Mechanics of a Plotter
Building a Simple Plotter
Click on the video below to see what you will be making.
Building a simple 2D plotter is not difficult. You will need some tools and supplies to do this work:
Tools:
• A metric ruler
• A knife or scissors
• Glue gun
Materials:
• Foam tray
• Bamboo skewers
• Metal spacers
• Two small motors
• 8-32 screw and square nut
Step 1: Measure and cut a piece of foam 3 x 2.5 cm.
Step 2: On the bottom of this piece of foam, glue two metal spacers that have bamboo skewers inside. Make sure that these spacers and the skewers are parallel. This makes the slider (car).
Step 3: Cut two additional pieces of foam. One is 3.3 x 5 cm and one is 3.3 x 4.5 cm.
Step 4: As shown in the photo below, glue one end of the bamboo skewers to the 4.5 x 3.3 cm foam piece. This foam piece is under the skewers. The foam piece of the slider should be on top of the skewers. Make sure the slider can move freely along the skewers to the foam piece.
Step 5. Glue the second foam piece on the other end of the bamboo skewers. This foam piece is under the skewers. The gap between the foam pieces where the slider (car) can travel should be 8 cm. Push the car back and forth to assure it travels easily. Remove any glue that may inhibit smooth operation.
Step 6. Once you have the car running on the bamboo track, you are ready for the next step of attaching the motor. First, cut a small (2 cm) piece of aquarium tubing. This will serve for coupling the motor to the drive screw.
There are two types of motors. The first has a gear on the shaft. Connect it to the machine screw with a piece of aquarium tubing. It should be a tight, but flexible coupling. See the photo below:
If you have a motor with a smaller drive shaft, take a piece of wire insulation (green in the photo below) and slip it over the motor shaft. It should be very tight. If it isn't tight, it can be hot glued to the motor shaft. The machine screw can now be connected to the shaft. It should be tight, yet flexible. See the photo below for an example:
With the motor attached to the machine screw, line-up the motor on the pad as shown in the photo below. This is an important step. Don't glue yet!
Depending on the motor you use, you must leave enough room under the drive shaft to allow another drive shaft to fit underneath. See the next photos to see how the drive shafts are positioned. You haven't mounted the second motor yet--these pictures are just to show you what to expect so you can position the first motor correctly.
Gear Motor Placement
Notice that the horizontal gear motor needs to be arranged with spacers underneath to lift it above the vertical motor. If you have a small motor with a gear you will need to add a layer of foam under the motor.
Plain shaft motor
The larger motor with the smooth shaft does not require a spacer under the horizontal motor. Notice that the vertical motor will need to be lifted up by a layer of foam.
You may need to examine a model first hand so you can see how you can assemble this. Your instructor will have one of each motor style to examine.
When you are sure you have proper alignment (the shaft is level and straight in both directions--look at it from the top and the side), glue the motor to the foam pad. Position the nut as shown and glue it carefully to the slider (car). Be careful not to get glue on the treads of the nut or machine screw! If you do, wait until it gels and peel it off.
Once you have the motor mounted, turn the shaft and see if the car will move. Test the motor on your 3 Volts of power for the gear motor and 6 volts for the shaft motor. Ask your instructor how to get 3 volts out of your six volt supply!
Part 2
With the car, track and motor operating it is now time to make a sliding table.
Step 7 Turn over the car and track assembly and place two metal spacers as shown.
Make sure the bamboo rods are parallel through these spacers. Glue one spacer to the underside of the motor so it is in the center of the mass of the motor. Glue the other spacer closer to the center of the track as shown.
Step 8. Cut two rails 4 x 14 cm.
Glue the bamboo skewers onto these rails as shown in the photo below. Make sure that the car and track can glide smoothly on these skewers. As shown in the photo, make sure there is at least 8 cm between each long foam piece.
Cut off any bamboo that sticks out past the foam rail after the glue is dry.
Step 9. This last step is mounting the second motor. Take a look at the photo below. The long foam piece will need to be built-up on one end to accommodate the motor. Cut a small piece of bamboo to place under a pad that is glued to mount this second motor.
Build up this pad so that the motor shaft can run under the other motor as shown. This may require some adjustment and a bit of shaving of foam to assure that there is good alignment. When you are sure you have a good fit, glue the motor and the nut in place.
Test both motors to see if you have two dimensional motion!
If so, you are ready for motor control.
Alternatively, you can explore different kinds of mechanisms that allow motors to move platforms up, down; left right; etc. To get a sense of how mechanical systems operate, take apart a printer! See: Take apart a printer!