Hey mate
Out of interest where did you have to file etc to make the profile work?
saw photos the other day looked great. Cant see any photo's now though
The rotors are machined with a .005 clearance from each other and the blower case. IN REALITY you factor in
Back lash in the CNC machine. Backlash is just a reality. Every machine that costs 1200 bucks to build has it. Under .001 even after 3 years of use.
The resolution of the CNC machine. Another factor that is just a reality that has to be dealt with.
When setting up the machine X, Y, and Z must be set up perfectly.
When the case was machined the hole pattern to bolt on the bearing plate was created. Then the case was rotated 180 degrees, and the two rotor bores were made, the bores had to line up with the bolt pattern that is now at the bottom of the case. Factor that error. (only missed by .006, Not bad)
All these errors and a half dozen other things that can go wrong can pile up.
The first thing I did was grab a piece of sand paper and measure how thick it was (.006). Then I turned a piece of stock .012 smaller in diameter than the finished size of the valleys and made sure they were exactly to size. After all 6 valleys were done the rotors would turn about 3/4 of a turn freely. Then I installed the rotors in the case and sanded the bores until both rotors spun in the case freely. Then installed them both, geared them together and gave them a twirl. Dissassemble and look for scuffs. Then polish, assemble , spin, dis assemble, polish. Keep tracking down the spots that rub until nothing rubs anymore. Its very time consuming but needs to be done unless you have a half million dollar machine and 20,000 dollar software.
If everything was spot on none of that would have to be done but I'm not that good.