Hi there!

I am currently studying Robotic's Software Engineering at Universidad Rey Juan Carlos in Madrid, Spain. In our studies, we are using the TurtleBot2 as a base for learning ROS 2.

Initially, the TurtleBot2 was equipped with a RPLidar A2, but during the early stages of the platform's development, the sensor was attached using velcro straps. However, that is no longer the case!

I took the initiative to design a mounting bracket since the holes on the top table of the TurtleBot2 did not match those on the sensor. Now, with this new mounting bracket, the sensor is firmly secured in place, ensuring correct alignment as well!
 

Printing tips:

• As I couldn't find information about the temperature the sensor reaches on the contact surface with the bracket, I always use ABS/ASA as a rule of thumb for printing parts that will be in direct contact with electronics. This material can withstand high temperatures easily, so it's better to be safe than sorry!
• The mounting bracket has enough contact surface with the bed to avoid brims or rafts, and it should be printed in the original orientation, as the countersunk holes will support themselves. Simply use your regular settings for your chosen printing material.
• I have also added three walls in an effort to improve the strength of the part where the screws will apply pressure.

Required additional hardware

• M3 x 8mm countersunk screw (DIN7991) (4 uds.) NOTE: According to the RPLidar A2 datasheet (Page 17) the screw should be a maximum of 4mm to prevent any damage to the sensor. Since the mounting bracket is also 4mm thick, the 8mm MAX LENGTH for these screws should be respected!
• M4 x 16mm screw (DIN912) (4 uds.)
• M4 washers (DIN125 | DIN9021) (4 uds.)
• M4 self-locking nut (DIN985) (4 uds.)

Assembly instructions

1. Use the M3 countersunk screws to fix the sensor to the mounting bracket. Screw them all the way down, but avoid forcing the screws to prevent any damage to the sensor. The screws should lay flat with the surface of the part. Don't worry if it's not perfectly flat, as this face of the mounting bracket will meet the table of the TurtleBot.
   • Mini-Tip: The bracket has a tiny indentation with the silhouette of the sensor to help with the center alignment of both the mounting bracket and the sensor.
2. Use the M4 screws along with the M4 nuts and washers to secure the mounting bracket to the table. You can use any holes you prefer, but for optimal placement, follow the configuration shown in the photos (1 column of free holes on each side and 3 rows of free holes on the remaining sides). This will ensure that the sensor sits right at the center of the whole system! The nuts should fit snugly into place just by hand-pressure; however, two situations could occur:
   1. The nuts do not fit: In this case, try using the screw to pull the nut inside the hole all the way down. Then, unscrew the screw and proceed with mounting the bracket to the table. If it fits tightly, applying heat with a heat gun could also be helpful, or maybe gently tap with a hammer.
   2. The nuts are loose in the hole: Don't worry, the walls around the nut will provide enough resistance to hold the rotational force of the screw. Simply hold the nut with your finger to keep it in place until you have the screw almost all the way down. A wrench is not needed!
3. Optional: You can use the remaining free holes on the table to securely route the cable to your controller with zip ties.
4. Enjoy your securely fixed sensor!

Feel free to check my GitHub profile! Cheers!
 

Model update (30/11/2023) (V1.0.1)

Two main features were modified for the new version:

1. The reference for the holes were not set properly, thus causing that the flat head screws did not sit flat with the surface of the bracket. Now, the holes are dimensioned with DIN standard on mind, making the conical room for the screw bigger.
2. The pocket for the M4 nuts might not be big enough, making them uncomfortable to work with. Now the walls will cover the total height of the nut.