Improving Time Efficiency Using CNC Equipments In Wood .

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International Journal of Current Engineering and TechnologyISSN 2277 - 4106 2013 INPRESSCO. All Rights Reserved.Available at http://inpressco.com/category/ijcetResearch ArticleImproving Time Efficiency using CNC Equipments in Wood Processing IndustryHektor Thomaa, Erald Kolaa, Leonidha Perib, Entela Lato a, Muhamet YmericaDepartment of Wood Industry, Faculty of Forestry Sciences, 1029 Tirana, AlbaniabDepartment of Forestry, Faculty of Forestry Sciences, 1029 Tirana, AlbaniacFaculty of Applied Sciences, University of Prishtina, 70000 Ferizaj, KosovaAccepted 12 June 2013, Available online 17June 2013, Vol.3, No.2 (June 2013)AbstractThe use of CNC machines is changing radically the furniture making industry. Time consuming techniques in theproduction process, such as cutting curves, became much easier. CNC machines are 'programmed' to perform severalsteps at a time, cutting down on the time required for human action. With the advent of wood based panel products suchas particle board and medium density fiberboard (MDF), CNC equipment has now been widely a dopted for theproduction of components for many types of furniture. This study is focused in showing the advantages of the use ofCNC equipments in furniture making industry in Albania. We have considered the processing of wood based panels forproducing furniture parts using CNC machines in comparison to the traditional methods used up -to-now in a woodprocessing company. The efficiency gains in production of “side elements” for wardrobes sized 2400 x 580 x 18 mm aremeasured in terms of production time, raw material quantity used and quality of the product and compared to the abovementioned elements resulting from the traditional production techniques. Production of “side elements” for wardrobes isdone in a drilling CNC machine type “Biesse Rover 20”, which is one of the CNC equipment used a wood processingcompany for production of furniture parts. Saving in production time and raw material used results in decreasing costsper unit of production and the better quality of the parts gives the company a potential higher margin of profit per unit.Keywords: CNC equipments, furniture parts, time efficiency, drilling process1. Introduction1As in every field of industry, even in the furnituremanufacturing industry, efficiency is a key factor whichaffects the performance of the firm activity. As such, it isaimed to increase the efficiency of using the time of laborand raw materials. By “using of time of work in themanufacturing process” is intended to achieve that stage ofthe technological process where the coefficient ofutilization of machinery to be in such values so themachinery doesn’t have idle time during working shiftsand by “utilization of working time during the assemblingprocess of finished wooden objects” is intendedimplementation of all necessary operations in such a wayas to eliminate as many "minor works" of assembling fromthe assembling workforce. By “exploitation of rawmaterials” is intended reducing as much waste as possible(J.T. Black and S.L. Hunter, 2003).The traditional production process and assembling ofbedrooms include several processes as cutting, edgebanding and fixing elements. Final assembling is a verylong process in time, because the assembling workforceshould carry out a series of measurements in a way such toachieve a accurate and qualitative assembling.*Corresponding author: Hektor ThomaToday, with the introduction and use of numericcontrolled machinery (CNC) many production processesin the wood processing industry including the productionof bedroom parts are revolutionized. Computerizednumerically controlled (CNC) woodworking machinerycan automatically control the movements of a spindle andtable. Recently, CNC woodworking machinery has beenwidely introduced in wood industries for automaticallycutting, drilling, and shaping operations (T. Ohuchi and Y.Murase, 2005).In a similar direction are moving also many woodprocessing factories in Albania. We have seen in the lastyears in the wood industry in Albania, investments mainlyin 3-axis and less in 5-axis machining technology. 5-axismachining provides flexibility and efficiency that cannotbe obtained with 3-axis milling, cause a 5-axis machinecan produce parts with more complex geometry using asingle setup without the need for complex and expensivefixtures. Such machines can produce special geometry,eliminating the use of specialized cutters often used in 3axis machining (C.T. Leondes, 2004).There are many studies in the field literature onefficiency of CNC machinery (Y.L. Liberman, 2010)related to many aspects influencing it directly orindirectly. Ohuchi and Murase (2005) studies the cuttinginstruments consuming effects on efficiency. The666

Hektor Thoma et alInternational Journal of Current Engineering and Technology, Vol.3, No.2 (June 2013)Figure 1. Accessories used in assembling of wardrobes (Hafele, 2012)Figure 2. Dimensions of a side element of the wardrobeTable 1. Holes list and their l depth No. of holes2081421441421418monitoring and evaluation of consuming of cuttinginstruments or other CNC machine tools have been studiedby several authors (W. Weis, 1994; R. L. Lemaster et al.,2000; P. Iskra, and R. E. Hernandez, 2012). Tonshoff et al.(1988) and Byrne et al. (1995) studied the requirements tobe meet by sensors for process monitoring of CNCmachine tools influencing direct or indirect the processefficiency.CNC machinery have a positive impact in terms oflowering costs and the realization of large volumes ofwork in relatively short time and its continuous utilizationwith minimal operator involvement. In some cases it ispossible to exploit the machine during all the shift, exceptcases of defects and maintenance interventions (FANUC,2012).Realization of large volumes of work in pieces is animportant factor in lowering the costs of productions,specially the fix costs, when the wood industry has thenecessary large market to sell these quantities of products.Local market for wood products in Albania isn’t a largeone and this is a factor, which is hindering somehow theextensive use of CNC technology in the country (S. H.Suh et al, 2002)NotesHorizontal holesHoles for metallic sleevesHoles for wood dovelsHoles for metallic connectorsHoles for Varianta screws and shelf supportsIn our study case we will analyze two approaches in theproduction of side elements of the wardrobe in order toachieve higher production time efficiency through usingCNC technology. Here we are dealing with verticaldrilling operations, horizontal drilling operations and fiberchannel sawing. In such cases, drilling programs are betterto be created in the machinery editor as it is more practicaland focused on demands.The general physical layout of manufacturing systemsof the factory as a major determinant of a firm's efficiencyis not taken into account. With the rapidly-changingenvironment facing most firms today, as well as theshortened life cycles of many products and processtechnologies, facility rearrangement and redesign becomecritical in sustaining productivity and competitiveness(C.T. Leondes, 2004). Anyway the focus of the paper ismore related to time efficiency of single operations.2. Materials and methodsAs already mentioned above in the introduction part thepaper is focused in analyzing two approaches in theproduction of side elements of a wardrobe in order to667

Hektor Thoma et alInternational Journal of Current Engineering and Technology, Vol.3, No.2 (June 2013)Table 2. Drilling unit initial 3030achieve higher time efficiency through using CNCtechnology.After the side elements are worked in the edge bandingthey are ready to be drilled in the CNC machine, whichrealizes drilling, milling and fiber channel sawingoperations. In this way the assembling of bedrooms can beperformed in very short time, not necessarily by two orthree people as traditionally done, with qualitative RTA(Ready To assemble) accessories who are quality certifiedand aesthetic appearance.During the study will be taken in consideration timeneeded for the realization of the drilling process of sideelements of a wardrobe. A single side element is sized2400 x 580 x 18 mm and should be drilled for accessoriessuch as Minifix, Rafix, Varianta screws, shelf supports,plastic feets, etc. Some of these accessories are presentedin Fig. 1 above. The dimensions of the side element of thewardrobe and drilling positions are presented in fig. 2.Inthe tab.1 is presented the list of holes to e drilled and theircharacteristics, mainly according to their function relatedto the accessories to be used.The drilling process is realized with a CNC machinerytype Biesse Rover 20, produced in year 2002 andaccording to Machine User's Manual of NC processingcentre Rover 20, with characteristics as below:Depth of nterCounterCounterCounterCounterCounterCounter- Drilling group, the saw aggregate and electro spindleare showed in the fig. 3 below.- Space working of pods and rail table of aluminumelements “easy to position” size 3200x900x100 mm- Electro spindle power 7 KW- Equipped with saw aggregate, disc diameter 120 mm,which moves along X axis- Equipped with drilling group with 10 vertical drillinginstruments and 6 horizontal drilling instruments- Equipped with tool changer with three positionsFigure 3. Graphical representation of drilling group and apicture of the saw aggregate and electro spindle of theBiesse Rover 20- Machine control NC 500, with three axisFor purposes of the study we configured the drilling groupaccording to the characteristics presented in the Table 2.668

Hektor Thoma et alInternational Journal of Current Engineering and Technology, Vol.3, No.2 (June 2013)Table 2. Recommended drilling unit 505050Drilling ble 3. Comparison of time before and after improvement of drilling unit configurationTime measurementInitial configurationof drilling unitRecommended configuration ofdrilling unitNeeded time (in sec.)TotalDrillingSawing200128 (64%)72 (36%)160124 (77%)36 (23%)- 8 horizontal holes, depth of 20-21 mm and feed rate of2m/min (changes in depth are made to eliminatesimultaneously drilling two a single decrease on Z axisof the drilling group)- 22 vertical holes, depth of 14-15 mm and feed rate of3m/minFigure 4. Different types of drilling tools, counter, lanceand normalAll CNC machine tools require some form of work setting,tool setting, and offsets (compensation) to place the cutterand work in the proper relationship. Compensation allowsthe programmer to make adjustments for unexpectedtooling and setup conditions (Krar and Gill, 1999).3. Results and discussionInitially we measured the time required for the executionof the program of drilling and fiber channel sawingoperation for the side element of the wardrobe, whichinclude measurements related to the time required for theexecution of:- fiber channel sawing, feed rate of 4 m/min, in a lengthof 2.4 m, depth of 9 mm which will be achieved withtwo steps, because of the consumption of the circularsawGiven the product we want to process with the CNCmachinery, we start to write drilling program for the sideelement of the wardrobe. Thus, as can be seen from thetab.2 we have to execute vertical and horizontal drillingand fiber channel sawing operations. Horizontal holes aredrilled with an advancing speed constant of 2 m/min,vertical holes are drilled with an advancing speed constantby 4 m/min, while the operation of fiber channel sawing isprogrammed with advancing speed of 4m/min and thenumber of steps.Accessories placement is generally standardized andwe have to adapt to their requirements. Instruments in themachinery are placed once in machine, are calibratedcarefully and with accuracy and their physical669

Hektor Thoma et alInternational Journal of Current Engineering and Technology, Vol.3, No.2 (June 2013)configuration must necessarily be reflected in machinecontrol program.Instruments changes are made in case of damage andinstruments repositioning and configuration are advised tobe determined according to the drilling unit configuration.According to the scheme of assembling required,drilling program and drilling group initial configuration,measurement of time shows that the execution of theprogram requires about 200 seconds. The timemeasurement is done once, because the execution time ofthe program is unchanged. Within this period of 200seconds about 36% of the time the time spent for disk fiberchannel opening.After executing the necessary operations according theinitial configuration of the drilling unit, the drillingscheme is changed and the drilling unit is reconfiguredaccording to the parameters shown in the tab.3.By measuring the execution time of the program forthe changed drilling scheme and a new configuration ofdrilling unit it turns out that the program execution timetakes about 160 seconds. Within this period of 160seconds, 23% of the time is spent for the fiber channelsawing, because a sharpened cutter blade with diamondtipped teeth is used.The result of the study is obvious and can be summedup in the fact that an optimal drilling scheme and a goodconfiguration of machine drilling group influences the useof working time significantly, reducing the time requiredfor the execution of a drilling-sawing program by 25%. Acomparison of the time required for the realization of theside component of the wardrobe before and after theimprovement of drilling group configuration is shown inthe tab.4We can say that drilling group configuration andcalibration of the instruments is a process that requires alot of time and tests at the beginning of the work, but weachieve a higher precision in work and higher efficiency.A great influence in the time efficiency of the drillingsawing operation has also the quality of circular saw.On the other hand the time efficiency increases by the useof CNC machines lies also in the fact that assembly timesof the elements are significantly reduced and volumestaken in packing and transportation, affecting at the sametime the transport costs.A greater impact would have the use of a postprocessor to achieve the transfer of data directly from .dxfCAD formats in the machine language (P. Ashley, 2003).It would reduce even more the time needed to realizemilling operations. Anyway it can be times, as in productreplication within a large sheet of material cases, when itcan be advantageous to make use of both CAM andmanual programming techniques (A. Overby, 2010).ConclusionsThe use of CNC machines is changing radically thefurniture making industry. Time consuming techniques inthe production process, such as cutting curves, becamemuch easier. With the advent of wood based panelproducts such as particle board and medium densityfiberboard (MDF), CNC equipment has now been widelyadopted for the production of components for many typesof furniture.This study is focused in showing the advantages intime efficiency of the use of CNC equipments in furnituremaking industry in Albania, specially in the production offurniture parts. We have considered only the drillingsawing operations on a side element of a wardrobe andmeasured the program execution times for two drillingschemes and corresponding drilling unit configurations.The optimization of the drilling scheme and especially thedrilling unit configuration can increase the time efficiencyof the drilling-sawing operation by 25%.In this paper the efficiency gains in production of “sideelements” for wardrobes sized 2400 x 580 x 18 mm aremeasured only in terms of production time of a singleoperations, but we have to consider also other severalfactors influencing the time efficiency as use ofappropriate cutting/drilling instruments in order to set highand correct interpolation speeds, use of appropriate postprocessors, to avoid writing by hand drilling and millingprograms, manufacturing large capacities, productstandardization, etc.On the other hand, increasing the time efficiency ofproduction operations through using CNC technology caninfluence the time efficiency of other operations asassembling, through decreasing it.ReferencesP.Ashley (2003). Improved high value-added furnituremanufacturing in Australia using Computer NumericallyControlled (CNC) equipment”. Gottstein Trust fellowshipstudy report. Available at the Gottstein Trust website,www.gottsteintrust.orgJ.T. Black and S.L. Hunter (2003). Lean Manufacturing Systemsand Cell Design. SME 2003.G. Byrne, D. Dornfeld, I. Inasaki, G. Ketteler, W. Konig and R.Teti (1995). Tool condition monitoring (TCM)—the status ofresearch and industrial application. Ann CIRP 44(2):541–567FANUC America (2012). Total Cost of Ownership - the total costof a CNC over the life of a machine tool, White Paper.Document No. MWA-015-EN 03 1211. Available atwww.fanucfa.comHafele. (2012). Furniture/Cabinet Hardware Catalog. Germany.P. Iskra, and R. E. Hernandez (2012). Toward a processmonitoring of CNC wood router. Sensor selection and surfaceroughness prediction. Wood Sci Technol (2012) 46:115–128S. Krar and A. Gill (1999). CNC Programming Basics: A Primerfor Skills VICA Championships, Industrial Press, Inc.R. L. Lemaster, L. Lu and S. Jackson (2000). The use of processmonitoring techniques on a CNC wood router. Part 1. Sensorselection. Forest Prod J 50(7/8):31–3.C.T. Leondes (2004). Computer Aided and IntegratedManufacturing Systems. A 5-Volume set. In Vol. 1 SystemsTechniques and Computional Methods. World Scientific Press.Y.L. Liberman (2010). Efficiency of numerically controlled metalcutting machines. Russian Engineering Research, 2010, Vol.30, No. 1, pp. 81–83. Allerton Press, Inc.T.Ohuchi and Y. Murase (2005). Milling of wood and wood-basedmaterials with a computerized numerically controlled routerIV: development of automatic measurement system for cutting670

Hektor Thoma et alInternational Journal of Current Engineering and Technology, Vol.3, No.2 (June 2013)edge profile of throw-away type straight bit. Journal of WoodScience 51:278-281. The Japan Wood Research Society.A. Overby (2010). CNC Machining Handbook: Building,Programming, and Implementation. McGraw-Hill/ TABElectronics. 1st Edition.S. H. Suh, S. K. Kang, D. H. Chung and I. I. Stroud (2008).Theory and Design of CNC Systems. SpringerH. K. Tonshoff, J. P. Wulfsberg, H. J. Kals and W. Konig (1988).Developments and trends in monitoring and control ofmachining processes. Ann CIRP 37(2):611–622W. Weis (1994). Survey: industrial applications of TCM systems.WBK, University of Karlsruhe, Germany (cited by Byrne et al.1995, Lemaster et al. 2000)671

- Machine control NC 500, with three axis For purposes of the study we configured the drilling group - Drilling group, the saw aggregate and electro spindle are showed in the fig. 3 below. Figure 3. Graphical representation of drilling group and a picture of the saw aggregate and electro spindle of the Biesse Rover 20

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