The blank is what RockCAM thinks the part is cut from. Get it wrong and you get toolpaths for material that is not there — or, worse, no toolpath for material that is. Setting the blank is usually the first thing to adjust when a program does not match the shop.
Since version 1.4.1, RockCAM supports two blank shapes: the bounding block and the part contour.
The RockCAM blank settings page showing blank type and stock fields.
Bounding block #
The bounding block is a box around the part, with stock in the X, Y and Z directions.
You can also think of the stock values as a statement about which faces are already to size. Setting an axis to zero tells RockCAM that face needs no machining, so it leaves the outer profile alone in that direction. If only X has stock, only the X faces are machined.
The stock fields for a bounding-block blank, with X, Y and Z values entered.
Part contour #
The part contour follows the outline of the part along the OP direction, with a small offset. It is common after wire EDM, where the outer shape already exists and you are only cleaning it up. Roughing a contour blank usually uses a contour spiral or a 3D strategy.
A part with a contour blank applied, showing the small offset around the outline.
Cylindrical blank #
A cylindrical blank takes stock in Z and a radial stock per side. As with the box, a value of zero means that direction needs no machining, so a blank with zero radial stock produces no radial toolpaths.
The Z and per-side stock fields for a cylindrical blank.
Marking faces as already machined #
Above the stock fields there are three checkboxes for faces that are already finished. The most common is the thickness: ticking top face already machined means zero stock in Z, and the finished program contains no thickness machining.
The three “already machined” checkboxes above the stock fields.
Case: a block blank with all six faces to size #
With zero stock in X, Y and Z, none of the outer profile is machined. Only the pockets get roughing and finishing toolpaths.
The resulting toolpaths, showing machining inside the pockets only and nothing on the outer profile.
Case: cylindrical blank with the top and the sides already to size #
Set Z stock to zero and the radial stock to zero, and neither the top nor the outside is machined. Again, only the internal features get toolpaths.
The resulting toolpaths on a cylindrical blank with the top and sides already finished.
Where the stock values are used #
The roughing allowance is a separate setting, but the blank tells RockCAM where the material starts. Between them they decide how much is cut and where. If a program is cutting air, or finishing a face you had already finished elsewhere, this page is where the problem is.