Open an STL, OBJ or 3MF as a solid body — PartCraft help

PartCraft opens STL, OBJ and 3MF meshes as solid bodies. The body works like any other solid: cut it, add to it, drill it, pattern it, use it in an assembly or for machining, and sketch on its flat faces. It has no history of its own: a mesh is only triangles, so its sizes cannot be changed, only added to or cut from.

Open a mesh

Choose Open or press ⌘OCtrl+O, and pick the .stl, .obj or .3mf file. Or drop it on the 3D view.
PartCraft reads it, repairs what it safely can and shows what it found: how many triangles and points, each repair, and whether the mesh now closes.
Check Units in the file and Up in the file. STL and OBJ do not say their units, so millimetres is the guess; a 3MF file says its own. The Size here line shows the body's size with your choice, so a part that comes in 25.4 times too small is easy to spot (it was in inches).
If the part on screen is empty, choose Open as a body. If it already has features, choose Use it to (add to the part, cut from it, or keep only the overlap), then Add to this part, or New part to start again with the mesh.

An Imported1 feature appears in the history. The status bar says, for example, "bracket.stl is a solid body: 15200.512 mm³, 14 flat faces to sketch on."

What PartCraft repairs

Repair	What it means
Doubled corners joined	An STL repeats every corner for each of its triangles; they are joined into one point
Triangles with no area removed	Slivers whose corners lie on one line
Doubled triangles removed	A triangle written twice is kept once; two facing opposite ways (an inner wall) are both removed
Small gaps closed	Edges that almost meet (within a thousandth of the part's size) are joined
Holes filled	An opening whose border lies flat is filled whatever its size; a warped one only when it is small
Triangles turned to face outward	Triangles facing the wrong way are turned to agree with their neighbours, and the whole surface to face out

When a mesh does not close

A solid needs a surface with no openings. When PartCraft cannot close one, the dialog says how many openings and open edges are left, and there is no body to add. Close the openings in the program that made the mesh, or export it again as a closed (watertight) mesh, and open it again.

PartCraft leaves an opening alone when filling it could guess wrong: a large warped hole, or two openings in the same plane (a ring-shaped face that is missing, where filling each border would cover the hole in the middle). An edge shared by more than two triangles is also reported: such a surface does not have one clear inside.

Sketch on its flat faces

Flat areas made of many triangles are merged into one flat face each, so a sketch can sit on them: click the face and choose Sketch on this face. A face that is cut or added to later stays a face. Round areas (a hole, a fillet) stay triangles: they are not faces you can pick, and the view draws their outline from the angle between triangles.

Change it later

Select Imported1 to see the file it came from, how many triangles it has and what was repaired. Units in the file, Up in the file and Use it to can be changed there; each change is one undo step.

Where it is kept

The repaired mesh is stored inside the .partcraft.json file, so you do not need the mesh file again. A part file with a mesh body is version 5: an older PartCraft refuses it by its version. A 200,000-triangle mesh adds about 1.2 MB.

Limits

At most 3 million triangles and 200 MB in one file.
A body made from a mesh is built by the mesh kernel. With the exact kernel on (developers only), it says so and is not built.
OBJ materials, texture coordinates and free-form curves are left out; 3MF colours, materials and support objects are left out (the dialog says how many objects were skipped).
The body is as fine as the mesh: a coarse STL gives coarse round faces. Holes you drill into it are as round as your own features.