Hi people
there is a thread called "Show how to build a CNC machine from the very beginning to the end" where a chinese manufacturer attracted people how to build an CNC Machine (similar to Tormach, Novakon, Syll, Optimum machines ) some people (like me ) have invested and since long time nothing has happened ,..
So while waiting there is in that thread a discussion about VMC mill designs.

Do this thread will be in general about pro cons and designs stuff of this kind of machines. And i will make my requirements clear.
Hast to be able to do Steel , X axis 400mm y axis 200mm Z axis 200mm or bigger.
CNC is a must. It should not stall and small batches should be able as well. Later an ATC would be nice.

So sayed that there is the possibility to retrofit an "old" VMC mill (you can search for my Bridgeport 412 Retrofit thread so i know what i am talking about ) this option is not covered here.
And i will also do no look on mach3 , linuxcnc or similar i expect servos or steppers in that size of machine.

Machine Frame :
there was an discussion if it has to be casted or can be welded in steel.
I think it depends of the quality of steel if you have good quality steel why not weld it there is an given wall thickness you need for the needed strengt.
So in my opinion there is no need of cast for an VMC mill

Linear Rails or dovetails.
i have seen heavy and precise dovetail an machines (deckel or similar) i personally think that proper dimension linear rails make more sense for an cnc machine because the friction is less. so fast and small moves will work better.

Ballbearing Spindle.
I personally think that this is the hart of an cnc machine and has to be also properly sized and high quality.

Drives.
Depending on the requirements i think that in small sector overpowered steppers are acceptable. and in closed loop there is only the end speed the differiaenciator of servo and stepper.
If my intention is alu and high speed feeds then an servos system might be a good choice so i think that in that case the manufacturer should offer that option.

Spindle.
Here i guess it is complicated and depends on that requirement
for instance on my CNC Router i insist on ATC why because i do PCB´s with it. When i have to mill ALU i change the spindle and use the normal Kress with it.
But sayed that i think that the ISO30 Spindle is more expensive but has more pros that cons (i never worked with an R8 of tormach )
I guess that often used tools can be prepared and known by tool database
i also have the advance that the spindle motor force is mechanically transportet by this small blocks.
If the BDLC motors are really that big advantage i would like to hear your opinions

Fazit
If i look for instance on an optimum BF46 and the cnc optimum i can not see why this should be an bad optimum ?
Mr Handlewanker gave me the impression that there is something bad by using the frame of an stable VMC mill and use it as CNC
i have now looked all the dfengs pictures through and can not really see the big advantage.
it seems that cast is cheap compared to EU (i guess less regulations cheap energy ) but i would like to see where is really that big thing.
i almost bought an Syll machine and they are also straight forward.

so i am looking forward for an nice and constructive discuss