Open-source 🥽

The LongMill MK2 project is the successor to the LongMill project, both at their core being open-source projects. With much striving towards making design choices that would make the MK2 project as replicable and well-supported as possible, the MK2 wavers a little further away from replicability than its predecessor mainly in its rail design and reduced usage of 3D printed parts. If you want to understand why we made these choices, know it wasn’t taken lightly and we discussed it more on our blog post: https://sienci.com/2021/12/30/all-about-the-longmill-mk2/

Other than these changes, all other aspects of the LongMill MK2 project are shared with the original LongMill which will continue to be maintained (and can be referenced here: https://resources.sienci.com/view/lm-open-source-and-modifications/). We believe that by making this design open-source, we will be able to drive the CNC community forward through sharing and improving CNC technology. The idea is for:

  • Users to modify and improve their machines to fit their needs
  • Machine owners to share their designs with the community to help others that have similar needs
  • Makers to use our design ideas and design philosophy to create other types of machines, such as laser cutters, plasma cutters, and 3D printers
  • Us to gain inspiration from the community to help us guide our development of current and future products and features


This is accomplished by putting the project under a Creative Commons BY-SA license:

  • The entire mechanical design of our LongMill MK2 Benchtop CNC available in a range of 3D file types and as drawings where applicable
  • Any internal assembly jigs and other supporting hardware for the LongMill
  • Documentation of general manufacturing techniques used to produce the LongMills various custom components including general 3D printing settings
  • All educational information provided within the LongMill MK2 Resources area including machine assembly instructions and modifications
  • The mechanical BOM which documents all the components required to build a LongMill
  • Every aspect of the electrical design behind our custom LongBoard CNC controller including BOM, schematics, gerber file, etc.

and by sharing the LongMill MK2 modified firmware profile, a small modification of the GRBL open-source project, under the GPLv3 license just as the original project is.

All this information is continually updated as the LongMill MK2 project continues to be revised, with more openly shared information being made available at each new major revision and licensing continuing to be applied to all previous major versions. By making this information available, the LongMill MK2 project fulfils the Open Source Hardware Association’s definition of open source hardware, and we think that’s pretty cool 🙂

LongMill MK2 CNC

The LongMill MK2 will soon be released under its first major design iteration in the coming weeks:

  • MK2 distinguishes itself from the original LongMill project by a couple key factors. Though many of the common components carry over such as v-wheels, lead screws, motors, anti-backlash nuts, etc. the biggest differentiator is the use of two completely custom designed extrusions for each X and Y-axes which allow for much higher rigidity, easy of assembly, reduced part count, and more rigid mounting of the Y-rails to the tabletop surface. The MK2 design was also further optimized by the shape of the X, Y, an Z carriage plates to squeeze more travel out of the same length lead screws while also increasing the CNCs rigidity by how the v-wheels are located. The blank canvas of the MK2 also meant we could ensure that add-ons our customers have been enjoying on their existing LongMills could be make available on the MK2 with much simpler implementation such as dust shields, dust shoe, and limit switches.
  • Batch 1 began production in October 2021 and started shipping in April 2022.

You can find the BOM and designs of every part and assembly of the LongMill MK2 Benchtop CNC in the linked Onshape and spreadsheet documents below.

MK2: https://cad.onshape.com/documents/59335d21bb649cd2b941a693/w/290c65d1d584435649b87e46/e/99a028de0f32d790196bbe8a

BOM: https://docs.google.com/spreadsheets/d/1MqOwPg3VSUTMtn3ff6rXjfvliAWnFqg8ez2eZasJLCE/edit#gid=1540965623

LongBoard CNC Controller

The LongBoard CNC Controller is the control system and brains of the LongMill. This board was designed by our friend Chris Hadjuk and the Sienci Labs team with KiCAD. This design has been carried over from the original LongMill project’s LongBoard which had four major public revisions but in the context of the LongMill MK2 it’ll continue moving forward from the most recent 1.4.3. You can find the designs of every version in the form of gerber, assembly, schematic, and BOM files in their respective zip files below as well as a link to a more readable BOM for every board version if you’d like to source your own components.

Original LongBoard Project Designs

Rev-1.4.3 LongBoard Design

BOM of every version: https://docs.google.com/spreadsheets/d/1qlHlp576s9GIBMPfp4JU8Yr7xBM5gUNruvHFBVFoDOM

Other Add-ons

We also share a record of every part and assembly of every version of add-on that we’ve released alongside our LongMill MK2 CNC since the projects conception. Each of these designs can be found in the linked Onshape documents below:

LaserBeam Air Assist Body: STL Download for 3D printing

Vortex Rotary Axis:

Vortex Rotary Axis Switching PCB:

Touch Plate (3-axis / block-style): https://cad.onshape.com/documents/b76785c85e8458b0e88b64a5/w/0eed2327264503a991f2d6eb/e/52643898e09eacae9cfe69aa

MK2 Magnetic dust shoe: https://cad.onshape.com/documents/59335d21bb649cd2b941a693/w/290c65d1d584435649b87e46/e/fe3b50adb5e27c41f23cd9cc

MK2 Magnetic dust shoe body: STL Download for 3D printing

T-Track and hold down clamps: https://cad.onshape.com/documents/4002cf32491a7a7a17c84759/w/f9f2dc06d2e8375fa2fb89a3/e/b15017972da9d310d5b53e22

MK2 Inductive Sensor kit: https://cad.onshape.com/documents/59335d21bb649cd2b941a693/w/290c65d1d584435649b87e46/e/8798d6686ac6483e61334a3b

MK2 Dust Shields: https://cad.onshape.com/documents/59335d21bb649cd2b941a693/w/290c65d1d584435649b87e46/e/f8ea1bc43d5996622ad6bbb5

BOM of all add-ons: https://docs.google.com/spreadsheets/d/1MqOwPg3VSUTMtn3ff6rXjfvliAWnFqg8ez2eZasJLCE/edit#gid=1028766194

3D Printing

To read more about our print settings to help you print your own parts, read this post here: https://sienci.com/2019/11/11/3d-printing-settings-for-longmill-parts/

STL files can be directly downloaded from the Onshape document. You may need to make an account to download STL files.