Georgia Institute of Technology George W. Woodruff School of Mechanical Engineering ME Creative Decisions and Design. Fall 2012 STUDIO II

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1 Georgia Institute of Technology George W. Woodruff School of Mechanical Engineering ME Creative Decisions and Design Fall 2012 STUDIO II MACHINING & MECHACTRONICS PROJECT: ANGRY BIRDS LAUNCHER In order to successfully design and build a product, you must understand the capabilities of the tools and supplies at your disposal. For example, you must understand how motors and sensors work. Furthermore, you must have knowledge of manufacturing processes, such as machining with milling machines and lathes. This project will help you develop an understanding of the supplies and manufacturing processes available to you in ME Your goal is to build a pneumatic-powered catapult that shoots Angry Birds (squash balls) to knock down pigs that have stolen their eggs. A photograph of the catapult system is shown in Figure 1. You will be assigned a group that will share the supply kit. Due to this and the fact that there are a limited number of machine tools available in the lab, your section will be split into two sub-groups, Group A and Group B. This studio is pass/fail. You must complete the assigned tasks to pass the course. Figure 1 Photograph of Angry Birds Catapult System ME 2110 Studio II P a g e 1 of 13

2 Week 4 in Studio (9/10-9/14) Group A: In Week 4 of the semester, Group A will learn how to program the controller box, as well as use the sensors and actuators in the supply kit. You will have to complete the tasks found in Mechatronics Lab Tasks: Group A in the Mechatronics Section of this document. You will have to demonstrate proper execution of the tasks to your Studio Instructor or TA. They will sign your assignment sheet, indicating the tasks have been completed. Group B: In Week 4 of the semester, Group B will learn how to use the tools in the machine shop. An instructional seminar will take place in the lab in which the TA will instruct the group on proper lab safety, tool checkout procedures, and proper use of all of the lab tools. You will then begin to construct the components needed to complete the catapult. To do this, you are provided a detailed process plan and mechanical drawings for the components, located in the Manual Machining Section of this document, and you will receive plastic (Delrin) workpieces from which you will construct your launcher. Week 5 in Studio (9/17-9/21) Group A: In Week 5 of the semester, Group A will move on to the machining section of the project. They will undergo the same machining seminar as Group B and receive their own plastic workpieces. Group B: In Week 5 of the semester, Group B will learn how to use the supply kit. They will complete the Mechatronics Lab Tasks: Group B found in the Mechatronics Section of this document. Week 6 in Studio (9/24-9/28) Group A and B: In Week 6 of the semester, everybody will have the opportunity to work on whichever part of the assignment that they still need to complete. Outside of Studio (9/11-10/5) In addition to doing work inside your scheduled studio time, the lab will be open for other periods of time throughout the week. These are known as Open Lab. Any ME 2110 student may use either of the ME 2110 rooms during Open Lab. The Open Lab schedule is posted on the ME 2110 website. Due to limited time during scheduled studio, you may need to utilize Open Lab to complete your deliverables. You will also need to use the ME computer cluster to create a drawing for a nametag for your final competition machine. This task is detailed in the Automated Machining Section of this document. ME 2110 Studio II P a g e 2 of 13

3 Week 7 in Studio (10/1-10/5) By Week 7 of the semester, you will have completed your pneumatic-powered Angry Birds catapult and gained sufficient knowledge of the supply kit to compete against other students in your studio to determine who can score the most points with the best combination of accuracy and distance. Figure 2 shows a schematic diagram of the competition setup. You will get three Angry Birds to shoot at pig targets whose distances range from feet away. You must complete the catapult assembly using the Angry Birds Cradle and Catapult Pivot that you constructed in the studio. The objective of the contest is to knock the pigs from their foam blocks such that they hit or are touching the ground. Each successful pig destruction is worth 10 pts. You get three shots at the same setup. The pigs are not reset in between shots. The Angry Birds system has multiple catapults allowing one to be launching while others are being assembled by the next competitors. Therefore it is critical that you test your launching skills using both catapults since you will be assigned either one during the competition. The catapults will operate at a maximum of 100 PSI air pressure and will be actuated using the manual trigger button on the pneumatic valve. You can set the air pressure and position of the cradle as you need to hit the targets. You should practice several times in order to maximize your effectiveness with three shots. Pneumatic Valve Air Tank Individual Cradle and Pivot 10 pt. each 12 Shared Catapult (provided) Figure 2 Angry Birds Competition Setup (not to scale) 1,2 ME 2110 Studio II P a g e 3 of 13

4 Deliverables Table 1 shows the deliverable schedule for this project. Table 1 - Deliverables for Each Individual for Next Two Weeks of Studio Group A Group B Deliverables due at the Beginning of studio in Week 5 (9/17-9/21) Deliverables due at the Beginning of studio in Week 6 (9/24-9/28) Deliverables due at the Beginning of studio in Week 7 (10/1-10/5) - 3 completed and signed Mechatronics Lab Tasks: Group A - All 5 completed and signed Mechatronics Lab Tasks: Group A - 1 machined plastic component - All 5 completed and signed Mechatronics Lab Tasks: Group A - Both machined plastic components - 1 Drawing for a Nameplate - 1 machined plastic component - 3 completed and signed Mechatronics Lab Tasks: Group B - 2 machined plastic component - All 5 completed and signed Mechatronics Lab Tasks: Group B - Both machined plastic components - 1 Drawing for a Nameplate References 1. Enemy Behind the Sticks and Stones. Angry Birds Online. Accessed 1/11/ Angry Birds Pig Who Likes Them?. Angry Birds Online We Angry Birds Rio & Seasons. Accessed 1/11/2012. ME 2110 Studio II P a g e 4 of 13

5 Mechatronics Section This lab will provide experience with integrating electrical, mechanical, and pneumatic systems. The lab is broken down into two weeks. During the first week, Group A of your team will complete part of the lab; the second part will be completed by Group B during the second week. Although the programming style will not be graded, the code written during these two labs should be helpful in developing the code for the final project. Therefore, it is important to program using a standard structure and adequately comment the code so the program will be easy to follow when referred to later on. The suggested format for your code is: Constants Table Program Variables Main Program Subroutines Before attempting to perform these programming tasks, it is helpful to read through the Mechatronics Kit Manual and Pneumatics Manual which are available on the website. These should provide a good background to the layout of the controller box and how to implement the electro-mechanical-pneumatic components in a design. This project has three checkpoints: at the beginning of studio in Week 5, Week 6, and Week 7. At that time, each student is responsible for showing progress through the assignment as indicated by a signed task checklist. The task checklists for Group A and Group B are provided in the subsequent pages. After each task is completed, have the professor or TA initial the checklist to verify that the program works. Remember that each individual needs separately signed checklist. Feel free to ask the professor, TA, or peers for help in completion of this assignment. ME 2110 Studio II P a g e 5 of 13

6 Mechatronics Lab Tasks: Group A, Name: 1. Have the DC Motor run for 2 seconds, stop for 2 seconds, run for 2 seconds, etc. 2. Connect a microswitch to P0 (START) and have the DC motor run at full speed when the switch is held down and turn off when the lever is released. Hint: Connect the microswitch to P0, read in the value of P0 when the lever is pressed and the value of P0 when the lever is released. The variable name corresponding to P0 is IN0 (it does not have to be defined). Note: This is what will happen during the competition. The machines will begin when the circuit on P0 is shorted (lever is pressed) and will stop when the circuit is opened (lever is released). These couple lines of code will be very important in your final design project. 3. Connect two microswitches and the pneumatics. The program starts with the cylinder retracted. When one switch is pressed, the cylinder should extend and remain extended after the switch is released. When the other switch is pressed, the cylinder should retract and remain retracted. This process should run indefinitely. 4. Connect two solenoids and two microswitches. When one microswitch is pressed, one solenoid is activated for 2 seconds and then release. When the other microswitch is pressed, the other solenoid is activated for 500 ms and then release. When one actuator is active the other cannot be activated. 5. Same as #4, only now the other actuator can be activated when the other is active. Hint: Put a short pause in the program loop and assume that the time through the loop is equal to the length of the pause. You ll know when to turn off the actuator by counting the number of times through the loop. Checklist for Group A: ME 2110 Studio II P a g e 6 of 13

7 Mechatronics Lab Tasks: Group B, Name: 1. Connect the stepper motor and the DC motor. Make them run clockwise for five seconds, stop for 2.5 seconds, run counter-clockwise for five seconds, and then stop for 2.5 seconds. Repeat this sequence five times. 2. Perform the same act as #1, but always have the stepper motor and the DC motor rotating in opposite directions. 3. Connect the IR distance sensor and one stepper motor. Have the motor run if the reading > 128 and have the motor stop if the reading <127. Put a two-second pause between distance sensor readings. 4. Connect the encoder and have the DC motor run at full speed when the encoder is being rotated and stopped when it is not being rotated. 5. Connect the encoder and the pneumatics. When the encoder is rotated 5 complete revolutions, the actuator should extend and remain extended until the encoder is rotated 3 complete revolutions. The cylinder should only extend 4 times and then remain retracted regardless of how many times the encoder is rotated. Checklist for Group B: ME 2110 Studio II P a g e 7 of 13

8 Manual Machining Section Pneumatic Angry Birds Launcher In the machining section of this project, you will build the components needed to complete the Angry Birds Catapult. A sketch of the catapult assembly with labeled components to be machined is shown in Figure 2. Detailed step-by-step directions along with mechanical drawings for the components are given on the last few pages of this handout. You need to use both to correctly machine your parts. Angry Birds Cradle Catapult Pivot Figure 3 Isometric Assembled Views of Angry Birds Catapult ME 2110 Studio II P a g e 8 of 13

9 Automated Machining Section Acrylic Nameplate In addition to machining the plastic parts for the catapult, you will also create a drawing for an acrylic nameplate which you can mount on your final competition device. This nameplate will be cut by your TA out of acrylic sheet using the laser cutting machine. Here are some tips and suggestions on constructing your drawing: Drawing a Nameplate for Laser Cutting: 1. This task is most easily done by creating a 2-D drawing in AutoCAD of the nameplate profile. 2. The outline of your nameplate does not have to be rectangular, but the design must fit inside a 2 x1 rectangle. 3. For lines that you want to cut completely through the material, the color of the line should be changed to red, and the thickness of the line should be changed to 0 mm. 4. For areas that you want to etch (cut only part-way through the material), the fill color should be black. The area outline color should also be black. 5. Once your nameplate is finished, save it as a.dxf file. Use the following file name format: SectionLetter_LastName_FirstName.dxf (ex: A_Singhose_William.dxf). the file to your TA to complete the deliverable. 6. Figure 3 shows a 2-dimensional nameplate designed in AutoCAD, and the resulting acrylic nameplate that will be produced on the laser cutter. Figure 4 Nameplate AutoCAD Drawing and Resulting Acrylic Product ME 2110 Studio II P a g e 9 of 13

10 Suggested Process Plan for Catapult Pivot: 1. Obtain nominal 2.5 length of round 1 diameter Delrin stock. 2. Face one end on the lathe to make it perpendicular to the axis of rotation. 3. Flip the piece over and face the other end, leaving the final length of Turn down 0.50 length of the stock on one end to a diameter of Use multiple axial paths with approximately 0.05 radial depths of cut per pass. 5. Mount the tailstock onto the lathe. Chuck the small center drill into the tailstock Jacobs chuck. Use the center drill to start a centered hole in the end of the workpiece. 6. Replace the center drill in the tailstock chuck with the 5/16 drill bit. Use the tailstock and drill bit to drill a diameter hole through the entire workpiece. The drill may need to be advanced and retracted multiple times to clear machining chips from the drill flutes. 7. Reverse the workpiece in the chuck in order to machine the other end. Turn down 0.50 length of the stock to a diameter of 0.65 similar to the other side. Use multiple axial paths with approximately 0.05 radial depths of cut per pass. Suggested Process Plan for Angry Birds Cradle: 1. Obtain the nominal 2.5 piece of square 1 Delrin stock. 2. Using the mill, endmill one end of the workpiece to make its face perpendicular to the longitudinal axis of the block. 3. Then, endmill the other end of the block to a total length of Next, use a #25 drill bit to drill a centered hole the full length through the block. Do this on the large drill press. Use a backing material under the workpiece to avoid drilling into the vise itself. 5. Using the small tap wrench and #10-24 tapered tap, cut internal threads on the inside of the hole. Do this on each end of the block to a depth of at least Next, the actual cradle for the squash ball must be made. Choose one large face of the block to cut out a cradle feature. The feature can take any shape you think will be most effective in holding the ball until flight. Use the endmill to cut this feature into the block face. You may machine multiple faces on the multiple block faces but take care not to cut into the hole drilled through the center of the part. ME 2110 Studio II P a g e 10 of 13

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13 MACHINE SHOP SAFETY ALWAYS WEAR SAFETY GLASSES Even when you are not working on a machine, you must wear safety glasses. A chip from a machine someone else is working on could fly into your eye. MACHINING Follow directions. If you don t know how to do something, ask. Before you start the machine: Study the machine. Know which parts move, which are stationary, and which are sharp. Double check that your workpiece is securely held. Remove chuck keys and wrenches. Do not leave machines running unattended. Clean up machines after you use them: a dirty machine is unsafe and uncomfortable to work on. Do not use compressed air to blow machines clean. This endangers people's eyes and can force dirt into machine bearings. Report all broken or non-working machines. CLOTHING, JEWELRY, AND HAIR Wear long pants (to your shoes). Wear short sleeves or roll up sleeves. Wear closed toe shoes and socks. Remove all jewelry - watches, bracelets, rings, necklaces, dangling earrings. Long hair or beards must be tied back. If your hair is caught in spinning machinery, it will be pulled out if you're lucky. If you are unlucky, you will be pulled into the machine. No ties, scarves, and dangling clothes. SAFE CONDUCT IN THE MACHINE SHOP Be aware of what's going on around you. For example, be careful not to bump into someone while they're cutting with the bandsaw (they could lose a finger!). Concentrate on what you're doing. If you get tired, leave. Don't hurry. If you catch yourself rushing, slow down. Don't rush speeds and feeds. You'll end up damaging your part, the tools, and maybe the machine itself. Listen to the machine. If something doesn't sound right, turn the machine off. Don't let someone else talk you into doing something dangerous. Don't attempt to measure a part that's moving. No fooling around. VIOLATIONS OF THESE RULES WILL RESULT IN IMMEDIATE EJECTION FROM THE MACHINE SHOP. ME 2110 Studio II P a g e 13 of 13