MaybeCube - CoreXY 3D printer with linear rails

thingiverse

# MaybeCube The **MaybeCube** is an engineered CoreXY 3D printer with a linear rails motion system. The MaybeCube MC350 variant has a print volume of approximately 230mm by 230mm by 200mm. The dimensions of the main MC350 cuboid are 390mm by 390mm by 400mm, and the enclosing volume (including the display, extruder, and feet, but excluding the spool holder, Bowden tube and hotend wiring) is about 405mm by 475mm by 415mm. ## **Assembly instructions** The "standard" size is the MC350 variant. I have built the MC300 variant for two reasons: to test sizing (if the components fit in the MC300 variant, then they will fit in larger variants); and because had a quantity of 300mm extrusion and the right size heated bed from an earlier project. The assembly instructions and the BOM for the MC300 variant are [here](https://github.com/martinbudden/MaybeCube/blob/main/MC300/readme.md). The assembly instructions and the BOM for the MC350 variant are [here](https://github.com/martinbudden/MaybeCube/blob/main/MC350/readme.md). The assembly of the different two variants is essentially the same, the differences are in the printbed and the placing of the PSU on the back panel. Larger variants naturally have a larger printbed and to support this can optionally have Z-rods on both sides of the printbed. I plan to make a series of YouTube videos giving build instructions, when I have done so I will post a link here. I won't start these, however, until I have completed the BabyCube build videos. If you would like to build a smaller printer, you may be interested in the MaybeCube's smaller sibling, the [BabyCube](https://www.thingiverse.com/thing:4911835). ## **Tools required for assembly** The MaybeCube requires a minimum of tools for assembly: essentially just a set of allen (hex) keys, an electric drill and set of bits and wire cutters and crimps for the wiring, and a set of small files for finishing the printed parts. Useful, but not essential, tools include a drill press, a 3mm tap and tap wrench (for starting self tapping holes) and a countersink bit which I sometimes find useful to finish holes in printed parts. The extrusions need to be end-tapped - you can either purchase them tapped, or tap them yourself in which case you will need a tap wrench and either a 5mm or a 6mm tap, depending on the extrusion. Some of the parts in the BOM are specified as CNC'ed parts - this is just for the convenience of people who have access to a CNC, all these parts can be drilled by hand. ## **Design Goals** 1. **Create a high quality engineered 3D printer capable of producing high quality prints** 2. **Make the MaybeCube more easily usable in home environment (as opposed to garage or workshop)** * try and make it easy to transport and store the MaybeCube, so: * integrated design, everything is enclosed within the printer's frame with. This includes the motors, the motion system, the power supply, and the circuit boards. The only exceptions are the extruder motor and the spool holder, both of which can be removed for transport and storage. * include base plate so underside of printer is not exposed * all protrusions from frame (filament spool, extruder, power connector) are on the right hand side to minimise desk clutter and allow the back of the MaybeCube to be pushed right against a wall * all protrusions from the frame can be easily removed for storage * clean wiring - route wiring in extrusion channels where possible and minimise exposed wiring 3. **Improve ease of assembly** * Use internal blind joints on the frame * printed parts designed so that bolts are accessible and can be tightened when frame fully assembled (that is bolt holes are not blocked by other parts when assembled) * divide the main assembly into a number of independent sub-assemblies. * where possible printed parts push up right against frame and so "auto-align" * facilitate building in different size variants 4. **Use linear rails for the x and y axes** * linear rails are now not much more expensive than linear rods * linear rails make design and assembly easier, reducing the need for custom printed parts * linear rods are used for the z-axis, since linear rails offer no advantage here 5. **Maximise frame rigidity** * one of my goals is to experiment with high print speeds. A highly rigid frame allows higher acceleration settings * use 2040 aluminium extrusion, corner joints are about 4 times more rigid than 2020 corner joints and 2-3 times more rigid than 3030 corner joints 6. **Maximise build volume for selected extrusion lengths** * Z-axis assembly is on the left side of MaybeCube. This means the Z-axis assembly does not impede travel in the Y direction * The printhead is quite compact, so does not significantly restrict travel in the X and Y directions 7. **Enable a fully enclosed print volume** * The cubic shape makes enclosure straightforward. * Additionally a panel can be placed between the electronics and stepper motors on the back face and the build volume * A slide-in front panel can be added * A top enclosure can be placed on the frame 8. **Try and keep the costs down** * the aim is not to be as cheap as possible, but rather to avoid unnecessary costs * use standard extrusions lengths, as far as possible, so no custom cutting is required 9. **Facilitate customisation and experimentation** * Open source design * Parametric design in OpenSCAD * The open design of the frame and the easy accessibility of parts means the MaybeCube is fairly easy to customise - most parts can be changed without the need to disassemble large parts of the frame * The design of the X_Carriage means it is easy to customise to support different hotends and extruders * Support other printhead systems, including EVA, XChange, and, in principle, the Jubilee and E3D toolchangers ## **Variations** The canonical form is the MC350 variant. Variant | Extrusion Sizes | Rail/rod lengths | Approx Build Volume | Bed Size | Frame Dimensions --------| -------------- | ---------------- | ------------------- | ---------- | ------------------- MC250 | **x250 y250 z350** | x200 y250 z250 | **concept variant** | 180mm | 290 x 290 x 350 MC300 | **x300 y300 z400** | x250 y300 z300 | **180 x 180 x 200** | 214mm | 340 x 340 x 400 MC350 | **x350 y350 y400** | x300 y350 z300 | **230 x 230 x 200** | 235mm | 390 x 390 x 400 MC400 | **x400 y400 y450** | x350 y400 z350 | **280 x 280 x 250** | 310mm | 440 x 440 x 450 For reference, the original [HyperCube](https://www.thingiverse.com/thing:1752766) has extrusion sizes of x340 y303 z350 to give a build volume of 200 x 200 x 155. ## **Frame rigidity** The MaybeCube is a cuboid with 6 rectangular faces. Rectangles have no inherent rigidity and are subject to shearing. The rigidity of a rectangle is provided solely by the strength of its joints, and these often do not provide sufficient rigidity. A small movement at a joint is magnified into a much larger movement at the end of a 400mm extrusion. There are three main ways to increase the rigidity of rectangles: 1. triangulation, where the a diagonal piece divides the rectangle into two triangles, this is exemplified in [truss bridges](https://en.wikipedia.org/wiki/Truss_bridge) 2. using a shear plate, this is exemplified in the [sheer boards](https://en.wikipedia.org/wiki/Shear_wall) used to stiffen wooden framed buildings 3. reinforcing the joints. The MaybeCube uses 2040 extrusions, these have twice the contact area at the joints and provide significantly more joint rigidity than 2020 extrusions. Additionally the MaybeCube uses shear plates on the bottom, back, left and (optionally) right faces to stiffen the frame. The front face of the MaybeCube is the most subject to shearing, since it needs to be open to allow access to the printbed. Two measures are taken to counteract this: 2080 rather than 2040 extrusion is used at the bottom of the face, and the idler mounts at the top are extended to provide some triangulation and reinforcement of the upper joints. ## **EVA modular printhead system** In its default configuration the MaybeCube has a E3D V6 hotend with a Bowden extruder. However I've created adaptors so that the [EVA modular printhead system](https://main.eva-3d.page) can be used. The EVA system supports a wide variety of hotends and extruders. The adaptors are available at https://www.thingiverse.com/thing:4912099 ## **Printermods XChange quick change tool head** There is and adaptor for the [Printermods XChange quick change tool head](https://www.kickstarter.com/projects/printermods/xchange-v10-hot-swap-tool-changing-for-every-3d-printer), see https://www.thingiverse.com/thing:4924355 ## **E3D tool changer** Currently there is no adaptor for the [E3D tool changer](https://e3d-online.com/pages/toolchanger), however I think it would be fairly straightforward to create one. There should be room to dock at least two, and perhaps three [E3D ToolChanger Tools](https://e3d-online.com/products/toolchanger-tools) in the back of the MC350, this would allow experimenting with the E3D docking system in a framework considerably less expensive than the [E3D Motion System](https://e3d-online.com/products/e3d-motion-system). ## **Jubilee tool changer** The [Jubilee 3D printer](https://www.jubilee3d.com/index.php?title=Main_Page) has a [tool changer](https://www.jubilee3d.com/index.php?title=Tools) compatible with the E3D tool changer. I have a proof of concept showing that this tool changer system can be used on the MaybeCube. Note that this is incomplete and still requires an X_Carriage adaptor for the Jubilee plates.