Linear Screw Double Rail




Introduction: Linear Screw Double Rail

About: Avid 3D printer builder, currently completing my 3rd printer design. If you like what you see and maybe even implement what provide, consider supporting me on

The original screw driven rail lends itself nicely to having one of each on each side of a 3D printer. Up and down is accurate but BY itself, it doesn’t have a lot of lateral support.

Since I’m looking into cantilever designs, I revised the rail to introduce a second linear rod, widening and thus stabilizing the linear screw. I intend to use this implementation in a revamp of my Cantilever printer

I'm a big fan of Auto bed leveling so I did not design the End-stop as an integrated component but instead went with a detachable End Stop incorporating a much smaller micro switch

STL files are included with the Instructable but if you want to download the entire model you can do this on

Step 1: Parts

There are 3 printed components to this rail (4 if you count the optional End Stop Case). The STL files are included. You can print using PLA (0.2mm 15% infill). All fittings are tight, so each 3D printer may need a little scaling tests.

following components can all be found on but if you have time and patience you can possibly source many from for less.

Flexible Shaft Couplings 5mm to 8mm:

2-Pack - Linear Motion Rod 8 mm x 406mm Shaft:

micro switch:

1010 72 inches (8020 inc.):

nema 17 1.7A (5 pack):

SCS8UU Linear Motion Ball Bearing:

M4 8mm:

m3 10mm:

Lead Screw 8mm:

In case you do not have access to a 3D printer you can purchase the printed parts here:



Update 3/15/2018: Per request, I've added the STL files ( for a 2040 extrusion assuming a 2020 cross bar to fit in slider

Update 4/26/2018: I've added the STL files for 12mm Rods as they appear to offer much more stablility

SCS12UU Linear Motion Ball Bearing (2x) $16.40
Linear Motion Rod 12 mm x 400mm Shaft (2x) $25.74 (+shipping)

Step 2: Assembly

Like with the original Linear Screw Rail, All components were specifically designed for the 1010 aluminum extrusion WITH grooves. The attached picture shows the connections are strong. Holes have been added to the components to screw it on using a t-nut (I'v seen no need for that).

All components couple to the extrusion side ways (no caps). This allows for moving it for best position based on your use.

The lips on the Carriage are similar to the lips that clamp it's own components to the rail. This allows you to insert 1010 extrusion perpendicular to this rail. There are two holes with room between the SCSUU blocks for screws and possible t-nuts.

Step 3: Testing

I use the marlin software and a bare RAMPS 1.4 that is controller via pronterface
I use Marlin 1.1.x to test and have the screw rail connected to the Z-axis In the Marlin configuration.h file make sure you set the proper length for the screw rail // Travel limits after homing (units are in mm)

Based on the length of the screw rail, rails lost in coupler and end end connector and the height of the carriage, the range for travel is 0 to 290mm. Not setting the Z_MAZ_POS in the configuration may damage the rail as it would try to travel beyond it's capacity.

#define X_MIN_POS 0
#define Y_MIN_POS 0
#define Z_MIN_POS 0<br>#define X_MAX_POS 200<br>#define Y_MAX_POS 200<br>#define Z_MAX_POS 290

The Lead screw is 2mm pitch 4 start. For Marlin \thist comes to 400 steps/mm

#define DEFAULT_AXIS_STEPS_PER_UNIT   { 80.08748,80.08748,400,456 }<br>

If you liked this check out my other instructables or visit my website at

Step 4: Parts at Work

In case you're wondering what you can do with this component check out this video



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    12 Discussions

    Would you consider modifying the design for 2020 and 2040 as they seem to be more popular and selfishly i have a bunch sitting around.

    8 more answers

    Done, added new stl files ( in the parts step that use a 2040 rail as support and accepts a 2020 cross rail in the slider. I put the LC8UU as close together as possible, still allowing to tighten t-nuts from the back (to support the crossbar).

    The 2020 and 4040 that you have around, does it have the grooves, or is it smooth? Much of the design is currently in the tight clip-on capability into the grooves.

    I'm currently redesigning this rail for 12mm linear rods and LC12UU block. I was a bit surprised about the flexibility in the 8mm rod. After that I can look into 2020 and 4040. In return would you be willing to return the favor by considering to support me on ;-)

    I sent you a message. Thx!! I will look into the linear Actuator as well. That one might be a bit more challenging as the timing belt runs inside the groove. Since it is more shallow (6mm compared to the 8mm in current design), creating a working slider might become a tight fit

    should be doable the Cetus3d printer has their belt running like yours in a 2020

    I'll give it a shot. I'm not entirely sure how the cetus3D has their belt connected. They may very well use a closed loop belt.

    I just ordered a few pieces to make sure all fits when I design it.

    i was wondering if you could upload this to Shapeways, for those of us bereft of 3D printers and have them ordered from there

    2 more answers

    If you have a shapeways account you can upload the STL files (included with this instructable) and order the parts that way. To be honest I just uploaded a single piece and it was $26. That's crazy. I can come up with a better price than that. Shoot me email at