First I have to thank the great community here in the zone!
You helped me a lot. I started with nearly zero knowledge about cnc-buliding one year ago, reading through tons of treads here and I learned very much and finally I got addicted to it.
Two months ago I thought I have collected enough information to design my own CNC-build.
But I have some minor limitations on designing.
-First is of course the price - I am still a stundent and money is a raw-material - you know.
-Besides I am not very well equipped for machining, so i will have to reduce the complexity of my design to nearly basic. I just have normal homeworkertools and nearly no tools for metal machining. I will maybe gain some access at my school. They have tons of Mills and that stuff.
And I got already the rails and blocks for free (nearly) from some friends and picked up an great Mitsubishi VFD on the bay.
For the X-Axis I have two SIZE 20 1390mm Bosch-Rexroth rails
The Y are the same but SIZE 15 and 1140mm long and on the Z I got some pretty completely new and sealed THK rails (450mm long).



The idea to my concept:

Regarding to my situation the size of my build was already defined by the rails I got.
for this reason it has to be a relatively big machine design. So my first idea with an MDF/Wood structure died because of my requirement to mill some Aluminium or maybe small amounts of Steel and the high resulting forces applied to the long gantry.
So I chose Aluminium. - The sides, some of the base framing and the Z-Axis will be made out of watercutted 20mm Aluminium sheets. As far as I know that is the easiest sollution for my lack of tools. (note: lasercutting is nearly impossible for that thickness and miling would be too expensive for me)
The other structures will be made with aluminium extrusions (30x60 for the base and 30x120 for the Y-Axis)
I chose a dual X-Axis concept because it reduces the deflection from the gantry and I will be also able to make the base more massive. I gonna drive it with two stepper motors an each side because I am afraid that the so extremely long timing belt that would be required when only one stepper in the middle would stretch too much resulting to a high backlash.
But all steppers are belt reduced. That lets me choose if I want double the resolution (2:1) or the double the speed (1:2) or let it genuine by 1:1 simply by changeing the pulleys or/and buying 4 additional belts for 1:1. Belt width will be 9mm or more.(would you prefer HDT 3mm?)

SCREWS:

All screws will be ballscrews (class7) with 5mm pitch (20mm dia and 16mm for Z). At the moment I think I will buy them from chai because of his very low price (I have already read the stories about him). Here in Austria I dont think that I will get a ballscrew lower than at least ten times that price. (also C7)

DRIVE:

For the drives I chose 3NM stepper (NEMA 23- bipolar parallel setup to 2.8AmppP)
I will get them for a fair price from BZT in Germany.

DRIVER:

I am going to use a Gecko540 because of its really great quality compared to the price. I think I cant do much false when i take it.

SPINDLE:

One very important part to me is choosing the right spindle motor. I think it is an very common problem to many DIY-CNC-builders. Most try to save money by taking a Kress spindle or something like that and let that poor device mill some aluminium until its bearings are dead. Others invest in these cheap china spindels which are pure crap for metal milling. I have some connections to some manufacturers and nearly all trustable are saying that they are only designed for wood engraving (noway metal!).
But I found a chinese spindle which is designed for milling and engraving soft metals. It is equipped with 4 quality nsk bearings and has a power input of 1.2kW. Compared the the cheap china spindles it has 0.96 Nm torque (cheap 1.5kW ones have only around 0.6Nm. and it weights about twice as much (8kg) It has an ER20 collet and it is water cooled. But that sucker is only being shipped for around 400€ - anyway it seems to be a great deal - and i dont want to save money on the wrong place.

My goal is to gain an accuarcy of about 0.05mm per 300mm (including deflection, pitch error and run out of course) Pitch errors can be a little bit compensated by Mach 3 - so C7 ball screws arent not a too big problem
As said before I will mill aluminium and some steel but also PCBs, wood and huge foam blocks (ex .:for molds).
Maybe I could later make some money by firing it up for Milljobs in the architecture and hobby-aircraft sector.

My first costlimit was 1000€ but with my needs and my actual design I am FAR away from that.
I was really shocked when I saw the price for an 1000x1000 20mm aluminium sheet (560€). I have calculated the sheet surface i need for my parts. it is 0.86m² (so around 450€ on sheet material only). I have no plan how expensive the watercut will be - anyway I am afraid from that.

...enough text...HERE are the renderings of my first design:
(more information is blow them)






You may have detected that my Z-Axis is lookig a bit different than regular designs. I really prefer it, because it makes the Z-Plate much more stiffer and gives me a bit more travel. The only con is that the Z-Stepper has a bit more work to do, because he always have to lift itself and the rails. But I think I can live with that. That method seems to be a tick easier and also saves me a little bit of aluminium sheet.

At the moment the spindle can travel 900mm on Y, 1150mm on the X and 220mm on Z. That is more than I would ever need, but I dont want to cut my already existing rails down. I have already increased the distances between each pair of blocks - to reduce the momentum (torque I guess in English)

I will use just a simple MDF board as a working surface for my first couple of tests. It doesnt hurt my wallet if the spindle goes to much down the Z. Maybe I will change to an Aluminium T-Slot surface later then. For Metal milling I think that I will remove the MDF board and mount the work pieces directly on the base extrusion framing (you can see it in the 2nd picture)

So that is all I have to say first - now you have to tell me what I should improve. If you need any plans, please send me an PM with you e-mail adress. I can send them as an e-drawing 3D file.

By the way: what do you think about "BLOCKSTROYER" as the name for that machine? (honestly)

A website with the coming build progress will be released soon, so please look back later for further information.

I hope my English isn´t too confusing for you! Please feel free to correct me. (PM)

grz. Max!