Automated System for Track Finishing Process



8/6/2009Team Tie-MasterAutomated System for Track Finishing ProcessBrittany Ballardbrittanyballard@vandals.uidaho.eduCam Lesliecleslie@vandals.uidaho.eduSteve Maysteven.may@vandals.uidaho.eduSubmitted to:Mac’s Custom Tie-DownsExecutive SummaryThe University of Idaho senior design team Tie-Master, is currently developing a machine to perform the final manufacturing processes on tie-down tracks for Mac’s Custom Tie-Downs. Currently, a grain is applied to the surface, chips and cutting coolant removed from the track and the extruded ends de-burred, all by hand. This solution involves a significant amount of human labor, during which no other manufacturing processes can be preformed. By developing a machine to perform these operations, Mac’s will be able to significantly improve their productivity as well as minimize the amount of human interaction, and therefore cost required to produce each track. Research and testing have been conducted, and components used for surface finish, de-burring, and chip clearing have been selected.Table of ContentsCover PageiExecutive SummaryiiTable of ContentsiiiBackground 1Problem Definition2Concepts Considered3I. Surface Finish and De-burring 3II. Track Movement 4III. Chip Clearing 6IV. Dust Suppression 8Concept Selection8System Architecture 11Project Management15Future Work16Appendix A 17 Appendix B18Tables and FiguresFigure 1. VersaTie Track 1Figure 2. Specification Chart2Figure 3. Functional Breakdown for Creating the Grain3Figure 4. Functional Breakdown for Track Movement5Figure 5. Functional Breakdown for Debris Removal6Figure 6. T-slot Prototype7Figure 7. Brass Brush (Before and after testing)7Figure 8. Finishing Methods decision matrix9Figure 9. Scotch-Brite Pad Stack10Figure 10. Chip Clearing Decision Matrix10Table of Contents (Cont.)Tables and Figures (Cont.)Figure 11. Sketch of System11Figure 12. The feed system on a horizontal band saw13Figure 13. Concept render of a debris separator14Figure 14. Concept render of the modified T-slot cleaner15BackgroundMac’s Custom Tie-Downs is seeking to improve the finishing process used on the VersaTie products [Figure 1]. The VersaTie series consists of 4 different track profiles made from 6061-T6 aluminum. The extruded aluminum pieces arrive in the form of 24’ blanks, and then the blanks are machined using a CNC mill. Currently, the finishing technique involves clearing chips from the channel of the track with a screwdriver, de-burring edges and creating a grain using an abrasive pad, and removing any extra debris with compressed air. This process is labor intensive and expensive. When manually finishing a track using the current method, the result is an inconsistent finish on each track. Since these tracks are finished by hand, the individual performing this process may also be exposed to health hazards associated with long-term exposure to the debris produced from this process. Figure 1. VersaTie TrackBy creating a system that will complete the entire finishing process with minimal human interaction, efficiency of the process and overall track output will increase. Quality of the tracks will also increase by providing a consistent surface finish and removing all debris along the entire length of the track. Problem DefinitionUsing information gathered from the initial interview, we divided the overall finishing system into four main areas: Track Movement, De-burring of the Edges, Creating the Grain (Surface Finish), and Removing Debris. These areas were divided further into specific functions that we want the system to perform [See Appendix A]. To move the track, the system needs to be able feed the track automatically while controlling the movement and placement. There also should be a support in place to accept the finished tracks. The ends and holes created form the milling process will be de-burred. Surface finishing will involve making a grain that is parallel to the length of the track, as well as produce a smooth, uniform finish over the entire surface. Debris removal will include suppressing dust in the area, removing coolant before the surface finishing process, and clearing chips from the channel of the track. From these functions, we developed a list of specifications where “3” is a must, “2” is a want, and “1” is a wish.General RequirementsSpecific RequirementsAcceptable PerformanceRatingSurface FinishUniform FinishParallel, continuous grain3?Chips removedAll chips cleared from grooves (100%)3?Coolant removedAll coolant removed from surface3?Conform to 4 different profilesUniform finish for all profiles3?Logo Stamped on track1 logo/foot on inside of track1?Be able to remove surface defectsDefects blended into finished surface2?De-burring endsSharp edges eliminated3Minimize Size/SpaceMax stock length 24' max length3?Minimize footprint4'x4'x2'2?Minimize track travelAuto-feed of track into machine3??One pass of track3Human Interaction Minimal operator interaction4 controls maximum1and PowerMinimize power requirements110 V max1??One start/stop per track1?Minimize tool changeover timeLess than 1 min2?Minimize noiseLess than 60 dB2Time/ Life-CycleIncrease track output 5 min per track3?Finishing Media life-cycle25 tracks per unit2?Finishing Media life-cycle25 tracks per unit2Figure 2. Specification ChartConcepts ConsideredIn order to meet the specifications stated by our clients, and by using the functional breakdown, four major functions were researched and developed. For each function, multiple concepts were considered and tested. I. Surface Finish and De-burringFor surface finish, several general finishing techniques were considered. These concepts included tumble finishers, vibratory finishers, abrasive machining techniques (including linear and rotating media), abrasive blasting, and chemical abrasives. The functional breakdown for “Creating the Grain” outlines the major functions in Figure 3.Figure 3. Functional Breakdown for Creating the GrainTumble finishers work by essentially tumbling the parts to be finished together for a specified length of time. By forcing the parts to contact over and over again eventually the surfaces are finished by the other parts. Tumble finishers have the advantage of being able to finish a large batch of parts with minimum supervision. This concept was discarded because Mac’s Custom Tie-Downs is beginning to implement lean manufacturing principles including one piece flow. Also tumble finishers are unable to achieve a parallel continuous grain, which is one of our main design specifications. Vibratory finishers are similar to tumble finishers in the sense that a large batch is added to the machine however the finishing action is different. Instead of being finished by contact with other parts, the parts are finished through interaction with added media, usually small abrasive pyramids. These finishers operate at high frequencies and can finish parts quickly. Vibratory finishers are an improvement on tumble finishers in terms of cycle times and feature finish but suffer from the same batch sizing and non-uniform grain problems of the tumble finishers. This technique is also very costly. Abrasive blasting works by propelling a stream of abrasive material against the surface. These abrasive particles then finish the surface. Both wet and dry techniques exist. Although abrasive blasting is able to create the continuous parallel grain quickly, it also creates various safety and cleanliness issues and was quickly discarded. Abrasive machining works by using abrasive media to finish surface of the part by actuating the linear or rotating media with a machine. The part or the media is then moved all around the part to finish the surfaces to the desired amount. Abrasive machining is cheap, highly customizable, and is able to achieve whatever grain desired. This could also be adapted to de-burr ends using similar media. However, these techniques create dust hazards and the separate track profiles will require some modifications to the design, such as creating separate heads for each profile.II. Track MovementIn order to move the track through the machine and achieve the desired finish using our media, a technique to advance the tracks was needed. Several ideas were considered including using wheels, treads, clamps and guides. The functional breakdown for “Track Movement” outlines the major functions in Figure 4.Figure 4. Functional Breakdown for Track MovementWheels could be used to drag the track through the machine, and they could be implemented inside the inner track or on the outside surfaces or sides. The advantages of wheels are they are easily obtained, cheap and easily replaced. Some disadvantages include reduced surface contact because of the nature of a circle and need for multiple contact points. Another concept considered for track movement was the use of treads. Treads made out of rubber would have the advantages of being driven from a remote location and having more surface contact then the wheels. However, the complexity of the system increases dramatically. Clamps could be used with the tiger stop currently at the shop. These clamps could be driven at a constant rate to be determined by the user. The clamps could be pneumatically, hydraulically or mechanically driven. This would have the advantage of using technology already in use. The disadvantage is because the process would have to stop in order to use the tiger stop since it will be driving the drilling process.III. Chip ClearingIn order to clear the chips from the inner track several ideas were developed including a solid obstruction method, air-knife, and or brushes. Eventually it was decided that using several methods together was the best solution. The functional breakdown for “Debris Removal” outlines the major functions in Figure 5.Figure 5. Functional Breakdown for Debris RemovalSolid obstruction methods such a “T-slot cleaner” would dislodge stuck on chips from the manufacturing process [Figure 6]. This t-slot would be inserted in one end, travel the length of the track, conforming to the profile and push out the chips. The advantages of this are that it is durable, removes stuck on chips, and is cheap to implement. Disadvantages include debris back up and tight tolerances.Figure 6. T-slot PrototypeAir knives work by using compressed air through a nozzle or an array of nozzles to remove debris. There are many different configurations and styles for a wide variety of applications. Some advantages include no replacement parts or contact with track, and it is very cheap after initial investment. Disadvantages include noise, and inability to remove attached chips.Brushes can be created to conform to the inner profile of the track and would be rotated during the process to remove attached chips and spit debris out of track [Figure 7]. This method would have the advantages of removing attached chips and other debris. However, the bristles wear down over time and can melt if speeds are too high, as observed during preliminary testing. Other disadvantages are the tight tolerances and extra debris created by loose bristles. Figure 7. Brass brush (Before and after testing)IV. Dust SuppressionDust suppression is an area that is also covered in the functional breakdown in Figure 5. When the tracks are finished and chips cleared, dust generation is a significant problem as it is hazardous to workers. To mitigate this hazard, several ideas were generated: a vacuum concept, a funnel concept and the sealed case concept. First a vacuum concept was developed. The idea was to keep an on-site vacuum that runs while the machine is in operation and captures the dust before it can escape the machine and pollute the shop atmosphere. This vacuum could be local or could be located elsewhere throughout the premises.Another concept considered was having a funnel that all the dust and chips would collect in. This idea was eventually modified since much of the dust would be airborne and not collect below the machine.The final concept was a sealed Plexiglas case with a funnel and a vacuum to suppress the debris from the process. This prevents the dust from escaping, provides the vacuum with the need suction and allows the dust and chips collect in the bottom for ease of removal. The Plexiglas also allows the user to look inside and watch the process to ensure quality and accuracy.Concept SelectionIn order to choose from the large amount of ideas generated, testing was preformed and decision matrices were developed based on the tests. The first matrix was developed to analyze results from the finishing technique testing. Abrasive machining was chosen for testing due to its relatively cheap initial investment, versatility and uniform finishing properties. Four different products were tested, Scotch-Brite High Strength Finishing Discs, De-burring and Finishing Wheel, High- and Low- grit sponges, and the hand pads currently being used. We tested all of these media several times and the decision matrix below was generated using several categories. The categories chosen for testing were: Grain (how well the media created the uniform and parallel grain), Debris Remaining (how much debris the media left behind), De-burred Ends (how well media de-burred the ends), De-burred Edges (how well media de-burred the edges), Remove Surface Defects (could the media remove surface defects), and Cost. From our matrix it has been determined that the Scotch Brite High-Strength Discs are the solution recommended by our team [Figures 8, 9]. Figure 8. Finishing Methods decision matrixFigure 9. Scotch Brite pad stackFor chip clearing we tested three ideas and generated another chart to compare the strengths and weakness of the solid obstruction method, air knife and three types of brushes [Figure 10]. The categories analyzed include: radial/linear/other (line of actuation), profile fitting (whether or not it would conform to all profiles), price, modification required, and its chip removal ability.Figure 10. Chip clearing decision matrixFrom the chart in Figure 10, it was decided that a combination of a T-slot cleaner and Air would be used together to achieve the require chip removal. The T-slot cleaner will remove large chips that remained attached after milling, and then the air will follow to remove the remaining debris from the track.System ArchitectureThe conceptual design process was driven by a “chronological” view of what the track must experience before, during, and after our machine touches it [Figure 11]. A macroscopic perspective begins with a track (as large as 24ft) being fed into the machine by hand, from approximately 12ft away (at the center of the track). This implies that the feeding must be accomplished with minimal accuracy required by the human operator, allowing quicker changeover for the next track or operation. A simple funnel can guide the track into the machine effectively. More focus on this concept will occur during the detailed design phase. Figure 11. Sketch of System Once the track has been guided into the machine, it must be secured and fed further along automatically. This function implies two things: 1. An interference switch must be placed such that when the track is at a certain place, the machine turns on and grabs the track, and 2. Once the track is secured and in position by either a more precise guide, or an extension of the funnel, a drive wheel will roll it along the chosen gravity conveyor table until the end passes through. The interference switch will also cue the finishing wheel motor to start. Since the switch will be activated due to the track’s presence, another switch on the far side of the finishing wheel will continue to keep the machine operational until the end has passed all the way through the machine. An issue with clamping the track to the table as well as the finishing wheel is maintaining constant pressure. The clamps are easier since there should be no radial wear on the caster wheels from contact with the track. A simple pneumatic ram system can accomplish this task. The finishing wheel will have considerable wear; reducing the radius of the pad stack will cause uneven finishes. Since the media is homogeneous, constant pressure can be applied to obtain a continuous, parallel finish. The pneumatic system on a horizontal band saw uses the weight of the saw head assembly pressing down on a ram [Figure 12]. Figure 12. The feed system on a horizontal band saw. The speed of the head is controlled by a valve letting out fluid at a constant flow rate. The same concept will work with the finishing wheel. As the wheel wears down, a ram will change its linear position and move the system until the forces are in equilibrium. A digital readout (DRO) could display the force exerted by the wheel on the track for calibration purposes. A simple fish weight scale may accomplish this task. A similar setup will work on the clamping system, however if the caster wheels are driven by motors, the transmissions (if any) must be able to cope with changes in the wheels’ planar position. Before the track can be finished, all coolant and chips must be cleared from the top surface of the track. Ideally, the majority of the debris will also be cleared from the inside channel of the track. A nozzle will direct compressed air at the various surfaces of the track profile, angling away from the finishing wheel, towards the front of the machine. The debris will fall to a debris separator, isolating the chips from the coolant [Figure 13]. A vacuum system will do work via manifolds to collect the debris in separate containers. Figure 13. Concept render of the debris separator.After the track is finished, a solid obstruction will break any chips or burrs still attached to the track profile as a result from the milling process. A modified t-slot cleaner can accomplish this task, and will be able to rotate at low speeds to reduce the possibility of binding or building up of the chips [Figure 14]. Figure 14. Concept render of the modified t-slot cleaner. Project ManagementThe first semester of this project was dedicated to gaining knowledge to complete this project through research and testing. Project goals and specifications were established early in the design process. From the specifications, we began testing various components for each of the areas outlined. Testing for chip clearing, grain creation, and de-burring has been completed and components have been chosen. Areas of future focus include dust suppression, debris separation, and track movement. The next semester of this project will involve working on designing and testing a detailed track finishing system. We will use the results from testing to determine the final components, including the abrasive media that will be used for the surface finish. Once we have decided on the final components for the entire system we will fabricate a working machine. This machine will go through multiple tests and re-designs to ensure that the quality of the tracks matches the required standards . The final system will be delivered in ready-to-use condition by the December.Future PlansAlmost all of the major components of the machine have been thoroughly researched, tested, and brainstormed to final selection. The next step is to fabricate a rudimentary test frame to simulate the track being moved at a constant rate. This frame will be able to incorporate the major components simultaneously, and aid in design of the final machine case. Further tests of larger abrasive stacks will validate the previous work done with smaller stacks. Also, a better t-slot cleaner will be machined to test for its feasibility in the process (i.e. will it fit easily, wear out, do more harm than good, waste time, etc). Parts that meet the specifications will be ordered and incorporated into the test frame. Assembly instructions will be compiled to aid in maintenance once the final case has been designed. The project will have more focus on detailed design and fabrication rather than project learning and conceptual design. The “Project Plan” includes future deadlines and deliverables, as well as previous work completed [Appendix B]. Detailed Design will begin at the end of August and continue through the first week in October. Once the overall design has been completed, Fabrication will begin mid-October and continue until late November. The final product will be delivered to the client by early December. Since the fall is much more hectic than the summer, quicker decisions on designs (with proper research/documentation) will be the key to success. Individuals will have to make decisions on their respective components, but always must design for manufacturing, assembly, and integration. Appendix AFunctional BreakdownAppendix BProject Plan ................
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