I have a long 4" OAL 1/4" bit I use for its 1.5" cutting length. I have always had that bit come somewhat loose likely due to the increased vibration of its long length. However I was cutting out a robot for an automaton I am working on for a 2x4 contest. I was a little ways in cutting the figure out and noticed that the bit was taking about a 1/4" bite. I stopped the Shapeoko 3 and the collet on my Dewalt router was loose. I just stopped the job and took the bit out and cleaned the collet and router inner shaft. I was surprised at how much black dust was inside the router shaft. I have never cut anything black and still do not know where the black dust came from. I cleaned the collet with brake cleaner and sprayed the brake cleaner on some q-tips. I had to use 3 on both sides to get the inner router shaft clean. After the cleaning the collet nut did not come loose for the rest of the job. I have had issues with that particular bit loosening slightly so I occassionally pause and check the tightness of the collet. I am sure that is due to the increased vibration of that long bit.
In this picture you can see the line where the bit came loose. Luckily I did not have to replace the material and it cut the rest of the way fine. I sanded the line off and it turned out well.
I wanted a face on the robot body and decided a frown was appropriate for the overworked robot.
Still working on the automaton and may have to slightly change the design. The cams rotate and there is a 3/8" square rod that lifts the robots hammer arm up but the piece gets stuck on the cam. I saw a youtube video about a similar automaton and that person used a lever riding on the cam that lifted the robots arm up and down. The bests laid plans of mice and men often go awry.
The good part about making the cams on the CNC is you can quickly redesign them. I rounded the parts but they still do not work. I also designed a cam that is just two high spots in an oval but that had the same problem. Back to the drawing board.
Here is what the automaton plan looks like made of cardboard.