README.md

# UrumbotXY 2.0

<img src="img/overview.jpg" width=80%>

This project aims to push the limits of easy-to-replicate, high performance cable driven motion. This coreXY motion platform uses a nylon-coated steel cable under high tension to transmit fast and precise motion.

## Fabrication

This design uses a mix of flat parts, and 3D printed parts.

The flat parts can be laser cut or waterjet out of a material 3-5mm thick. A file containing all the parts can be found [here](./design/cut/), and fits on an A4 page:

<img src="img/plate_cut.png" width=80%>

The files to 3D print can be found [here](./design/print/), and fit on a standard Prusa bed. The recommended material for the print is **PETG**, though PLA can be used if no other option is available. The main issue with PLA is that is will creep overtime, offering no long term guarantees on a mechanical part.

<img src="img/plate_print.png" width=80%>

Once the files are ready, gather all the hardware you'll need and follow the assembly steps below.

## Assembly

Here are the parts you'll need to assemble one of the two carriages supporting the gantry:

<img src="img/gantry_parts.jpg" width=80%>

On the top of the carriage, place the V-wheels and the flexure:

<img src="img/gantry1.jpg" width=80%>

In between the two plates, come the three wheels, with spacers on both sides:

<img src="img/gantry2.jpg" width=80%>

After adding the bottom plate, finish off with the bottom flexure. This one is designed to hold the nuts in place:

<img src="img/gantry3.jpg" width=80%>

Tighten the screws holding the two V-wheels. Start tightening the third screw, but do not tighten it all the way:

<img src="img/gantry4.jpg" width=80%>

After sliding the carriage onto an extrusion, the flexure should help tensioning the carriage to just the right amount. If that is not the case, your extrusion might have a different pitch, and you'll need to print a different flexure. If the motion seems smooth while pressing onto the extrusion the right amount, tighten the last screw to finish off:

<img src="img/gantry_assembled1.jpg" width=80%>

After repeating those operations for a second carriage, build the frame with four brackets on the **bottom side**:

<img src="img/gantry_assembled2.jpg" width=80%>

You can now assemble the toolhead's carriage. The construction is similar, but starts with inserting M3 nuts on the bottom side of the top flexure part. This part is more complex, as it is also used to terminate the cable.

<img src="img/carriage1.jpg" width=80%>

Place the flexure on the top plate, and insert the M5 screws:

<img src="img/carriage2.jpg" width=80%>

Add the wheels and the front plate, which also serves as spacers for the two wheels in the front.

<img src="img/carriage3.jpg" width=80%>

Finish off with the bottom flexure:

<img src="img/carriage4.jpg" width=80%>

As before, tighten the two front screws only, and keep the third one pretty loose:

<img src="img/carriage5.jpg" width=80%>

After sliding the carriage onto the gantry's extrusion, tighten the third screw. You might need to insert the extrusion at an angle.

<img src="img/gantry_assembled3.jpg" width=80%>

Secure the top plates using screws and T-nuts:

<img src="img/gantry_assembled4.jpg" width=80%>

On the bottom side, insert printed spacers and secure evering with more screws.

<img src="img/gantry_assembled5.jpg" width=80%>

Add the corner holding the pulleys on the top left and right corners.

<img src="img/bracket_pulleys.jpg" width=80%>

Secure the motors to their respective plates, and the capstan onto it. You'll need to insert M3 nuts in the slots, then fasten the screws while keeping it well-centered.

<img src="img/motor_assembly.jpg" width=80%>

Assemble the motor's corner pieces on the main frame, and add the capstan pulleys. Note that there are two bearings that need to be inserted in these, as well as a spacer in between to avoid putting compression force on the two bearings.

<img src="img/pulley_assembly.jpg" width=80%>

Start routing the cable by tightening and M3 screw on the carriage and inserting the cable's end under the screw.

<img src="img/cable_routing1.jpg" width=80%>

Route the cable to the pulley, then to the capstan assembly. Make the cable circulate around the two capstans, from the bottom to the top groove.

<img src="img/cable_routing2.jpg" width=80%>

Here is capstan assembly, with the cable in place:

<img src="img/capstan.jpg" width=80%>

Guide the cable to the pulley on the back side of the machine.

<img src="img/pulley_back.jpg" width=80%>

Here is the complete path taken by the cable:

<img src="img/one_loop.jpg" width=80%>

Tighten the end of the cable to finish off this loop:

<img src="img/cable_routing3.jpg" width=80%>

Add tension to the loop by sliding the pulley and tightening the screw holding it:

<img src="img/pulley_tension.jpg" width=80%>

Repeat the same operations for the other loop to complete the machine. Congratulations, you should have a nicely tensioned coreXY motion system. You can optionally add the feet, or you can mount it on your favorite extrusion assembly.

<img src="img/overview.jpg" width=80%>

## Demo

![](video/motion.mp4)

## Download

The files to 3D print can be found [here](./design/print).

The files to laser cut or waterjet can be found [here](./design/cut).