It is important for the 3D printed part to fit properly. Tolerances of the design error on the tight side.

Check that the burr drive pegs fit the holes of the conical burrs. If it’s too tight, apply a small amount of sanding to the impeller and you’ll be in good shape.

Do not sand the flat part of the center hole. Only sand the curved part slightly if needed. The flat part takes the most stress from the drive shaft.

The gap here should be small with the new part. If it's too tight, you can sand the edges slightly.

Here's a video of the fit-up with the Shapeways printed part.