3D Printed Mecanum Wheels

Hey, I'm Devadath PR, a 2nd year robotics engineering undergraduate student at JEC Thrissur in the Kerala state of India. This is the robot me and my team members- Navaneeth, Jerin Peter and our mentor Lentin Joseph made for Artpark Robotics challenge.

The challenge was to create a robot that can autonomously pick up the trash, clean the floor, countertop and sink. I wanted the robot to be as simple and elegant as possible. The base of the robot houses almost everything from The 15L water tank to the electronics and the battery pack. A gasketed lid closes the water tank to seal it from the electronics compartment above. The robot also has a vertical actuator to move the arm of the robot up and down- So it can reach the floor as well as the countertop. The arm is a 2 stage telescopic linear actuator inspired by the hello robot stretch. The top assembly of the robot houses a Realsense D435 on a 2 axis gimbal, an emergency stop button and the idler pulley and belt tensioner for the vertical actuator.

Did I tell you that the robot is mostly 3D Printed? I 3D printed most if the robot as it was the cheapest and the most accessible way to make such a design for me. The entire robot used 6.7Kgs worth of 3D prints. The main part of the base is a single 42x42x20 cm 2.3Kg 3D print with integrated motor mounts, water tank with baffles that also act as the structural ribs for the base.

The highlight of the base are the mecanum wheels- which is also mostly 3D printed to save costs and keep the design aesthetic of the robot. These wheels cost me half of what an equivalent off the shelf wheels would have cost. The red parts were printed with ABS+. The black rollers were printed with TPU. The rollers have bushings printed with Igus i150 polymer bearing filament inserted into it. This wheel was designed for a stationary shaft, so, the wheel has bearings inside and the drive motor powers the wheel through its gears. This instructable will teach you to make these mecanum wheels. Rest of the robot is still very much under development. The instructable for the other sub systems of the robot will be published later as Part 2.

3D printing filaments:

• ~410g of ABS+
• ~340g of TPU
• ~65g of Igus i150
• ~20g of PLA

Note: ABS has to be 3D printed in a printer with an enclosure or a heated build chamber. TPU also needs to be printed in a printer capable of printing flexibles.

Other parts:

• 8pcs 6901ZZ ball bearing
• 20pcs M3X50mm socket head cap bolt
• 8pcs M3X10 socket head cap bolt
• 36 pcs 3x60mm SS dowel pin

• Print 2pcs each of "Inner half", "Outer half" and their mirrored versions, 4 pcs each of "Clamp" and "gear" with ABS+. These should have at least 4 perimeters, top and bottom layers and 30% gyroid or cubic infill.
• I printed the 36 pcs TPU rollers at 0.24mm layer height, 5 perimeters and 20% infill. Managing stringing with TPU is a bit tricky.
• Print 72 pcs of Igus "i150 bushing". But first. print one and check your fit in the M3 dowel pin. It should spin smooth without any play. You may have to make some adjustments to get that right.
• Print the 4pcs of "End cap" with regular PLA+. This is just for aesthetics.

1. Insert the bearings into the "Outer halves" and the "Inner halves" 3D prints.
2. Insert the polymer bushings into the TPU rollers.
3. Screw in M3X10 bolts into the clamps
4. With the clamp in between, join the "Outer half" and "Inner half" and the gear with the M3 bolt. It should thread into the gear.
5. With the rollers between the "Outer half" and the "inner half", insert the dowel pin into the wheel body, through the rollers
6. Press fit the black PLA cap over the bolt heads

The wheels are ready to be attached to the robot!

Despite this being the first prototype, these wheels did end up working well. But, the design of the wheels can be improved a lot. Currently, assembly and attachment of the wheel is a tedious task. Next iteration will have massive QoL improvements. If you want to build these, I recommend you wait for that.