I have been extremely busy with few projects last couple of months, so I haven’t had the time to post anything. But this will be a guide/summary to how I fixed my broken Roccat KONE scroll wheel.

Breaking of the scroll is a very common problem with the Kone. Mine lasted for about 2 years and when it finally broke, I decided to investigate what’s the problem with the mouse. So here are few pictures of the mouse and what lies inside it.

Now let’s go further: disassembly of the scroll mechanics and finding out what broke.

The final picture shows what’s the cause of the failure. The shaft that connects the scroll wheel and the rotary encoder is only 1.75 mm in diameter. The other reason why it breaks, is the plastic. Classic cheap, glossy, flimsy, fragile plastic used in cheap consumer electronics. I was quite careful while taking it apart, but I still managed to break the plastic in two places while disassembling it. Yes, I wouldn’t have a problem with it if they had used this kind of plastic in a 10€ mouse, but the thing costs about 80€. Cutting costs on the plastics of the scroll wheel? What on earth were they thinking?

So, how to fix this little bugger? Yes, you guessed it: let’s use the magic of 3D printing!
First however, I needed to 3D model the mechanics of the thing. Took me 2 evenings of measuring&modelling and I finally ended up with this.

While doing the model, I was annoyed by the encoder they had chosen for the mouse. It has a hex shaped hole in the middle, so my first idea was to find a hex key, cut and file it a bit and use it as my new encoder shaft. After few minutes I realised the error in my idea. They don’t manufacture hex keys with 1.75 mm diameter, what a disappointment. So I considered milling one out of aluminium or steel, but that seemed an awful lot of trouble and effort. My final solution was to 3D print that also, won’t be that strong and reliable, but will do, at least for a while. They could have used a encoder with a 2 mm shaft hole – this would have added some strength to the shaft itself and would have made the repair process a lot simpler. The encoder itself however, feels nice and robust.

After finishing the model, I ordered the parts from Shapeways and here they are.

I had the parts made out of “Strong & Flexible Plastic” aka PA 2200. The quality was good in general, the parts required some filing and doing, but this was expected, considering the 3D printing technology. I was a bit disappointed by that the scroll wheel was missing the hexagon shaped hole in the middle, there was only a slight couture of it. So to fix this, i grabbed my scalpel and cut the shape out manually under a microscope. Annoying work I have to admit. This maybe wouldn’t have happened if I had the shaft and wheel in one piece. But for the first prototype it felt more reasonable to have them made separately.

After that I had to assemble the mechanics again. Pictures follow.

Assembling the mechanics wasn’t very problematic and all went nicely, Looking at the timestamps on the photos taken, it took me less than half an hour to put the thing together and fit it back inside the mouse. After assembling the mouse once again, came the moment of truth: will it work? The answer is YES and has been working for few months now.

So the verdict.
1) The general structure of the scroll mechanism is not that bad, could be a bit stronger however, considering that this still wants to be a gamer/performance mouse. The shaft that connects the scroll wheel and the encoder is an epic fail, the engineer who designed it – shame on you.
2) The encoder feels nice and robust, as I mentioned earlier, but the 1.75 mm diameter hex hole is a fail in my eyes.
3) The material used for the scroll mechanics sucks. No more comments.
4) The centre button is quite hard to click, this could have been avoided very easily, but it wasn’t. I have clicked the central button <50 times since I bought the mouse, mainly because it requires effort and concentration to press it right. I even considering desoldering the button and buying a button that was easier to click, but couldn’t be bothered.
5) Was the repair worth the time, effort and the money spent? Probably not, but it was a fun hack to do.

I hope that you enjoyed reading this and maybe this will help you repair your mouse. I have also included the 3D models of the mechanics below in SolidWorks and STL formats.

Download HERE!