The time has come. Us in Team Tropical Escape has finished assembling our yo-yos and are ready to go on a tropical escape with all of our Bitcoin money. But, before reviewing the final product, below we'll discuss a couple of the pieces.

Snap ring- The snap ring fabrication was completed between last Friday, Dec. 7th and this Monday Dec. 10th. We did not encounter any of the difficulties with burning that had been occurring earlier the week before. To complete the fabrication as quick as possible, we utilized three shoulder bolts acting as shafts to allow us to place the bolt inside the snap ring.

Stockline line overmold- This piece was completed last Friday, Dec. 7th, and has a sleek, elegant look. While fabricating, we were tinkering with he shot size and pressure profile because short shots were occurring. However, we noticed that the orientation in which we placed the stock line into the overmolding core affected how the filling occurred. We experienced flashing and short shots because of this. Given that the stock line is not an even design, this can explain the discrepancies. Furthermore, we still continued experiencing flashing along the outer diameter of the are where this piece snaps in to the snap ring. This then would not allow the pieces to snap. 

We believe the flashing is primarily due to the core of the overmold being to deep or too wide. Yet, due to time constrains, we could not fix the issue. But, we solved it by using an exact knife to cut off the excess plastic, and this worked well.

'B' overmold- 'B' overmoding was completed on Monday, Dec. 7th and also provides a sleek second half to the housing. With this piece, we were encountering dishing, but adjusting the pressure profile and packing time allowed us to improve this aspect. Though sleek, this part has the defect of a scratch present in the biggest outer diameter of the part. It is due to a scratch that was present in the cavity, but that we had not noticed and then had no time to fix. Below is an image.

Now, finally, images of the yo-yo in separate pieces and the assembled yo-yos can be seen below.

Thermoforming- We had some issues with the original design of having to half that would fold and hold together via a series of positive/negative holes. the issue encountered was that getting the holes to work was not working. Thus, we pivoted to a Duncan yo-yo inspired design of casing, but with our own creative flavor. Below you can see the old mold (greater in length) to the new mold (with a dome life feature).

Furthermore, here is the finished thermoforming casing that is held in place with the use of papers.

If you want to learn more about what the team has been doing these past few weeks, please read the paper placed blow, as well as out team vide!

Watch our amazing Team Tropical Escape video here!

Our final report can be found here.

Extra information/all we have handed in this semester can be found here.

We would like to thank the 2.008 staff, Prof. Hart and Dr. Wendell, as well as the TAs and the shop staff for helping guide us in this journey. We learned a great deal and have a fun yo-yo to show for it.

Team Tropical Escape!

It turns out mass production is difficult, especially when unsolicited problems arise. 

This week, we have been focusing on making our snap fits, overloading our stock line and our Bs. Below is chart of our tasks as well as the quantity that we need for the parts.

A. Snap Fit

We made our production run of 25 disturbed parts by allowing a piece of the part to get burnt.

However, we then struggled to remove this feature. We tried decreasing the injection pressure profile and the injection speed. That decreased the amount of burning but did not entirely eliminated it. We then continued decreasing the injection speed a bit more drastically in order to fix the defect. In doing this, the snap ring showed no defects associated to decreased injection pressure, and that is why we decided to continue tinkering with this parameter. What did finally work was scratching both the cavity and core in the area where the burn was occurring. 

Tropical Escape began final production runs the Wednesday before Thanksgiving, November 20th. Our final 'B's  were produced!

To try get rid of dishing, we went over different parameters and increased the speed profile, increased the hold time, and played with decreasing the cooling time. The final numbers used were the following:

60 pieces were produced.

The stockline overmolds were also made!

For both pieces (B and stockline), the original color was intended to be gold (deviating from our original CAD design) because we believed it would provide portray a classier, more polished look. However, its contrast with the black was barely noticeable, so, we decided to switch back to a lime yellow color.

For our snap fits, we had fixed our design from last time because the inner diameter was too small to fit with our overmolded parts. However this time, it was too big by forty thousands (0.40").

We have been able to advance in preparing our spacers, by increasing 0.25" inner diameters by around one thousands. 71 of these have been fabricated and are ready to go. Our last piece of the project is the thermoformed packaging. Various iterations were performed last Friday to test parameters, and we are having some trouble getting the two halves of the packaging to stay together. We will be re-machining a new mold to adjust for this.

Next week is our last week for full production, as the final presentations will be Wednesday, December 12th. Our schedule for next week is:

More updates coming the following week!

Team Tropical Escape!

Team Tropical Escape has been hard at work this week with the first fabrications of each of our pieces. For it, we have been injection molding and creating/editing our molds.

A PDF of the write-up for our first injection molded parts can be found here.

The fabrication of our pieces has been exciting because it has allowed us to bring to life what we have designed and has also revealed to us many of the functioning and non-functioning parts. For each piece, we have had a problem, and through this have learned of the importance of beginning production early to allot time for debugging and fixing molds if needed. Within this past week, we've had to re-machine two molds. However, for those molds working from the start, we were able to start fabricating pieces. We have been using the ENGEL machine and experimenting with the following parameters to be able to reach the adequate production values: shot size, packing time, and cooling time.

For all parts, we have experimented with short shots, flashes, and some dishing. The process of fabricating the parts has not only taught us time management is critical, but it has also shown us many unaccounted or unexpected problems that had not been thought of before arise when preparing to produce parts. Furthermore, we have also learned that some issues can be fixed by switching parameters in the machine rather than re-doing a mold. For example, to decrease flashing, we have decreased the shot size. For the dishing occurring in our B, we will increase the injection pressure and the hold time.

In the upcoming days, we will be optimizing our parameters and testing them to begin the fabrication of our production pieces.

Below are pictures of our molds along with pictures of produced parts.

• All the molds and some fabricated parts scattered around

• From L to R: Bitcoin (B) mold, B overmold mold, cavity mold

• Fabricated Bs

Note: We have noticed the line in the top left edge indicating the meeting of two flowing points for the B. To eliminate this, we will experiment with increasing shot size and increasing the injection pressure.

• Overmolded Bs

• Stockline
  

• Stockline overmold
  

• Snap rings are not fitting with the dome of both sides. Mold might need to be re-machined because the snap-fit interference with the B overmold is not aligning.
  

• Thermoforming pieces
   
   

More updates will be coming soon!

Team Tropical Escape!

This past week has been exciting! We finalized our CAM for our 'B' mold and fabricated the first 'B's. 

We began the fabrication of the 'B's by varying parameters such as the shot size, the cooling size and the speed profile. We have created a spreadsheet with all this information including the 15 parts we fabricated. The information can be found here. 

We increased the gate size for our last injection mold and will now be edging a bit of the surface on the mold. Before achieving this part of the process, we noticed earlier that some of the outer pins were going too deep into the part (picture can be seen below- second one down). We started with all pins 5.812", then we moved the outside ones (not the 2 middle ones) one size down to 5.695". As for mounting the mold,  we had a total of .015” of shim.

Here are some pictures of the 'B's and of the mold on the injection molding machine.

Here's a picture of the mold in the injection molding machine as well as the calculations made for the ejector pins.

We have also been able to fabricate our thermoforming mold. See image below.

Team Tropical Escape!

This past week we began the process to make the mold designs for our parts.

The idea for making the dome of the yo-yos was to oversold the 'B' logo and the stock line.

Below you will find the preliminary designs for the molds. After the feedback received we will be updating the designs to then be able to start the CAM for them. 

• Stock Line (cavity and core)

• 'B' design
  The general feedback we received for this was that for the 'B', we needed to make sure we drafted the edges by about 3 degrees. We also decided to make the extrusion a bit less than what it currently is. Furthermore, to overmold the 'B' and stock line, we will create those parts first, and from that measure them to create the overmold core molds. To overmold, the 'B' and the stock line will be fitted into the oversold core cavity, and the cavity for the overmold will be stay the same, it'll just be the dome shape. To sum up, for the first molding process ('B', stock line), we believe we can have 1 cavity for two core molds. For the overmold, we believe we can have the same cavity as before but with 2 more core cavities for the overmold. Thus, in total, we will have 5 molds to make (1 cavity, 4 cores). Below is a general picture of how it will look.

The steps before next lab are to finish the mold designs and do the CAMs for them. After that we can start machining and begin the injection molding process.

Team Tropical Escape!

After our chat with Joe and Dave last Wednesday, October 10th, the team made some changes to the mechanism and aesthetics of our yo-yo.

• Bitcoin logo side
  1. The Bitcoin logo will snap-on to the dome or will be over-molded. The manufacturing technique is still TBD. 

• Stock Market side  
  1. The stock market line will be be a snap-on, an overmold or will be painted on. Thus, we have deterred from the original idea of making the line a channel in which a liquid with gold glitter (like that in snow globes) will be inserted and will be able to move around freely within the channel.                                                                 

• Shaft for string gap
  1. As for the shaft originally designed, we will change to those manufactured in class because this knot and bolt design could cause some problems with the string while the yo-yo is spinning. Firstly, the string could get touched, and secondly, there might be too much friction and the yo-yo will not be able to go back up.
  2. Below is the old design and right below that one is the design of the 008 shaft, the one we'll be using.

• Thermoformed packaging
  We know have the design of our thermoformed part which will be used for the packing of our yo-yo.

• • Custom case molded over single mold

  • Single piece

Those are all the updates at the moment, but after the Yo-yo design review (Oct. 17th) we will be updating on any changes to this current design.

Go Team Tropical Escape!

Bonus Kermit meme: https://goo.gl/images/ft9vJc 

The images above are the first drafts of our chosen yo-yo theme: The Bitcoin Yo-Yo!

Details

• The yo-yo will be comprised of four parts, all injection molded
• Black snap fit on the Bitcoin logo side
• The color scheme will be black and gold
• Shape: The shape will be like that of a dome- sketch below

The Yo-Yos will be held with a casing made through thermoforming. The details and design for that component are still TBD.

Side 1: Bitcoin logo

The Bitcoin logo will be extruded and integrated as part of the dome, thus, it will be injection molded as one in the gold color. The non-extruded area will then be filled with a black snap fit. Finally, there will be a gold colored rim.

Side 2: Bitcoin stock

This side of the the yo-yo will have the tracing of the Bitcoin stock at the moment. The lines representing the stock will have a channel in which a liquid with gold glitter (like that in snow globes) will be inserted and will be able to move around freely within the channel.  

Example of glitter in a globe

As with the dome in side 1, this part will be injection molded and a black filling will be placed on top of this dome. Finally, a gold rim will be placed. 

That's it for now!

Go Team Tropical Escape!

This the first set of deliverables, and the second blog post, in which we share our team ideas for the yo-yo project through sketches.

Globe yo-yo

This globe yo-yo would have each of the faces have one side of the globe.

Cryptocurrency yo-yo

What better way to join the cryptocurrency movement than to build a Bitcoin yo-yo? On one side we would have the Bitcoin logo and on the other the stock market for Bitcoin.

MIT Beaver

We're looking to showcase school spirit with this yo-yo! On one side we would have our mascot's face and on the other the MIT logo.

Porgs from Star Wars

Who doesn't like Star Wars?!? We're looking to showcase Porgs by having its face on one side and its wings on the back side.

 Poker chip yo-yo

The poker chip yo-yo would have a series of extrusions each specific to a section (ex. spade symbol, middle of the poker chip, etc.). The details of the yo-yo, such as the spade symbol, would be inspired by MIT. 

Tropics

Inspired by the tropical islands in the Caribbean, this yo-yo would feature pineapples and palm trees.

Team Tropical Escape!

From left to right: Jeremy Noel, Susan Yoon, Ethan Perrin, Anna Yoon, Nina Fraticelli-Guzman, Mitchell Guillaume.

Welcome to the Team Tropical Escape 2.008 yo-yo blog!

We are a group of undergraduate mechanical engineering juniors and seniors at MIT who happen to all want to build a cryptocurrency themed

yo-yo! We come from a variety of backgrounds, experiences, and places, and though we all have different interests, what we do have in common

is our excitement for mechanical engineering and enthusiasm to build a great yo-yo. Please continue following this blog so you can see the

entire development of our cryptocurrency yo-yo. Who knows, maybe the entire production of this bitcoin inspired project could provide us with

enough money for a tropical escape!