Georgia Institute of Technology George W. Woodruff School ...singhose.marc.gatech.edu/courses/me2110 Summer13... · Mechatronics Lab Tasks: Group A, Name:_____ 1. Have the DC Motor

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Georgia Institute of Technology George W. Woodruff School of Mechanical Engineering

ME 2110 - Creative Decisions and Design Summer 2013 STUDIO II

MACHINING & MECHACTRONICS PROJECT:

HALF-TIME SHOW SHOOTING CONTEST

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 2110.

During half-time at many basketball games, a contestant from the crowd is brought down to the court to shoot baskets. Your goal is to build a machine to win a half-time shooting contest. You will build a pneumatic-powered catapult that shoots squash balls at a target in order to score points. A photograph of the Half-Time Show Catapult System is shown in Figure 1. You will be working in your final project teams. Due to limited mechatronics supplies and machine tools available in the lab, your team 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 Half-Time Show Catapult System

Pneumatic Pump and

Distribution System

Laser Sight

Squash Ball Projectile

Launcher 2 without

Attached Delrin Components

Launcher 1 with Attached

Delrin Components

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Week 3 in Studio (May 29-30) Group A:

In Week 3 of the term, Group A will learn how to program the controller box, as well as use the sensors and actuators in the mechatronics 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 3 of the term, Group B will learn how to use the machine tools in the lab. An instructional seminar will take place 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 components.

Week 4 in Studio (June 5-6) Group A:

In Week 4, 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 4, Group B will learn how to use the mechatronics kit. They will complete the Mechatronics Lab Tasks: Group B found in the Mechatronics Section of this document.

Outside of Studio 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 the ME 2110 design studio and machine shop 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.

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Week 5 in Studio (June 12-13) By Week 5 of the semester, you will have completed your pneumatic-powered squash ball 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 squash balls to shoot at the target which will be placed 18 feet away. You must complete the catapult assembly using the Cradle and Pivot that you constructed in the studio. The objective of the contest is to land the ball inside the center target hole. Each successful shot into the center hole is 27 pts, each shot into the outer hole is 9 pts, hitting the side of the target is 3 pts, and shooting the ball at all is 1 pt. Shots that hit the floor or inanimate surroundings before hitting the target will count.

The launcher system will utilize one catapult this semester. An automated compressor is attached to the pneumatic launch system and will re-pressurize the system to 80 PSI when you press the white long-arm switch. The black long-arm switch will activate the pneumatic valve causing the catapult to actuate. You can set the position of the cradle as you need to hit the target. You should practice several times in order to maximize your effectiveness with three shots. Consistent shooting will require you to minimize the variability in your setup. Keep this in mind as you control the re-pressurization, cradle angle, cradle location on the lever arm, and yaw of the launcher system.

Figure 2 – Half-Time Show Contest Setup (not to scale)

Air Tank

Pneumatic Valve

17’

27  pt.  

12’’

Shared Catapult (Provided)

Individual Cradle and

Pivot

19’ 18’

9  pt.  

3  pt.  12’’

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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 4

(June 5-6)

-All 5 completed and signed Mechatronics Lab Tasks: Group A - Both machined plastic components

Deliverables due at the Beginning of studio in Week 5

(June 12-13)

- Both machined plastic components

- 1 Drawing for a Nameplate

- All 5 completed and signed Mechatronics Lab Tasks: Group B

- 1 Drawing for a Nameplate

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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 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 one checkpoint at the beginning of studio in 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.

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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:

1. __________

2. __________

3. __________

4. __________

5. __________

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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:

1. __________

2. __________

3. __________

4. __________

5. __________

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Manual Machining Section Pneumatic Half-Time Show Launcher In the machining section of this project, you will build the components needed to complete the Half-Time Show Catapult. A sketch of the catapult assembly with labeled components to be machined is shown in Figure 3. 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.

Before studio, review the machine shop safety rules in the Machine Shop Safety section at the end of this document. Be sure to familiarize yourself with these rules and arrive to studio dressed to machine.

Figure 3 – Isometric Assembled View of Half-Time Show Catapult

Cradle

Pivot

Possible Cradle Mounting

Locations on Lever Arms

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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 in the Invention Studio. 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). Email the file to your TA to complete the deliverable.

6. Figure 4 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

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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 2.00”.

4. Turn down 0.50” length of the stock on one end to a diameter of 0.65”. 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 0.3125” 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 2.00”.

4. Next, use a #25 drill bit to drill a centered 0.1495” 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 0.1495”

hole. Do this on each end of the block to a depth of at least 0.5”.

6. 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.  

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Cat

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Cat

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t Cra

dle

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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.