The idea of this project was designing
an autonomous controller for small three axis machines, capable of
interpreting and processing an input file. As input, we decided to
take a G-code file, as we believe it is the more standard,
traditional and simple way to program a CN machine, also allowing
great power and flexibility. Moreover
is a
good starting point to add
higher levels of
abstraction like
programming using CAD / CAM.
More information
about G codes: http://en.wikipedia.org/wiki/G-code
We
decided to use
Microchip PIC 8-bit microcontrollers.
This choice was made because these are the microcontrollers which
Electronic Engineering students in Valladolid were familiar with and
we wanted to do something more serious than what we have done in
practice during the degree. We wanted also in some way that our
project could serve as an example of a more advanced application for
other students and facilitate the project could be completed more by
other students.
We worked with an automatic drill model
Bungard CCD / ATC. It has three bipolar stepper motors for
positioning axes and a brushless motor for the tool. The image does
not correspond exactly to the model used since this is the model with
automatic tool change, and our model did not have this feature.
The system was designed to be as
modular as possible, with a general control unit responsible for
acting on the drivers we design for each of the engines. The heart of
the control unit are two microcontrollers PIC18, more specifically
the model 18F452. Basically one of the microcontrollers is in charge
of reading the file and computing trajectories while the other
generates, with this processed information, the clock signals for
controlling the drivers of the motors.
In upcoming posts we will explain a bit
more about these modules and upload the schemes and programs.
Until next time!
