3018 Z-Axis Sliding Table

Doesbot's sliding table swaps that for a complete metal axis. The slide, the lead screw, the nut and the motor mount arrive as one assembled block that bolts to the X carriage and carries the spindle on its front plate.

• Screw: T8 stainless steel, supported by a 688 bearing in the base plate.
• Nut: copper with an anti-backlash design, so reversing Z does not lose a fraction of a millimetre.
• Motor mount: for a Nema 17 (42BYG) stepper; the motor is not included.
• Body: aluminium, gold on the 70 mm models and black anodised on the 90 mm CST90.
• Mounting: an aluminium profile with two M5 nuts on each side, and M6 × 1 threaded holes for the spindle plate.

Three builds exist. The CNC-3018-Z-1 is the bare 70 mm slide. A second version adds a 52 mm spindle fixture for a 300–500W motor. The CST90 stretches the stroke to 90 mm and adds a spindle plate drilled for several hole patterns.

The upgrade order entry covers where a metal Z fits among the other frame upgrades.

Steps per millimetre come straight from the lead. A Nema 17 stepper makes 200 full steps per turn, and the driver's microstepping multiplies that.

A 4 mm lead gives twice the resolution and more holding force on Z. The screw turns twice as far for the same move, so the axis resists being pulled down by cutting forces and its own weight when the stepper is off.

• 8 mm lead: faster Z moves, the same GRBL value as a stock 3018 in most cases.
• 4 mm lead: finer steps, more force, half the top speed for the same motor rpm.
• Both: the anti-backlash nut removes most reversal play, which helps drilling and 3D finishing passes.

Check the value by jogging Z 10 mm and measuring with a caliper against the spindle plate. Adjust setting 102 until the move matches.

Slower Z top speed rarely matters on a 3018. Plunges are short, and rapid moves on Z only cover a few millimetres of clearance height between cuts.

Two paths are common. On a 3018 that already has a metal X carriage, the slide bolts on with M5 hardware. On a frame with the moulded carriage, an X-axis upgrade kit with metal bearing blocks comes first, then the slide mounts to it.

1. Remove the old Z carriage, spindle and Z motor, keeping the motor for reuse.
2. Fit the X-axis upgrade kit if the frame needs one, and square it to the rails.
3. Bolt the slide on through the M5 nuts in its side profile, checking it hangs vertical with a square against the bed.
4. Mount the Nema 17 on top and connect it through the coupling.
5. Fit the spindle plate: the 52 mm fixture for a 300–500W spindle, or a 43 mm clamp for a 775 using the M6 holes.

The CST90's plate is drilled for 58 × 20, 67 × 20, 70 × 20 and 80 × 25 mm hole patterns, which covers most common spindle clamps. The 70 mm slides use a 70 × 20 mm M6 pattern.

• Z height: a longer slide raises the whole spindle; check the gap between the collet and the bed at full travel.
• Limit switch: move the Z switch to the new top of travel and reset GRBL setting 132 to the new stroke.
• Cable: the Z motor lead may need an extension on taller slides.

The Doesbot slide replaces the whole Z axis with a generic metal block. It suits other-brand 3018s and scratch builds, and it costs some fitting work.

On a Genmitsu 3018-PRO, the brand's own assembly is the simpler fit: it matches the frame, arrives with limit switches and linear bearings installed, and lifts effective Z range from 40 to 56 mm. For a CNCTOPBAOS, RATTMMOTOR or unbranded 3018, the Doesbot slide is the more flexible choice.

• Pick the 70 mm slide for a stiffer Z with the stock 8 mm lead and simple GRBL settings.
• Pick the 70 mm with 52 mm fixture when a 300–500W spindle goes on at the same time.
• Pick the CST90 for the longest stroke and the finest Z steps, and for the multi-pattern spindle plate.

Before ordering, measure the X carriage and note the Z motor's shaft size. The CST90 coupling expects a 5 mm shaft, the size most Nema 17 motors on a 3018 carry. Weigh the spindle too: a metal slide and a 500W motor add real mass to the gantry, and the X rods and carriage have to carry it without sagging.