OpenChuckCAM User guide
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7. Add the operations

An operation is one machining job with one tool. You will add two: a roughing operation that removes most of the material quickly, and a finishing operation that cuts the final surface. Roughing and finishing explains why there are two.

Choose + New operation. The list of strategies shows what the program can do:

The strategy list: Rotary roughing and Facing under Roughing; Helical, Axial, Indexed, Simultaneous 4-axis finishing, Rest machining and Pencil clean-up under Finishing; Edge and curve following and Swarf under Specialist.
Figure 1. The strategy list, grouped under Roughing, Finishing and Specialist.

Each entry has a one-paragraph description. Swarf is greyed because it needs a STEP model.

Roughing

  1. Name the operation Rough and keep Rotary roughing as the strategy. The setup (Setup 1), the tool (Z1 O-flute 3.175x25) and the material preset (the setup’s Hardwood) are already right.
  2. Press Add.
The Add operation dialog with the name Rough, strategy Rotary roughing, Setup 1 and the O-flute tool.
Figure 2. The Add operation dialog for the Rough operation.
  1. In the Inspector, set Stepdown to 1 mm. This field starts empty (“required”): the program will not guess how deep a layer should be.
The Rough operation's Inspector: cutting feed 1000 mm/min, stepover 2.2225 mm, stock to leave 0.3 mm and stepdown 1 mm.
Figure 3. The Rough operation's settings: stepover 2.2225 mm, stock to leave 0.3 mm and stepdown 1 mm.

The rest comes from the tool and the strategy. Two to look at:

  • Stepover 2.2225 mm is 70 % of the tool’s diameter, from the tool’s cutting data.
  • Stock to leave 0.300 mm: roughing stops 0.3 mm short of the part so that the finishing tool has a little to cut.

The cutting feed shown is the programmed feed; the machine profile’s own feed limits can slow moves that turn A (the export dialog in step 10 reports the effective feed). Stepover, stepdown, scallop and stock to leave says more about these settings.

Finishing

  1. Choose + New operation again.
  2. Choose Helical finishing, name it Finish and pick the tool Z1 ball 3.175x22.
  3. Press Add.
The Finish operation's Inspector: ball tool T204, feed 500 mm/min, stepover 0.4536 mm, stock to leave 0.000 mm.
Figure 4. The Finish operation's settings, with the ball tool T204 and no stock to leave.

Helical finishing follows the surface in a spiral around the part as the tool moves along it. Its stock to leave is 0, so it cuts to the model. The description warns that “the tool may not reach tight inside corners”: a ball of this size cannot cut a sharper corner than its own radius.