Our video can be found at this link:
https://www.dropbox.com/s/b0tfaxj4t1xfb8u/Final%20Movie.mp4
Tuesday, December 10, 2013
Sunday, December 8, 2013
Blog Deliverable 5
1) Cost Analysis
For our final cost analysis, including a cost per yo-yo graph, see our spread sheet:
https://www.dropbox.com/s/veivodlpqhscq71/producton%20cost%20analysis.xlsx
2) Yo-Yo Design Reflection
Our yo-yo design was influenced by the 2.008 manufacturing equipment in terms of size of the yo-yo. We determined the outer diameter of our yo-yo body from the size of the molds we were given and the sizes of the inserts from the size of our yo-yo body. Also we were restrained by having to make our own shaft collars. We would have been able to put the nuts farther into the yo-yo otherwise.
We would change our design for mass production by adding a rotational alignment feature such as a notch on each piece. This would allow for the machine to align and snap fit our parts automatically. We would also redesign the "spider" insert to have a greater draft and thicker runners such that the part would pop out of the mold more easily (the runners are clipped off of the side of our spider prior to snap fitting). We will also try to minimize material per yo-yo and our waste fraction.
3) Recommendations for Class Improvements
| Ashby cost model | ||||
| AJH 10/21/13 | ||||
| Total run | 100000 | |||
| Desired rate | 1000 | /day | ||
| Run length | 100 | days | ||
| Machine throughput | 432 | parts/day | ||
| Machines needed | 3 | machines | ||
| Machine cost dedicated | 1500000 | total | ||
| 15 | $/part | |||
|
|
||||
| part mass | 0.05 | kg | ||
| mtl cost | 2 | $/kg | ||
| waste frac | 0.3 | |||
| C1 (matl) | 0.14 | $/part | ||
|
|
||||
| prod rate | 0.3 | parts/min | ||
| equip cost | 500,000 | $ | ||
| load factor | 0.9 | ("uptime") | ||
| lifetime | 10 | yr | ||
| 5256000 | min | |||
| C3 (equip) | 0.35 | $/part | ||
|
|
||||
| Ct | 10000 | $/tool | ||
| nt | 100000 | tool lifetime (parts) | ||
| n | 100000 | total run (parts) | ||
| C2 (tooling) | 0.1 | $/part | ||
| 10000 | total | |||
|
|
||||
| Coh | 50 | $/hr | ||
| prod rate | 60 | parts/hr | ||
| C4 (overhead) | 0.83 | $/part | ||
For our final cost analysis, including a cost per yo-yo graph, see our spread sheet:
https://www.dropbox.com/s/veivodlpqhscq71/producton%20cost%20analysis.xlsx
2) Yo-Yo Design Reflection
Our yo-yo design was influenced by the 2.008 manufacturing equipment in terms of size of the yo-yo. We determined the outer diameter of our yo-yo body from the size of the molds we were given and the sizes of the inserts from the size of our yo-yo body. Also we were restrained by having to make our own shaft collars. We would have been able to put the nuts farther into the yo-yo otherwise.
We would change our design for mass production by adding a rotational alignment feature such as a notch on each piece. This would allow for the machine to align and snap fit our parts automatically. We would also redesign the "spider" insert to have a greater draft and thicker runners such that the part would pop out of the mold more easily (the runners are clipped off of the side of our spider prior to snap fitting). We will also try to minimize material per yo-yo and our waste fraction.
3) Recommendations for Class Improvements
We believe that the reading quizzes, although helpful, were
often too specific in their questioning and a lot of the time spent preparing
for class was used trying to remember specific facts rather than the general or
conceptual lessons that meant to be taught.
On the topic of the topics covered in class we think that
the class did a very good job of covering almost every type of manufacturing
out there in at least some detail, no easy task. We also think, however, that
too much time was spent on the specific details of metal manufacturing and
cutting, especially the “Nerd Work” as Professor Culpepper called it. Most of
these processes are described in detail with a quick Google search and while
learning about the physics of it should definitely be a part of every
mechanical engineer’s training the time we spent on it was unnecessary. With
things such as 3D printing we just covered the basics of the process and how it
looked from the outside, yet knew how to run the process. This is how we think
that the metal cutting section of the course should run.
With regards to the problem sets we think that too many of
the problems seemed unnecessarily convoluted and that giving a problem that
might actually appear in the workplace may be more useful. A better way to
explain this might be that nearing the end of the semester many of the members
on our team realized that the best way to solve many of the problems on the
problem set was just to look through the notes and find the applicable
solution, which was invariably buried on some page, then plug and chug. Instead
of having these kinds of problems we suggest having a problem where the
students are made to think critically about the manufacturing line in question
and, even though the math may become a bit easier, ask them more specifically
about the Cost, Quality, Rate and Flexibility of the process being studied. We
feel like these would be more like the questions asked of a manufacturing
engineer rather than finding the cutting force of a specific machine, for
example.
In addition we would like to thank Dave & Dave for putting up with us and putting all of our teams on their backs.
Friday, December 6, 2013
Blog Deliverable 4
| Specifications Comparison Sheet | |||
| Specification | Planned Dimension | Measured Dimension | |
| String Groove | .25” +/- .005 | .058 +/- .01 | Didn't meet design specifications because we shortened the string gap after manufacturing |
| Base Inner Diameter | 2.25+0.0/-.005 | 2.245 +/- .002 | Part was easily injection molded and met specification |
| Snap Fit Part 1 (Triangles) Outer Diameter | 2.21''+.005/-0.0 | 2.26 +/- .001 | Part was easily injection molded and met specification |
| Snap Fit Part 2 (Spider) Outer Diameter | 2.21''+.005/-0.0 | 2.26 +/- .002 | After much tinkering with the injection molding, part met specification |
| Mass Base | 13.12 g+/-10% | 15.5 g +/- 8% | Part was outside of design mass, but consistent |
| Mass Snap Fit Part 1 (Triangles) | 9.71 g+/-10% | 7.5g +/- 4% | Part was outside of design mass, but consistent |
| Mass Snap Fit Part 2 (Spider) | 2.11 g+/-10% | 2.4 g +/- 10% | Part was outside of design mass, but consistent |
| Mass Thermoform Right | .348 g+/-10% | .340 g +/- 10% | We made multiple runs until we got the process to the point where we liked it. |
| Mass Thermoform Left | .3812 g+/-10% | .392 g +/- 10% | We made multiple runs until we got the process to the point where we liked it. |
| Mass Total | . 05078 kg+/-10% | .0541 kg +/- 10% | Since all of the parts were consistent, the whole was consistent. |
| Max RPM | .047m/s+/-10% | 3350 RPM | Roughly what we calculated! |
https://www.dropbox.com/sh/ata8l7eibfgm1lj/2GHzJ_hOIX
Monday, November 18, 2013
Blog #3
Blog Deliverable #3
1. Triangle Insert Parameter Process Sheet
The parameters for the triangle insert were improved through the trial and error of runs. We started with values close to what we deemed were plausible to produce a quality part. With each run, certain parameters were changed in order to create a better product. We came away with values of 8 seconds and 20 seconds for the holding time and cooling time, respectively. The screw feed stroke was set to 2 inches while the screw feed delay time was 0 seconds or not necessary. The injection speed profile from V12-V21 ranged from .2 to 3.5 with an injection pressure of 1101 PSI. The injection pressure was chosen in order to ensure full packing of the mold and to make sure no vacuum voids would form during the cooling period. The injection pressure also allows for the mold to be completely filled with plastic while not allowing flash along the outer edges of the part. The ejector counter was set at 2 and the ejector pin lengths were 5.647 and eight of them were used.
The parameter process sheet for the triangle insert:
Below is a stack of optimized triangle inserts.
2. Process Optimization
The process optimization labs allowed the Aperture Science team to work on fixing molds and production processes in order to produce a quality Yo-Yo. Through this work, several part and mold redesigns were found to be necessary to improve our product. We had to remachine the triangle spider because a defect was created in the mold from where a tool broke while machining the mold. However, no dimensions were changed from the previous mold. The triangle insert involved the most rework. A new cavity mold was machined for the triangle insert. The triangles were made higher and larger so the part would cool better and more uniformly. This also helped with reducing the void in the corners of the triangles on the underside. A ten degree draft angle was added to the triangle as well. This made the part easier to remove from the mold, reducing its chance to stick to the mold. The inside of the triangle mold was sanded as well, in order to eliminate machine lines. The string gap was also changed. Our original specification for the string gap was set at .25 inches. This was a rough estimate without any reference. When it came time to machine shafts for the body of the yo-yos, we realized this initial guess was far off from an acceptable dimension especially since our mold thickness was .25 inches. Our string gap was reduced to .075 inches. Much like the numbers for the triangle insert, the other parts were run and our group selected appropriate values for the speeds and pressures in order to create the best part we could. Through our groups testing, we came away with a completed optimized working yo-yo which spins around 3350 RPM.
Here is a picture of the new triangle insert mold:
Below are pictures of various parts of the Yo-Yo (body, triangle inserts, triangle spider):
Here is a picture of Kyle working hard optimizing the body of the Aperture Science Yo-Yo:
Below is a video of Ben playing with a completed Aperture Science Yo-Yo.
Below are the process parameter sheets for each part of the Aperture Science Yo-Yo. These include both thermoforming and injection molding parts. The triangle insert is located up above in part 1 of the deliverable.
Sunday, October 20, 2013
Blog Deliverable 2
Injected Molded Part Presentation
These are the core (left half) and cavity (right half) mold
of our ‘triangle insert’ piece. This piece is going to be snap fit into the
main body and will make up the main triangle shape of the Aperture Science
logo. The large triangles in the core mold on the left will be the triangles in
the logo while the small triangles on the cavity mold on the right are meant to
thin the part so that it cools more evenly. The small indents around the
outside of the cavity mold are to make runners for our ejector pins to push off
of.
To calculate our mold dimensions our first reference was the
inner diameter of the body piece. We needed to make sure this would be able to
snap fit in so we sized this piece’s outer diameter to be 0.01” larger than the
inner diameter of the body. Then we had to scale the mold to allow for
shrinkage. We measured the size of dimensions on a mold from a past year for a
part of similar volume and thickness. We found a part with a mold diameter of
2.4” and an average part diameter of around 2.36. After measuring a few other
dimensions on the mold and on the injection molded parts we determined that the
parts shrank by about 1.5%. We scaled our mold up by this amount accordingly
before creating the tool paths in Mastercam.
All of the work for this mold was done on the mill. The core
took about 1 hour and 20 minutes to machine including tool switching time and
the cavity took around 45 minutes. The longest process on the core mold was
machining the triangle holes. Each has a 1/16” radius in each corner which was
first drilled with a 1/16” end mill, then the pocket was machined with a 1/8”
end mill and remachined with the 1/16” end mill to clean up anything that had
been left.
Manufacturing Time
The machining time require to produce our yo-yos includes
the manufacturing time for the molds, each injection molded and thermoforming
piece in the final production run and time due to process optimization. We
assumed that the time to change tools is zero in the machining process. Also,
we assumed that the process optimization for thermoforming parts is less than
that of injection molding parts. The time to produce each mold was taken from
Mastercam’s toolpath times. The spider cavity mold will take 6 minutes while
the core will take 154 minutes for a total of 160 minutes or 2 hours and 40
minutes. The triangle insert cavity will take 46 minutes while the core will
take 105 minutes for a total of 151 minutes or 2 hours and 31 minutes. The body
cavity mold will take 4 minutes while the core will take 8 minutes for a total
of 12 minutes.
To find
the cycle time for each injection molded piece, we used the typical cycle of
injection molding from lecture with incorporating each pieces individual
estimated cooling time. In order for a piece to be cool enough to inject, the
thickest part of the piece must be at a temperature where there is no viscous
rubbery flow of material and the polypropylene exhibits plastic material
behavior. We used AutoDesk Simulation Mold Flow Advisor to estimate the cooling
time of each part made for our yo-yo assembly. The
simulation provided us with cooling times that we added into our cycle time for
each piece. The body piece will take 45 seconds, the spider 16 seconds, while
the triangle insert will take 40 seconds to produce one of. Multiplying these
out to produce 50 yo-yos, 100 of each component will need to be produced.
Assuming no time lost to change tools, the production run will take 75 minutes,
27 minutes, and 67 minutes respectively for the pieces above. For the
thermoforming Portal insert, we expect a time to complete one piece in the
range of 15-60 seconds. For 100 of them, the estimated time is between 25-100
minutes.
The
total time estimated to complete the yo-yos is the mold fabrication, total
production run for the injection molded pieces plus the estimated time for
thermoforming and the time to assemble the yo-yos. Our total time estimated is between 11 hours 7
minutes to 12 hours 22 minutes depending on thermoforming time.
Process
|
Time to Manufacture
|
Final Production Run (time x 100) Makes 50
yo-yos
|
Process Optimization
|
Body
Mold Fabrication
|
12 minutes
|
||
Spider Mold Fabrication (cavity + core)
|
160 minutes
|
||
Triangle Insert Mold Fabrication (core +
cavity)
|
151 minutes
|
||
Portal Insert Thermoforming Mold
|
|||
Body Injection Molding
|
45 seconds
|
75 minutes
|
60 Minutes
|
Spider Injection Molding
|
16 seconds
|
27 minutes
|
60 Minutes
|
Triangle Insert Molding
|
40 seconds
|
67 Minutes
|
60 Minutes
|
Portal Insert Thermoforming
|
25-100 minutes
|
30 Minutes
|
|
Assembly
|
180 seconds
|
150 minutes
|
120 Minutes
|
Total Time (Mold manufacturing time + Final Production
Run+Assembly)
|
642 minutes
|
Manufactured Molds
Triangle Insert
Triangle Insert Mold
Triangle Insert Core Mold Being Machined
Potential rework machining for the triangle insert mold may be needed in order to get the snap fit to work correctly between pieces.
Below is a movie of the mold being machined
Body
Body Cavity Mold, Body Core Mold, Body Molds
Potential rework machining may be needed on the body core mold in order to get the snap fit to work between pieces. The size of the core diameter may need to be smaller due to shrinking of other pieces.
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