non-uniform grind, engineering flaws (may be ver. 1)
I recently purchased the KA Proline when my old grinder gave out. Have many issues with it. As it, it is not capable of a uniform grind. KA is sending a replacment, but I believe the problem is how the device is engineered. Will wait to I get the new, replacement unit (KA is out of stock right now, probably due to a roll to new colors).
Anyway, the issue is the plastic threaded part used to adjust the grind and the bearing used inside it to hold the shaft. In combination, these allow the shaft of the augur/burr assembly to wobble. As the augur forces beans into the burrs, it wobbles. You can feel this in the adjustment head cap during a grind.
You can see how this happens by disassembling the burr and adjustment parts as if to clean the burrs. Put the augur drive into its slot and see how loose it is due to low tolerances. Now put the plastic threaded part with its bearing onto the shaft tip of the augur. Press the burr plates together with one hand to eliminate play from the plate. Notice how much play there is where the plastic and bearing meet the drive shaft. Put the threaded plastic into the heavy front plate assembly and repeat with the augur/burr drive part outside the unit. You might think all that metal in the retaining plate would help, but it does not really. Plus the plastic threads are not very tightly fit into the screw threads of the adjustment plate - another source of wobble.
Test this theory empirically. Grind uniformity is greatly increased by pressing hard on the cap during a grind. This reduces, but does not eliminate wobbling of the moving burr plate, and greatly increases grind uniformity.
This is really sad because without much more material expense KA could have fixed this problem. Of course it presumes the design engineer thought of this because it involves more than just a parts swap. First would be to extend the part of the drive shaft that goes into the bearing by about an inch, and use a longer bearing inside the threaded plastic part. Even better would be to do this, and use metal instead of plastic for the threaded piece. That's not much extra cost.
Situation may be different with other devices. But this is an obvious design flaw with my current one. As noted, I am waiting to get a replacement from KA to see if this machine is as capable as many have found it to be -- meaning mine must be an early unit. Looking at the pictures in the quick review, I think not, and the issue is expectations related to grind uniformity.