CNC3018 modification

I bought a CNC3018 on E-bay  few years back, because I wanted to be able to mill my own PCB boards. As was to be expected from a very cheap machine, the rigidity and precision is not great. There was play in the bearings, the z-stage was not rigid enough. 

This is a retrofit of Aviran_N's beautiful CNC design for the base of my CNC3018, trying to salvage the best parts of my CNC3018. You need to print the following parts of Aviran's design:

• lead_screw_knob X2
• X_carriage
• X_carriage_chain_top_holder
• Z_carriage
• z_endstop_cover

Salvageable from CNC3018

• bottom section with 20x40 profiles, front and back plate, rods & table
• motors and lead screws (except for z-axis, that one is too small). The x-screw should be sawed to size
• the motor-to-axle couplings
• the 10 mm linear bearings from the x-carriage
• one of the 20x20 alu profiles, though it needs to be shortened to 290 mm
• the control unit
• the spindle motor (though I have a bigger and better one available, air cooled 400W)
• possibly: the laser, if you have a pro model

Extra parts (and what they're for)

• 2x 10 mm rods (290 mm long)
• 1x 8 mm rod (290 mm long)
• 2x LM8UU linear bearings (for the x-carriage) (I had to replace the ones from the CNC3018, but you might be able to reuse yours from the z-axis carriage)
• 4x LM10UU linear bearings (for the x-carriage)
• 1x new lead screw for the z-axis (160 mm long, either TR8x8 or TR8x2, pick what you like)
• 2x anti-backlash nuts for x- and z-lead screws (make sure you have the right thread)
• 1x GT2 pulley 20 teeth 8 mm hole (6 mm belt type)
• 1x timing belt 6 mm GT2, 158 mm closed
• 1x GT2 pulley 20 teeth 5 mm hole (6 mm belt type)
• endstops for all axes (I see I forgot to incorporate the x-stops in the design, sorry about that, instead I opted to add them to the X-carriage with threaded inserts and M2.5 bolts, as shown in the pictures)
• 2x aluminium ring with a headless bolt (don't know the technical name for it) to keep the z-lead screw from moving up and down (I made mine by drilling out some old pulleys, see pictures)
• 1x mounted ball bearing 8 mm internal flat (sometimes called ‘type B’ on E-bay) (for mounting the x-lead screw)
• 2x 608 ball bearing (z-lead screw)
• 2x M3x6 headless bolt (lead screw knobs)
• 4x M3x10 hex (mounting the z-motor)
• 2x M3x16 (endstop cover)
• 14x M3x20 hex (fixating rods, a.o.)
• 4x M3x30 hex (mounting anti-backlash nuts)
• 4x M3x40 hex (mounting the x-motor)
• 12x M3 washer (mounting z-motor + trapezium nuts)
• 14x M3 square nut (fixating rods, a.o.) 
• 8x M3 locknut (mounting anti-backlash nuts)
• 2x M4x12 hex (mounting the mounted ball bearing 8 mm)
• 2x M4 threaded inserts (mounting the mounted ball bearing 8 mm)
• 20x M5x10 (mounting the gantry to the bottom section + mounting the 20x20 profile)
• 20 x M5 T-nut (mounting the gantry to the bottom section + mounting the 20x20 profile)

I think that's it. Hope I did not forget anything. Please comment if you find errors.

Printing

I had the problem that the motors got pretty hot during some tests, which resulted in deformation of the X-carriage. Make sure you print that one in PETG or, even better, ABS or ASA for better temperature resistance. All construction parts were printed with 0.2 layer height, 25% infill and 4 walls, but I think I'll redo the X-carriage with a higher infill.

Notes

• The current gantry fixtures are straight. While printing I realized I could have better offset the top from the bottom, so that the centre of mass would be nearer to the center of the clamp. Hindsight sucks. May correct it in a future version.