Robotics

(see also: Powered Boat)

Standard Statement:
3.1.4 A Explain the parts of a simple system and their relationships to each other.

Content Objectives:
Students will be able to:

1. Identify the basic terms associated with the areas of movement of a robot.
2. Properly demonstrate the basic tool and assembly skills needed to construct the robot.
3. Demonstrate an understanding of fluidics.
4. Identify appropriate applications for a pick and place robot.

Assessment Strategies:

1. Performance assessment

2. Group assessment

3. Individual reflection

Procedures:

This hydraulic robot is designed to be a pick and place robot. A hydraulic robot is powered by fluid under pressure. Hydraulic power is widely used for robots, especially in situations where lots of power is needed. In this case, the syringe plunger provides pressure on the water in the syringe and tubing which acts on another syringe and its plunger. This second plunger is attached to mechanical parts to activate a rotating base, shoulder, arm and wrist joints. When the syringes are first operated, they may work pneumatically (they work on air). As the plungers wear a little, they must be powered with fluid.

Note: Have students work in groups of two to four.

Have each perform the following steps:

Part Construction
Styrofoam Parts

1.      Use templates to lay out the following parts:

2.      Obtain an oblong piece of 1" x 11" x 24" and a 7" square piece of high density Styrofoam.

3.      Lay all patterns (except the circle) on the oblong piece of Styrofoam as shown in Figure 2. Careful planning avoids wasting materials. Lay the circle pattern out on the 7" square. Draw around the templates with a pencil or marker.

Figure 2

4.      Turn on the Styrofoam cutter. Caution! Do not touch the cutting wire; it is very hot! Always use a piece of wood to remove pieces of Styrofoam from the hot wire!

5.      Place a piece of Styrofoam on the Styrofoam cutter table and start feeding the Styrofoam into the hot wire. Push the Styrofoam into the hot wire until the wire contacts the outline. It is important to move at an even pace - do not go too quickly and bend the hot wire or too slowly and burn the Styrofoam. Continue until all pieces are cut out.

6.      Smooth the edges of the Styrofoam with medium grit abrasive paper. Inside curves may be sanded on a spindle sander. Other kinds of power sanders tend to melt the Styrofoam rather than smooth it.

Wooden Parts

7.      Obtain 15 tongue depressors and a can with about one inch of warm water in it. Place the tongue depressors in the warm water and allow them to soak for about five minutes on each end.

8.      Place each tongue depressor in the center punch of a three-hole paper punch. Punch holes in both ends of each tongue depressor.

9.      Use templates and lay out the following wooden parts:

10.  Using straight metal snips, cut each tongue depressor in the shape of a template. Parts #11 need to have the tongue depressor cut only once to make two parts, thereby getting eight pieces out of four depressors. Sand off any sharp splintery edges. Punch new holes in the end of part #9 and #12.

11.  Obtain the dowel cutting fixture and a 1/4" dia. dowel (approximately 25"). Clamp the fixture in a vise. Put the dowel through the hole in the fixture as shown in Figure 4. Cut ten 2" long pieces with a hacksaw or coping saw. Sand all sharp corners.

Figure 4  -  Dowel Jig  -  Dark Line is 2" from The Right Edge

Cardboard Pieces

12.  Obtain two 7" cardboard squares and the 6 1/2" diameter template. Draw two 6 1/2" circles on the cardboard using the template. Also, mark the center hole of each piece. Using scissors, carefully cut out the two circles.

Figure 5 - Grommet Tools

13.  Obtain the grommet kit. Identify pieces as shown in Figure 5. Place the marked center hole of one piece of cardboard on the scrap wood block. Put the 3/8" center punch (A) over the mark. Strike the punch hard with a rawhide mallet to cut the hole. Do the same with the other circle.

14.  Place a grommet (D) post up on the base (C). Center the holes in the cardboard over the tube.

15.  Place the washer (E), rounded side up, tightly over the grommet tube and circles. Insert the handle (B) into the tube. Strike the handle firmly with the mallet until the cardboard pieces are held together but loose enough to turn easily.

Now you should have all the parts needed for assembly.

Assembly

Note: To operate the robot, it is important that all parts move correctly. Once the glue is applied, it is not easy to rearrange parts to improve movement. For this reason, study the diagrams and make a trial fit before gluing. Assembly should be done in three subassemblies. They are the arm, base and end effector.

Arm Subassembly

16.  Plug in the hot glue gun. Work with the gun on a piece of sheet metal to catch the melted glue. Caution: melted glue is very hot and can burn you!

17.  Use the assembly jig (Fig. 6) to glue two #11 pieces at right angles. Let the assembly cool about two minutes and then remove the piece. Get two more #11 pieces and repeat the process.

Figure 6 - Assembly Jig

18.  Glue one of the pieces made in step 17 to the Styrofoam forearm (#5) as shown in Figure 7. For exact placement, lay the forearm next to the outer end of the upper arm.

Figure 7 - Jig

19. After looking at the robot picture, place hot glue on the biceps plunger attachment (#11) and fasten it to the upper arm.

Figure 8 - Position of Bleep

20.  Put a piece of 1/4" dowel rod through the hole in the end of the biceps plunger attachment then put another #11 wooden piece on the dowel to align the hinge. Glue the second wooden piece in position on the other side of the Styrofoam. Remember, you do not get second chance to change the position of the piece, so be accurate!

21.  Glue the shoulder hinge (#9) in position on the upper arm as shown in the robot picture and as shown in Figure 9. Follow the instructions used in step 19.

Figure 9 - Position of Shoulder Hinge

22.  Connect the forearm and upper arm to make an elbow joint by using the 2" dowel rods. To do this, carefully align the arms leaving about 1/4" space between the pieces. Then take a sharpened dowel rod to stab a hole in the Styrofoam to connect the arms. Insert a 2" dowel through the wood and Styrofoam.

Figure 10 - Elbow Joint

23. Glue the biceps cylinder attachment (#10) to a large syringe. It is very important to get the correct angle of alignment, so look carefully at the picture. Place glue on the side of the syringe, and then press the wood piece into the heated glue until it cools. Align another #10 piece on the opposite side of the syringe and glue. Glue the Styrofoam plunger attachment (#8) to the end of the syringe plunger.

Figure 11 - Bleeps Cylinder

24.  Attach the upper cylinder attachments (#12) to a small syringe. Glue the Styrofoam plunger attachment (#8) to the end of the syringe plunger.

25.  Stab a hole in the center of the plunger attachment, then attach it to the hinge on the forearm with dowels. Connect the other end of the upper cylinder attachment to the shoulder hinge on the upper arm with a dowel.

Base Subassembly

26.  Place the cardboard base swivel hinge on the base (#1) in a position similar to the sample. Draw a circle where the center of the swivel will be located. Press the Styrofoam down in the area under the grommet so that the cardboard circle will lay flat. Do the same on the base swivel (#2).

27.  Using the hot glue gun, attach one side of the cardboard swivel hinge to the base and attach the base swivel (#2) to the topside of the swivel hinge.

28. Hot glue the base swivel attachment (#15) to the base swivel. Make sure the end with the hole is sticking out as shown in Figure 12.

Figure 12 - Position of Base Parts

29.  Align the holes in the base swivel cylinder attachments (#14) then glue to a large syringe. Glue a plunger attachment (#8) to the end of the syringe plunger. Use the same method as on the upper cylinder.

30.  Using a sharpened dowel, locate the large syringe on the base swivel pivot base (#7). Now attach the syringe with a dowel. Also, stab a hole in the plunger attachment and attach it to the depressor using a 2" dowel.

Gripper Subassembly

31.  Place the Y support (#11) and two gripper attachments (#13) in position on the assembly jig (see Fig. 13). Glue in place. Let the glue cool, then remove the piece from the assembly jig and assemble another Y support.

Figure 13 - Position of Gripper Support

32. Carefully line up both pieces made in step #31 on opposite sides of a small syringe so they are even and the holes line up. Place a line of glue on the syringe along the side that does not have finger grips. Now attach the Y assembly to the syringe. After the first side is in place, repeat the process on the other side.

Figure 14 - Position of Gripper Syringe

33.  Place the gripper jaws (#6) in the Y assembly and stab a hole through the gripper jaws. Now attach the gripper jaws using dowel pegs (see Figure 15).

Figure 15 - Position of Gripper Jaws

34.  Remove the plunger from the syringe and punch four small holes in its handle with an awl (see Fig. 16).

Figure 16 - Placement of Holes

35.  With fine wire, attach two pieces of clear plastic tubing, each 1" long, to the plunger handle (see Fig. 17).

Figure 17 - Attachment of Tubing

36.  Cut two pieces of heavy wire 7 1/2" long using side cutters. Using pliers, bend the wire around the fixture provided for this purpose until the wire is shaped as shown in Figure 18.

Figure 18 - Forming Wire

37.  Take the gripper rods just made in step 36 and run them through the tubing attached to the end of the plunger. Put the plunger back inside of the syringe. Position the gripper jaws tightly together with the plunger all the way in. Keeping the jaws straight, press the wire ends into the gripper jaws as shown in Figure 19.

Figure 19 - Attachment of Wire

38.  Using a sharpened dowel, make a hole in the forearm (#5) for the tubing that operates the gripper to go through. Do not go through the narrow part of the arm, it will reduce its strength (Figure 20). Cut a three-foot piece of clear tubing and put it through the hole. Now attach it to the syringe in the Y assembly.

Figure 20 - Placement of Tubing

39.  Glue the Y assembly to the forearm.

40.  Glue the bottom of the body to the swivel base. Hold the parts in position until the glue is completely cooled. You may want to add two triangle supports to strengthen the body piece.

Powering The Robot

41.  Obtain two small and two large syringes from the teacher. Cut two pieces of tubing one-foot long and one piece two feet long. Attach these to the syringes. Place the end of the tubing in a can of water. Draw the water into the syringe until it is full. Hold the tubing high in the air so any trapped air will go to the top of the syringe. Now force out the air by pushing on the syringe plunger. After the trapped air is removed, attach the tubing to the matching syringe located on the robotic arm. You may discover other ways of eliminating the air bubbles.

You are now ready to operate your robot.

Click on the images to enlarge. Then follow the directions under each image.

This template is shown at 75% of the original size. Enlarge it to 125% on your photo copy machine.

This template is shown original size. You do not need to enlarge it.

This template is shown at 75% of the original size. Enlarge it to 125% on your photo copy machine.