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Custom Mini CoreXY 3D Printer

About the Design

This is the biggest project I have ever taken on, my custom designed Mini CoreXY 3D printer.  All plastic parts used in this printer as well as the printer as a whole, and even the laser cut acrylic enclosure for the electronics, were designed solely by me.  Since I started this project back in February of 2017, I've been constantly redesigning every part trying to figure out the best possible way to approach every single detail.  Now, I believe the design is finally complete and as such, I am in the process of building the last iteration of this printer right now.

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Before I started designing this printer, I messed around with quite a number of other 3D printer concepts.  My intention was to create a fairly cheap 3D printer mostly using parts I already had lying around, that is extremely fast, accurate, and reliable.  After years of constantly tweaking and improving my design, I believe I have perfected it as much as possible.  Here is a list of all features and capabilities of my design...

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  • Highly portable

    • Printer connects to the electronics using one large plug while the electronic enclosure plugs into a standard US power cable.

  • Extremely accurate

    • CoreXY mechanics with 0.9 degree stepper motors in 1/256th stepping mode allows this printer to be more than 64x more accurate than most 3D printers.

  • Perfect reliability

    • All printed parts created for this printed were designed to be extremely strong and rigid while the printer is in use.

  • Extremely fast

    • Thanks to the lightweight design of the toolhead, the low resistance linear motion system, the extended heater hotend, and the added benefit of using CoreXY mechanics, this printer is not only able to move extremely fast (1000 mm/s+), but it can also print extremely fast while maintaining accuracy and reliability.

  • Easy to assemble

    • After getting many requests to help others build my design, I began focusing more and more on this as I tweaked the design overtime.  Although this printer uses many threaded inserts, these inserts make the printer as a whole extremely easy to assemble and piece together, reducing user error as much as possible.

Design Features

  • Independent Dual Z axis' with custom bed centering mechanism (Levels the bed to be parallel to the X axis of the toolhead)

  • Sensorless homing

  • 32-bit Duet 2 WiFi electronics with separate touchscreen controller

  • Compatible with any E3D or Slice Engineering hotend

  • Compatible with any bowden extruder (including the E3D Titan or Bondtech BMG)

  • BLTouch autobed leveling

Design Timeline

Version 1.0

This was the first complete design of my custom Mini CoreXY 3D printer.  All parts were designed using AutoCAD.  To the left you will find pictures of the build for this design as well as a render made using AutoCAD at the time.  Although this initial design had some flaws, this version ended up being the basis for future iterations.  It also became the basis for remaking the design later on using Solidworks.

Version 1.1

Not much was changed between version 1.0 and this version.  Most of what was changed was the electronics used and the electronic enclosure.  While version 1.0 used the RADDS controller to power this printer, it was eventually decided to use the Duet 2 Wifi instead.  Therefore, the primary difference between these two versions was the new electronics used, and the enclosure made to house electronics.  Besides housing a different set of electronics, this enclosure was an improvement over the previous one as it used a detachable plug to make it easy to transport, it used a touch screen to control the printer, it had fans on the back that adjust their RPM to the CPU temperature, and it also has a proper power plug and switch on the back to make it especially portable.  The design of the enclosure was designed by me and made with acrylic that I myself cut with a laser cutter.

Version 3.0

A number of things were changed in this design as compared to v2.0.  For one, it was decided to revert back to using linear rods for the X & Y axis'.  It was found that by using linear rails attached to the frame, a perfectly linear movement was nearly impossible to achieve unless the frame was perfectly cubic.  It was found that linear rails provided more resistance when moving as compared to using linear rails.  Thus, after spending much time trying to build the ideal toolhead mount around linear bearings, I finally settled on a design I am more than satisfied with.  This design allows for a larger print volume, it works with almost any hotend, it is fairly modular, and it allows for easy belt tension adjustments.

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The other significant change in this design has to do with the Z axis.  This design allows for each side of the Z axis to home independently.  It also allows for the printer to adjust the level of the bed after probing, to be exactly parallel to the X axis of the printer.  Therefore, only the Y axis would have to be compensated while printing.  The coolest thing about this design is not only does it allow each motor on the Z axis to move unsynchronized, but it even manages to keep the bed centered when the bed is angled.

Version 2.0

This design version provided one of the biggest set of changes over the previous iteration.  One of the most significant aspects of the design that was changed in this version is the X & Y axis'.  It was decided for this version to switch from using linear rods on the X & Y axis', to using linear rails.  One of the reasons for doing so was to increase the accuracy of the printer while increasing print volume.  Using linear rails also made it much easier to design parts around.  The other significant change over the previous version was the complete redesign of the Z axis.  After doing much research, I found that a belted Z axis often provided better layer alignment as compared to the standard leadscrew used in most 3D printers.  As such, I designed a belted Z axis that uses a pulley system to increase the accuracy of the Z axis, and prevent the bed of the printer from falling when power is cut.

Version 3.1

Version 3.1 is currently a work in progress as it is the result of adjustments made after building and testing version 3.0.  When building version 3.0 from scratch, I came across many small details that were adjusted to make the assembly process easier and quicker.  After building version 3.0, I also came across various minor problems that are addressed in the current version.  Some of those changes include the following...

  • Adjustments to the design of various motor mounts so they don't warp as easily if the motors get too warm

  • Added additional linear bearings to the Z axis mounts to prevent the bed from shaking as much

  • Redesigned the toolhead mount to include a fan shroud

  • Redesigned the lower Z axis bracket assembly so that the mounting screws for the Z axis motors can be accessed without having to remove the entire assembly

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2021 by Robert Douglass, Multidisciplinary Design Engineering

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