Quick Change Knife Connection for New Holland Disc Mower: Design and Implementation, Study Guides, Projects, Research of Principles of Theater Design

Download Quick Change Knife Connection for New Holland Disc Mower: Design and Implementation and more Study Guides, Projects, Research Principles of Theater Design in PDF only on Docsity! 1 Phase 3 Report New Holland Quick Change Knife Team 9 December 7, 2001 Keith Abraham Dawn Cintavey Melissa Wanner Sponsors Melanie Harkcom Ed Priepke 2 Executive Summary New Holland, the sponsor for this senior design project, is a company based out of New Holland, Pennsylvania who designs, manufactures, and sells industrial farm equipment. The focus of this project is the disc mower, a machine in which a number of rotating discs with knives attached cut and lay crop on the ground. The objective is to create a quick release connection between the knife and the disc on New Holland’s disc mower. The knife is currently connected with a bolt and specialized nut. The changing procedure of the knives is lengthy and awkward and they may be changed as often as every day. Some of New Holland’s competitors already boast a quick- change knife, which increases the need for New Holland to design and implement such a connection. This project will not only benefit New Holland as a company but will also increase their customers’ satisfaction with the disc mower. The first step in generating an effective solution was identifying New Holland, Agricultural Equipment Dealers, and farmers as the main customers. They were kept in mind while generating and evaluating possible designs. Also, constraints, such as aspects of the current design that cannot be modified, were provided by New Holland. A list of customer wants was developed, with the top wants being to secure the knife, reduce the knife changing time, and make the design user-friendly. A great deal of time went into benchmarking and research. Many patents were reviewed including not only disc mowers, but more common lawn mowers as well. By talking to dealers, a quick-change knife on the market was found, which was a bent piece of metal bolted to the underside of a disc, which acts as a leaf spring to hold the knife in place. This spring plate design has many advantages, including being simple and making the knife able to be easily changed. Based on this spring plate on the market, a similar design was used to secure the knife on the New Holland disc. To change the knife a specialized tool, similar to a pry bar, is used to deflect the spring plate, which is bolted on the underside of the disc, enough to release the knife. The metal plate also has a nub welded onto it that fits in the hole in the knife to hold it steady. The next step is to incorporate our selected concept into a design that will fit with New Holland’s product. Three parts will need to be designed to create the spring plate. First, there is the plate. It will have the necessary bends to fit within the shell and bolt holes for mounting. The second part is the nub, which the blade will be secured to and fit upon. It will be welded to the plate and the extending nub will provide the surface for the knife to rotate on and securing fit into the shell. The third part is the disc insert, which the nub fits into. This part provides a pocket for the nub to set in, securing the blade. To validate the chosen design, each of the metrics and target values were satisfied. The cost of manufacturing the spring plate is $2.69. This cost includes the amount of material needed, heat treatments, and manufacturing processes. New Holland will be continuing this project by field testing the design for two seasons and hopefully putting the quick change connection into production in 2005. 5 As a solution to this problem, a spring plate was designed to secure the knife while decreasing the changing time. The design uses the spring properties of a steel alloy plate, which is attached underneath the disc, to hold the knife in place. To change the knife a specialized tool, similar to a pry bar, is used to deflect the spring plate enough to release the knife. The plan of this report will be to first discuss the design process, including our customers, design criteria, concept solutions, and evaluations. The chosen design concept will then be described in depth along with the manufacturing process and cost analysis. The verification testing will be outlined and explained, and finally a hand-off package will be included to facilitate New Holland with continuing this project in the future. 6 Method Team Management The team is based on mutual respect. It was decided at the start of the project to address all issues as they arose with the entire team present. Since the team is only three members, all meetings, decisions, and actions were taken with all members present. Available Resources A five hundred dollar account was allotted at the beginning of the project, funded by the University. The University also offered a machine shop, rapid prototyping, and computer-aided drafting tools. New Holland made available many resources including a machine shop, rapid prototype machine, finite element analysis, and testing facilities. Schedule A tentative schedule was created at the start of the project to ensure enough time to finish within the given constraints. Our final schedule (see Appendix B) shows how the project progressed through the three stages. Phase I, Synthesize Concept, consisted of concept generation and making a project plan. Customers and their wants were recognized; these were weighted and converted into metrics. Research lead to benchmarks and target values. The concepts generated were then graded based on these metrics and target values to find the best solutions. In Phase II, Design Concept, a solution was chosen. This solution went through the process of being designed, checking calculations of feasibility, and being built as a prototype. This solution was presented at the Phase II review shown on the schedule. However, phase II was extended past its original schedule so that a different design could be considered. The new design went through the same process as the first solution. It was then agreed upon to freeze the improved design to move to Phase III. Phase III, Prototype Concept, consisted of verifying that the solution met all the requirements of the problem. Three prototypes were built. A check was run through a series of tests to be sure the metrics were all satisfied. A hand off package was finalized to give to the sponsor. Customers The first step in generating an effective solution to this problem was to decide who the main customers were. It was important to keep them in mind at all times while generating and evaluating possible design concepts. New Holland is obviously the main customer, and as the manufacturers of the disc mower, they will be profiting from this improvement to the disc-knife connection. It is 7 also important to fulfill the company’s needs and wants because they invested the time, money, and effort into sponsoring this project. Melanie Harkcom, a design engineer in the Hay Tools division at New Holland, is the main contact and sponsor of the project. She is also the engineer that will be taking over the design process when it is passed on to New Holland. Ed Priepke is also greatly involved as an advisor because he has worked at New Holland for a number years and has also been involved with several University of Delaware of senior design projects. Farm equipment dealers are also customers. At Ag-Industrial, a Case-New Holland dealer, representatives agree that with the current connection, the knife is difficult to change. Triple H is a European dealer handling mainly Krone, Kevernland, Greenland, and other European brands. Jim Miller, an operator and mechanic at this facility, also felt that the current bolted connection was in need of improvement. These dealers are important customers because they perform maintenance on disc mowers and maintain a close working relationship with the company. The farmers and operators are also important customers, as they will be the ones using and buying the equipment. Buddy Dixon, who owns a farm in lower Delaware, expressed his concern with the time consuming current connection and looks forward to a quick release alternative. Constraints The following constraints were provided by New Holland and must be adhered to: • The knife must be able to rotate back behind the shell for protection if it hits rock, at least a 270º rotation. • Some discs rotate clockwise and some counter clockwise. The connection must be able to handle both. • After the blade is worn on one side, it is flipped over to use the other side. Ideally, there should be the same connection on each knife regardless of the orientation of the knife. • The new connection must work with the lifter, bolt guard, and disc. As little modification to each is desirable, and if modifications are necessary they should also be included in the scope of this problem (See Appendix C for New Holland disc assembly). • The cutting edge of the knife cannot be modified. • The knife height cannot be modified. • The lowest most point under the knife cannot go any lower, currently this is the bottom surface of the specialized nut. • Αll clearances under the knife must be considered. 10 Results Concept Selection All of the concepts generated were judged using the weighted metrics. Having the best results, Kevernland's spring plate concept was chosen. The spring plate is the simplest of all of the designs. It is only a single piece that bolts to the disc. There are no exposed areas of the spring plate above the disc needing protection from crop wear. And most importantly, minimal modifications to the disc would be necessary to incorporate this concept into the current design. Since Kevernland’s concept is going to be used, New Holland's legal department searched for a patent on their design. The results found were that there is no patent on their design. This legally allowed us to move forward with this concept without infringing on any patents. Prototype Design The next step is to incorporate our selected concept into a design that will fit with New Holland’s product. The shell was first examined in order to determine how this concept could be adapted. Immediate concerns surrounded the limited amount of space that there was to work with. Clearances between the shell, cutter bar, and rotating shaft are all extremely tight. To overcome this constraint, the design of the spring plate will have to fit close to the contour of the shell before bending into the proper position to secure the blade. To conform to the symmetry constraint, the parts will lie on the axis in which the knife mounting holes and shell center are on. Therefore, the part is usable for either clockwise or counterclockwise rotation of the shell. The mounting holes will need to be located near the center of the shell to allow for an adequate moment arm. There must be enough leverage available to impose the necessary deflection. Upon completion of visual inspection and idea generation, a preliminary shape was sketched for the designing process. Other design specifications include a pre-sprung load to secure the blade, a required deflection of .015m, and a material that will not yield under the stresses that will be applied to the part. Three parts will need to be designed to create the spring plate. First, there is the plate. It will have the necessary bends to fit within the shell and bolt holes for mounting. It will also have an open hole in the end that will secure the knife (See Appendix G-1). This hole is for welding in the second part. The second part is the nub, which the blade will be secured to and fit upon. It will be welded to the plate and the extending nub will provide the surface for the knife to rotate on and securing fit into the shell (See Appendix G-2). The third part is the disc insert, which the nub fits into. This part provides a pocket for the nub to set in, securing the blade (See Appendix G-3). Drawings of the assembly of the nub and spring plate and the entire assembly in the New Holland disc can be found in Appendices G-4 and G-5. 11 The preliminary design was created using AutoCAD. Using the complete current design, also in AutoCAD format, the created shape was designed within the existing shell and cutter bar. Fit could be insured by visual inspection of all the parts assembled together. Also, 10B38 spring steel was preliminarily chosen for the spring plate and the nub due to the need for a higher yield strength. The preliminary choice of material for the disc insert is 4140 steel alloy, since that is what the current insert is made from. Once the part was adjusted to properly fit, the design was sent to New Holland. New Holland has a Finite Element Analysis department, which creates a computer simulation of applied loads and the resulting stresses. The results from their analysis created a model that revealed the locations of the highest stress points (See Appendix I). It also revealed the highest produced stress of 3480MPa, which is based on an inputted applied load of 2670N. This was located in an extremely small area near the bolt holes. Since theses stress concentrations are so small, they will not have any significant effect in causing failure. The highest stress seen over the broadest area to be concerned with is 1293Mpa, located near at the bend near the bolt holes. These results were based on a .018m deflection and the 1293MPa stress seen is below the yield strength of 10B38 spring steel, which is 1482MPa. This shows that the spring plate will not yield under the deflection it will see during use. In order to have confidence in the FEA results, a simplified model of the design was created to perform calculations. The part was taken as a fixed-end cantilever beam with the load applied at the end. By modeling it as a beam, the bending stresses will be able to be found, but any torsion the actual part would see will be ignored. Any stress concentrations due to bends, corners, and holes will also be ignored. These simplifications will account for some of the difference between the calculated results and the FEA results. The resulting force required for the .015m deflection was found to be 2797N. The pre-sprung load was also found to be 957N, based on 0.0015m interference. The bending force required was calculated using the distance from the end of the part to the to the mounting holes, which is about .110m. The pre-sprung load force was calculated from the end of the part to the bend before the bolt holes, which is about .073m, since this is where the majority of this deflection will take place. The stress at the mounting holes was then calculated for both the maximum load and the pre-sprung load using the length from the end to the holes as the moment arm. These were found to be 1538MPa and 349MPa respectively, giving an applied stress of 594MPa. The calculated necessary bending force is relatively close in comparison to the FEA results and the calculated bending stresses are within 25% of the FEA results. These similar results give strong confidence in the choice of 10B38 spring steel for the plate and nub (See Appendix H for calculations). Material Selection Based on the results from the simplified stress analysis and FEA results, it is evident that that the choice of 10B38 spring steel has the properties needed for the applications of the plate and nub. This material, as stated before, has high yield strength and is also heat treatable and weldable. This is necessary so that after forming the metal into the shape of the plate, it can be heat-treated to restore its original high strength. It also must be 12 weldable so that the plate and nub can be welded together. After reviewing all the results and discussing the matter with New Holland, it was decided that 10B38 spring steel will indeed be the material of choice for the plate and nub since it meets the necessary strength requirements. The disc insert will be made from 4140 steel alloy, which is not quite as strong as the 10B38 spring steel since it will see lower forces and stresses than the other parts. The current insert design is also made from this material, which has proven acceptable to this application. Material properties of both alloy steels can be found in Appendix J. Manufacturing There will be two different sets of manufacturing processes used. One set will be for the making the prototypes, which will use less costly methods due to the few that will be produced. The other will be for actual productions, which will involves more costly mass production equipment. Producing the prototypes will involve using breaks to make the bends and curvature of the plate. Prior to bending, the blanks will be cut out using their 3-D laser router and will then be annealed to prevent breakage during cutting of the blank and forming. Once it has been formed, a hole for the nub, that will secure the blade, will be machined. The nub will be made using a lathe and will then be welded into place, but this procedure first requires preheating of the material to prevent any heat damage. The disc insert will also be made on the lathe and then welded to the shell using the same procedure as the nub. After assembly is complete, the parts will undergo a heat treatment to give the material the required strength properties. When producing this part in mass quantities, dies will be used to form the plate. Dies are a costly expense, but are justified by the quantities that will be produced. The nub and disc insert will be made using automated CNC lathes. As before, the material will first need to be annealed before forming and preheated before welding. The rest of the proceeding steps remain the same. Cost Analysis Another calculation that was completed in our design analysis was the additional cost of the spring plate per unit. First, the cost of manufacturing each one was computed and found to be $2.69. This cost includes the amount of material needed, heat treatments, and manufacturing processes. Next, the assembly cost was considered by including the cost of the two bolts, nuts, and washers, which are required to attach the spring plate to the disc. This cost came to a total of $0.30, bringing the total cost of the leaf spring assemble to $2.99. In order to calculate the additional cost of the spring plate, the current bolted connection cost had to be evaluated. Through talks with New Holland, this price was found to be $2.15 and includes the bolts, nuts, and protectors currently being used to attach the knife. Finally, the difference between the spring plate assembly cost and the current bolted 15 occurring will not be a problem with the current and future models of New Holland disc mowers. Therefore, the target value was met and no design improvements are needed. An aspect of the current design that was required to stay the same was that the knife is able to rotate around the bolted connection. This is done so that if a rock or other hard object strikes the knife while it is in operation, it is able to rotate underneath the disc for protection. The current design rotates approximately 300º, but in order for the knife to be completely underneath the disc a rotation of only 270º is needed, and therefore, this angle was set as the target value. The prototype allows for 270º of rotation, which protects the knife and eliminates the need for design improvements. The total cost of the design is a large concern for New Holland because it must be cost effective to the company. $2.50 is the target value that was set by New Holland, and our prototype spring plate design comes to a total cost of $2.69. This includes $0.70 for the plate, $0.64 for the nub, and $1.35 for the heat treatment as explained above (See Cost Analysis, Page 12). This number is $0.19 over the target value, but by continually refining the manufacturing processes and eventually mass producing the parts, it is very likely that the cost will be brought down to within the originally set limits. Another want that New Holland expressed was to make the spring plate design adaptable to their disc and cutter bar. The metric chosen to measure this want was the number of modifications to the disc assembly, and the target values was set to less than ten after conferring with the sponsors. The prototype design only needs to have three modifications made to the assembly for adaptation purposes. The first of these are the holes that need to be drilled into the disc where the spring plate attaches. The second modification is that the disc insert that is currently welded into the disc must be modified. This insert was also designed as part of this project because it needed to have a seat in it for the nub of the spring plate to fit into (See Appendix G-3). The last modification is that the lifter mechanism that is used to left crop must be modified because it currently attaches at the bolt, which also attached the knife. The disc insert that was designed corrects this problem on the disc itself because it was design with grooves in it for the lifter to screw in. However, the lifter itself must still be modified. Appendix K-4 identifies each of the design modifications. The discs on the New Holland disc mowers rotate both clockwise and counter clockwise. This is done so that when a disc wears from crop constantly rubbing on one side, its rotation direction can be reversed, exposing an unworn face of the disc. This prolongs the life of the discs on the mower. In order for the prototype design to accommodate for both rotation directions, the prototype must be perfectly symmetric, which is the target value for the degree of symmetry metric. As can be seen in Appendix K-5, the two spring plates that are assembled on a disc are perfectly symmetric, thus satisfying the target value and eliminating the need for design improvements. 16 Hand off Package Future Testing Team 9 strived to verify the validity of the design with the resources available. At this point in the design stage, it is not possible to test the spring plate on a full mower due to minor changes to a spacer. Therefore, New Holland will conduct further testing at their facilities. They also have to ability to test in real field conditions. One of the safety tests is a toughness test. The mower will be run through piles of wood and rocks. This test is to confirm that the spring plate can handle impact without breaking. It will also prove that the plate is not too brittle and will not crack under such circumstances. The design will also be put through an actual field test. This will verify that the spring plate is still functional after a pre-determined number of hours. It will also show to what extent the design collects crop and mud. The durability will be examined as well. Drawing Package The design consists of three new parts: the spring plate, the nub, and the disc insert. Detailed, dimensioned drawings of each part are included as Appendix G-1, 2, and 3, respectively. Appendix G-4 gives the assembly, with the nub weld into the spring plate. The entire system, including the disc, cutter bar, and spring plate are shown in Appendix G-5. Future Design Modifications Generally, the spring plate fits well into the rest of the system. To fit the curvature of the disc better, the top corners of the spring plate should be rounded. Also, some of the material used as a spacer between the disc assembly and cutter bar will be removed for a better fit. Time Line New Holland will conduct their field tests, likely beginning this coming May, for the next two years. The quick-change knife could be put into production as early as 2005. 17 References Many of the references are experts in the area of disc mowers and farm equipment in general. Melanie Harkcom- Design Engineer, New Holland Ed Priepke- Design Engineer, New Holland Levi- Field Engineer- New Holland Jim Miller- Dealer/Mechanic- Triple H Representative from Ag-Industrial Co.- Dealer Dr. Wilkins- Advisor, University of Delaware Reference Websites www.newholland.com www.howtouseaquickrelease.html www.avibank.com/pindet.html www.rickethockey.com/frames.html www.innovative-dsgn-sol.tripod.com www.usinventionpatenting.com Numerous patents and drawings were also provided by New Holland for reference research. 20 Appendix C- New Holland Disc Assembly Drawing 21 Appendix D- Wants, Metrics, and Target Values Wants/Constraints Secure Knife Reduce Changing Time User Friendly Fit/Clearances Knife Rotation Total Cost Design Adaptation Fits CW/ CCW Discs Metrics Pre Load (Pounds) Seconds No. Tools No. Parts Interference Angle of Rotation Dollars No. Changes to Current Design Degree of Symmetry Target Values 100 lbs 45 s 1 ≤ 5 None 270° $2.50 <10 Perfect 22 Appendix E- Kevernland Photograph. . 1. Kevernland Disc 2. Kevernland Clamp 3. Close-up of Kevernland Clamp Appendix G- Drawing package 1. Spring Plate Design v 25  26 2. The nub to be welded into the spring plate. 27 3. Disc insert to be welded into the New Holland Disc Appendix H- Calculations Force required for .015m deflection (using mild steel): -modeed as a straight, fixed-end cantilever beam -ignored torsion _ Fe _ _ be 3HT I — 12 I T= 4E14mm"4 y= 015mm E =206.8 GPa, b =.075mh =.004m Lengths were taken at the bend where most of the bending will most likely occur Solving for F using a 016m deflection: F =2797N = 629 Ibf Pre-Sprung Load: y= .0015m ,1= .073m fF read = S57N = 215IbF Stress Calculation: Ade oa i (957}(.073)(.002) Onin = —————————_ = 349 MPa 4£-10 2797 .110)(.002 o _! M M 72) = 1538 MPa mae 42-10 a, = 594 MPa -below 10B38 yield strength (1482 MPa} 30  31 Appendix I- Finite Element Analysis Analysis done with 600 lb load downward at the free end of the plate resulting in a displacement on .73” 32 Appendix J- Material Properties Material Properties 1. Steel Alloy 10B38 Yield Strength 1482 MPa 215 ksi Modulus of Elasticity 207 GPa 30 x 106 psi Density 7.83 g/cm3 .283 lb/in3 2. Steel Alloy 4140 Oil-quenched and tempered (@315°C) Yield Strength 1570 MPa 228 ksi Tensile Strength 1720 MPa 250 ksi Percent Elongation 11.5 11.5 Modulus of Elasticity 207 GPa 30 x 106 psi Density 7.85 g/cm3 0.283 lb/in3 Fracture Toughness 60 MPa√m 55 ksi√in Composition (wt%): 96.8 Fe (min), 0.40 C, 0.90 Cr, 0.20 Mo, 0.9 Mn