I build and tested it older version made off plastic, and now constructing it as wooden version.
I created software for it, I am using arduino USB port to communicate with PC.
Parts:
Arduino mega 2560
Power Source 5V - 10A
3 servo motors(RC) 8 usd piece
3 encoders 13 usd piece
Line Bearings 10 pieces 10 usd
Wood 10 usd
Linear Shafts from eBay 20usd(used in printers)
Screw 40 usd
Connections motor/Screw,Screw/Encoder Free(made by friend)
Mill/cutting Engine 32 Usd

Step 1: Preparing Parts/cut Wood...

Those are plans for this machine.
Small warning 0.5mm error is very big error be precise.
You need to start build:
1. Normal printer, just print those images, just make sure size of small holes are 10mm or just use cdr file from corel.
2. Wood Planks 400x30x2500mm x2 pieces and Board 18x200x1000
3. cut one Plank and one board to 502 mm
4. cut four planks 500mm x 4
5. Cut 7 pieces 200mm from planks and one for 230mm
6. cut from board one piece 220 mm and two 112mm
7. Tape the parts with paper tape
8. Now you need adhesive glue in spray
9. Stick printed parts on paper to paper tape on wood(you probably know were most goes its easy)
Some are special requires measuring(first picture with plans got 3 object rectangular), first one is for motor(RC servo, you can edit it if you don't plan using servo motors), glue it to plank 500mm just make sure is in center
Second one is for encoder it goes to 500 mm plank.
And third one is for 502 mm plank, glue it not from flat part, use smaller side.
Only left to glue for pieces on left(first image with plans) cut them to separate objects and glue to edges of planks 500mm(both planks need to be very precise).
Now to the board 502mm cut in it hole 100mmx402mm in center.
Now wat is left to cut all parts.

When cuting holes be very close to line don't cross it, use drill to finich hole.

CNC.cdr
Download

Step 2: Assembly Time( Mechanical )

This is step two: Now is time to assembly.
For this part is required to have:

Chipboard 500mmx500mm(for bottom, just cut furniture or whatever :P).
Shaft linear 45.5mm x 4 pieces and 220mm x 2 pieces(12mm thickness)
Screw 10mm thickness, leghts: 390mm , 380mm, 140mm
Nut's they are 22mm diameter brass x2 pieces and one stell 12mm(all for professional usage)
Linear bearings LM12UU(10 pieces cost 11 USD on aliexpress)
Encoders 3 pieces(12 usd piece)
Motor: Servo Motor Standard Size RC 13Kg/cm(8 usd piece, metal gears)
Wood Screws(buy package)
Some way to connect Screw with motors/encodes:
There is 3 ways to do it:
1. Buy ready one
2. Make one on lathe(I used this version)
3. Use hose to connect them
And you need tools...
Just connect all part like you see on pictures, if need more of pictures I can add them.

To put inside bearling/Nuts you shuld use loot of force, then you wont be need glue.

Step 3: Electronics(preparation)

For this part you need to cut from plank 110 mm 2 pieces.
And is required some flat material(plastic,back from furniture...).
Cut from it pieces in cdr file, and cut side wall(it wont fit to A4 page), the same length as cover, height of it should be 44mm.
Also end stoppers 6 pieces, just mot them similar like I did(just make sure they wont get destroyed it machine goes to far).
As you can see, I added some stuff the Z axis by two pieces of board(left over's from it).

cnc_electronics.cdr
Download

Step 4: Electronic and Simple Calibration/testing

For this tep is requaired to have:
Arduino mega 2560
Relay board max four relays(optional)
Power source 5V 10A
HD44780 1602 LCD Module
Power cable for power source
Lots of small buttons, some diodes and some wires to wire all motours/encoders/limit switch's.

Connections:
Servo X to pin 4
Servo Y to pin 3
Servo Z to pin 2

limit switch X_A to pin 46
limit switch X_B to pin 48
limit switch Y_A to pin 44
limit switch Y_B to pin 42
limit switch Z_A to pin 52
limit switch Z_B to pin 50
Second side of limit switch to 0V and thru NC(normaly closed)

Encoder X chanel A to pin 18
Encoder X chanel B to pin 15
Encoder Y chanel A to pin 19
Encoder Y chanel B to pin 16
Encoder Z chanel A to pin 20
Encoder Z chanel B to pin 17

Diode 1 to pin 34
Diode 2 to pin 36
Diode 3 to pin 38
Diode 4 to pin 40

Buttons 1-10 to pins 27,29,31...43,45
Second side to 0V

Relay 1 to pin 47
Relay 2 to pin 49
Relay 3 to pin 51
Relay 4 to pin 53

Display:
RS to pin 8
enable to pin 9
D4 to pin 10
D5 to pin 11
D6 to pin 12
D7 to pin 13

I added Testing code to this step, upload it to arduino and test all limits switch, buttons, relays and diodes(they will be visible on screen).
Then use function DriveMotorY() in loop to try functionality of cnc.
The only param is direction -1 is left, 1 is right.Just make sure everything works fine.

On any trouble with encoders remove from inside 78L05 and connect first pin with last pin using wire.