Georgia Institute of Technology
George W. Woodruff School of Mechanical Engineering
ME 2110 - Creative Decisions and Design
Fall 2011
Studio II
machining & electronics project: pneumatic 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 abrasive cutters. This project will help you develop an understanding of the supplies and manufacturing processes available to you in ME 2110.
Your goal is to build a pneumatic-powered launcher that shoots a Q-tip at a distant target. The launcher will be controlled by the ME 2110 controller box. You will be assigned a group that will share the mechatronics 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 groups, Group A and Group B, where half of each project team is in each group.
This studio is pass/fail. You must complete the assigned tasks to pass the course.
Week 2 in Studio (8/29-9/2)
Group A:
In Week 2 of the semester, Group A will learn how to program the controller box, as well as use the sensors and actuators in your mechatronics kit. You will have to connect and program the electronics to complete the tasks found in Electronics Lab Tasks: Group A in the Electronics 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 2 of the semester, Group B will learn how to use the tools in the machine shop. A quick 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 a pneumatic launcher. To do this, you are provided a detailed process plan and mechanical drawings for the device, located in the Manual Machining Section of this document, and you will receive plastic (Delrin) workpieces from which you will machine your launcher.
Week 3 in Studio (9/5-9/9)
Group A:
In Week 3 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 3 of the semester, Group B will learn how to use the mechatronics kit. They will have to complete the Electronics Lab Tasks: Group B found in the Electronics Section of this document.
Week 4 in Studio (9/12-9/16)
By Week 4 of the semester, you will have completed your pneumatic-powered Q-tip launcher and gained sufficient knowledge of the mechatronics kit to compete against other students in your studio to determine who can shoot a Q-tip with the best combination of accuracy and distance. Figure 1 shows a schematic diagram of the competition setup. You will get three attempts to shoot a Q-tip at a target approximately 40 feet away. Landing a Q-tip in the middle ring of the target will earn 5 points, landing in the outer ring of the target will earn 3 points, and shooting the Q-tip anywhere past the front of the target will earn 1 point. You must secure your device using the provided vice with adjustable launch angle. The vise is designed to fit into the channels on your launcher Baseblock. Note that you must share your computer controller and the pneumatic supplies with the other members of your team.
Outside of Studio (8/29-9/12)
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 work 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 will need to utilize Open Lab to complete your deliverables. In addition to using Open Lab to complete the manual machining and electronics assignments, you will also need to use the ME computer cluster to create a drawing for a bracket for one of your mechatronics components. This task is detailed in the Automated Machining Section of this document.
Deliverables
Table 1 shows the deliverable schedule for this project.
Table 1 - Deliverables for each Individual for Next Three Weeks of Studio
Group A / Group BDeliverables due at the Beginning of Studio in Week 3 (9/5-9/9) / - All 5 completed and signed Electronics Lab Tasks: Group A / - Both machined plastic components
Deliverables due at the Beginning of studio in Week 4 (9/12-9/16) / - All 5 completed and signed Electronics Lab Tasks: Group A
- Both machined plastic components
- 1 Drawing for a mechatronics bracket / - All 5 completed and signed Electronics Lab Tasks: Group B
- Both machined plastic components
- 1 Drawing for a mechatronics bracket
Electronics 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 two checkpoints: at the beginnings of Week 3 and Week 4. 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.
Electronics 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:
1. ______
2. ______
3. ______
4. ______
5. ______
Electronics 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:
1. ______
2. ______
3. ______
4. ______
5. ______
Manual Machining Section
Pneumatic Cotton Swab (Q-Tip®) Launcher
In the machining section of this project, you will build the components for your pneumatic launcher. A sketch of the launcher assembly 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. It is suggested that you use both to correctly machine your parts.
Figure 2 – Isometric Exploded and Assembled Views of Pneumatic Launcher
Suggested Process Plan for Pneumatic Launcher Barrel:
1. Obtain nominal 2.4” 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 2.00”.
4. Turn down 0.40” length of the stock on one end to a diameter of 0.50”. 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 #36 drill bit. Use the tailstock and drill bit to drill a 0.1065” 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.
- Use the ½-20 UNF die to cut external threads on the 0.5” cylinder of the workpiece. The shared die is located on the drill press bench and has red-taped handles. Use the vice located on the same bench to hold the workpiece. Be sure to apply constant downward pressure on the die handles as you turn it. Ask the TA for assistance since this is not trivial.
Suggested Process Plan for Pneumatic Launcher Baseblock:
1. Obtain the nominal 2.4” 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 2.00”.
4. Next, facemill channels on opposite sides of the block. The channels should be centered along the length of the block and should be 1.00” wide. Machine the first channel to be 0.125” deep, flip the block over, and machine the other channel such that the thickness between the channels is 0.75”.
5. Now clamp the workpiece on end. Use a center drill to start a hole in the center of one end face of the block.
6. Next, use an 8.50mm 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 in the vise to avoid drilling into the vise itself.
7. Next, use a 29/64” drill bit to drill a centered hole 0.70” deep into one end of the block.
8. Using the large tap wrench and ½-20 UNF plug tap, cut internal threads on the inside of the 29/64” hole.
9. On the other end of the block, use the large tap wrench and M10x1 plug tap to cut internal threads on the inside of the 8.50 mm hole.
Automated Machining Section
Mechatronics Kit Brackets
In addition to machining the plastic parts for your pneumatic launcher, you will also create a drawing for a bracket for one of the mechatronic kit actuators. The TA will use this drawing on a computer-controlled OMAX Waterjet Machining Center to cut your bracket out of ¼” aluminum plate. Your bracket can then be used to mount certain mechatronic actuators in your final project device. There are three separate brackets to choose from: Small DC Motor Bracket, Large Solenoid Bracket, and a Pneumatic Actuator Bracket. Each person in your team for this project need to draw a different bracket. If your group has four people, two people need to make the pneumatic actuator bracket. Drawings are provided in this document for reference. In addition, here are some tips and suggestions on constructing your drawing: