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3D models (beta)

MillPath is growing into 3-axis 3D machining for mould making. This part is in beta: roughing works today, finishing comes next.

Opening a model

Import takes .step .stp .iges .igs .stl .obj. STL and OBJ are read straight away. STEP and IGES are read by OpenCascade running in your browser (downloaded once, about 7.6 MB, only when you first open such a file). Surfaces become triangles within 0.01 mm of the true shape, and every triangle remembers the CAD face it came from.

Nothing is uploaded: the model stays in your browser.

Placing it

The stock is sized round the model — 5 mm round it and 1 mm above it by default — with Z0 on the stock top. Under Stock & setup → 3D model:

  • Pick the top face — then click the face of the model that should face the spindle; the model turns so that face points up (as Select Z axis / plane in other CAM programs). Flip turns it upside down; Turn 90° about X, Y or Z for the rest.
  • Work zero: the nine points on the stock box or on the model box, and Z zero on the stock top, the model top or the table.
  • Stock round it / above it: the room left round and above the model.

A notice tells you if the model is not a closed solid (open edges are treated as holes) or is several bodies touching.

3D rough

The 3D rough operation clears the stock level by level, leaving the stock to leave on the model:

  • At each level MillPath works out where the tool can stand without coming nearer the model than the stock to leave (the drop-cutter: the tool lowered onto the model at every point), and clears that area with the same adaptive, load-limited clearing as the 2D Adaptive operation.
  • Flat areas of the model get a level of their own, so no floor is left a step above its height.
  • Flat, bull-nose (a flat end mill with a corner radius) and ball end mills.
  • Rest roughing: tick it on a second 3D rough and only the material the operations before it left is cut (they are replayed on the stock) — a smaller tool after a larger one gets into the corners, a smaller stepdown takes the steps down.

Seeing what was machined

In the 3D view, once there are operations, four buttons at the bottom right: Model (show or hide it), See-through stock, Compare to model and Toolpath (lines on or off). With Compare to model the machined stock is coloured against the model:

  • red — cut into the model (a gouge),
  • green — on size (within ±0.05 mm),
  • blue — up to 0.6 mm left,
  • yellow — up to 3 mm left,
  • brown — more left,
  • grey — not touched.

How we check it

  • Every cutting move is measured against the model with the real tool shape before export.
  • The drop-cutter is tested against shapes whose answer is known exactly: a sloped plane, a sphere, a round rim (bull nose within 0.001 mm), a concave fillet.
  • Next: comparing our toolpaths with an established CAM on the same models, and measured test cuts in a mould shop.

Coming next

3D finishing — parallel, waterline, steep & shallow, flat areas — then pencil, scallop, rest finishing and hole recognition from STEP faces.