

Meshmixer is a free 3d modeling and mesh editing software maintained by Autodesk.  It offers an efficient meshing and remeshing tool set, making it a common last step in 3d design prior to 3d printing or publishing.    

Understanding a Mesh:   

A 3d mesh is a form created from vertices or nodes (points in a 3d grid), lines, and faces.  Note - not all 3d designs qualify as a “mesh”.   

Mesh: will it mix? 

A true 3d mesh is ideally polyhedral: a 3d solid.  A 3d cube is a mesh, as all sides are covered by polygons, planes suspended between lines and points.  If one deletes a face of this cube, it may look solid from five sides, yet it is no longer a solid, or a mesh. Keep in mind each plane (face) of the cube has no thickness, and with nothing to define as an “inside” and an “outside”, the shape will not be 3d printable or have “integrity”.  This sort of issue may arise in large projects and may not be evident (Meshmixer has a “make solid” tool for this!)    Meshmixer is best used with models that are designed to be solid, with distinct inside and outside faces.   

Meshmixer Utilities: Edit 

Upon opening Meshmixer with a STL file, the first round of actions will be done in the edit menu.    

  • Use “align” to center your file, then use “transform” to scale by percent or to a specific L/W/H dimension.   
  • It is recommended to run “close cracks”, which is primarily a way to clear very small errors prior to a remesh.   
  • Use “plane cut” to slice a flat surface from your model - this is the recommended way to create a flat base for a 3d print model, and is favored over using a Boolean subtraction for simplicity.  

The Make Solid Tool

The “make solid” tool not only provides a remedy to “incomplete” meshes (a model may look solid, but any error - no matter the scale - will prevent an object from being polyhedral, with an inside and outside). This tool is a catch-all solution to be certain an object will 3d print.  Upon opening the tool, your model will be rendered solid using a fast, low resolution algorithm.  Edges will not be sharp:  this tool is essentially draping a mesh “fabric” around your model, sealing it but also approximating every facet.  Click here for official documentation on this tool and process. 

After clicking “Accept”, your work space will have now two objects:  the original and the solid.  To view all objects in your work space, enable the “Objects Browser” under “view” or hit Shift+Command+O (on a Mac).  There is no need to delete other objects until it is time to export, and toggling different objects in the browser can be a form of version control. 

Tips and Boolean Operations: 

The "make solid" tool may strand (become unattached) small parts of the form that where previously attached.  A common example of of this is re-meshed fingers "floating" in front of a hand.  Using the Select tool,  double click the body you wish to keep, which will auto select one complete contiguous form.  Hit “i” on your keyboard to invert the selection, to select all floating excess pieces.  Use “x” on your keyboard to remove the excess. 
 
A Boolean operation in CAD software is to modify one body with another body.  Common operations include joining / merging, subtracting and finding the difference between objects.  Objects must be solid (ideally with the make solid tool) for a Boolean to work.  To access the tool set, use the Objects Browser (Shift+Command+O) and select two solids. 

In Meshmixer, these Boolean operations are: 

  • Combine:  this should retain features of both objects (inside and out), but result in one form.  This is rarely useful in 3d printing, as it may result in strange interior forms or errors.  
  • Union:  This tool does the same as Combine but only preserves outward facing features.  This is akin to “merging” or “adding” bodies.  This is a common operation.   
  • Difference:  This allows one object to be subtracted from another, destroying the object or “tool” after the operation is accepted.  This is an efficient way to make calculated, inverse  modifications to objects very quickly.   Points of common struggles with this tool include: the second object in the browser you select will be the “tool” used to subtract from the first object selected.  This can be very confusing!  This tool will behave very strangely with incomplete solids.  If there are persistent errors, try remeshing both entities with the make solid tool before trying again.  
  • Intersection:  This is tool only retains the shared space between the two objects, destroying both originals.   

To export a STL ready for printing, ensure: 

  • There is one object in the Objects browser 
  • This object is an error-free solid 
  • The object is the correct size- use edit → transform to view dimensions 
  • The object is selected → use Command+E or File-Export 

The resulting .stl file is ready!  Please use OneDrive or your preferred cloud storage provider to submit your file, as remeshing may drastically increase file size.   


Follow the link below to submit: 

https://campus.plymouth.edu/it/print-depot/ 

For pricing information, follow this link: 

https://support.plymouth.edu/index.php?/Knowledgebase/Article/View/614/0/the-print-depot-overview 

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