CAM fourth axis

Since 26.3, rotary-axis support is built on Machine definitions. A Machine (.fcm) declares its rotary axes (name A/B/C, rotation vector, limits, table or head role and wrap strategy) and is assigned to the Job on the General tab. The Post-Processor commands the rotary positions for an Operation on a tilted Work Plane, and dedicated operations and dressups generate continuous 4-axis toolpaths.

introduced in 26.3: An Operation links to zero or one Work Plane through its Workplane property. A Work Plane is a named frame that the Job holds, and several Operations can link to the same Work Plane. The local +Z of the Work Plane is the Tool Axis. An Operation with an empty Workplane property works in the XY of the Job, which is Z-up milling.

A Work Plane that is not parallel to the Machine table makes the Operation Indexed (3+2). The Operation generates its Toolpath in the frame of the Work Plane: the origin of the Work Plane is zero and the Tool Axis is Z. Each depth and each height of the Operation is a distance along the Tool Axis from the Work Plane. The Toolpath of an Indexed Operation contains no rotary words. The read-only Placement property of the Operation holds the frame of the Work Plane and positions the Toolpath on the Model.

The Operation does not read the Machine when it generates the Toolpath. A Job accepts a Work Plane of any orientation, also when its Machine has no rotary axes. When the Machine has rotary axes and cannot index to the Work Plane, the Operation writes a warning to the Report view and generates the Toolpath.

The Work Plane page describes how to create a Work Plane and how to link an Operation to it.

The Rotary Surface operation (experimental, requires OpenCAMLib) machines a part mounted on a single rotary axis by dropping the cutter onto the model at successive angles.

Properties in this group: Start X and Stop X (axial extent), Start Angle, Stop Angle, Step Over (axial advance per revolution), Angular Resolution (default 5°), Radial Stock To Leave, Cut Mode (Climb/Conventional), Cut Pattern (Spiral, Parallel, Rings), Feed Mode (Surface Speed / Axial Only), Max Feed (feed clamp near the centreline), Boundary From Faces (restrict to selected faces).

Properties in this group: Linear Deflection, Angular Deflection.

A cylindrical Stock is assumed.

The 3D Surface operation’s Scan Type = Rotational produces a drop-cutter scan around Rotation Axis X or Y between Start Index and Stop Index (degrees), with Cutter Tilt and Drop Cutter Dir options; the result is emitted as A (or B) axis moves. Retract and recompute reliability were improved in 26.3.

The Axis Map dressup wraps a flat toolpath onto a cylinder by converting one linear axis into a rotary axis: Axis Map (X→A, Y→A, X→B, Y→B, X→C, Y→C), Radius of the wrapped surface and Reverse (invert rotary direction, introduced in 26.3). Feed rates are converted to degrees per minute and the Job’s centre of rotation is updated so the toolpath is drawn on the cylinder.

Toolpaths with A/B/C words are drawn about Path.Center using the full angular travel since 26.3. Machine-based post-processors expand rotary moves according to the axis Wrap Strategy (unwound, wrapped, shortest) defined in the Machine; legacy post-processors output the angle words unchanged. Feed handling for rotary-only moves was fixed in 1.1.

The Toolpath of an Indexed Operation has no A/B/C words. The 3D view, the simulators and Inspect position the Toolpath of an Indexed Operation with the Placement of the Operation.

The Post-Processor solves the rotary positions from the Placement of the Operation when it writes the output. A change of Machine requires a new post-process run, not a recompute of the Operation. The Rotation Strategy of the Machine sets the form of the output. The rotation_strategy value in the kinematics of the Machine (.fcm) holds the Rotation Strategy:

A Machine file that has dwo_supported set and no rotation_strategy value loads with the Rotation Strategy dwo.