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RailCore II

by kraegar, published

RailCore II by kraegar Jun 27, 2017
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Fusion 360


RailCore II by kraegar is licensed under the Creative Commons - Attribution license.

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RailcoreII is a Core-XY based Reprap 3d printer designed by J. Steve White & Tony Akens. The initial idea to collaborate on a printer started in the #RepRap IRC channel, and centered on some common goals we both had in mind for a new printer design.

Core-XY motion.
All Linear rails for movement
Space & Cost Efficient, enclosable frame
Key components being printable, or able to be milled
Flexibility and Scalability in the design
A professional looking printer
Self Sourced and Easily customizable

Steve had previously built the “railcore”, the “alpha” version of this printer. We took what he’d learned from it, and began the design on the new printer. All design work was done in Fusion360.

As we progressed, we decided to “publish” this printer in an open, documented format for others to build as well.

The frame is designed to be 1515 aluminum extrusion. This was a space efficient choice, and it makes building the printer easy, as standard M3 hardware works like a T-Nut, fitting into the extrusion nicely. To add rigidity, we use melamine sides to stiffen the frame. (These can be cut out of any material you prefer, including plywood, acrylic, aluminum, etc). The total cost for the actual frame components (Extrusion, corner cubes, and sides) is roughly $100.

From there, some key design decisions were to make the build volume a 250mm cube. This kept the total printer size to what we considered reasonable. The design is easily expandable to 300mm cubed, and a new version at these dimesnions is forthcoming. Some notable aspects of the design: dual leadscrew Z-Axis with a belt drive between them, Stacked idlers duo-planar belt path, and lots of flexibility. The electronics in the design are the Duet (Wifi or Ethernet), 24v PSU, 0.9 degree steppers. We used an E3D v6 for the design, as it’s the most common hotend at this time. Support for other hotends will be forthcoming (needing only a different Y carriage). Semi-Direct drive or full bowden is supported.

A special thanks to Filastruder, Duet3d, E3D, SeeMeCNC, and 713Maker for supporting the project.

Link to the Bill of Materials:

Full CAD assembly in Fusion 360: http://a360.co/2z30VXH

Link to the Assembly Guide (Work in progress):

Gallery of sample prints: https://imgur.com/a/QNLli

Facebook discussion group for RailCoreII builders & owners: https://www.facebook.com/groups/RailCore/

10/23/17 Update: Almost all the files renamed to match the BOM and documentation better. Orientation of all models fixed to show how to best print them.

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I really like this design. Thanks for sharing your project!

I will make this 3d printer. At first I was thinking to wait for the 300x300 version but at the end I have decided to go for 250x250 as I have already a 300x300 printer.

Almost all the items are already on the road! Hope to start the assembly within 1 month, when I will have most of the items! I think I'll enjoy the work and hope to reach your great results! Anyway, thanks again for putting all here.

Excellent - as you order, be sure to look at the item name / description to make sure the parts match up. (We had an instance of a link in the BOM switching from the 5mm ID idlers)

I'm curious what you'll be doing for side panels? I will be able to cut HDPE side panels soon, as sourcing the melamine has been difficult.

Also, you may want to join our facebook group for comments and help during your build.

You'll love the RailCoreII!

Yeap, the BOM has been checked many times to confirm that all components are the correct ones, specially for me as I had to buy all from other shops that allows shipping to Italy.

About the side panels, I was thinking to use some transparent plexiglas panels, width 5mm. I have found them at 21 euro each and they seems nice. Or 3mm width at about half of the price. Anyway, that's one of the last things that I'll buy as I will take them from a local store.

I'm already on the facebook group, and of course will post some pictures when I'll start the work on RailCore 2!

The only changes I have done were the heater and the heat bed.
I am using a 230v silicon heater (with a SSR) so that I can use a smaller and fanless PSU (and also improve the energy efficiency).
About the heat bed, I have edited the project to use a plain surface on the back, and use the temperature sensor already included in the silicon heater.

Sounds like you've thought it out well! I'd recommend HDPE if you can find it over plexiglass. It can be cut on a CNC or lasercut, and won't crack like plexiglass can. Though plexiglass should be fine. If you can't get approximately 1/4" (6.35mm) then the printed stepper & idler mounts may need modified to suit. I can assist with that if needed.

Sounds like you've got it well thought out - if I can help, hit me up here or on Facebook!

(If you're going with a 713maker bed & carrier, I do know they'll ship to Italy, if not, I'll be interested to see what you come up with for the bed!)

Is the one Y-axis rail rigid enough to carry a direct extruder?

Yes - we use a very short bit of PTFE between the extruder and the hotend, but it's essentially direct drive. All of the weight is on the Y rail.

Any chance you could please upload full build's 3D model here?

It's available at this fusion 360 link: http://a360.co/2z30VXH

That way what you're downloading is always up to date, rather than me trying to keep every file on thingiverse updated all the time.


As a note, the BOM is going through some final revisions, and the assembly guide is going through final edits now. Should wrap up in the next week or so.

Great work! and I love the detail that you put into the manual.

Thanks! We have a couple guys building them now, and they're shaking out a few bugs here and there, but it should be all tidied up soon.

I'll me building the gantry for my modified Duplicator 5S.

I’m looking at building my first printer. I already have a Maker Select v2.1, but wanted something bigger and quicker.
This printer looks almost exactly like what I want except for one thing. I would like a 300x300 print bed. How hard would it be to scale it up to allow a bigger bed?

We're looking into redesigning at a 300mm^3 volume, it's definitely the most common question we get. For the most part, things will scale just fine. Scale up the extrusions, the linear rails, bed, heater, and sides, and you're mostly good to go. Where the trouble is most likely to come in is spanning the Y axis unsupported over that distance as it is (just a linear rail holding the Y carriage). We have various ideas around that, but nothing solid planned due to time constraints. Possibly simply bolting on a 1515 to the back of the rail, modified X carriages, and a change in how the layer cooling is done would solve it, we just haven't laid it out yet. The Z axis may need slightly bigger lead screws, but we're working on some other interesting ideas there as well.

So, it'll be coming at some point, we just don't have an ETA yet.

(Currently we're working with a vendor who's going to be able to supply milled aluminum motor & idler mounts. While not required, they'll look great, and provide some good stiffness to the belt path)

For some sample prints off of the current design, you can see my gallery here: https://imgur.com/a/QNLli

Thanks for the quick reply. I'll keep an eye out for a bigger version. I'll keep looking for something completed in the size I'm looking for and maybe once you have something released, I can build another one.

I love the design, though I have a few questions, firstly, why did you not use double synchronized Z instead of the current solution? And secondly, why not 3030 extrusion instead of 2020?

Using a single stepper with belt drive for the Z axis means we don't have to worry about the two steppers getting out of sync on power down, etc. A single stepper has plenty of power to drive both leadscrews, so using two was completely unnecessary. However, we are looking into a new duet feature of using three independent steppers for Z, to due true bed levelling. We'll likely use three nema 14's for that.

For the extrusion, we actually use 1515, not 2020. The side panels are bolted directly to the 1515 extrusions, acting as giant braces reinforcing the entire side of the printer, tying all of the extrusions on a side together at once. By having 5 of these panels on, the printer is drastically more rigid than most built with larger extrusions with an open frame. Using 1515 was space & cost efficient, and also let us use m3 hardware in place of T-Nuts, so putting it together was cheaper and easier as well.

Interesting. Another small question have you considered creating variants of the 3d printed parts for 3030 extrusion that seems to be more commonly available and used (thus basically provide an upgrade path for people having Hypercube or some other printer based on 3030 extrusions)?

We haven't - the 1515 is pretty integral to the design... and the total cost for Misumi pre-cut 1515 for the printer is only $32. That's for the entire frame, including the Z Axis. We're working on a scaled up version of the design, but it will continue to use 1515.

Though I'd drop in a sample pic printed with RailCore II:


Nice design, could you share more pictures ? Include one of the Z bed mount ;-) thanks

Thanks! More pictures are coming! I took hundreds during my build, which is mostly complete now. Just a little tidying up to do on the wires, and some other small details. I'll try and get some pictures up ASAP.