3018 CNC Z and X Axis Upgrade

The 3018 Pro from SainSmart is a great little CNC that is suprisingly good given how inexpensive it is. It's main weakness, as many have identified, is the lack of stiffness and play in the axis and spindle holder which causes the bit to chatter and produce rough cuts when attempting anything more than light engraving. 

Borrowing the idea from a design by The Hardware Guy and others (I did buy The Hardware Guy's 3D model, but it doesn't fit a SainSmart 3018, so I designed my own), I have added a 3rd X-axis rod behind the machine, improving stiffness. The Z-axis carriage/spindle holder is also longer, reducing movement, but is still designed to hold the standard 3018 spindle motor.

The result eliminates almost all play in the spindle, allowing faster, smoother cutting, with no chatter. The modified machine cuts 3mm acrylic sheets (in multiple passes) with ease and with high accuracy.

The design includes two options for the 3rd X-axis rod supports. One for a genuine SainSmart rod with a tapped hole at each end. The other alternative design is to clamp a standard 10mm bearing rod that is more freely available. The design re-uses the LM8UU bearings from the standard Z-axis and the X and Z axis screw rod hardware. It needs new longer Z-axis rods and longer X-axis bearings. I did initially re-use the X-axis bearings, but the very slight bowing in the X-carraige print caused some minor binding of the bearings on the rods. The single longer LM10UU bearings run super smooth.

Design is compatible with my dust shoe design which sucks up 80% of the chips produced, while still giving visibility of the cutting bit

https://www.printables.com/model/524392-3018-cnc-dust-extraction-shoe

All parts printed in PETG, 25 - 50% infill, 5 perimeters for strength. I printed at 50%, but I'm sure less would be fine if you want to save filament.

Linear bearings are a push fit into the prints. A drop of CA glue can be used to hold them permanently in place. Everything else bolts together in a similar manner to the original parts, though the Z-axis stepper motor bolts directly to the carraige and doesn't need the spacers used in the SainSmart design.

Parts Required, with Amazon UK links as of June 2023:

400mm x 10mm Bearing Rod for 3rd X-axis rail:

https://www.amazon.co.uk/gp/product/B07MV7ZVZC/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&th=1

LM10UU 10mm x 55mm linear bearings X 3

https://www.amazon.co.uk/gp/product/B07H952ZWL/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&th=1

150mm Lead Screw for Z-axis

https://www.amazon.co.uk/gp/product/B07QYLVRYG/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Lead Screw bottom bearing for Z-axis

https://www.amazon.co.uk/gp/product/B082PSWM9D/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

150mm x 8mm Bearing Rods x 2 for Z-axis

https://www.amazon.co.uk/gp/product/B07QYLVRYG/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

M5 T Nuts to clamp 3rd rail supports to 3018 Base extrusion

https://www.amazon.co.uk/gp/product/B07L11H3MC/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

M5 screws to attach 3rd rail supports. M4 screws to clamp 3rd rail. M4 screws and nuts to clamp spindle motor

In case you want to replace the Z-axis linear bearings:

https://www.amazon.co.uk/gp/product/B07H943RL6/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&th=1

I also upgraded the spindle motor with the SainSmart 20,000 rpm version. Not essential, but it does produce smoother, faster cuts and it generates less interference, so the CNC is more stable. It isn't quieter, the “Noise Suppression” in the description is electrical noise:

https://www.amazon.co.uk/gp/product/B08DTHDSMV/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1