Accurate Strong Gantry

[JAZZCNC]

I am seriously thinking of the moving bed option now it is just 5-700 mm longer space and can forget many trouble i.e the dual motor, heavier spindle
My goal is a bit better an more accurate machine than a router so called semi industrial so within a 4000 -4500 GBP budget I would like to reach the best performance.

If you have the space then Fixed Gantry is the way to go without any doubt but the principle still applies regards motors and moving mass. There is nothing wrong with regular steppers if sized correctly and if used with quality Digital drives and external motion control card, which you would 100% require for servo's, then they won't lose position and will hold high accurecy without any encoders.

Regards Hybrid easy Servo's then I'm sat on the fence because while I know they work excellent I agree they are too expensive and Servo's can be bought for not much more money.! . . . BUT . . .And for some it's a very Big BUT.!! Servo's require more knowledge of setting up to get the best from them and can be nightmare to tune correctly, espicially if other electronics are not done correctly and noise is introduced has they are much less tolerant of noise in the system. (It's not uncommon for some one to turn on a dodgy radio or some noisey appliance and Servos take off at full speed.)
I have seen people, experienced people, build machines or retro fit Mills with servo's only to change them at a later date with steppers because they can't get them running correctly or reliably. . . . Reliably being the key word.!! . . . . Now I'm not saying don't use servo's but I just mean be aware that they are not simple and can turnout to be more trouble than there worth for the inexperienced.
Hybrid easy servo's don't have this issue as they are essentially steppers with encoders for checking/correcting position.

Regards the machine I Try to always keep in mind the three most important goals of a CNC machine which in my opinion is accuracy, repeatabilty and finish quality.
Accuracy and repeatabilty comes from component quality and suitabilty along with machine ridgidity and attention to build.
Finish quality comes from some of the above but mostly from Ridgidity and machine design and while all three are important aspects the quality of finish is what I'm always aiming to improve. Achieving the best best finish quality is mostly about lessening tool deflection and chip clearence.
So if you can keep the tool stickout distance from spindle to a minimum and have the shortest Z axis extension you'll get the best possible result and it's here I'd look to improve machine design and in my opinion you won't go wrong if you follow this design. (which I'm sure he stole from my Head. ) Just make a better, stronger Job and put proper spindle on it.