This is an experimental drawing robot. It was designed to be portable, light and fast.

Facere is Latin for “do”, “create” or “make”.

I’ve had a few requests to do a tutorial on how to build this so am adding more details on the machine below. Feel welcome to post questions in the comment section of this post. Also I host a support group for people who want to build stuff like this called hack613. You can join the google group there.

How it’s Made

I wanted something portable (around Letter or A4 size) that was built light so it’s easy to carry and could be fast.

I drew it up roughly in Sketchup Make to do a reality check on what length of linear bearings I’d need. I decided to go with very small linear rail as it seems very rigid and simplifies construction.

The gantry and carriage are made from a piece of extruded aluminum angle and three plates of hardboard. The plate that forms the carriage has a feature to capture the belts.

The belt system is coreXY using two Nema17 stepper motors. I considered HBot, Etch A Sketch and a 3 motor configuration of my own. I eliminated HBot since it seems to be more prone to racking of the gantry. The Etch A Sketch seemed to be prone to backlash and racking. I did do some Etch A Sketch experiments and eventually added gears to an actual Etch A Sketch. My own 3 motor configuration looked promising but being new I couldn’t rely on prior art when it came to control and also in a thought experiment it came forward that moving X at the same time as Y would require the X motor to be very fast. Another advantage of coreXY is it is two shorter belts instead one long so you can make a bigger machine with given belt segments.

Once I settled on CoreXY I then drew the machine up in Sketchup as a plate. I’d use 1/4-20 bolt/rod, roller skate bearings and delrin washers to constrain the belts. The main bed needed four holes for 4 belt constraints and the gantry needed four holes for the same reason.

The XY motors became the front “legs” of the machine. I then made risers for the rest of the plate (this leaves enough room under the machine for all the electrical. Also a retractable handle was added. The machine can be carried like a briefcase.

The Z axis was made using a rack and pinion I fashioned from a piece of hardboard for the gear and CD material for the rack. Works pretty well, I’m surprised. I designed the rack and pinion using Matthias Wandel’s gear generator.

The pen holder is magnetic and it’s very easy to swap and adjust pens.

I used a CNC machine to cut out all the parts and glued/bolted it together.

I decided to go with GRBL as firmware for the Arduino so the machine could run g-code. What this means is it is like a CNC machine and you can create g-code from whatever process you want. I just have a pen instead of a cutter.

Bill of Materials

The electrical:
1-Arduino Uno
1-CNC-shield V3
3-A4988 stepper drivers
2-NEMA17 steppers
1-NEMA8 stepper motor
1-12V power supply (6 amps)

Precision parts:
2-MGN7 300mm rail
1-MGN7 250mm rail
1-MGN7 100mm
3-MGN7C bearing blocks
16-Roller skate bearings (1/4″ ID)
2-16 tooth pulley, 5mm ID, 2mm pitch
1-belt, 2mm pitch (will measure soon)
6-bolts for belt control, 1/4-20 sizes to follow
26-1/4-20 nuts (two different thicknesses details to follow)
1-rack and pinion (cut from hardboard and discarded CD)

Fasteners:
8-M3 bolts to mount NEMA17 steppers
4-M2 bolts to mount NEMA8 stepper
20-M2 bolts to mount square rail

Chassis:
hardboard for base, handle, electrical stow
3/4″ extruded aluminum angle

Pen holder:
8-6.3mm x 3mm neodymium magnets

Extra
1-RasberryPi in the works so it can be remotely controlled.

Related

Reddit discussion.

This machine covered in the Arduino Blog and their Instagram.