Thanks guys for your posts...
And sorry about delay with my answers, was out of office few weeks...
I think my problem is: I have not explained situation how we work...
We are furniture producers. Each day we cut approx 50 laminated chipboard sheets (around 3-5km long cutting way per day)
Yes, with one thing I agree, with expensive bits is possible to reach 22m/min. and more. If you are on MDF cutting daily... Unfortunely, we using MDF boards really rare. If you cutting laminated chipboard, is absolute nonsense to use expensive bits. They loose sharpness very quick. In that case we buy cheap Chinese bits and after just throw them away... But with cheap Chinese bit you never reach speed more as 9m/min. Our partners have 24000rpm. And they are able with same bits to cut approx 20% faster as our 18000rpm...
That is point about idea to increase rotation speed. For me is logical: more rpm=more working speed.
We need to increase our production speed. We have a choice to buy another faster spindle or enter the second shift. For third CNC router we have no place available...
sincerely