FreeCAD Pad to Last Option Explained

This article explains the function and practical usage of the "To last" pad option in FreeCAD's PartDesign Workbench. Readers will learn how this extrusion type operates, its parametric advantages over fixed-dimension pads, common use cases, and the key requirements needed to avoid modeling errors.

In FreeCAD's PartDesign Workbench, the Pad tool converts a 2D sketch into a 3D solid feature. When configuring the Pad parameters, the Type dropdown provides several methods to define the extrusion's termination. Selecting the To last option commands FreeCAD to extrude the sketch profile until it intersects the farthest (last) boundary or face of the active body in the direction of the pad.

How It Works

Unlike the default "Dimension" type, which requires a specific numerical length (such as 10 mm), "To last" automatically calculates the distance dynamically:

  1. FreeCAD projects the sketch geometry along its normal extrusion axis.
  2. The software detects all intersecting faces of the existing solid body along that path.
  3. The extrusion extends entirely through any intermediate voids or faces, stopping only when it hits the outermost or final face of the solid.

Parametric Advantages

The primary benefit of using "To last" is design resilience. In parametric 3D CAD, dimensions of base features often change during the design lifecycle. If you use a fixed dimension to bridge a gap, changing the underlying geometry requires manually updating the pad depth to prevent gaps or unwanted protrusions.

By utilizing "To last," the feature remains fully parametric. If the main body is thickened, lengthened, or reshaped, the pad automatically recalculates its depth to always reach the outer boundary without manual intervention.

Requirements and Limitations

For the "To last" function to work correctly, certain conditions must be met:

  • Existing Geometry: The sketch must be part of an active body that already contains solid geometry. "To last" cannot be used on the very first feature of a body (the base feature) because there is no existing geometry to target.
  • Direct Path: The projected sketch must directly intersect an existing face of the solid. If the extrusion path shoots into empty space without encountering a terminating surface, the operation will fail and return a geometry error.
  • Reverse Direction: If the pad projects away from the body instead of toward it, you must check the Reversed box so the software looks toward the existing solid faces.

Common Use Cases

  • Internal Ribs and Gussets: Creating structural supports inside an enclosure where the rib needs to span completely from an inner wall to an outer wall.
  • Mounting Bosses: Extending screw bosses or standoffs from a base plate to the underside of a complex top cover.
  • Filling Cavities: Adding solid material across complex, non-planar internal cavities where calculating an exact extrusion distance would be difficult.