Profile for Screw Compressor?

[Roger]

My piston compressor is very noisy, and has to run a lot when I am machining with air blast and pulsed mist. I want a quiet compressor - but with adequate pressure and flow.

A screw compressor would be nice, but they tend to be larger than a big piston compressor, and they also tend to be $$$$. Their advantage is that they are much quieter.

Could I make some small screws on a CNC with a 4th axis? If I had the profile I am sure I could have a go. But typically the screw has only 3 or 4 flutes, and the profile is going to be ... odd. There has to be full engagement  to lock the air in of course. Has anyone any ideas? (Is this a gear? Dunno ...)

Cheers
Roger

[ArtF]

Hi

  Lookes to me to be quite a job depending on the screw design.. Might it be better to
try a roots blower first? Looks like the simplest form of a screw compressor...

Art

[Roger]

A Roots Blower ...
Now there's an idea! Much simpler. But do you have the equations for the impellors?
I wonder how noisy the sync gears would be at full RPM?

Cheers
Roger

[ArtF]

Roger:

  You can generate them now, they are a form of noncircular gear.
GM doesnt generate the housing, but does allow any number of lobes,
the houseing is simply 2 ovarlapping circles drawn from shaft center.
  Easy to draw in Cad once you have the two roots on the drawing..

  Many roots blowers have small relief channels , like a small tube from
top chamber to bottom to limit lock pressure ,
Its way beyond the accuracy of my machines to do them, but if your into
metal and lapping, they should make quite a compressor and can be put
in series with the right connection gears to increase pressure.

  Typically, Roots Blowers are quite expensive I notice, probably due
to difficulty of manufacture, but Im willing to bet their a damn site
easier to build than screw compressor rotors.. Were I to try
to build such a beat, Id try a 2-3 lobe roots first..

Art


 

[Roger]

According to Wikipedia, the problem with Roots Blowers (for my needs) is that they are more high volume /low pressure. I need 5 or 6 bar, and I don't think a Roots can do that? But I don't know.

Cheers
Roger

[ArtF]

Probably not.. unless you ganged a few together... thatd be a tricky thing to gear..

Art

[Roger]

I have collected a few theory papers for the screw shape off the web.
The maths for the screw shapes is ... a bit intimidating. Yes, I could program the curve, but HEAVY! Roots are much simpler, but limited for pressure.

Hum - moving on to scroll compressors ... the maths is simpler.

Cheers
Roger
Edited to clear up the confusion - sorry Nate.

[Nate]

I have collected a few theory papers off the web.
The maths for the rotor shapes is ... a bit intimidating. Yes, I could program the curve, but HEAVY!

Really?  I was under the impression that (simple) roots lobes could be constructed using epicycles and hypocycles, which isn't so bad.
https://en.wikipedia.org/wiki/Roots-typ ... iderations