Table of contents
Abstract
Geared rotary actuator driven by a Trinamic stepper motor and Analog Devices motor controller. The rotary actuator is part of a thread tapping machine. This is an update in the "Start a Movement" design challenge.
Project
Intro
This rotary actuator subsystem uses the Analog Devices TMC5272-EVAL Kit and Nema17 Trinamic stepper motor to create a thread tapping machine.
System Description
The rotary actuator subsystem uses the planetary gearbox from an electric screwdriver to reduce the speed and increase the torque of a stepper motor as it drives a chuck with square jaws designed to hold a thread tapping bit.
There is a set screw shaft coupler to join the 5mm stepper motor shaft to the 2mm drive shaft of the planetary gearbox. The 2 mm planetary gearbox driveshaft is fabricated from a spoke originally used in a bicycle wheel.
the planetary gearbox is coupled to the chuck using a 1/4 inch hex to half inch square drive adapter. The chuck itself is mounted in a 20mm thrust bearing pillow block. The 3D printed chassis ensures all components in the drive chain are properly aligned and held in the correct position. It also also the whole subsystem to be mounted on the linear actuator subsystem, described in the previous blog.
Video - Assembly and Demo of the Rotary Actuator Subsystem
The following video shows how the rotary actuator is assembled, and demonstrates the motor in action:
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Video - Demonstration of the Thread Tapping Subsystem
Design of the Rotary Actuator Chassis
Discussion
The rotary actuator machine is a key subsystem in the thread tapping system. There are lots of moving parts that all need to be positioned and aligned very accurately for the system to work and the mounting arrangements need to be robust enough to handle the power required by the system. In a one-off custom prototype like this, there is great potential for something to be too flimsy or just not work properly. It is quite gratifying to see the system work smoothly without misalignment issues. I am happy with the results so far, especially since most of the tricky mechanical systems are functional. It is somehow satisfying to watch the precisely controlled motions.
On the thread tapping system, there is still some work to do on mounting things, and I somehow have to accurately measure the rotary speed and linear speed so they can be correctly synchronized.
On the Connector tester apparatus, I have a lot of work left to position and mount connectors as well as make some chassis' for the electronics and displays.
Chassis .stl file
Next Steps
- Design the connector brackets and print them
- Program and test the connector tester motor control
- Program and test the thread tapping motor control
Links
- Project Blog 1 - Unboxing
- Project Blog 2 - Connector Tester Electronics and Firmware
- Project Blog 3 - Linear Actuator
- Project Blog 4 - Rotary Actuator
- Start a Movement Design Challenge page
- Analog Devices TMC5272 page
- TMCL-IDE page
