low-cost, modular motion stages

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The goal of the OpenMotion project is to develop and make freely available several low-cost, modular linear and rotary motion stage designs. The motion stages will use a common mechanical interface to enable combination of the stages into multi-axis positioning systems.

Need a custom motion stage design for your project? Please message this project and lets see what we can come up with.

Motion Stage Requirements:

  1. shall be zeroed using limit switches
  2. shall use a common mechanical interface between stages
  3. shall use NEMA 17 stepper motor frame size
  4. structural components shall be laser cut from 300x600mm sheets of 3mm thick birch plywood
  5. shall use 4x13x6mm v-bearings for all linear guides
  6. shall use commonly available 3D printer mechanical components
  7. shall include wire routing features
  8. should use 3x100mm cable ties for all structural connections

CNC Motion Control:
The OpenMotion project uses the open-source grbl CNC motion control architecture:

CNC Motion Control Interface:
The OpenMotion project uses the open-source cncjs CNC motion control interface ->

Development Plan:

  1. multi-axis systems
    1. two axis gimbal
    2. XY table
    3. XYZ gantry

The latest OpenMotion design files

x-zip-compressed - 18.90 MB - 07/21/2023 at 03:52


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John Opsahl wrote 07/21/2023 at 04:02 point

Design files have been released. See the "Files" section of this project.

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xgpt wrote 07/19/2023 at 18:51 point

Do you think there could be a variation to improve accessibility for those of us purchasing boards from American hardware stores like Lowe's / Home Depot? Specifically 1/8" boards? Is that wiggle room between 3mm and 1/8" inch going to be within tolerance?

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John Opsahl wrote 07/19/2023 at 19:21 point

I decided to use 3mm thick plywood for OpenMotion because 1/8" thick is increasing becoming harder to find online. I have found vendors on Amazon to be the cheapest way to source 3mm baltic birch plywood. They even sell it in 300x600mm sheets just for laser cutting. 

If there is enough interest in this project, I would think about creating 1/8" thick versions. I would not recommend using 1/8" thick plywood for a 3mm thick plywood design. Likely to have issues with the thicker 1/8" thick plywood for tabs and slots on a 3mm design.

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Florian Festi wrote 06/12/2023 at 14:35 point

Are there any CAD files or at least drawings? So far I only see a few pictures. Or am I missing a link to some repository?

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John Opsahl wrote 06/12/2023 at 14:56 point

Nothing has been released yet. My current plan is to release step and dxf files of each stage when I have completed the second design iteration for each. Happy to release anything earlier upon request.

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Florian Festi wrote 06/11/2023 at 15:42 point

That's something that would also look great in my project ( Although I understand if you don't want to switch from CAD to Python.

Here a few lessons I learned while laser cutting plywood for mechanical things:

Use fully closed boxes as much as possible. Cutting big holes into the sides is fine but any open side will be a large weak spot. This is especially true if you have dynamic loads or diagonal or twisting forces.

Mixing wood and steel is tricky due to the large difference in surface hardness. Ball bearings typically work well as they increases the surface area from the steel bolt inside to the wood on the outside. Rolling on wood is problematic. Ball bearing balls will get pressed into the surface on all but lightest loads and cause permanent damage to the rolling surface. Full ball bearings are much better as they have larger radii and allow full width of contact. But if they are rolling on the edge of the wood they have similar issues as the bearing area is just too small.

As it looks like this is what you are doing with the V groove bearings I expect some issues there. Bumps will create dents in the edges so the guiding will deteriorate quickly. Having smooth ball bearing roll on perpendicular surfaces is much more robust - no matter whether is it the surface of the plywood or an cut edge.

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John Opsahl wrote 06/11/2023 at 19:58 point

Thanks for the comments. All great points. 

I admire what you have been able to do with the project. A great project!

If interest in this project grows I will certainly think about parametrized designs.

When bolting to wood, I use washers at the wood to distribute the load and lock washers to correct for any deformation of the wood over time.

I have had good results with these v-bearings riding on the edge of 3mm plywood with my other cnc machines. I think success has come from using enough v-bearings to distribute the load on the rails and radially preloading the bearings to account for the deformation of the wood over time. Agree that there are much more robust options, but v-bearings are cheap and don't take up much volume. Will definitely look into it if this project gathers enough interest.

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