OSOCool

INJECTION MOLDING? | DEFINITIONS | PROJECT OVERVIEW | PROOF-OF-CONCEPT | DESIGN OVERVIEW | FABRICATION |

| TESTING AND RESULTS | MEET THE TEAM | ACKNOWLEDGEMENTS | PUZZLE SOLUTIONS |





WHAT IS INJECTION MOLDING?

Injection molding is a process by which heated plastic or resin is forced into a cavity of a mold. There are four main steps to the molding process, and they are as follows: clamping, injection, cooling, and ejection.

PRODUCT VIDEO

CLAMPING

During the clamping process, the mold halves are closed, and the mold cavity is created from the empty spaces between the two mold halves. During this time, molten resin is heated and store in the barrel of the injection molding machine.  Fig. 1a shows a simplified diagram of this process.

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Fig. 1a: Clamping process with mold halves flush and empty mold cavity.  Heated resin in barrel of injection molding machine. [1]

INJECTION

During the injection process, the molten resin is forced from the barrel into the mold, filling the mold cavity and creating the needed shape. Figure 1b shows this step in simplified form.

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Fig. 1b: Injection process with heated resin entering mold cavity. [1]

COOLING

The cooling process occurs after the injection of the heated resin in complete and lasts until the part is ejected from the mold. During this process, the molten resin solidifies. The mold halves pull apart at the end of this process. At the same time, more resin enters the barrel and begins the heating process. Figure 1c shows a simplified diagram of this step.

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Fig. 1c: End of the cooling process; the mold halves pull apart to allow for the final step. [1]

EJECTION

During the injection process, the part is pushed from the mold with the use of the ejector plate and the associated ejector pins. The mold then closes so the next cycle can begin.  A simplified diagram of this process is shown in Fig. 1d.

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Fig. 1d: Ejection process with the part being released from the mold and the mold cavity. [1]

*[1] “Aclaryn Plastics.” Aclaryn Plastics. N.p., n.d. Web. 27 Apr. 2015.

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DEFINITIONS

Here is a list of all of the terminology that will be used throughout the webpage to best understand the process of injection molding all together.

1. Hot Side (or A Side): Side of the mold where the molten plastic enters the mold.

2. M.U.D. Insert: Mold insert that is slid into the Master Unit Die (M.U.D.) frame. These inserts will house the aluminum inserts.

3. Guide Pin: Pins that assists the mold to close at the start of a new cycle. They prevent offset of the aluminum inserts when the mold is closed.

4. Aluminum Insert: Houses the mold cavity to be filled with plastic and is bolted into the M.U.D. insert.

5. Vent: Small, empty area that allows air to escape from the mold cavity during injection.

6. Runner: Guides molten resin, or plastic, to mold cavities.

7. Gate: Small entry point from runner to mold cavity. Allows plastic to fill mold cavity.15_10_resinwheel

8. Injection Point: Location where the molten resin is first injected into the hot side.

9. Turn Gate: Runner system cut into the sprue bushing that allows plastic to fill either two cavities or all four cavities.

10. Ejector Side (or B Side): Side of the mold where the ejector pins are housed.

11. Return Pins: Pins that assist in pushing the ejector plate back to the correct location before a new injection cycle.

12. Ejector Pins: Pins that push the cooled product from the mold cavities.

13. Core Pins: Pins that create the snap fit female holes in the product.

14. Ejector Plate: Plate that holds the ejector and return pins at the same height.

15. M.U.D. Frame: DME product that allows for molds to be easily interchanged. [2]

16. Retainer Plate: Plate that fastens to the ejector plate, holding the ejector pins in place.

17. Mold Fastener: Bolt and clip that tighten so the M.U.D. inserts say in the M.U.D. frame.

18. Sprue Bushing: Mold component that contains a passage which allows molten plastic to flow from the injection nozzle to the runner system.

*[2] DME Company. Website {http://www.dme.net/}.

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PROJECT OVERVIEW

Injection molding is a well-known manufacturing process that has a diverse spectrum of applications from creating plastic food-safe products to automotive bumpers and dashboards.  In fact, most products that are mass produced today and made of plastic are created through injection molding.  As the method is so commonplace with industry, it is imperative that engineering students leave college or university understanding the basics behind the process. Therein, OSOCool has been tasked with designing and fabricating a mold for the injection molding machine that was donated to the University of Nevada by a local injection molding company, ClickBond, Inc.  Figure 2 displays an injection molding machine similar to the one donated to the University.

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Fig. 2: A picture of an Arburg 270 all-rounder injection molding machine similar to the one that OSOCool will be using.

The mold that OSOCool designed and developed, dubbed OSOMoldular, will be used in a senior level lab class to teach engineering students about the injection molding process.  The mold will incorporate the advantages of industrial manufacturing – high repeatability and accuracy, a low cycle time, and low overhead costs – while also detailing common design considerations – the pressure constraints of the injection molding machine, the finishing requirements of a final product, and the ease of machinability of a mold. The final product that the mold outputs, referred to as OSOStellar, will be similar to common wooden 3D puzzles and resembles a star. A SolidWorks rendering of the final product is shown by Fig. 3.

15_10_Assembled PuzzleFig. 3: A SoldiWorks rendering of the final product that OSOCool’s mold, OSOMoldular, will create with the Nevada logo. This piece, OSOStellar, will be the focal output of the lab course currently being developed at the University of Nevada.

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PROOF-OF-CONCEPT

OVERVIEW

The team’s current design concept is to create a mold that can be used in conjunction with the injection molding machine located in the Palmer Engineering Machine Shop. The final design of the mold will create 12 identical pieces. These 12 pieces will snap-fit together in pairs to form six puzzle pieces which can ultimately be combined to create a star-shaped puzzle, aptly named OSOStellar. Figure 4a shows CAD drawing of a single one-twelfth piece, and Fig. 4b shows the mold designed for Proof of Concept fabrication.

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Fig. 4a: A CAD rendering of a single, one-twelfth puzzle piece produced as part of the Proof of Concept. The leftmost diagram shows innards of the piece where each circle represents either a pin or a pin hole for snap-fit; the middle diagram shows a side-view of the piece yielding the best view of the pins extruding from the piece; and the right most shows outer planes of the piece.

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Fig. 4b: A CAD rendering of the two-sided OSOMoldular mold produced as part of the Proof of Concept. The left side of the image displays the ejector side of the mold; whereas, the ride side displays the hot side with a test runner.


THE NEED FOR PROOF-OF-CONCEPT

The need to test all the fit constraints of the final part is heavily reliant on the cost of a mold die. Due to the expensive nature of the mold die and the limited resources faced by the team, the final mold must be completed with negligible error.

THE 3D PRINTED PARTS

In order to validate the CAD model of the final part, shown in Fig. 3, OSOCool  used a 3D printer to create a prototype. The prototype was for a full test OSOStellar puzzle, so 12 identical pieces were printed.  The constraints of the 3D printer do not allow for the testing of the pins nor the holes that would be used to snap-fit two single pieces together to form one of six puzzle pieces. To compensate for this deficiency, the team used an adhesive to merge two individual pieces into a single puzzle piece. The purpose of the 12 printed pieces was to determine whether or not the design could successfully realize an entire puzzle.

Depending on the fit of the puzzle as a whole, OSOCool had two options: if, the pieces fit together to form an entire puzzle, OSOCool would be able to continue on to their next Proof of Concept phase; if the pieces did not fit together to form an entire puzzle, the part would have to be re-designed to ensure proper fit. Fortunately, the physical model would assist in determining which design features of the part were deficient and which tolerances needed to be adjusted.  On the other hand if the pieces fit together with minimal finishing, the next stage of the proof of concept could be realized. Figures 5 and 6 display several different elements of the results from the 3D print Proof of Concept.

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Fig. 5: The completed 3D print of the pieces that create OSOStellar. Number’s 1 & 2 display two halves of a piece that would then be snap-fit together to create one-sixth of the puzzle. Number 3 displays a complete, fully-assembled 3D print of the OSOStellar puzzle.

The final results of the 3D prototype verified the CAD model as the puzzle fit together with minimal sanding shown by the red triangles in Fig. 6.

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Fig. 6: One-sixth of the final 3D print of the OSOStellar puzzle. The red triangles highlight the minimal finishing that the piece requires.

TEST MOLD AND RESIN CAST

The test mold allowed the team to determine the capabilities of the CNC machine equipment located in the Palmer Engineering Machine Shop at the University of Nevada.  It is important to know the limitations of the “in-house” CNC machinery, as the final mold will most likely be produced using this equipment. Unfortunately, if the test mold could not be successfully machined, OSOCool would have had to determine an alternate method of mold machining, most likely by contracting the machining to an outside source. In addition to testing the machining equipment and the machinist, the test mold would also be used to cast a test of the final part with a material such as plaster. By casting these test pieces, the final part could be validated in correlation to the mold, and the mold could also be validated as a viable design. Once the test mold has been validated, OSOCool would be able to start the preparations for machining the final mold, whether that be “in-house” or “out-of-house”. The machining process, resulting test mold, and casting of a single piece are illustrated in Fig. 7, Fig. 8, and Fig. 9, respectively.

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Fig. 7: The machining process, resulting test mold, and casting of a single piece. The aluminium block before being machined down is shown at the upper left of the image; the C.N.C. machine used is shown at the upper right of the image; and the resulting test mold cavity is shown at the bottom of the image.

 Fig. 8: The full resulting test mold that was used to create the test cast shown in Fig. 9.

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Fig. 9: The prototype, Aluminium mold was used to create a test cast of the piece as shown as a means by which to test the final aspects of the Proof of Concept.

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DESIGN OVERVIEW

The final design concept selected was a 3D puzzle that, once assembled, had the appearance of a star. This puzzle is created from six identical puzzle pieces, one of which is illustrate in Fig. 10. Due to the varying depths of material of a single puzzle piece, part shrinkage would not have been isometric, and the full assembly may have been impossible to achieve.

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Fig. 10: The proof-of-concept 3D printed piece emphasizing the divide line along the piece.

In order to circumvent this constraint, the team decided to divide a single puzzle piece in half along the axis, shown in Fig 10, and hollow out the part. By creating a shell, constant wall thickness would be maintained and allow for similar shrink values along the entire part. The CAD model would also allow the needed simulations that gathered fill time, cycle time, and gate location which would be used for mold design. The two halves would create a single puzzle piece using pins and holes that will allow two parts to snap together.

Once the part design was completed, the CAD model for the mold was created using SolidWorks and the Mold Tool package. This mold model included all the relevant engineering specifications such as gate location and size and cavity surface area. The model of the mold surface is illustrated in Fig. 11a and the model of the entire mold is detailed in Fig.11b.  Both figures included all of the mold components such as the runners, the gates, the pins, and their respective holes. The numbering in Fig. 11a and 11b corresponds to the following: (1) Hot side or A side, (2) M.U.D. insert, (3) Guide pins, (4) Aluminum insert, (5) Vents, (6) Runner, (7) Gate, (8) Injection point, (9) Turn gate, (10) Ejector side or B side, (11) Return pins, (12) Ejector pins, (13) Core pins, (14) M.U.D. frame, (15) Ejector plate, (16) Retainer plate, (17) Mold fasteners, and (18) Sprue bushing.

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Fig. 11a: A final SolidWorks rendering of OSOMoldular mold surface. Each element of the design is labeled both on the image and in further detail in the Definitions section of the webpage.

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Fig. 11b: A final SolidWorks rendering of OSOMoldular. Each element of the design is labeled both on the image and in further detail in the Definitions section of the webpage.

The proof of concept performed by the team included a 3D print of the 12 puzzle halves so that a full puzzle could be assembled and the part could be tolerance, the machining of a test mold using the model shown in Fig 9 to determine the “in-house” machining capabilities of the CNC machines, and a resin cast of a single puzzle half using the test mold to have a visual inspection of the final product created by the test mold. While all of these proof of concepts were highly successful, they did show that minimal re-design of the part would be needed before final manufacturing of the mold could occur. The team also re-designed the mold so that two of the four cavities would need to be finishing to remove the gate from the part; the other two cavities would be designed so that the gate would be sheared from the part during ejection, eliminating the need for finishing of the part. Figure 12 illustrates the re-designed and finalized puzzle half and the final mold design.  All relevant design characteristics are labeled.

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Fig. 12: Two views of the re-designed, finalized puzzle half that OSOMoldular will create. The left half shows the inside of the piece; whereas, the right half shows the outside appearance of a final puzzle piece.

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FABRICATION

OSOCool first purchased the Master Unit Die (M.U.D.) shown in Fig. 13. The M.U.D. is composed of six pieces as shown: the hot-side frame, the ejector-side frame, the hot-mold insert, the ejector-mold insert, the ejector plate, and the retainer plate. The hot-side frame will hold the hot-mold insert which then contains the hot-side aluminium insert. The same general concept applies to the ejector frame, the mold insert, and the aluminium insert. In the case of the ejector-side, the ejector-frame will house the ejector plate and the retainer plate.

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Fig. 13: The Master Unit Die (M.U.D.) that was used to supplement OSOMoldular.

PRELIMINARY STEPS AND PRE-MACHINING

In order for the mold inserts to house the aluminium inserts, pockets were machined into the mold inserts. Here, rectangular pockets shaped for the aluminium inserts were machined into the mold inserts, thereby creating a cavity so that the aluminium faces fit flush, or level, to the mold insert faces. These inserts are illustrated in Fig. 14.

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Fig. 14: An image of both sides of the tooling steel mold inserts that have been hollowed to meet the fit requirements of the aluminium inserts. OSOCool has established that this step is best addressed prior to mold machining as it yields the exact dimensions upon which the aluminium inserts are to best fit.

The team also purchased a 12″ x 12″ x 1-1/2″ block of aluminium to serve as material in which to machine the inserts. The block was separated into seven pieces: six sharing the dimensions 3-2/3″ x 5″ and one block of excess material with no relevant dimensions. The block of aluminium is illustrated in Fig. 15 after the divisions were made.  Two of the like-dimensioned blocks were then utilized to create the OSOMoldular inserts which will later fit into the aforementioned mold insert pockets, shown in Fig. 14.

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Fig. 15: On the left is the 12″ x 12″ aluminium block reassembled back to its appearance before it was cut. On the right is the block separated into seven smaller pieces. The six blocks bordering the bottom and the top of the image were all dimensioned at 3-8/12″ x 5″, and two blocks were then further to be machined to create the inserts for the mold.

THE FABRICATION OF THE ALUMINIUM INSERTS

The aluminium inserts designed for the mold pockets were created using the respective dimensioned aluminium blocks: one block for the hot-side of the mold and the other for the ejector-side. The fabrication process will herein be described with respects to each side of the inserts.

THE HOT-SIDE

Machining the hot-side insert, or the A-side, was the first step in completing OSOMoldular. As the hot-side of the insert contains the mold cavities into which the resin will be injected, the team began by finding the correct mill bit for the Computer Numerical Control (C.N.C.) machine located in the Machine Shop. Using the correct bit type and size is imperative for the success of any project where precision is held paramount.

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Fig. 16: A graphic representation of the ball end-mill (left) and the flat end-mill (right) were the mill bits that OSOCool decided would be most effective in outputting the hot-side of the mold.

For the aluminium block, a 1/8 in. ball end-mill was first used across the entire mold as to obtain the smooth slope necessary in creating the OSOStellar product. A 1/32″ flat end-mill was then used to smooth out the horizontal faces of the mold while avoiding creating unnecessary roughness for the mold cavities. Both the ball end-mill and the flat end-mill bits are shown in Fig. 16.

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Fig. 17: The SolidWorks part-files that were used to create the G-codes for the hot-side insert. The right side is the schematic used for the ball end-mill bit and, therefore, has an extra 1/12″ of material above the actual surface as not to destroy the face of the plate. The left side is the schematic used for the flat end-mill bit and has filled mold cavities.

This technique was accomplished by creating two unique sets of G-codes from different SolidWorks part-files: the first drawing followed the general shape of the insert but had an extra 1/12″ of material above the mold face so that the ball end-mill would not cause roughness across the top face of the insert; whereas, the second drawing portrays a flat plane across the true face of the insert filling the mold cavity, which prevents excess machining and potential damage to the cavity. Using the second drawing, the 1/32″ flat end-mill was then able to shears the face of the insert down to an acceptable roughness without interfering with the smooth and defined edges that the 1/8″ ball end-mill had created within the cavity. The SolidWorks drawings that were used to best create the mold are illustrated in Fig. 17, and the working hot-side insert is portrayed in Fig. 18.

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Fig. 18: The final hot-side insert created by the C.N.C. machine has both a flat face and a smooth, gradual slope along the walls of the cavity. This wanted effect was obtained by using multiple SolidWorks drawings each yielding their own G-code.

This method of machining was established in response to the mold-deficiencies created during the first trial of the C.N.C. machine. Previous to the final OSOMoldular hot-side insert, OSOCool attempted to machine the hot-side using the ball end-mill followed by the 1/32″ flat end-mill throughout the entire block using just the one finished SolidWorks model which portrayed the aesthetic appearance of the final mold. However, the mold yielded damaged corners and an undesirable slope across the cavity of the insert, as shown in Fig. 19.

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Fig. 19: The first attempt at machining the hot-side was unacceptable as it yielded an undesirable slope across the cavity of the insert and an unnecessary roughness across the face of the insert.

The undesirable slope across the inner cavity was created by the flat end-mill as it did not flatten the slopes but rather continuously etches into the sides of the cavity which has been smoothed by the ball end-mill; likewise, the unnecessary roughness across the flat surface of the mold was created by the ball end-mill bit as it rounded the flat surface, forging ridges into the face of the insert. The difference between the ball end-mill and the flat end-mill is illustrated in Fig. 16. By designed two codes from two difference SolidWorks models, OSOCool was able to overcome these minor setbacks and continue with production as scheduled.

THE EJECTOR-SIDE

Machining the ejector-side insert, or the B-side, was the next step in completing OSOMoldular. As the ejector-side houses the ejector pins which release the final OSOStellar part from the mold core extrusions, OSOCool approached the machining with the foreknowledge gained from the hot-side of the insert and began by identifying the correct mill bits to best manufacture the insert.

It was determined that OSOCool should first use a 1/2″ flat end-mill to remove the bulk of the material from the insert, as shown in Fig. 20. A 1/8″ ball end-mill was then used to create the extrusions, as shown in Fig. 21.

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Fig. 20The ejector-side being machined using the 1/2″ flat end-mill.

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Fig. 21: The ejector-side being machined using the 1/8″ ball end-mill.

In the pursuit of being thorough, OSOCool made an extra step in using a 1/32″ flat end-mill that unfortunately had no general impact on the piece each time it was run. The code ran the 1/32″ flat-end bit three times with little effect, which set the team back with respects to project completion time. As the team has had no prior experience machining to this level of accuracy, mistakes were bound to have been made – especially as the team was under the impression from the early stages of designing that all machining would be done by an outside source. The ½” flat end-mill was then used again to remove a portion of the material that the 1/32″ was unable to remove.

Finally, the 1/8″ flat end-mill was used to machine the ejector-side down to its final shape which is shown in Fig. 22. As the extrusions will be concealed by the final product, the finishing precision was not nearly as necessary when considering that the surface of the piece produced is not meant to be in contact with any outside source and should be enclosed during the final product assembly.

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Fig. 22: The final ejector-side of OSOMoldular is displayed. The purpose of having the layer of material protrude from the base of the ejector-side is to prevent warping and deformation; however, the precision of the respective extrusions is not necessary beyond ensuring that the resin is able to dry across the final injected piece without inducing any uneven shrinkage.

THE EJECTOR PLATE & PINS

As both the hot-side and the ejector-side of the aluminium inserts had been fully machined by the C.N.C. machine, OSOCool was then able to use the drill press to create all of the necessary holes in which the ejector pins may be placed.

Due to the level of accuracy needed for the pins, the team purchased them from an outside vendor. For the ejector plate, 25 pins were needed: 20 pins were ordered at a diameter of 3/32″ with an approximate head diameter of 7/32″ and 5 pins were ordered at a diameter of 5/32″ with an approximate head diameter of 9/32″ Here, the grinder was used to cut the pins down to their correct height. These pins are shown in Fig. 23.

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Fig. 23: The pins that were used for the ejector plate were made in two sizes. The 5 pins that were machined to a diameter of 5/32″ are shown above the 20 pins that were machined to a diameter of 3/32″.

Once the pin height had been reduced, the ejector plate was drilled 25 times in the respective locations, shown in Fig. 24, for the pins to fit.

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Fig. 24: Lauren Guevel drilling the final holes into the ejector plate.

Four additional holes were then drilled into the ejector plate so that it may be fastened to the retainer plate. Simultaneously, four holes were threaded into the retainer plate (or the plate that keeps the pins from releasing from the ejector plate) so that it may be fastened to the ejector plate. The retainer plate was then fastened to the ejector plate using four 1/4 -20 UNS bolts as illustrated in Fig. 25.

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Fig. 25: The ejector plate with the pins plugged into their respective slot is fastened to the retainer plate using the 1/4 -20 UNS bolts.

THE RUNNERS

After the aluminium inserts had been machined, the runners were added to both the hot and ejector inserts. The runners were created using the C.N.C. machine. The sprue runner, highlighted in blue in Fig. 26, was first machined using a ¼” ball end-mill. The part runners, highlighted in red in Fig. 26, was then machined using a 7/32″ ball end-mill. The results from this step are illustrated in Fig. 26.

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Fig. 26: The runners highlighted on the final inserts. The sprue runner is highlighted in blue; whereas, the part runners are highlighted in red.

THE GATES

Following the machining of the runners for the inserts, the gates were created. The gates are the holes that allow the resin to enter from the runner system into the mold. For this machining aspect, OSOCool used a 10° tapered conical drill-bit rotated to a 40° angle as to ensure that the gates would shear the runner correctly as prescribed by the design. The machining process for the gates is shown in Fig. 27.

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Fig. 27: The machining process for the gates. Here, Dillon Smith is using the 10° tapered conical drill-bit rotated at a 40° angle to create the gates.

THE VENTS

The vents were added to the hot-side aluminium insert after the gates and runners were added as vents should always be aligned across from the runners. Vents are an essential element in mold fabrication as they allow for resin to best fill a mold insert. More specifically, when the resin is injected into the closed mold cavity, the resin is able to better fill the entire cavity with the inclusion of vents as they allow air to escape, significantly reducing the pressure that the mold experiences. The vents are illustrated in the final SolidWorks rendering shown inFig. 28.

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Fig. 28: The final SolidWorks rendering of the finished product.

FINAL MACHINING STEPS

At this point in time, the only machining left to complete was to drill the holes through the ejector-side insert for the ejector pins to fit with an extremely low tolerance of error. Multiple attempts were made for this final manufacturing step as OSOCool was not prepared to handle such a high level of precision. The first attempt at drilling holes into the ejector-side was ultimately in vain as the holes were created just slightly too large. This fact rendered the entire ejector-side unusable, and the team needed to restart the entire machining process for the ejector-side of the aluminium insert. The damages created during the first attempt are illustrated in Fig. 29.

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Fig. 29: A picture of the damages created during the first attempt at drilling the holes into the ejector-side. The holes were created too big, so the piece was unusable.

This error was wholly manufacturer based. If the mold were to be created out-of-house, the reliability of the part with respects to tolerancing would naturally be guaranteed; therefore, it is strongly encouraged by OSOCool to any individual interested in repeating this project that they seek out a manufacturer for the fabrication process unless they are competent in regards to all of the machining steps listed or have sufficient time for the entire process.

The second attempt at drilling holes into the new ejector-side was accomplished but ultimately set the team back a week of machining. The final product is shown in Fig. 30.

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Fig. 30: The final OSOMoldular ejector-side with the correct holes and pins.

MOLD ASSEMBLY

Once all machining has been completed, the mold was finally ready to be assembled. The hot-side and the ejector-side with the pins and plates attached are each placed into the tooling steel mold inserts as shown in Fig. 31. The mold is now ready to be tested using the injection molding machining.

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Fig. 31: The final OSOMoldular product.

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TESTING AND RESULTS

Before the mold could be placed in the injection molding machine and tested, the team first needed to ensure that the two aluminum mold inserts would be able to fit together and create a flush parting surface (the surface where the two mold halves meet). A blueing die was spread on the surfaces of the ejector side that would have the most interference with the hot side of the mold. The mold halves where then pressed together and the points where the mold halves interfered were stained with the blueing die. If the interference points were not desired, the mold was filed down in these locations and the process was repeated. Figure 32 shows the blueing process.

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Fig. 32: Dillon Smith (left) testing mold fit with blueing paste and mold face (right) with blueing paste on high interference points.

The team completed three separate testing session with OSOMoldular. Figure 33 shows the mold when it was loaded into the Arburg injection molding machine.

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Fig. 33: OSOMoldular loaded into the Arburg injection molding machine with the use of the M.U.D. frame.

The first test was very successful for the team in that the part produced from the machine where the correct size and shape.  In regards to the mold, the first testing session was less than desirable in that only 50% of the mold could produce viable parts. A second issue with the mold was the runner for the self-shearing portion of the mold would not “stick” with the ejector side.  This “sticking” problem resulted in a pause after each cycle to remove the “stuck” parts from the hot mold cavities and is shown in Fig. 34.

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Fig. 34: Parts and runner “stuck” in self-shearing cavities (left) and successfully ejected non-shelf shearing parts (right).

To rectify this “sticking” problem, the team added runner pullers with the help of High Dessert Tool and Mold, a professional mold manufacturing company.  The pullers are simply rings cut into the inside surface of the ejector pin hole as shown in Fig. 35.

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Fig. 35: SolidWorks representation of runner pullers, undercuts that encourage runner to stay in the ejector side of the mold. Diagram shows the cut view of one runner ejector pin hole.

The addition of these cuts encourages the runner to stay with the ejector side of the mold until the ejector pins force the plastic out. While this addition prevented the runner from “sticking”, the part halves in the self-shearing cavities continued to have the same problem.  Cuts were added to the surface of the ejector extrusions to again encourage the parts to stay with the ejector side of the mold.  These cuts are shown in Fig. 36.

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Fig. 36: Cuts to the extrusions of the self-shearing ejector surface to encourage part halves to stay with ejector side.

The addition of these cuts allowed the mold to function at a 75% success rate, and the team was able to shoot approximately 800 part which yielded approximately 65 puzzles as shown in Fig. 37.

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Fig. 37: OSOStellar puzzle created from second successful testing session.

The cycle time for to shoot 3 out of the 4 cavities was a 1.15 second fill time and a 26.0 total cycle time.  The resin temperature at injection was 500°F with an injection pressure of approximately 59MPa, or 4.3 tonnes per sq. inch. These results and the other data collected from this day of testing were all within the desired ranges that OSOCool had previously determined.

The third test session included the addition of core pins to the mold so as to test the snap-fit fastening that team had previously designed.  The team also added additional cuts the the self-shearing core extrusions in the ejector side of the mold to increase the success rate of the mold to 100%.  The core pin addition and the cuts are documented in Fig. 38.

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Fig. 38: Core pin addition to OSOMoldular (top) and additional cuts to core extrusions (bottom).

The modifications the team made to the final mold functioned as desired. The snap-fit functioned as designed, and a whole puzzle could be created without the need for adhesive. The addition of the cuts to the mold ejector extrusions allowed all parts to eject without the “sticking” issues making the mold 100% functional. Figure 39 is a .gif that shows the successful ejection of all 4 parts and Fig. 40 shows the snap-fit and a full puzzle assembled with only snap-fit connections.

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Fig. 39: Successful ejection of parts from all 4 mold cavities.

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Fig. 40: Single snap-fit puzzle half (top left), single snap-fit puzzle piece (top right), and fully assembled snap-fit puzzle (bottom).

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MEET THE OSOCOOL TEAM

OSOCool is made up of five rad Engineering students at the University of Nevada. They have undertaken the task of designing a product and mold for the injection molding machine in the machine shop of Palmer Engineering.

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Fig. 32: OSOCool in front of the Arburg injection molding machine with final mold and assembled puzzles. From left to right, they are Dillon Smith, Kelsey Scalaro, Lauren Guevel, Sam Ashmore, and Andrew Mc Neilly.


SAM ASHMORE

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After completing her first Bachelor’s in Electrical Engineering in December of 2014, Sam Ashmore is on her way to completing her second degree in Mechanical Engineering at the University of Nevada by graduating this spring. Both degrees have been equal parts challenging and rewarding, and she is looking forward to having both complete.

She currently works at NV Energy and plans to continue doing so after graduation. Otherwise, she is also considering continuing her education with a graduate degree in Electrical Engineering and possibly an MBA. She will also be perusing her Professional Engineering licence in the near future.

She is the OSOCool Team Leader for the spring semester and a member and officer of Tau Beta Pi, the Engineering Honors Society. Other organizations include the Institute of Electrical and Electronic Engineers and the American Society of Mechanical Engineers. In her free time…she has no free time, but what engineer does?

 


LAUREN GUEVEL
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Lauren Guevel is graduating with her BS in Mechanical Engineering at the University of Nevada, Reno in 2015. She previously held an internship with LSP Products, a company that makes plumbing and injection molding products. After graduation she is working for Innovative Drive, a company that specializes in medical robotics in Reno, Nevada as well as the Bay Area.

In addition, she was the president and co-founder of Wolf Pack Racing, a student club which builds vehicles for the Formula SAE and Baja SAE challenges, and has successfully completed her duties as the OSOCool Team Leader for the fall 2014 semester. In her free time, she enjoys hiking, climbing, kayaking, and yoga.


ANDREW MC NEILLY

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Andrew Mc Neilly is a senior level student at the University of Nevada actively pursuing his Bachelors of Science in the field of Mechanical Engineering. He strives to work in themed entertainment like Walt Disney Imagineering where he hopes to create, design, and reimagine the attractions of tomorrow, today. He currently works as a seasonal employee for the Walt Disney Company in ride operations stationed primarily in the Magic Kingdom.

Future planning aside, he is also an incredibly active student in terms of on-campus extracurricular activities; currently, he is the president of the university chapter of the American Society of Mechanical Engineers, the vice president of the Engineering Leadership Counsel, the Differential Funds Committee Chairmen for the Mechanical Engineering department, the vice president of the Creative Development Association, the leader of his ImagiNations Competition team, and the New Member Initiation Instructor for Theta Tau, a professional engineering organization.

Otherwise, he is also a member of the American Society of Civil Engineering, the Society of Automotive Engineers, the Society of Women in Engineering, and the Blue Key Honor Society. As a dual citizen between the United States and the United Kingdom, Andrew enjoys exploring and traveling to new and far off destinations in his free time – whether that be in a kayak, hiking, or on a plane.


KELSEY SCALARO

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Kelsey Scalaro is a Mechanical Engineering senior at the University of Nevada. She hopes to pursue a career in aerospace and plans on continuing her education as a graduate student next fall. She participates in an internship with Aerojet during the summer months and currently works in the Mechanical Engineering department as a teacher’s assistant where she helps students understand and use the cad software SolidWorks and basic robotics.

In her free time, she enjoys hiking, rock climbing, and traveling. She loves being outside and is currently planning a 5 month backpacking trip of the Pacific Crest Trail.

She is also been an incredibly active student within student clubs and organizations like the Society of Women in Engineering, the American Society of Mechanical Engineers, ARLISS, AIAA, and the NEVADA Climbing Club.


DILLON SMITH

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Dillon Smith is a senior mechanical engineering student at the University of Nevada. He interned for LSP for a summer and currently works on university campus in the media and printing departments of the @One.

In his spare time, he likes to do anything and everything outdoors. He enjoys camping, backpacking, and hiking. In the summer, he likes to travel to Santa Cruz and surf and camp on the beach. Then in the winter, he can frequently be found skiing. When he’s not out and about, he likes to relax and play video games.

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ACKNOWLEDGEMENTS

OSOCool would like to express their sincerest thanks to the following people and companies:

DR. EMIL GEIGER, P.E.

In addition to being the team’s sponsor, Dr. Geiger offered the team valuable advice pertaining to injection molding and possible design directions.

CLICK BOND, INC.15_10_Click Bond

Click Bond, Inc. donated the injection molding machine to the University of Nevada, Reno. They also continued to provided support to OSOCool and the University in the form of their knowledgeable employees, who donated many hours to assist in the successful completion of this project. Those employees include, but are not limited to Dave Dinius, Jimmy Redmond, and Dave Foley.

 DAVE DINIUS

Dave was an extremely valuable source of knowledge in injection molding and mold design. Without his advice, the team would have struggled to learn standard injection molding design practices. The complexity of the final mold with a two cavity system would not have been possible without his advice and insistence that it would be “easy”.

TONY BERENDSEN

Tony was an important consultant in regards to machining processes and applications. Not only was he willing to help acquire scrap material for proof of concept prototypes, he instructed the team on the use of the CNC mill and various equipment. His experience and input was invaluable for the fabrication of the final mold.

DAVE FOLEY AND JIMMY REDMOND

Dave and Jimmy were extremely helpful and knowledgeable in the testing process. They were enthusiastic about the team’s project and sacrificed weekends to help the team finish the testing process in time for Innovation Day.

JEREMY SHELDON AND HIGH DESERT TOOL AND MOLD MANUFACTURING15_10_hdtmlogo

Jeremy is a professional mold maker who owns and operates High Desert Tool and Mold. He took time out of his very busy schedule to help the team make improvements to their final mold.

LSP PRODUCTS15_10_LSP logo

 LSP Products generously donated 25 pounds of resin to OSOCool.

PEACOCK COLORS, INC.15_10_PEACOCK

 Peacock Colors, Inc. generously donated 6 pounds of blue colorant to OSOCool.

 

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PUZZLE SOLUTIONS

If you are the proud owner of a puzzle and completely stumped (or just interested), solutions to OSOStellar are contained below in the link. OPEN AT YOUR OWN RISK.

Assembly Instructions for OSOStellar

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