PEMAMEK面板加工机的整体设备效率分析外文文献

Analysis on overall equipment effectiveness of a PEMAMEK panel processing machine R Sivakumar R Manivel Department of Mechanical Engineering M Kumarasamy College of Engineering Karur 639113 India a r t i c l ei n f o Article history Received 9 May 2019 Received in revised form 31 May 2019 Accepted 3 June 2019 Available online 22 July 2019 Keywords Panel processing machine PEMAMEK machine Overall equipment effectiveness Work study Time study a b s t r a c t The PEMAMEK is a panel processing machine after 6 years of usage the overall equipment effectiveness O E E of machine is gradually reduced to 50 To improve O E E of machine initial analysis is taken on availability performance and quality The company is expecting to produce 250 m sub panel for every 120 min but actual is 110 m To improve the O E E used the Work Study and Time study method Actual availability of machine is 45 which is increased to 70 by properly using manpower and reduc ing rework of welding availability time of the PEMAMEK has been improved effi ciently 2019 Elsevier Ltd All rights reserved Peer review under responsibility of the scientifi c committee of the International Conference on Recent Trends in Nanomaterials for Energy Environmental and Engineering Applications 1 Introduction PEMA assembly and welding station is an innovative solution for manufacturing tubular and conical work pieces The assembly line can befully integratedwith PEMA column and boom and PEMAcon trol systems therefore the operator is able to assemble and weld in the same station 1 It is a CO2gas welding in which 4 sub panels is welded in 2 passes It is also called fl at fi n welding It is used for weldingafi ninbetweenthetwo tubes usedforwaterpanels ripple type and plain type tubes It is fully controlled by the PLC 2 First the tube and fi n is fed through two pairs of roller shafts The roller shafts are attached with form rollers depending upon the diameter of the tube As the tubes and fi ns cross the second pair of roller shaft the fl ux cored wire fl ow takes place and the welding torch is adjusted for weld with appropriate adjustment of side 3 Flux cored wire is of 1 6 mm diameter Flux cored wire is fed at the top of the hopper it is heated at temperature ranges from 60 to 70 C The side pressing rollers and fi n bar supporting unit is used to avoid the air gap between the fi ns and tubes 4 As the tubes and fi ns passes across the welding torches after welding the fl ux are sucked by the vacuum valve and the tube enters the third and fourth pair of roller shafts The fl ux vacuum valve is operated pneumatically The conveyor draws out the fi nished fi ns and tubes Even though it is an eight torch welding machine in this only six torch are active and the remaining two torches are ideal The active torches in the machine system are A1 A2 B1 B2 C1 and C2 The ideal torches are D1 and D2 5 It is a CO2gas welding in which 4 sub panels are welded in 2 passes It is also called fl at fi n welding It is used for welding a fi n in between the two tubes used for water panels ripple type and plain type tubes It is fully controlled by the PLC First the tube and fi n is fed through two pairs of roller shaft The roller shafts are attached with form rollers depending upon the diameter of the tube 6 As the tubes and fi ns cross the second pair of roller shaft the fl ux cored wire fl ow takes place and the welding torch is adjusted for weld with appropriate adjustment of side Flux cored wire is of 1 6 mm diameter Flux cored wire is fed at the top of the hopper It is heated at temperature ranges from 60 to 70 degreesC the side pressing rollers and fi n bar supporting unit is used to avoid the air gap between the fi ns and tubes 7 The basic technique for GMAW is quite simple since the elec trode is fed automatically through the torch By contrast in gas tungsten arc welding the welder must handle a welding torch in one hand and a separate fi ller wire in the other and in shielded metal arc welding the operator must frequently chip off slag and change welding electrodes GMAW requires only that the operator guide the welding gun with proper position and orientation along the area being welded 8 Keeping a consistent contact tip to work distance the stickout distance is important because a long https doi org 10 1016 j matpr 2019 06 132 2214 7853 2019 Elsevier Ltd All rights reserved Peer review under responsibility of the scientifi c committee of the International Conference on Recent Trends in Nanomaterials for Energy Environmental and Engineering Applications Corresponding author E mail address sivamech637 R Sivakumar Materials Today Proceedings 21 2020 367 370 Contents lists available at ScienceDirect Materials Today Proceedings journal homepage stickout distance can cause the electrode to overheat and will also waste shielding gas Stickout distance varies for different GMAW weld processes and applications For short circuit transfer the stickout is generally 1 4 inch to 1 2 in for spray transfer the stick out is generally 1 2 inch The position of the end of the contact tip to the gas nozzle are related to the stickout distance and also varies with transfer type and application 9 The orientation of the gun is also important it should be held so as to bisect the angle between the workpieces That is at 45 degree for a fi llet weld and 90 degree for welding a fl at surface The travel angle or lead angle is the angle of the torch with respect to the direction of travel and it should generally remain approximately vertical However the desirable angle changes somewhat depending on the type of shielding gas used with pure inert gases the bottom of the torch is out often slightly in front of the upper section while the opposite is true when the welding atmosphere is carbon dioxide 10 The Fig 1 shows the GMAW Weld Area An installation produces outputs by transforming inputs An installation is a certain well chosen level of corporate assets where a transformation process takes place For instance in the welding line of a car factory steel input is transformed into car doors out put However steel is not the only input Labor and energy are other examples of an input productivity is defi ned as the actual output over the actual input e g number of cars per employee The effectiveness of the installation is the actual output over the reference output Productivity can be infl uenced not only by changing the effectiveness but also by altering the effi ciency this is the actual input over the reference input Tables 1 3 It is obvious that installation effectiveness is one of the impor tant factors that infl uence the production cost prize Other con tributing factors are raw materials utilities people and work methods Raw materials as input can be actual raw materials as well as semi manufactures altering the raw material to create a portion of but not the fi nal product from a previous installation but they have to be exterior to the own installation It should be clear that the maximization of installation effectiveness can t be the one and only goal The costs of maximizing effectiveness should not outweigh the benefi ts 2 Overall Equipment effectiveness OEE calculations The value of the OEE is a measure for the effectiveness of the installation in the available time for production The OEE is quantifi ed as OEE Valuable operating time Available production time The value of the OEE is an indication for the size of the technical losses as a whole The difference between the value of the OEE 0 or 100 indicates the share of technical losses in relation to the avail able production time 2 1 Planning factor Planning factor is a measure for the utilization of the installa tion in the theoretical production time and can be quantifi ed as follows Planning factor Available production time Theoretical production time The planning factor indicates the percentage of the total theo retical production time planned for or realized without express ing anything about the way the installation has been used in terms of effectiveness It is a measure for the extent of not utilizing the installation The available production time is the time in which normally production is planned realized The span of the available produc tion time can vary for the planned as well as the realized value It depends on the amount of planned and unplanned external losses that in turn depend on the market needs Seasonal fl uctua tions cannot always be overcome or prevented The theoretical production time is the maximum amount of time units hours days available in the observed period and is a constant in time A day always consists of 24 h of 60 min A week always consists of 7 days of 24 h A year always consists of 52 weeks With an increase of the planned unplanned external losses the value of the planning factor will inevitably decrease the theoretical production time is a constant value for a fi xed observed period 365 days Note that the planning factor as desig nation is not completely correct as it can be changed by an unplanned event for instance a lack of raw material 2 2 Total OEE Total OEE Valuable operating time Theoretical production time The total OEE is an indication of how effectively your machine has been used compared to how its use could theoretically be max imized The consequences of not working during weekends or hav ing two 8 hour shifts a day instead of three are refl ected in this factor Note that the total OEE can also be calculated as follows Total OEE OEE Planning factor 2 3 Effectiveness factors The previous diagram indicates that the availability is a mea sure for the down time losses The defi nition is as follows Fig 1 a Diagram of the GMAW Weld Area Table 1 Technical data Diameter of the tubes25 4 76 1 mm Tube wall thickness2 3 10 mm Width of the fi n bars10 110 mm Thickness of the fi n bars5 12 mm Panel length4000 25 000 mm Max width of panels2500 mm Tube materials Carbon steelSA192 SA210A1 SA210C Alloy steelSA209T1 SA213T11 Stainless steelSA213TP304H SA213TP321H SA213TP347H 368R Sivakumar R Manivel Materials Today Proceedings 21 2020 367 370 Availability Gross operating time Available production time When down time losses are zero the availability is 1 or 100 the gross operating time equals the available time for production In other words the installation throughput equals zero in no point of time during the available time for production At the end of the installation there is continuously an output and this without interruption 2 4 Performance The performance only concerns the gross operating time A property of the gross operating time is that the speed exceeds zero at any time There are no down time losses in the gross operational time The speed is not zero but this does not mean that the refer ence throughput is continuously achieved The performance factor is a measure for the speed losses and is quantifi ed as follows Performance Net operating time Gross operating time Speed losses can be calculated as P Number of parts produced Gross operating time Theoretical cycle time In order to quantify speed losses the theoretical cycle time has to be known This is not necessarily the design cycle time The the oretical cycle time depends on installation and product It is useful to pay attention to its value If it is falsely calculated parts of the losses are not visible and a better effectiveness is shown than is the case These false calculations come about by taking into account unavoidable losses These are for instance losses caused by cleaning activities Imposed from a legal hygienic point of view food industry Necessary to prevent contamination of products It can t be stressed enough that it is worthwhile to fi nd out the manner in which the value of theoretical cycle time comes about Usually the client becomes aware of the importance to correctly quantify the theoretical cycle time and the consequences if this is not done properly The theoretical cycle time can in principle be determined by a neutral instance It is necessary that production and maintenance be consulted 2 5 Quality factor During the net operational time no down time or speed losses occur In other words the output related to the net operational time is the product of the reference throughput units per time unit the number of time units of the net operational time How ever it is not certain that the total produced output is conform quality specifi cations To gain insight into this the quality factor is defi ned Quality factor Valuable operating time Net operating time Table 2 Availability Overall equipment effectiveness calculation No operator No Cranes and Equipment Breakdown Time are consider as zero DateTotal Availability Time NO Load TimePlanned Maintenance Time Loading TimeJob Setting and Change Over Time SUMOperating TimeAvailability 20 02 201912020010020208080 00 21 02 20191202509525257073 68 22 02 201912020010015158585 00 25 02 201912020307030304057 14 26 02 20191200012025259579 17 27 02 201912015010518188782 86 28 02 201912015010510109590 48 01 03 201912010011015159586 36 02 03 201912010011019199182 73 06 03 201912010011023238779 09 07 03 201912015010516168984 76 08 03 201912000120181810285 00 09 03 20191200012025259579 17 11 03 20191205011520209582 61 12 03 201912050115151510086 96 Table 3 Performance and OEE S NoPerformance Quality OEE A P QOEE 156 2588 890 4040 00 264 29100 000 4747 37 388 2493 330 7070 00 450 0075 000 2121 43 573 6885 710 5050 00 648 28100 000 4040 00 752 63100 000 4847 62 844 2188 100 3433 64 967 03100 000 5555 45 1071 26100 000 5656 36 1166 29100 000 5656 19 1252 9481 480 3736 67 1368 4292 310 5050 00 1489 47100 000 7473 91 1590 00100 000 7878 26 R Sivakumar R Manivel Materials Today Proceedings 21 2020 367 370369 Product specifi cation and product planning at what time what product should be produced are the starting points for quantifying quality losses When reasoning in this way there are only approved and rejected products Producing products that are not included in production planning means that the entire production is rejected resulting in a zero quality factor and OEE This is also the case if products are made according to the production plan but do not conform to product specifi cation This resembles a black and white situation and this is not always necessary or wanted A conscious decision for differentiation of quality losses should be made If opting for quality differentiation a decision has to be made concerning producing not conform product planning other products than required agreed In principle production should be considered not conform in this case But then there is still the question of what to do with product that is in the not conform category For example A product is produced that does not fi t the original specifi cation yet it is acceptable for a different lower cost product specifi cation So this lower spec lower cost product may be sold In this case the product is not a complete loss and some money can still be recuperated But there is still some loss since the machine and tools used to make this product are designed to deliver a different product The investment is probably higher in this case so you have to calculate some losses This should be addressed in the product specifi cation portion of the planning A decision has to be made when a product is completely rejected and subsequently the different quality levels must be determined with the accompanying product specifi cation When determining the number of quality levels one should reckon with what still can be traded in the internal or external market Per class hard criteria and norms will have to be defi ned possibly with the help of quality aspects Finally per class the total size of the loss should be quantifi ed For example when producing a product of a certain quality class 14 of the produced volume numbers are losses because they do not live up to the quality specifi cations of that class An overview table will have to be made per product indicating The different quality levels The quality specifi cation per level The factor per level to quantify the losses 2 6 Overall Equipment effectiveness OEE The three effectiveness factors offer a second way to quantify the OEE OEE Availability Performance Quality factor The individual value of the three effectiveness factors lies between 0 and 1 Studying each one of the effectiveness factors independently a satisfactory value would be 0 9 or 90 The value of the OEE is in this specifi c case 0 9 0 9 0 9 0 73 The size of the technical losses is in this case approximately 27 of the avail able time for production which is a serious amount This results mainly from the multiplication effect of the three factors Note that in many cases down time losses also cause speed and quality losses The reference throughput is not immediately achieved after a down time of the installation and the fi rst products do not neces sarily comply with quality specifi cations The use of effectiveness factors helps with prioritizing the size but does not indicate the fi nancial consequences that can differ per factor 3 Conclusion The Availability Performance rate and Quality rate were increased by 40 The labor hours can be effectively utilized which consequently increases the production rate to 20 Occurrence of breakdown could be reduced to an extent of one part O E E of PEMAMEK is increased considerably upto 70 if the suggestions were implemented By using the time study the machine idling time 20 min reduced which can be calculated useful during main tenance The reduced