We briefly show how to design a mould out of a cranioplasty implant. This mould can be 3D-printed in order to fill it with bone cement to actually create the implant that will be used in the operating room. The model is standard and should be refined according to the needs outlined by the surgeon in charge.

We thank engineer MaurĂ­cio Morinigo from Da Vinci Anatomics (Brazil) for defining and outlining this workflow.

1. Implant object

First we take the implant that we made in a previous session, and explode it with command Explode. As we are going to create one half of the mould, we select the inner part of the plate and its contiguous fillet surface, and hide them (by moving them to a Rhino layer and hiding that layer).

Initial implant.

Inner part of the plate.

2. Offset curve

We duplicate the inner edge of the plate with command DupEdge, and offset outside radially from the inside of the plate (in this case we move to one of the side views to do so), with command Offset. In this case we choose an offset of 2 mm.

Offset curve.

3. Offset curve on surface

We create a rectangle plane (command Plane) to the side of the plate to which the mould will be projected (in this case at the same side view like before). We go to the side view and run command OffsetCrvOnSrf, then select the offset curve and the plane, and choose zero as offset value. The curve will be projected onto the plane.

Offset curve on surface.

4. Trim and jon with lines

We run command Trim with the projected curve as cutting object, and the rectangle plane as object to be cut. We will get the inner part of the rectangle defined by the curve. We run command Line to join the duplicated edge curve with the offset curve, and another time to join the offset curve with the projected curve.

Trim and join with lines.

5. Sweep2 rail and finish

We run command Sweep2 to join the rails defined in previous section. We run it once to join the duplicated edge curve with the offset curve (with its joining line as cross-section curve), and again to join the offset curve with the projected curve (with its joining line as cross-section curve). We will obtain the first half of the mould as a series of surfaces that we can join to form a solid object.

First half of the mould.

6. Second half of the mould

We repeat all steps above now with the outer part of the plate, carefully re-doing operations in opposite sense. In the end we will obtain the second half of the mould, and overall the full mould.

Second half of the mould.

Two parts of the mould together.