Introduction: Vex and Arduino Drawbot
Welcome! This Instructable is meant to acompany the science project, "Voltage Input & Robots" that was entered into the Solano County Science/STEM fair. This Instructable will cover the material and procedure required to build the Drawbot. Note, that the materials and tools required to build the Drawbot may be expensive or hard to acquire. We encourage those trying to build the Drawbot, to seek out the resources of various STEM and robotics programs at nearby schools, to help gain the tools and materials required. For those living within Solano county and/or have attended the Solano County Science Fair; some schools within the Fairfield-Suisun Unified School District, as well as the Travis Unified School District (specifically Armijo High School and Vanden) have exceptional VEX Robotics programs with said resources. But with this considered, ALL materials required for this project can be bought online through the various links provided within the "Materials" section of this Instructable.
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Step 1: Materials and Tools
Some of the materials listed from the VEX Robotics site come in packs. As a result, there will be some spare parts leftover after the construction of the Drawbot. But, some of the pack materials can also be bought individually from other sites; we are simply providing the most trusted buying solution.
Bolded parts down below cannot be found on the Vex Robotics site, and are sold elsewhere on another site. Again, it is encouraged to take advantage of Vex Robotics programs at various schools, to possibly gain access to individual materials, rather than spending more on packs. The other alternative would be to buy individual Vex pieces from other sites, as said previously.
- 1x5x35 C-Channel (x1)
- 1x2x35 C-Channel (x5)
- 2x2x35 Angular (x5)
- 17.5" Long Linear Slide Track (x4)
- Rack Gearbox Bracket (x2)
- 2" Standoff (x12)
- Vex Angle Gusset (x4)
- 2" Drive Shaft (x2)
- 3" Drive Shaft (x3)
- Shaft Collar (x16)
- Screw 8-32 x 0.750" (x50)
- Screw 8-32 x 0.250" (x50)
- Screw 8-32 x 0.375" (x50)
- Keps Nut 8-32 (x50)
- Hex Nut 8-32 (x10)
- Rack Gear Version 2 (x12)
- Outer Acetal Slide Truck (x4)
- 12 Tooth Gear (x2)
- 36 Tooth Gear (x2)
- 4.6mm Spacer (x2)
- 8mm Spacer (x13)
- Thin Teflon Waster (x10)
- Bearing Flat (x4)
- 0.125" Nylon Spacer (4)
- 0.500" Nylon Spacer (x2)
- Nema 17 Bipolar Stepper Motor (x2)
- Nema 17 Bipolar Stepper Motor Mounts (x2)
- Gorrilla Tape (x1)
- Gorrilla Glue (x1)
- Arduino Uno (x1)
- Arduino Uno GRBL Shield (x1)
- A4988 Motor Driver Chip (x4)
- Jumper Cables (x10)
- 2 Amp Power Supply/Battery Equivalent
- 0.3" Maximum Diameter Pen
- Whiteboard (1.5' x 1.5' Maximum) (x1)
- 5/64" Hex Driver
- 3/32" Hex Driver
- Hand Held Metal Saw/Electrical Saw
The link down below is a Google Sheet with the links to buy the materials and packs
Step 2: Axis Base
Begin by constructing the bottom level of the axis base as shown. 2 of the Angulars are screwed into the C-Channel with standoffs on the bottom, to make a box. The base may be fragile at the moment, but will improve once another level is set. Next insert 2 screws on each corner of the base, facing upward. Then, mount a 4.6mm spacer onto the screws, followed by standoffs.
Finally, created another level with C-Channels and Angulars. Connect the metal by inserting 2 screws on each corner downward, so that they match with the standoffs on the first level of the base. Connect both levels of the base together.
Step 3: X and Y Axis Tracks
Both of the main X and Y Axis are identical. Start by connecting V2 Rack Gears down the length of 2, 17.5" Long Linear Slide tracks, leaving 2 holes minimum at the end of each track. One side of each tracks will have an extra hole, but it does not matter.
Step 4: X and Y Axis Sliders
Next, create the sliders with the stepper motors for both axis. Cut a 1x5x10 C-Channel - the result being a 5 hole wide C-Channel, by 10 holes long. Then, slide one Outer Acetal Truck to one of the Gearbox Brackets. Mount both Trucks with the bracket to the C-Channel's 5 holes sides using 0.250", 8-32 screws. For the Truck without the Bracket, use Teflon washers to space it with its opposite counterpart, so that both are the same height..The face/head of the screw should be on the part of the C-Channel with extending sides. The Brackets and Trucks should be on the opposite end, the flat side of the C-Channel. The threads of the screws should dig into the plastic of the Trucks, and secure both the Brackets and the Trucks to the C-Channel. Repeat the previous steps to create 2 identical sliders.
Step 5: X and Y Axis Stepper Motors
For the following steps, it is best to leave screws slightly loosened until the end. To mount the stepper motors, first bend the end of an Angular Gusset until it is almost flat. Take 2, 7.50" Screws. Attach 1, 0.125" Nylon spacer and 2 Teflon Washers to both of the screws. Mount the 2, 0.750" Screws in this location of the C-Channel; notice the location of the Trucks, to help mount the screws in the right spot (See image). Be sure to have the head of the screw on the same side as the head of the Truck screws, opposite of the Gear Bracket. On the protruding end of the screw, mount the following respectively, 8mm spacer, Angular Gusset, Hex Nut. Mount the Angular Gusset so that the longer hole attaches the 2 screws together. The Hex Nut attaching the Gusset to the screws, should just barely cover the end of the screw.
Center the Angular Gusset so that there is space on either side of it. Take the Nema 17 Motor mount, and insert 2 of the 8-32 x 0.375" Screws, with the threads facing downwards. Insert the ends of the screws to the free ends of the Angular Gusset, screwing it in to the Gusset with a Keps nut. The end of the motor mount in which the motor would be facing, should be facing toward the Gear Bracket. Remember, it is best to leave the screws slightly loose in this step. Use the pliers to help secure the various Nuts.
Set 2 more 8-32 0.750" Screws in the position shown in the picture. On the head of the screw, set a 4.6mm spacer. While pushing the screw to the other side of the C-Channel, secure it with a Keps Nut. The screw should be directly under the Motor Mount, and will work as a tensioner to keep the mount in place. Leave all screws loose. The entire mount should be able to rotate a few degrees, but should be tight enough to not fall off. Repeat the previous steps so that there are 2 axis sliders with motor mounts.
Step 6: Stepper Motor
First, take a Vex Clutch and stick a small flathead into the small holes on the sides. Bang the flathead on all sides of the Clutch while holding it with pliers. Eventually, the top side of the Clutch should rotate, and split the Clutch into 3 pieces. The piece with the square insert is what is required. Take a 0.500" Nylon Spacer, and bang it into the Clutch. Apply a small amount of super glue around the portion of the Nylon Spacer, that is under the Clutch. The Nylon Spacer should fight tightly into Clutch.
Next, apply a small amount of super glue around the upper shaft of the Nema 17 Stepper Motor. Only a thin coat should be visible. Insert the Nylon Spacer and the Clutch onto the Stepper Motor, and let it dry.
Step 7: Linear Drive
Mount the Stepper Motor inside of the Motor Mount, lining up the Shaft hole with the last hole of the bracket. Insert 2 bearings inside of the brackets. With the Motor shaft facing right, mount the Bearing flats on the right side of both walls of the Bracket, with the head of the rivets on opposite ends of the walls.
Then, insert a 3" Drive Shaft into the Clutch, going through both of the Bearing flats, while also attaching spacers and washers. The order from left to right when looking at the shaft with all hardware attached should go as follows: 4.6mm spacer, Bracket Wall, bearing flat, washer, 12 tooth gear, 8mm spacer, bearing flat, bracket wall, finally followed by 2 shaft collars. The following is best illustrated in the included pictures.
Insert the 3" drive shaft into the last free hole on the bearing flats, on the opposite end of the Gear Bracket. The order of the hardware should go from left to right as follows: 2 shaft collars, a small teflon spacer, bracket wall, bearing flat, washer, 36 tooth gear, 8mm spacer, bracket wall, and finally 2 shaft collars. Repeat the following steps for both sliders.
Step 8: Mounting the X and Y Axis
Slide the Linear Tracks onto the Trucks. The Linear Truck with the Line Gears, insert on the side with gear brackets of course, and the bare linear track with the bare truck. Repeat this for both of the sliders. Mount one of the axis on the bottom side of the Drawbot in the middle. This will be the X axis.
Now, moving onto the Y-Axis. Cut 2 angular pieces measuring 10 holes in length. Mount the Tracks to the angulars; by inserting screws one off from the last hole of the angular. The screws should be facing upward. Attach the flat face of the angular to the top of the Drawbot. The free holes that were left without screws, should line up with the top C-Channel of the bot. Make sure that both Axis are centered on the Channels.
Ensure that both sliders can move freely on the tracks. Then, tighten all screws that are connected to the sliders, especially the motor screws.
Step 9: Step 9: Z Axis
Step 10: Setting Up the Arduino Motor Shield
Attach the Arduino Motor Shield to the top of the Arduino Uno. Take the a4988 Driver Chips and carefully attach them to the top of the motor shield. Then, careful insert the Motor Shield to the top of the Arduino Uno, and ensure that the pins are lined up before pushing downward to seat it all the way.
Step 11: Setting Up the G-Code Program:
A G-Code program can interpret and execute the axis movement necessary to draw pictures. There are multiple G-Code programs that can be used for this project, but this tutorial will cover a program called