Geometrical Tolerancing - Use of CAM Software - Assignment Example

Geometrical Tolerancing/ Use of CAM Software Course Tutor Date P 3.2: Describe how the Build-up of Tolerances on a Drawing Can Affect Assembly of Components Tolerance build-up in drawings is considered as a common problem among manufacturing industries across the world. The valuability of tolerance analysis in improving producibility has been observed in such areas as cost of precision, process selection and assembly of components as shown in the layout in figure 1 below. This discussion shall however focus on the effects of tolerances build-up on drawings and their respective effects on assembly of components. According to Raynor (2000) the technical aspect of tolerancing in drawings is to ensure that the majority of small and large parts can fit into the function that they are designed for when they are assembled together to form the final product. At the same time, disassembly and reassembly of the parts must be made possible inasmuch as tolerancing does not offer ideal situations for this to be carried out. This should be done under circumstances that are likely to save the technical team from time losses which may in turn affect the production and eventually the economies of scale. Figure 1: Effects of part tolerances (Chase & Greenwood, 1987). Given the basics above, build-up of tolerances in drawings affect the final assembly in several ways. Merkley (1998) shows that measurable deformation results from poor superimposing traditional tolerance analysis due to stacked block problem. Tolerance build-up in drawings is thus responsible of measurable deformation and poor forces such as kinematic shift during compilation or rather assembly of an item. Lack of compliance in tolerances bestowed on drawings is the major culprit for the magnitude of kinematic shift that is faced during assembly. An example given by Merkley in his authorship of ”Tolerance analysis of Compliant Assembly” is a case in which a press fit for cylinders requires mating parts which must be specified in order to ensure that the interference fit does not exceed the strength of the material. Tolerance build-up in drawings has also been blamed for misalignment of thin-shell parts that have been often observed as non-compliance components. Complying components however overcome this build-up as much as excessive variation through material properties such as warpage and shrinkage which add up to this issue. Design tolerances attribute to premature part failure due to undesirable aesthetics in nominal positions and vector loops. Using vector loops Merkley successfully indicated that tolerance can also result to rigid variations in the body of the final assembly. This observation is further replicated in statistical quantity analysis on completed assemblies which have defining factor in the interference between two parts which are supposed to mate in order to form a complete part. This contributes to even large interference and as indicated above rigidity beyond allowable limits which characterize variance and mean (Merkley, 1998). The vector loops method used in the analysis of the final assembly indicate that the assembly ends up with independent assembly points which consume a lot of time in the sense of manufacturing time. On the other hand, this sort of work ends up imposing an independent variation for each part since their manufacturing process is not mutually reliable on each other. For example in a final assembly that would require riveting as the final assembly methodology, there ends up being several point of riveting which make surface continuity an issue. This can lead to useless gaps which may affect the aesthetics of the final product contrary to the expectations of the designer. Random Bezier curves have been applied in defining such surface variance and geometric covariance between two parts that are expected to mate in the final assembly. Vector tolerance loop analysis procedure may also be used in performing a control to this issue in order to come up with a parametric approach towards reduced difficulties in the final assembly. P4.1: Write a CNC program on the attached programming sheet such that the fixing plate can be manufactured on a CNC machining centre. N. Pos. G Code X-Axis Y-Axis Z-Axis Feed Speed Tool No. / Offset Misc. Function 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 P4.2 Describe how CNC programming language can be adapted to aid the automatic assembly of components. Illustrate your answer using a suitable example. Several assembly lines have adopted CNC programming into their production as a means of meeting the ever rising customer requirements. CNC programming has also been utilized in coming up with various assemblies based on the advantages that arise from the quick customizability of the program in order to achieve a certain model of final product. Some of the advantages that have been pointed out include the ability to convert from metric to imperial system with ease based on the international standard approach that is incorporated with CNC programming. The flexibility that these programs pose to the manufacturing environment are tremendous in comparison to the traditional tape methods that were used in the early twentieth century. When it comes to interpolation, the manufacturer only needs to change a few dimensions in order to come up with a completely new product model. CNC programming is also easier in comparison with other existing programming languages as its codes resemble to English language statements (Khemani, 2009). CNC programming language is used to create flexible assembly systems due to various preceding product cycles. Flexibility requires the programming to allow for variety of product assembly owing to the small fine instruments that are confined within the machines high volume production. Successful execution of CNC programming ensures that high volume of production and reuse applications achieved in design. Although this majorly involves sensor automation, the fact remains that auxiliary tasks such as testing and ordering of pieces from the main production line has to be conducted by the assembly robots. CNC programming can be done on robots depending on the required levels of adaptability which may also varies from time to time. While flexible assembly is the main reason for programming and re-programming of CNC machines, the distinction among assembled products is easily achievable when the numbers of small pieces making up a complete part have a varied assembly within the programmer’s creativity (Halevi, 2003). Reasonable change is required in the main assembly systems from time to time as several years of operation have proven. Designing comprehensive systems which can be fine-tuned using programs as the trend has shown since the twentieth century. The change has further undergone growth to achieve its share in the robotic sector which is largely affiliated to automated production. Assembly operations are normally programmed by use of CNC codes which are predefined and still remain as a standard for most automation processes. Achieving versatility in the assembly line is entirely dependent on the innovativeness of design engineers and the complexity of the solution being offered by the end of the day. Assembly lines are therefore capable of producing complex creations depending on how deep the CNC programming language can be articulated by the designer (Nof, 1997). While predetermination of parts in assembly is an important approach to automation, changes can be determined at the assembly process especially in nonconforming cases. CNC machines are programmable to achieve this function in way of quality control so as to regulate the product before it lands in the hands of the client. Due to demand for customization in assemblies produced in CNC systems, the nature of the assembly line is dynamic owing to programmability. Achieving this kind of dynamism requires flexibility from the production line – a feature that needs new machine designs and hardware modifications. Instead of ordering for a new hardware to deal with this issue, programming has been found to be the ultimate solution to this problem. CNC programming has achieved this milestone even in heavy industries such as car production which need a change in manufacturing system from time to time. Programmable assembly has benefits that are easily observable from the way that these industries cope with the regular change in software instead of engaging in a cumbersome hardware change (Nof, 1997). Speed of assembly with regards to demand requirements, accuracy, power optimization and resource optimization can be easily analysed through CNC programming. Suiting assembly operations to the final dedicated production number in accordance to the prevailing demand levels is determined by parameters such as speed, value addition and types of tools available for operation. The types of tools available and speeds go hand in hand since material strength and tools type can be fed to the CNC systems through programming so as to reduce the down times. In a JIT environment, it is mandatory for the CNC systems to be calibrated in such a manner that allows for seamless production. Other integral variables may be observed from time to time as they arise so as to ensure production continuity (Nnaji, 1993). Dedication to speed variable comes in due to its effect on operations efficiency which is paramount to CNC programming. Special purpose assembly can be hastened in scenarios involving flexible programming for adjustment purposes and objective achievement. In comparison to normal assembly, CNC programming can be used to achieve desirable speeds at approximately fifteen parts per minute in examples if heavy industries and up to sixty parts per minute for the contrary. This however depends on the implemented assembly systems and the rate at which the batches are being produced. This might conflict with the speed if programming cannot be set to perform logging processes for daily analysis. Whenever the machine is on a downtime, this shall be considered as a speed reduction scheme – adjustable by observing the repeatability of such events. This shall help in conserving energy and maximizing resource usage which shall in turn reverse to process profitability (Halevi, 2003). Illustrating by way of example, heavy industries such as car production, require a dedicated but flexible system which allows for certain levels of tolerancing. Such tolerancing cannot be easily achieved under circumstances requiring manual adjustment each time it is noted. Therefore, in order to improve operations within such industries, CNC programmable machines pose as the best solution. Flexibility in tolerancing can be easily achieved by clever machines which are dedicated to certain levels of adjustment through the plethora tools available to it. Downtimes can be reduced through analysis of retrievable logs – this increases the efficiency as the recommendations of the analysis can be changed into programs allowing for activities to halt in such circumstances. Apart from fine-tuning of accurate systems, the car industries also seek to achieve a certain number of customised units and maintaining normal production to a given number. The alternation of these units is designed at the programming stage to avoid down times through manual changes. Similar units can be assembled by one CNC system without the need for new hardware. This aids in achieving an organisation’s business goals – a reason as to why cars are becoming cheaper by the day. P4.3 Explain how CAM software can be used to plan and monitor manufacturing activities. Your answer should make reference to sales forecasts, resource utilisation and the master schedule. Computer aided manufacturing (CAM) emanates directly from affiliated processes such as computer aided design. CAM by definition is the use of computer systems to carry out a series of planning exercises, management of the production line and operations control through computer interfacing or through indirect use of plant resources. Therefore, computer technology has assumed a number of procedures within the manufacturing environment such as process and production planning, quality control, management, machining and scheduling. 1. Resource Utilisation Tracking of resources in CAM systems is done by keying in all the information on the units available at all times into the integrated systems. The genealogical information and the current production rates are also important in resource planning as this is the only way the amount of resources remaining is likely to be planned for. Tracking resources through other information such as supplier, serial number, rework, measured data and related exceptions thus helps in providing the required information status to check the necessary tools, machines and devices required in order to execute the next level of production in a proper way. Scheduling resources can also be easily done when information is entered into the CAM system to aid in operations (Feng, 2000). In order to achieve advanced efficiency, CAM systems can be used to make resources available for a certain production activity before it commences. This gives the management an indicator to plan for human and equipment resources so as to avoid wastage. The resources are assigned with regard to the type of activity that succeeds the previous ones. Releasing of resources is eventually carried out in a timely manner so as to avoid time wastage as earlier stated. The CAM software offers material a plan for all the physical materials that are planned for a given task in order for the procurement teams to avail them in time. The rampant movement of inventories to work stations which eventually end up congesting the production cells is in turn controlled as materials can be maintained within the warehouses until they are really required (Feng, 2000). 2. Master Schedule The information that is required for master scheduling (build scheduling) rather known as manufacturing planning is documented within the CAM systems with the respective subtasks in cases where the manufacturing system is definite. Developing a master schedule is carried out by each of the departments that are part of manufacturing a certain item in conjunction with the planning department. The CAM systems not only make the departments accountable to their own resource usage but also aids in the planning and control. The master schedule must contain a list of products that are supposed to be made by a production company within a given period of time in accordance to the forecasts made and the deliverables. This information is fed to the CAM database with the units generally used to specify the deliveries being subjected to the processes that are required to come up with a complete item. The schedule is then made as the base for all the activities and sub-activities that are supposed to be accounted for by the manufacturing department (Feng, 2000). Individual components and subassemblies are planned according to the master schedule – the resulting parts are then keyed in the system in order to establish whether the set goals have been achieved. The master schedule aids in the scheduling of required resources as they head towards depletion. This information is obtainable from the integrated CAM system in terms of warning prompts or level determination through manual calculation. The CAM system must not reflect quantities that are beyond the producible levels of a manufacturing department. The master schedule provides the experimented or tested levels of production which are hereby referred to as the plant capacity. Capacity planning is then left for another department which has to set ion with the correct data for manpower and machine resources planning. By the end of the day, the master schedule is meant to achieve a company’s main objectives through process monitoring and end product control by using the highly efficient CAM systems which have been tested for this purpose (Mitsuishi, Ueda, & Kimura, 2008). Figure 2: Information required for master scheduling for CAM systems (Rao, 2004). 3. Sales Forecasts One major problem that has been facing the manufacturing sector is the ability to accurately forecast the projected sales. In order to come up with more clear sales forecasts information, CAM systems provide information on required output in order to facilitate for smooth operations management. Sales forecasts provide a better approach to operation planning due to the tentative manufacturing effort that they are provided with by this system. Keeping in mind that most companies maintain an integrated system may aid in the achievement of the results based on past experiences and emerging competition which must in turn be maintained within the database. The CAM system provides the top management with information for proper sales forecasting based on the units produced seasonally (Robinson, 1997). Ensuring seamless production in lean manufacturing for example, forecasting is the first input in the CAM software followed by the suggestions on how this forecast shall be met i.e. production and promotion of sales for a greater manufacturing vision. It is considered wasteful to forecast sales which the manufacturing team cannot achieve with the available resources. The received orders should therefore be approached painstakingly in order to avoid wasteful management of production time and other resources. CAM software has grouped the forecasting processes into four main areas of focus i.e. sales planning, production planning, stakeholder meetings and sales or operations planning meetings. The recommendations that are reached at in case of planning meetings and stakeholder concern are manifested into tangible data which is then translated into deliverables that are to be monitored within the CAM systems (Robinson, 1997). M2: Benefits of Computer Aided Production. As a production manager of a medium sized independent organisation, I have come up with some of the suggestions on the benefits of computer aided production. The justifications that I shall make regarding the use of computer aided production management purely focuses on the benefits of with respect to resource utilisation, real time production planning and management reporting and flexibility to meet changing customer demand. To begin with, the resource benefits associated with computer aided production include precision and standardisation of processes. This is due to fewer design errors that minimise inaccuracies during the drafting and documentation process. Data entry and transposition errors are also naturally eliminated in order to maintain a clean resource database which helps in materials follow up. Requisition placement also ensures that only materials required in fulfilling a certain forecast quantity are the only ones to be procured. This ensures high speed in procurement and availability of materials in time of need to so as to maximise human resource utilisation. More efficient space utilisation is likely due to reduction of asset inventories thus saving costs on raw materials too. Reduced movement in a CAM environment results to proper management of human resources and any costs associated with relocation. Introducing CAM systems to an organisational setup aid in the timely maintenance of the plants if a correct database is maintained for purposes of tool or part replacement after the lifecycle is complete – an automated approach to maintenance altogether. Real time production planning is dependent on the master schedule which is formulated prior to introduction of any part into the system. The master schedule is based on the sales forecast and the producible number of independent units or subassemblies. The master schedule also consists of the sub-processes that lead to one major objective that is worth achieving by the end of the day. Efficient process planning is achievable through use of CAM approach in process planning. The advantage is that the set of activities that are availed to the CAM system enable the selection of designs and tool selection including the associated fixtures. Human approach in planning process is reduced since thereby coming up with better executable plans which are virtually maintained in the systems and which are achieved through continuous improvement process. The integrated planning systems not only indicate the basic resources but also contain the in-depth information such as the expertise required, materials to be use, equipments and tools among other parameters. The use of computer aided production in planning offers a competitive approach to planning of production especially in environments that are automated. A summary of the benefits associated with use of computer aided production in planning on operations: i. Comprehensive planning of machine operations. ii. Pre-planned sequencing of operations based on the master schedule. iii. Automated selection and dedication of a machine or tool for production of a certain part or sub-assembly. iv. Integrated parameter calculation thereby achieving a JIT process in production. v. Preloaded setup requirements as part of the planning process. vi. Design of jigs and fixtures using preloaded data as part of production planning. vii. Auxiliary planning of material transfer and manual processes. Management reporting and CAM processes in meeting the customer demand entails partly on sales forecasting and automated report generation. In order to meet customer demand, sales forecasting is important part of production. The CAM systems are ardent in sales forecasting with respect to prior experience and information. The total periodical sales are maintained within the database for management assess in order to plan on how to meet the customer demands without straining the producible levels and overworking of machines and resources. The reports assessed on the database are also real time for continuous improvement processes facilitation. Instead of engaging human resources in reporting, the management can access the data directly and make upfront decisions in terms of bettering the output capacity or even informing the client on the possible delivery times of their orders. System and production audits are made possible through system management and accessibility using the historical data to manage any of the existing jobs. Reports that may be generated in a CAM virtual environment include; procurement reports, work in progress, work status, delivered number of pieces, pending work, material resource usage efficiency and accounts reports among others or as may be required by the management. References Chase, K. W., & Greenwood, W. H. (1987). Design Issues in Mechanical Tolerance Analysis. Provo, Utah: ADCATS. Feng, S. C. (2000). Manufacturing Planning and Execution Software Interfaces. Journal of Manufacturing Systems , 1-17. Halevi, G. (2003). Process and Operation Planning. Dordrecht: Kluwer Academic Publishers. Khemani, H. (2009, November 15). Problems Associated with the Conventional NC Machines, Advantages of the CNC Machines. Retrieved from Bright Hub Engineering: http://www.brighthubengineering.com/manufacturing-technology/55898-disadvantages- of-conventional-nc-machines-advantages-of-the-cnc-machines/ Merkley, K. G. (1998). Tmolerance analysis of compliant assemblies. Utah: Brigham Young University. Mitsuishi, M., Ueda, K., & Kimura, F. (2008). Manufacturing Systems and Technologies for the New Frontier: The 41st CIRP conference on manufacturing systems May 26-28, 2008, Tokyo, Japan. Tokyo: Springer. Nnaji, B. O. (1993). Theory of Automatic Robot Assembly and Programming. London: Springer. Nof, S. Y. (1997). Industrial Assembly. London: Springer. Rao, P. N. (2004). CAD/CAM: Principles and Applications. New Delhi: Tata McGraw-Hill Education. Raynor, E. (2000, March 16). Vehicle Integration/Tolerance Buildup Practices. Retrieved from NASA Engineering Network: http://www.nasa.gov/offices/oce/llis/0713.html Robinson, P. (1997). Sales and Operations Planning. Phil Robinson. Read More

 

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