DIY Homework Writing Machine Using Arduino - 2D Pen Plotter

Hi, in this blog I will show you how to make your own homework writing machine also known as 2d plotter.

This machine can write on any surface using any type of pen, pencil, sketch pen or marker. This is useful when you have to complete an assignment or draw beautiful and neat diagrams for your school/college project to fetch those extra marks.

The machine has a very simple construction and can be easily assembled provided you have the right parts available. In this blog, I will explain you the step-by-step assembly of the machine, explain you the parts used, and also provide you a part list in the end with buy links so that you can order them online.

Supplies

You will require a 20x20mm and a 20x40mm V Slot Aluminium extrusion profile of 400mm length each. you can also use 500mm length if you want a larger sized machine. i have prepared a complete part list/ BOM, which you can access through this link: https://bit.ly/3bKfPJJ

Step 1: Assembly - Y Axis

Take the 2040mm profile and attach the base plates to both the ends. Use the sliding nuts and m4 bolts to attach the base plates to the profiles. Now turn the profile and attach rubber feet to the bottom slots of the base plates. These rubber feet will hold the machine in place on smooth surfaces.

Step 2: Intersection Plate

Turn the profile back again, now attach the intersection plates and v wheel kits to the profile.

We will use Delrin v wheels to enable motion in the x and y axis. These wheels consist of 2 bearings and a wheel which runs on the v slot of the profile. This provides a smooth and sturdy motion system to our machine.

Take the top intersection plate, insert m5x45mm bolts to the plate, insert 6mm aluminium spacers on one side and eccentric spacers on the other side, 1mm shim washers, and then insert the Delrin v wheels, insert the spacers and washers again.

Now turn the 2040 profile again and place it on top of the intersection plate. The wheels and eccentric spacers are loose so the profile can be inserted easily. After the profile is inserted, place the bottom intersection plate and pass the bolts through the plate and fasten the bolts using m5 nyloc nuts. Now our intersection plate assembly is complete. Turn the profile back again and tighten the eccentric spacers using a spanner. The wheels should have a firm grip on the profile, also do not over tighten them.

Step 3: Y Axis Motor and Belt

Now we will insert the gt2 timing belt in the y axis profile. Insert the belt through the v slots in the 2040mm profile. Fasten the belt using cable ties in the slots on the intersection plate. Leave some space for the gt2 pulley and idler pulley. Attach the NEMA 17 stepepr motor to the top base plate, and attach the gt2 timing pulley to the motor, pass the belt through the timing pulley. On the bottom base plate, attach the idler pulley and pass the belt through it.

You can use one technique to make sure that there is enough tension in the belt. Before fastening the belt to the intersection plate using cable ties, you can loosen the bottom base plate and bring it closer towards the intersection plate. Once the belt is attached, you can then pull the plate towards the end, which will tighten the belt and thus there will be enough tension in the belt for smooth movement.

By this we are done with the assembly of y axis.

Step 4: X Axis Assembly

Take the 20x20mm profile and attach the motor plate and idler pulley plate to both the ends using sliding nuts and m4 bolts. Insert 2 extra m5 sliding nuts in the profile between the motor plate and idler pulley plate. Now turn the y axis assembly and place it on top of the 20x20mm profile. There are 2 holes in the top intersection plate, which are for attaching the 2 axis to the intersection plate. Align the m5 sliding nuts to the holes and attach them using m5x12mm bolts. Turn the frame upside down.

Step 5: X Axis Motor and Pulley

Attach the stepper motor using m3x12mm bolts and attach the idler pulley to the other end of the x axis. Use a gt2 timing belt of approx. 1 meter length and loop it from the motor and pulley

Step 6: Pen Holder Plate

Now we will attach the pen holder plate to the x axis.

the pen holder plate includes 4 3d printed parts, 2 3mm springs, 2 3mm 80mm long stainless steel shafts, 1 20mm 3d printer bed spring, m5x15mm bolt and m5x20mm bolt.

take the base plate, insert the 3mm shafts from below, now place the movement plate above the shafts, move the shafts towards the top. now insert the springs between the shafts and the top holder, and push the shafts to the top holder. the holders are designed with tight tolerances, and the movement plate has enough gap to allow smooth movement through the shafts.

Attach the pen clip using the M5x15mm bolt, tighten the bolt to have tight movement of the clip, in order to tilt the pen while writing. now place the 20mm spring between the 2 clips, and insert the M5x20mm bolt to keep the clip intact.

Step 7: Mount the Pen Holder Plate

Now attach the pen holder plate to the X axis using V Wheels, the same way which we attached the intersection plate. use the eccentric spacer to tighten the grip between the wheels.

once the plate is in place, pull the pulley plate slightly outwards, to provide tension to the belt, and tighten the m5 bolts under the plate once there is enough tension in the belt.

Step 8: Electronics

we are using an Arduino UNO along with CNC shield V3.0 for this project. we will also require 2 DRV8825 drivers to drive the stepper motors.

to power the machine, we require a 12V 2A power adapter. attach the arduino to the mount plate, and attach the mount plate to the machine

Step 9: Attach Servo

Attach the MG90s servo motor to the pen plate from the back side. use the screws provided with the servo to mount the servo motor. attach the one sided arm provided with the servo from the front and secure it with a screw

Step 10: Wiring and Test Run

Plug the AC adapter, connect the wires to the CNC shield, and turn the adapter on. connect the USB from the arduino to your PC or laptop. now we can test the machine.