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Presentation Outline ( Suggested): 20 minutes Overview (Summary of Presentation)

EMIS 7305 Course Project – Presentation. Presentation Outline ( Suggested): 20 minutes Overview (Summary of Presentation) Pictures/Diagrams ( to increase understandability) Statement of Need and Problem Analysis/Study/Evaluation/Etc Results Summary and Conclusions (key points)

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Presentation Outline ( Suggested): 20 minutes Overview (Summary of Presentation)

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  1. EMIS 7305 Course Project – Presentation • Presentation Outline ( Suggested): 20 minutes • Overview (Summary of Presentation) • Pictures/Diagrams ( to increase understandability) • Statement of Need and Problem • Analysis/Study/Evaluation/Etc • Results • Summary and Conclusions (key points) • Grading Criteria • Understandability 10 • Follow-through 10 • Results 10 • 30

  2. Analysis of an NC Machining Process Project Presentation Blake Olson EMIS 7305

  3. Overview This presentation discusses the details of an analysis on the overall reliability of a manufacturing process called Numeric Controlled (NC) machining. • The NC machining process is comprised of three lower level systems. • NC Programming- Programmers write code (NC programs) that tells the machine how to cut a part • Setup and Operation – The machine operators setup the NC machines to run the NC programs • NC Milling Machines – The NC programs are run on 1 of 2 NC milling machines

  4. Overview (Cont.) NC Programmer #1 MACHINE OPERATOR #1 MAZAK NEXUS #1 COMPLETED PART Part Order NC Programmer #2 MACHINE OPERATOR #2 MAZAK NEXUS #2 NC Programmer #3 SHOP LEAD MAN

  5. Operational Need /Problem Statement • Operational Need: The Research and Development (R&D) department is at the core of innovation of any company. This is especially true within the world of defense contractors. Quick turnaround time between concept and physical product must be minimal in order to bring a new idea to market quickly. It is because of this need for quick response that the process of manufacturing R&D products must be robust and predictable with a high reliability. • Problem Statement: The reliability of the current NC process of my employer has not been determined. The reliability of needs to be assessed to understand if and where the weak links, if any, exist as well as to determine the overall robustness of the system.

  6. End Mill End Mill Metal Billet Metal Billet Background • NC machining is a manufacturing process that uses computer controlled machines to precisely cutout metal parts from raw stock using pre-written programs. • An NC milling machines use a spinning cutter, called an end mill, to remove material from the metal billet NC Milling Machine

  7. Background (Cont.) • NC machines can produce very complex parts that would otherwise be very time consuming or impossible to make by hand and have become a staple means for producing products in a wide array of manufacturing industries.

  8. Analysis Approach • The NC machining process can be broken into three basic parts which make up the system. • System #1: NC Programming • System #2: Machine Setup and Operation • System #3: NC Milling Machines • Evaluating the NC machining process in this way begins with an order for a new part coming to the NC department. After each of the three systems are stepped through, a completed part results. • To analyze the system the individual system reliabilities need to be determined first, then the entire system can be evaluated in a series configuration.

  9. Analysis Approach (Cont.) • The individual systems can be modeled as multiple elements in parallel. • The system consists of each of these three elements in a series configuration. System #1 System #2 System #3 NC Programmer #1 MACHINE OPERATOR #1 MAZAK NEXUS #1 COMPLETED PART Part Order NC Programmer #2 MACHINE OPERATOR #2 MAZAK NEXUS #2 NC Programmer #3 SHOP LEAD MAN

  10. Reliability Analysis System #1: NC Programming System #1 System #2 System #3 NC Programmer #1 MACHINE OPERATOR #1 MAZAK NEXUS #1 COMPLETED PART Part Order NC Programmer #2 MACHINE OPERATOR #2 MAZAK NEXUS #2 NC Programmer #3 SHOP LEAD MAN

  11. Reliability Analysis System #1: NC Programming • The first system is the NC programming stage. Here the order to create an NC program is taken and transformed into an NC program that the machines can read. • This process can be accomplished by any one of the three NC programmers and is programmed using Siemens NX CAM (Computer Aided Manufacturing) software • The two components created by the NC programmers are the NC programs and the machine setup sheets. • NC Program: Tells the NC machine the parameters for cutting a part • Speeds (Cutter RPM) • Cutter feed rate (inches per minute) • Cutter tool paths (go-to X,Y,Z coordinate locations) • Setup Sheets: Communicates setup information to the operator: • Tools to load into the machine • How to setup the part within the machine so that it will run correctly. • The weight of a successful program is in the hands of the NC department as they are the ones who direct and make the decisions on how a part will be made.

  12. Reliability Analysis System #1: NC Programming • For this analysis the reliability of each NC programmer needed to be evaluated. Because programming errors generally go down as programmers become more and more experienced, a model needed to be developed to show increasing reliability with time. • A modified Weibull distribution model was selected as a way of determining each programmer’s R(t). For this model I used a modified distribution that is equal to 1- Weibull with =0.4 and θ = 1.42

  13. Reliability Analysis System #1: NC Programming • Using a distribution equal to 1-Weibull results in a graph shown below. As the graph indicates, more years of experience results in a higher reliability. • The shape and scale parameters were estimated based on my observed trends within NC programming. Using =0.4 and θ = 1.42 yielded a curve that very much models skill increasing at an exponential rate with increasing years of experience. As the graph shows, experience plateaus and holds steady in the 94%-96% range after 20+ years of experience.  =0.4 λ= =0.7

  14. Reliability Analysis System #1: NC Programming • Calculating individual programmer reliabilities based on years of experience resulted in the following R(t) values: • These individual reliabilities for the three NC programmers are input into the system as shown below: R(t) =0.9589 NC Programmer #1 R(t) =0.8306 NC Programmer #2 NC Programmer #3 R(t) =0.6815

  15. Reliability Analysis System #1: NC Programming • Using the data calculated for each programmer, the parallel model is now used to calculate the reliability of the NC Programming system • Note: In order for this model to be valid, it is assumed that the NC programmer who programs the job has his work checked by the other two NC programmers. By checking each other’s work redundancy is established in the system and it can be effectively modeled as a parallel system.

  16. Reliability Analysis System #2: Machine Setup and Operation System #1 System #2 System #3 NC Programmer #1 MACHINE OPERATOR #1 MAZAK NEXUS #1 COMPLETED PART Part Order NC Programmer #2 MACHINE OPERATOR #2 MAZAK NEXUS #2 NC Programmer #3 SHOP LEAD MAN

  17. Reliability Analysis System #2: Machine Setup and Operation • The second system is the Machine Setup and Operation stage. Here the NC program and setup sheets that the NC programmers created are used to setup the machine. The NC program is then downloaded to the machine controller and run. • The two components performed by the operator are the machine setup and operation. • Machine Setup: The operator sets up the machine according the setup sheets made by the NC programmers. This task includes: • Setting up vise Location • Securing raw stock • Loading tools into the machine • Machine Operation: The operator monitors the machine as it runs the NC program and stops or pauses the job if anything doesn’t sound or look correct.

  18. Reliability Analysis System #2: Machine Setup and Operation • For this analysis the reliability of the Machining setup and Operation is defined to be the probability of correctly setting up and running an NC program on the machine. • Similar to the model developed for NC programming reliability, experience plays a key role in the reliability of the operator. In order to model this, a modified version of the Weibull distribution has again been used to show increasing reliability with increased years of experience. For this model I used a modified distribution that is equal to 1- Weibull with =0.6 and θ = 5

  19. Reliability Analysis System #2: Machine Setup and Operation • Using a distribution equal to 1-Weibull results in a graph shown below. As the graph indicates, more years of experience results in a higher reliability. • The shape and scale parameters were estimated based on my observed trends within NC programming. Using =0.2 and θ = 5 yielded a curve that very much models skill increasing at an exponential rate with increasing years of experience. λ=0.2 β=0.6

  20. Reliability Analysis System #2: Machine Setup and Operation • Calculating individual programmer reliabilities based on years of experience resulted in the following R(t) values: • These individual reliabilities for the three NC programmers are input into the system as shown below: R(t) =0.4385 Machine Operator #1 R(t) =0.5210 Machine Operator #2 SHOP LEAD MAN R(t) =0.7803

  21. Reliability Analysis System #2: Machine Setup and Operation • Using the data calculated for each programmer, the parallel model is now used to calculate the reliability of the NC Programming system • Note: In order for this model to be valid the operator setting up the machine must have his work checked by two separate people. First, a another pier operator checks his setup and then the Shop Lead Man must be called in to verify the setup before the job is given go-ahead to be run. By checking each other’s work redundancy is established in the system and it can be effectively modeled as a parallel system.

  22. Reliability Analysis System #3: NC Milling Machines System #1 System #2 System #3 NC Programmer #1 MACHINE OPERATOR #1 MAZAK NEXUS #1 COMPLETED PART Part Order NC Programmer #2 MACHINE OPERATOR #2 MAZAK NEXUS #2 NC Programmer #3 SHOP LEAD MAN

  23. Reliability Analysis System #3: NC Milling Machines • The third system is made up of the NC milling machines. There are two Mazak Nexus milling machines. Each are 3-axis machines with an effective machining area of 40” x 24”. • The machines go through scheduled Preventative Maintenance (PM) cycles every six months. The machine PM’s last about one week and during this time key components that are designed to wear out are replaced and the entire machine is re-trammed( a process of aligning the X,Y,and Z axis so that they are all perpendicular to each other). • The only other time the machines go down is when a non-standard component fails and must be replaced or if the machine crashes either due to programming error or operator error that needs to be fixed. MAZAK NEXUS #1 MAZAK NEXUS #2

  24. Reliability Analysis System #3: NC Milling Machines • For this analysis the reliability of each NC machine was determined by looking at the number of days the machine was actually running divided by the number of days that it was scheduled to be in service. • Modeling the NC machines as an r out of n parallel system with identical R(t) values yields an NC machining system reliability of 0.996.

  25. System Results System #1 System #2 System #3 NC Programmer #1 MACHINE OPERATOR #1 MAZAK NEXUS #1 COMPLETED PART Part Order NC Programmer #2 MACHINE OPERATOR #2 MAZAK NEXUS #2 NC Programmer #3 SHOP LEAD MAN

  26. System Results • The NC machining system can be modeled as three units in series. Each individual unit must function in order for the system to function. The results of each system reliability are shown. • Calculating the total system reliability yields System #3 System #1 System #2

  27. Summary • The NC Machining process is a robust system with R(t) = 93.5% • NC Programming R(t) = 0.998 • Setup and Operation R(t) = 0.941 • NC Milling Machines R(t) = 0.996 • Only about 6 out 100 parts will have to be scrapped or re-worked due to an error in the NC Machining process. Given that the company sets acceptable yield rates at around 85%, the NC processes sufficiently surpasses this benchmark. • Recommendations for improving the NC machining process primary lie in the Setup and Operation system. • Improving individual operator reliability: • Increase with further training • Will go up naturally with time as the operators get more years of experience.

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