To: / Meade Neal
From: / CleanKey designs
CC: / Jay McCormack
Date: / 4/28/2008
Re: / Final Design Report
Comments: / The purpose of this report is to transfer the intellectual property and research results obtained by the CleanKey Design Team to Key Technology. CleanKey believes that if their ideas are implemented with materials used in the industrial world, a sanitary gate can be produced. If additional information on the product is needed please do not hesitate to contact the members of the CleanKey group: Kate Boudreau at , Megan Lyons at , and Joe Osborn at .
CleanKey Design Team
Final Design Report
Sanitary Gate Design Project
Kate Boudreau, Megan Lyons, Joe Osborn
4/28/08
Executive Summary
CleanKey was able to solve part of the cable deflection problem seen at Expo by putting a counterweight on the cable/cylinder mechanism. Pictures and details on their final solution and how they arrived at this idea can be seen in the following report. In experimentation CleanKey was able to get perfect bowing action from the cable without the silicone on. When CleanKey installed the rubber, they were able to get good bowing action but then the rubber started to tear again. CleanKey decided that they did not have enough time left in the semester to order a commercial-made, grommet reinforced rubber, like the one Keyhas access to.CleanKey recommends that Key purchase a motor and an air cylinder. Then Key should experiment with commercially available products like carbon fiber rods instead of the cable used in this project. The flexible gate is technically retrofitable but may require a fair amount of installation time. After installation, CleanKey believes the flexible gate will save valuable shutdown time because it is more sanitary. This will result in a positive return on investment for the customer.
Contents
Executive Summary 3
Table of Figures 5
Background 6
Problem Definition 7
Concept Development 8
Product Description 13
Product Evaluation 15
Economic Analysis 16
Costs incurred in prototype development: 16
Estimated cost of the prototype: 16
Cost estimation for conceptual design: 17
Forecasted Cost of Production: 17
Testing 18
Conclusions and Recommendations 18
Appendices 20
Appendix A: Problem Specifications 20
Appendix B: Drawing Package 22
Appendix C: Equipment Assembly and Operation Instructions 24
Appendix D: DFMEA chart 26
Appendix E: Cost Analysis Breakdown/Bill of Materials 27
Table of Figures
Figure 1: Removable Film Layers Concept 8
Figure 2: Air Hockey Concept 9
Figure 3: Ice Gate Concept 9
Figure 4: Initial Flexible Gate Design 11
Figure 5: Silicone Baking Pan Prototype 11
Figure 6: Second prototype 12
Figure 7: Mechanism close-up 13
Figure 8: Open Flex Gate 13
Figure 9: Closed Flex Gate 13
Figure 10: Built Prototype with eccentric weight for shaking action. 14
Figure 11: Balancing weight for correct bowing action 14
Figure 12: Beginning of a rip. 18
Background
Key Technology currently has several directional gate designs. These gates change the direction of the flow of food products by dropping food onto other production lines. On a tour of ConAgra Foods Lamb Weston CleanKey learned that food particles build up on the underside of the shaker, as well as on top of the gate. This buildup is a result of the pneumatic slide gates that are currently used. Food product is accumulates on top of the gate and slides under the shaker. This is unsanitary and causes a health problem. The product accumulation also makes it difficult to open the gate for some of the production processes. This transfer of product makes the gate area difficult to clean the line and increases the shutdown time required for cleaning.
Often, the cleaning of this gate involves shutting the entire assembly line down.
Clients of Key Technology want to decrease the time that the processing line shuts down for cleaning. The entire processing line is shut down biweekly for a thorough cleaning. Most of the plants use foaming chlorinated cleansers and presser washers. As needed, the line is shut down for 5-10 minutes to remove build-up from the pneumatic gate. Often, a factory worker scrapes build-up off, which has to be done when the line is shut down so that scrapings of old food product don’t get processed with the food product, which is against AIB (American Institute of Bakers) and FDA standards
This problem affects Key Technology and the clients to whom they sell their gates, as well as the general public which consumes the food products. Processing companies using this gate need a gate that does not need to be shut down as long for cleaning, and consumers need products that are safe to eat.
Problem Definition
Key Technology has tried many designs for shaker bed gates. Key Technology makes a wide variety of gates, including the pneumatic sliding gate, a removable sliding gate, a swinging gate, a flip gate, and they have tried many different approved plastics for all of their gates. Key wants the CleanKey group to create an innovative solution for a gate that is more sanitary and easier to clean than their present designs.
The CleanKey group has taken two different approaches to making the gate more sanitary. Those methods are accumulation prevention-and ease of cleaning. There are a number of issues with cleaning and shutdown with current designs. CleanKey’s focus was to look at the pneumatic sliding gate and come up with design ideas to eliminate some of these problems.
In the design of a new gate, CleanKey had many things to consider. This gate needed to reduce cleaning time and prevent food particle build up. In order to be more sanitary than the previous design, CleanKey needed to eliminate places for food particles to go that would not be cleansed with a standard wash down. The gate must also comply with all AIB and FDA regulations for this type of product. This includes ensuring that the material is approved for food processing contact and that no foreign particles get into the food product flow. Ensuring the gate is sanitary also includes monitoring the amount of build-up that occurs and comparing it to the current slide gate.
Since the gate will be on a shaker bed that oscillates at 1.7 g’s, and be subjected to biweekly wash downs, the gate needs to be robust. It has to be able to last for five years because Key Technologies has a five year warranty on their shaker lines. The gate must not break during normal operating conditions or have adverse effects from the foaming chlorinated cleansers that are used regularly. It must be able to withstand a variety of food conditions, including hot (212°F), cold (-10°F), wet, and dry, foods. The new gate will need to be relatively easy to install: installation of the new gate should be comparable to the installation time of the current gate designs.
Finally, this design needs to be financially lucrative for the clients of Key Technology so that they will be willing to spend the money to replace current gates with CleanKey’s design.
This means the gate must be able to be retrofitted with the shaker bed design for the slide gate, so that Key can remove the current pneumatic gate and replace it with CleanKey’s design. The gate must also be functional. The full details on CleanKey’s definition of functional can be found in the problem specification in Appendix A.
Concept Development
During brainstorming CleanKey was especially proud of the following designs.
To reduce the amount of cleaning time, CleanKey thought it would be useful to be able to take off a layer of film on the gate. This way the buildup of food and batter could be easily removed. The removable film layers gate is shown in Figure 1 with the swinging gate, but it is also possible with other models. The problems with this model involved durability and plausibility. The flimsy film would not hold up in harsh wash-down conditions and it would be expensive to make custom designed film layers.
Another gate thought up during brainstorming is built like the surface of an air hockey table. It emits compressed air through holes in surface. This limits the contact between food product and the gate. A diagram of the concept is shown in Figure 2. The problem with this design was functionality and plausibility. CleanKey realized it would be very possible for food and food batter to get stuck in the holes on the gate. In terms of plausibility it would be expensive to pump pressurized air thru the gate’s surface.
The last concept was the ice gate and seen in Figure 3. If this concept were made, excess batter would be scraped off when gate opens. This design meets FDA regulations for shavings entering food. The factory would have to freeze gates in molds, and then replace when necessary. This would ultimately be a burden on the manufacturer.
Another idea CleanKey had was to experiment with different gate plastics. The reason CleanKey thought this would help was because during a factory visit, they noticed there was a large amount of French-fry batter sticking to the plastic. CleanKey also came up with the idea of a removable gate that could be snapped into place and easily removed for cleaning. This would cut down on showdown time, therefore saving money. When CleanKey compared these concepts they came up with the following decision matrix:
Concept / Effectiveness (30%) / Feasibility (40%) / Cost (30%) / Total score (out of 10)Ice Gate / 9 / 4 / 9 / 7
Diff. Plastic / 8 / 10 / 9 / 9.1
Air Hockey / 9 / 5 / 5 / 6.2
Removable film layers / 9 / 8 / 7 / 8
Removable Gate / 7 / 9 / 8 / 8.1
As one can see, the concepts that scored highest were to use a different plastic and to design a removable gate. When CleanKey presented these ideas to Key Technologies, they learned that Key has tried using a different plastic and they already make a removable gate.
Because their best ideas were taken away, CleanKey decided to go back to the drawing board. They knew they could come up with something better. In the following brainstorming session CleanKey decided to focus on getting rid of places for food to hide. To do that, CleanKey needed to design a gate with non-transient contact surfaces. This means they wanted to get rid of the surfaces that are in contact with food and then in contact with another surface, which encourages the growth and spread of bacteria.
CleanKey began looking at valve analogies and inspiration in nature. One of the analogies was capillary sphincters opening and closing. These sphincters are made out of a dynamic tissue. They constrict and expand when blood needs to be redirected. A way that man has mimicked this action already is in the production of Camelback water bottle valves. The nozzle is made of a flexible rubber and has a slit in it which opens when the sides are pinched together. To mimic this in a gate made out of flexible rubber CleanKey came up with the design seen in Figure 4.
This concept was first prototyped with a rubber baking pan and actuated by tongs. CleanKey decided to use a silicone baking pan because it is flexible, it fit their sizing needs and it is FDA approved. From this prototype CleanKey discovered that there were going to be problems with tearing. CleanKey believes the reasons for tearing were the connections to the base were too rigid and the rubber did not have a high enough modulus of elasticity. From this, CleanKey learned that a scissor action does not work well and that holes punched in the end of tears can stop the tear from propagating.
Based on lessons learned from the first prototype, CleanKey designed a second prototype made of two separate sheets of rubber as seen in Figure 6. There is a cable running along the lip of the rubber sheets; when the cable is compressed, the slit or mouth opens wide to let food through. This second prototype was difficult to keep open but it opened wide enough to let even large food particles through. From this, CleanKey learned that a pneumatic cylinder would be needed to keep the gate open and closed.
This second prototype was attached to a shaker bed at the corners. It is difficult to manipulate the rubber and prevent transfer of particles if is not attached on three sides. In order to have the material attached and still function, it needs to be elastic. Thin silicone is the best material that CleanKey found. They tried four different FDA approved rubbers. CleanKey learned that material thickness has a major effect on the elasticity of the rubber. CleanKey compiled all of these findings to make the final prototype which is discussed in the following section.
Product Description
The gate is composed out of a single sheet of silicone that is attached to the underside of the shaker bed. An open flex gate in a portion of a shaker bed can be seen in Figure 7. When the cable is compressed, it deflects downward, creating an opening for food product flow. Three of the sides are attached to the shaker bed, and one is wrapped around a cable. This design has no parts that move to the underside of the bed after contacting the food, meaning no particles are transferred and it is easy to clean and keep sanitary.