Once sure your impeller is worn out, you'll need a replacement part. I ended up modeling it and 3D printing it several times at the local library. I've made the final design available for printing at www.shapeways.com (See link below). Of course, you can also model your own design if you wish to spend the time.

Shapeways BCG600SIL Impeller Shop

Optional video of the ShapeWays part with a little background from when this was originally designed for the BCG800XL (The impeller is the same for both the BCG600 and BCG800 models): https://youtu.be/zB5F9ha1-zs

For a look at how well the new design holds up in a similar grinder (the BCG800) see my 2-year teardown here: https://photos.app.goo.gl/868a5ReyM2XAyj...