2.008 YY Project Milestones Spring 2020

Please read this document thoroughly and carefully at the start of the project!

The 2.008 yoyo (YY) project teaches the principles of manufacturing through a comprehensive hands-on team experience.  It practices and complements the fundamentals discussed in the 2.008 lectures and challenges.

In the project you will work in a team of 4 or 5 students to design and manufacture a yoyo including parts made by thermoforming and injection molding.  A typical yoyo will include 2-4 unique injection molded parts, and at least one thermoformed part. Of course, there are tradeoffs among creativity, complexity, and manufacturability; you will consider these in detail throughout the design stage of the project. In all cases, your team will produce 50 assembled yoyos, requiring at least 100 of each component (assuming your yoyo has a symmetric design).

Some previous 2.008 yoyos are shown below; you may also find many past 2.008 yoyo team blogs via a simple google search. Also see this gallery of past yoyos, which showcases various design and manufacturing details. And, note the design guidance on the class webpage: https://course2008.mit.edu/yoyo-design.

Some past 2.008 yoyos: (left) Hamster; (middle) Pennybags; (right) Mike Wazowski

The yoyo project follows a typical product design and manufacturing sequence that is practiced in many industries. The steps include

We choose to manufacture yoyos in 2.008 because their size and complexity is a good fit for the time and resources we have available, and because it enables us to learn and use forming processes, namely injection molding and thermoforming, which are highly versatile and scalable. That said, the lessons learned from injection molding and thermoforming will be applicable not only to plastics, but to a host of other materials as well. As you complete the yoyo project in the latter part of the semester, the lectures will address topics of manufacturing cost, systems and other topics. These topics will reinforce the principles of the project, and provide exposure to the broad context of advanced manufacturing for a wide variety of products and industries.

Summary of milestones

The milestones that accompany the yoyo project are all team-based, and are ordered as listed below. Unless otherwise noted, the content is due at the beginning of your lab section. Point values are given on the grading table.

Also please note

Team blog

At the beginning of the project, your team will create a blog. The blog will be used to share your progress with the other teams, and as a reference by future 2.008 students.  It can also be an element of your personal portfolio (such as for job and graduate school applications). You can find many past 2.008 team blogs and videos via a google search.

To create your blog:

Your first post can be a brief (~1-paragraph) introduction of your team and a team photo.

Your second post should summarize your (three) yoyo concepts, including brief descriptive text on how you selected the concepts, and clear sketches.

After this, you are expected to use the blog to record your progress, and to post ~weekly (on average). The blog will be used in the lab as a means of showing your progress to your peers and to the staff, yet will be graded only at the end of the semester. The content of your blog is up to you, and you are encouraged to highlight creative/fun/complex features you are incorporating in your yoyo, challenging problems you’ve solved, observations from the process that you find interesting, photos of successes and failures/defects, etc.  It should tell a story of your Yoyo from concept to finished parts, but need not capture all the details (that’s what the presentations and reports are for).

For instance, on your blog you could also include (but not be limited to):

To conclude the semester, your blog should include:

Yoyo design review and CAD

We will hold the yoyo design reviews during your lab section; this is an important milestone that will allow you to explain your design in detail, and your understanding of key design for manufacturing issues that will influence your success in the remainder of the project.  Likewise, this is a good opportunity to receive in-depth feedback on your work.  Because each yoyo design is different, your team may feel that a specific sequence and structure of content is best.  That said, we request the following elements be addressed in your presentation:

  1. Introduce your yoyo design, explain its inspiration, briefly mention other concepts that you considered, and discuss any important insights you gained from studying past 2.008 yoyos. It is critical that you take a “clean sheet” approach to your design, and not work directly from other examples that you have seen.
  2. Present a 3D printed prototype of your yoyo; this is mainly to show how the yoyo looks and feels, not as a functional prototype. Tell us what you learned by making the prototype, and if it prompted you to make any design changes. You can use any 3D printer(s) you wish, including the Ultimaker and Form2 printers in the shop, or printers in any other facility that you can access.
  3. Present your detailed CAD model of your yoyo design, showing all parts and how the parts will assemble. For clear communication you may wish to show an exploded view of your yoyo, and a section view of the assembly.
  4. Briefly describe each component of your yoyo (excluding any standard hardware, e.g., nut, string, etc); explain its geometry, how it mates with other components, how it will be manufactured, and which dimensions/features are critical to its function and appearance.  
  5. Create a table of the critical dimensions of your yoyo; for each dimension give the nominal value and estimated tolerance, and note how you will measure the dimension.  
  6. Identify the interfaces within your yoyo that will require you to consider shrinkage. Tell us the critical dimensions (e.g., inner diameter of ring, outer diameter of body) that would be assigned without shrinkage, and with shrinkage considered, and how you arose at these estimates.
  7. Select your most complex injection molded part, and explain where you expect to place the gates for molding, and what defects you would be most likely to encounter and how your part design, upcoming tooling design, and/or process parameters can reduce the likelihood of defects.
  8. Explain what design, design for manufacturing, and manufacturing considerations are critical to the aesthetics, overall quality, and functionality of your yoyo.
  9. Present a schedule (in Gantt chart or timeline format*) for the rest of the project, noting the timelines for mold design, mold fabrication, process optimization, and production for each part; and final assembly and documentation (e.g., final report and presentation). Your schedule should incorporate key due dates. Indicate how your team will divide the effort (i.e., who owns each part), and (this is very important) how you will ensure seamless communication of results with one another. *Trello is an excellent free online tool for building project schedule boards.
  10. Do you have any other concerns/uncertainties about the path forward?

Your presentation should be polished and professional, and in slide presentation format (though feel free to manipulate the CAD models to support your key points). You may speak for 15-20 minutes as a team, and we can take up to 30 minutes per team including discussion.  

Before your lab section begins please upload a .pdf of your presentation to the Dropbox file request linked below, filename = yourteamname_designreview_sp20.pdf: https://www.dropbox.com/request/yIH4Nmvrv3Mohw37sAHi 

Upload a near-final (>=90% content) draft no later than 24 hours before your lab section start time. Then you may upload the complete presentation anytime before your lab section start time.

If you wish to include vidoes also upload the Powerpoint/Keynote file, or present from Google, Slides on the classroom PC.

Yoyo design review feedback

In the lab following the design review, you will have the opportunity to share how you have implemented the staff feedback received after your design review presentation, and you will be expected to update your CAD to reflect recommended/resulting design changes. Your team will discuss these changes with your lab instructor, and as a result of implementing the feedback you may be awarded up to 1 point added to your design review score (1 point out of 8, where 8 = 8% of your course grade for the design review and CAD models).


Regrouping for remote instruction after spring break

When MIT announced its closure for the rest of the semester, we began brainstorming how we could offer the best virtual yoyo project experience, considering that each member of your team is in a different place. Initially, we thought that it may be possible for us (the staff) to be on campus (and therefore in the shop) while you all are remote, therefore, we thought about making (selected) yoyos at your remote direction. Ultimately, as MIT is now completely shut down, we needed to pivot to a fully remote approach. Therefore, during the week of March 16, we manufactured yoyo parts that everyone could receive. We settled on a very simple design, so we could make enough parts in a limited time and ship a package to each of you. In this package you will find a set of parts that will allow you to assemble three complete yoyos.  You’ll also get a package from Amazon with calipers and an object that you will study for the quiz.

Overall, in parallel you will continue to work with your team on your unique yoyo design, and use the parts that we made last week to perform simplified quality control and assembly exercises. After March 30, the Monday zoom lecture sessions will be led by Prof. Chun (as was the original post spring break plan) and John Lewandowski; Prof. Hart and Dr. Liu will still be engaged with you for the project, and working closely with the lab instructors behind the scenes.

Lab topics and activities for the rest of the semester

In addition to below, you are expected to keep up your blogs (reflecting your progress, and adapting to the new format of course) resuming for the week of March 30.

Lab 7 (week of 3/31)

In lab, we will:

Lab 8 (week of 4/6)

Note 29-Mar-20: We are still defining the content for the remaining lab sections, and, to some extent it will be fluid based on how things progress in the new format. To get a sense of what will be due, please see the prompts for the Go-to-Manufacturing report and Final report below.  

Lab 9 (week of 4/13)

Lab 10 (week of 4/20)

Lab 11 (week of 4/27)

Lab 12 (week of 5/4)

Go-to-Manufacturing report

Before the start of your lab section during the week of 4/20, your team will prepare and submit a report that documents your final yoyo design, tooling design, and instructions for manufacturing, as if you were submitting this information to another company/supplier to receive a cost estimate for mass production. The report should include the following elements:

  1. A description of your final yoyo design, with graphics (i.e., annotated screenshots, exploded views) to explain all the key features.
  2. A bill of materials for a complete yoyo, i.e., a table listing each part, material, process, and any other details.
  3. A description of the MoldFlow analysis that you performed for each part that is to be injection molded, including screenshots, estimates of shrinkage/warpage, etc.
  4. A discussion of changes you made to the dimensions/features of your yoyo parts based on the MoldFlow analysis, and how you chose the final dimensions to give a high probability of a successful assembly.
  5. Dimensioned drawings for tooling (i.e., core and cavity molds for injection molding, dies for thermoforming) that would be used to create each of your parts. The drawings (and accompanying CAD models) should include the gate/sprue/runner features that would be included for manufacturing of the parts in the 2.008 shop. The supplier will have CAD models of your tooling, so you need only label critical dimensions on the drawings.
  6. A sketch/diagram of how you would propose to lay out a factory for mass-production of 1,000,000 yoyos per year, accompanied by:
  1. an estimate of the cycle time required for each operation in the factory, guided by your MoldFlow simulations, assembly of the LMP yoyo, other experience lab, and intuition/research.
  2. a list of parameters/details that you would need to determine/calculate in order to estimate the cost of setting up the factory

This is not your “final“ answer; your responses will be used to (after this report) setup the factory simulation model and cost model that will be part of your final report.

  1. To support the above, you will share the CAM toolpaths for each of your molds with your lab instructor, and have the opportunity to discuss these in the lab session(s) prior to or during the week of 4/20.

Upload (https://www.dropbox.com/request/fZT0VbGipS6LDcGUUg7s) your report before the start of your lab section as .pdf and include a link to a google doc version of the report (read-only, we will make a copy).  Alternatively, upload both .pdf and word files (will allow the staff to make comments electronically and collaboratively). Include your lab section and team name in the filename.

Final report

We wish that we could be discussing real manufactured yoyos in your final report, but we’ll do our best here to use the report as a final reflection of how your design came together, and what you learned from the virtual activities during the second half of the semester.

  1. Describe your final yoyo design. You may copy this from your Go-to-Manufacturing report, and extend it as needed. For each component, summarize the key considerations for successful manufacturing (based on your analysis, learnings, etc.).
  2. Consider the critical dimensions to govern the fits between the components in your yoyo assembly (i.e., parts that snap together). List these dimensions and tolerances in a table, as mean and 3-sigma values.  Provide a brief explanation of how you chose the dimensions based on what you learned this semester.
  3. Present your Tecnomatix factory simulation.
  1. Explain the layout, and how you chose the sequence of operations that guided your factory layout.
  2. List the parameters you chose for each machine/station, and how you came up with these parameters.
  3. Present results of the simulation, verifying that you can meet the target volume of 1-10 million yoyos per year.
  4. Tell us more. We’d like you to choose what results to present depending on how you ultimately configured the simulation and used the software. You might think of asking a few questions (using the simulation) such as: what is the total (average) cycle time to make each yoyo? how long does it take for one yoyo (starting from the raw material) to be made (this is called the “flow time”)? could the factory adapt to a 10% increase in demand, a 50% increase? what is the effect of the buffer sizes between stations and/or machines? what machine/station in your factory limits the overall production rate?  You don’t need to answer all of these, and you can pose other questions as you see fit.
  1. Present a cost analysis in support of the proposed factory-scale manufacturing of your yoyo.
  1. First, document the costs of the “inputs” to your model. Use tables to present your data and assumptions clearly, and note your references. Include costs such as:
  1. Raw materials and other components of the yoyo
  2. Tooling
  3. Equipment (i.e., all the major equipment needed to fill the factory)
  4. Labor per hour, for the different jobs that would be present in the factory
  1. Now, calculate the cost for production of each injection molded or thermoformed component of your yoyo. Use a spreadsheet to calculate the cost-quantity relationship for each component, and present the output plot. What is the per-part cost (for each component) at the target annual volume of your factory (1-10 million units, exact number is your choice)?
  2. Estimate the total manufacturing cost per yoyo, at the target annual volume. Here, you must include the cost of assembly, but don’t worry about packaging. Explain further assumptions used to reach this estimate.
  3. Reflect on the realism of this analysis. How do your costs compare to the price of commercially made yoyos, and what might account for the differences?
  4. Could the cost be reduced significantly using additional automation? Explain any advantages and challenges. Would your answer be different if you had to increase the volume 100-fold? You don’t need to do in-depth analysis here.
  5. Upload your cost analysis spreadsheet as a separate file along with your report.
  1. Finally, we’d like to hear your reflections on what you learned in the yoyo project, albeit with a virtual outcome. What lessons did you find most/least valuable, most/least interesting? What should we have emphasized more, less? Make sure that your response reflects individual opinions as well as your collective experience. You are welcome to identify your individual thoughts, but that is not required. 

Final presentation

On the last day of class (Monday, May 11), each team will give a brief (5 minute maximum, plus brief Q&A) presentation, during the full-class zoom session.

  1. Introduce yourselves.
  2. Present your yoyo design (and inspiration), and how it would be made.
  3. Give us a “virtual tour” of the manufacturing and assembly process, using diagrams/videos/graphs from the factory simulation.
  4. Summarize your cost analysis for the target production volume.
  5. Do you think it would be possible to make 100x of your target volume at 1/10th the cost per yoyo? Tell us your reasoning based on the analysis in your final report.

Team evaluation

We will distribute a simple form, which you are to complete individually, reflecting on your team’s performance.

2.008-Sp20 YY Project Milestones