Asmograf Pen Plotter

thingiverse

Some time ago I felt a wave of nostalgia wash over me as I thought about an old pen plotter from the 80's called Alfigraf. It was manufactured in Czechoslovakia and primarily based on parts of a construction kit known as Merkur. A fascinating fact is that the first contact lenses were created using a machine built from Merkur components. To get straight to the point, I initially built the plotter using Merkur parts and then decided to design it for 3D printing so I could store the Merkur parts in their box. A short video featuring the plotter in action is available on youtube. It turned out to be a straightforward and compact design utilizing only parts that are printable or can be easily obtained from eBay/aliexpress together with your local DIY shop for all metal components. The steppers are NEMA17 (17HS2408) driven by TI DRV8825 and controlled by grbl running on ARM Cortex M3. The pen-up mechanism employs a 5V solenoid with a solenoid driver that reduces its consumption by applying full voltage only during the pen hit and then dropping to 0.5V just to keep the pen up. I experimented with using a servo but found better results with a solenoid, though both solutions have their advantages and disadvantages. As the Gcode controller, I utilized an STM32F3 based board that can be purchased online at an affordable price and its dimensions fit nicely with the plotter design. Useful information about the board is available here. The Gcode controller firmware is a port of grbl tailored for this specific MCU. Its repository can be found on github. I used SolveSpace for designing as it is my go-to 3D modeling tool, although I am aware that some users may find it a bit cumbersome due to its simplicity. I employed the latest version built from the git repository and cannot guarantee full compatibility with the prebuilt version available in their download section. If anyone wishes to play with my design or reuse it, the latest version of SolveSpace may be necessary. The git repository containing the model sources is hosted on github. Publishing is currently in progress...