Where to start?
Since this is my first project here on Hackaday I'm a bit unsure where to even start. This project started as a private project and ended as my graduation thesis. I want to share my ideas and how i made things here and hope to get a few new ideas on how to build things better and more rigid.
This is still an ongoing project up to date. The machine has a finished frame and some controls, but the mechanical parts still need some rework. So far the machine can move, but it is still far from milling metals due to weak connections between the drives and the mechanical parts.
The main reason behind this project entry is the lack of Trinamic drivers on some of the projects I've seen here Hackaday. These Components offer features you would usually expect in some kind of industrial equipment, but i still cant seem to find a lot of projects using these parts (or maybe someone doesn't know how to use the search bar? who knows...). Using these ICs is actually quite simple. With few external Components, Connectors and a suitable µC you can drive a rich set of stepper motors and have awesome features like stall-detection, silent stepping or dynamic power reduction.
Why would anyone want to use these ICs for their own projects?
Those ICs have a lot of features already built into them. The TMC4361 offers an SPI interface and inputs for two reference switches, a home switch and an emergency stop. All you have to add are components like opto-isolators or some kind of digital isolators.
The TMC262 is a control IC for driving external MOS-transistors. Like the TMC2130 you can already find in some newer Projects this controller offers similar features plus a few extra amps for your outputs. TMC262 can be used to directly drive stepper motors without a lot of extra features or you can use them together with some kind of motion controller like the TMC4361.
The motion controllers can also be used with 5V encoders to build a closed-loop feedback system for the stepper motors (ABN, SSI and SPI are supported). This way you can even achieve servo-motor like features with smaller stepper motor for a few bucks. The ICs and MOSFETs should be about 25-30 bucks for one motor. If you can get your hands on some PCBs and cheap connectors you have a closed loop stepper driver for about 40-50 bucks.
The main Motion-Controller
The main controller for this project is meant to drive three axes with up to 2.5A per motor coil. With some small changes the driver circuit can output up to 10 amps per phase. The driver ICs are split up into one driver stage and motion control IC with integrated ramp control and other features.
The setup for one driver stage can be seen here
The TMC4361 offer complete ramp and position monitoring on chip and can be used to get some load off of your µC or PC.
The cabinet build
Instead of a real switching cabinet I used a 5mm aluminum backplate as a base for mounting the necessary stuff to safely control the machine parts. The following picture shows the most important parts for the build.
- top left: two 24V DC power supplys
- top mid: a safety relay for switching the emergency stops
- top right: residual current circuit breaker and fuses (the type usually used for motors)
- bottom left: aluminum bar for cable mounting and terminals for all cables
- bottom right: raspberry pi adapter and motion control board
some more stuff should follow soon (hopefully...)