Materials and CAD Files

Structural Components

Electronics and Motors

Hardware

Custom Part Files

Tube Materials

Assembly Guides

Custom Part Manufacturing Guide

Full System Assembly

Cart Assembly

Tube Fabrication

Electronics Setup

Electronics Board Setup

Firmware Installation

Wire Management

Full System Test

Kinematics

Calculating Kinematics of a CTR

Implementing Kinematics

Troubleshooting Kinematics

Experiments

Installing Tubes

Homing the Robot

Graph Paper In-Plane Bending Experiment

Out-of-Plane Rotation Experiment

This actuation system was designed to easily allow for additional tubes. Each tube requires one cart for actuation. There are two variations of the cart, shown below. This page will detail how to build the cart on the left. Both carts use the same exact components; to build the mirror image, attach parts to the opposite side of the cart plate.

Instructions

1. Fasten linear motion bearings. Take one cart plate and insert linear motion bearings as shown in the image below. The square mounting plate of the bearing should be on the back of the cart plate, and the cylindrical bearing should extend through the plate to the front side. Insert four M4 button head screws into the square mounting plate of the linear bearing. On the front side of the cart plate, use 1 M4 washer and 1 M4 nut per screw to secure into place.

   <aside> 📎 Here, “one cart plate” is equivalent to two 1/4” acrylic cart plates sandwiched together. We install the bearings first to make sure that we line up the two plates. Finger tighten all screws for all bearings. Do NOT tighten fully at this stage if you are using 1/4” plates.

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1. Press a flanged ball bearing into the center hole in the cart plate. Again, this is to line up the two 1/4” cart plates. Tighten the M4 screws holding the linear bearings using a hex wrench and pliers.

   

2. Add heated inserts to bottom bearing hole. Using a soldering iron, press three M3 heated inserts into the bottom hole of the cart plate from the front. See image below for reference.

<aside> 📎 Hold the soldering iron straight upwards, perpendicular to the table. Place the tip of the soldering iron into the heated insert, making sure to only touch the metal. Press the insert straight down. You can twist the iron slightly as long as you ensure it remains perfectly upright.

Keep in mind that the metal insert might take a minute to heat up; you should not need to put a lot of force into this.

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1. Add heated inserts to center bearing hole. Move the bearing from the center hole to the bottom hole. Press the bearing in from the back. Add heated inserts to the holes around the center bearing hole from the back.

1. Fasten flanged bearings to the cart. Make sure you have one flanged ball bearing pressed into the bottom cart plate hole from the back side. Press a second flanged bearing into the center cart plate hole from the front side. Fasten with M3 x12mm button head screws into the M3 heated inserts. Add one M3 washer in between each button head screw and the bearing. See the image below.

1. Assemble stepper motors. Take two stepper motors and two 16 tooth pulleys. Attach the pulleys to the motors shafts such that there is 2mm of motor shaft left above the pulley.

1. Fasten the stepper motors to the cart. Bolt the two stepper motors to the cart plate such that the motor is on the back of the cart. Use four M3 x 15mm button head screws; add an M3 washer in between the button head screw and the front of the cart plate. Make sure to orient that motor such that the wire connectors face out of the cart.

1. Add heated inserts to the lead nut pulley. Using a soldering iron, insert four M3 heated inserts into the lead nut pulley piece.

   

2. Attach the lead nut. Use four M3 x 10mm button head screws to attach the lead nut into the pulley.

   

3. Assemble lead nut pulley. See the image below for detailed steps. (1) Insert the lead nut pulley piece into the lead nut bearing in the cart plate. The lead nut bearing is the one that is not in the center of the plate. (2) Insert the outer locking piece into the lead nut pulley. (3) Twist the outer locking piece 45 degrees, either clockwise or counterclockwise. (4) Insert the inner locking piece. This should snap into place as long as you have twisted the outer locking piece enough.

1. Assemble the tube pulley. This process is similar to step 6. Insert the tube pulley from the front of the cart plate. The tube pulley will be on the same side of the plate as the lead nut pulley. Use another pair of the outer and inner locking pieces to hold this pulley in place. See image below.

1. Add belts to the pulleys. Use the 280mm belt for the tube pulley and the 200mm belt for the lead nut pulley. Both belts will be slightly loose at this point.