cam gear 3d model

This is a partial arc cam gear used in an Olympic gas water heater. The shape is a semicircular gear segment with approximately 18 evenly spaced teeth along the arc. The gear does not rotate fully; it acts as a cam to control water and gas regulation. On the flat side opposite the teeth, there is a circular mounting hole for the control shaft. The inner diameter of this hole should match the shaft diameter shown in the reference image. The thickness of the part is uniform. Recreate the gear exactly: same tooth count, same arc radius, same center hole position, no extra details. Do not simplify or remesh aggressively. Output as a solid manifold 3D model (STL).