CONSIDERATIONS REGARDING THE STRENGTH CALCULUS OF MILLING CUTTERS TEETH

Transcription

1 CONSIDERATIONS REGARDING THE STRENGTH CALCULUS OF MILLING CUTTERS TEETH 1 Eng. Catăin ROŞU, University of Craiova, Facuty of Mecanics, Deartment of Aied Mecanics and Civi Constructions, Caea Bucuresti Street, no. 107, Craiova,Code 0051, Romania, rosu_catain1@yaoo.com Astract. In tis aer, I resent a strengt cacuus for miing cutter teet. I wi consider te oadings tat act uon te first toot, wen it removes te tooing aowance from te manufactured iece, ecause it is te most oaded one. I wi resent a te stes tat are made for te strengt cacuus. Te simifying assumtions and te cacuus reations (eseciay for te equivaent stress) are resented in an origina way. Keywords: miing too, toot, ending, equivaent stress 1. INTRODUCTION In tis aer we make a strengt cacuus for a miing cutter. Te most oaded arts of a miing cutter are its teet. So, I sa consider for te strengt cacuus, te first toot tat removes te tooing aowance from te manufactured iece, ecause it is te most oaded one. In order to manufacture, te miing too must overcome te materia of te roduct. So, it acts uon te iece wit a force namey caed te cutting force. In ractica engineering, determining its vaue is very imortant ecause, in some cases, it can e equa to dozens of kn (eseciay in te case of rouging miing for stees). Aso we can use its vaue to otimize te ciing condition. During te tooing rocess, it aears a force tat act uon te miing too teet, caed as te ciing strengt in Buzatu (1975)[]. In fig. 1. it is resented te working scemes and te cutting forces for te cyindrica miing. f f Fig. 1. Te cutting force and te working sceme for te miing; a. towards te feeding f;. in te oosite direction of te feeding f (from Buzatu (1975)[]) If we use miing cutters wit eica teet, we ave a tird cutting force caed as axia cutting force, wic is arae wit te miing cutter axis. Tis force is resented in fig Fiaiitate si Duraiitate - Fiaiity & Duraiity No 1/ 01

2 Fig.. Te cutting forces at miers wit eica teet (according to Buzatu (1975)[]). THE STRENGTH CALCULUS MODELLING FOR A MILLING CUTTER For tis modeing, I sa refer to te oading of te first toot tat removes te tooing aowance from te manufactured iece, ecause it is te most oaded one. Taking into account te scemes from fig. 1 and and te yotesis from te Strengt of Materias, te toot is oaded according to te sceme from fig. F t F a Fig.. Te oading sceme of te toot We can see tat te toot is oaded y: - F r force (comression); - F t force (ending in vertica ane); - F a force (ending and tangentia trust in side ane). Te cutting force F t is determined wit (1) (according to Buzatu (1975)). F 10 [N] (1) t F r 160 Fiaiitate si Duraiitate - Fiaiity & Duraiity No 1/ 01

3 We ave marked in (1) wit: is te sinter transversa section [mm ], is te secific ciing ressure [] wic can e found in taes from te iterature. Te oter two forces are determined wit (). Fa 0, 8 Ft ; Fr 0,5..0, 7Ft () According to Iincioiu (010)[], I wi determine te equivaent stress in tree section oints: te midde of te ase (marked as B 1 ), in te midde of te eigt (marked as B ) and at one corner (marked as B ). For te strengt cacuus, we sa consider te effect of a te forces. Te v F equivaent r Mmax Mmax qmed ecb stress in A Wy Wz 5 oint B is determined wit (). In () I ave marked wit and te ase and te eigt of te transversa section (rectanguar section). Te sear stresses in B 1 and B oints are determined wit (). 15, B1 B Te norma stresses in B 1 and B oints are determined wit (5). () () B B 1, (5) Te equivaent stresses (wit te strengt teory IVB from Iincioiu (010)) are determined wit (6). (7). ecb 1, ecb If te miing cutter as straigt teet, te equivaent stresses wi e determined wit ecb In order to comete te strengt cacuus, te next inequaity must e fufied: ecb 7 10 ecb (7) (6) max ec ecb 1 ecb ecb were σ a is te admissie stress of te mier materia. ; ; a (8) 161 Fiaiitate si Duraiitate - Fiaiity & Duraiity No 1/ 01

4 In order to determine te equivaent stress variations in function of te manufactured materia and te geometry of te toot, I wi consider a articuar case defined in tis way: = 80 mm; = 0 mm; = 0 mm; t = 5 mm; f z = 0,06 mm/dinte; D= 90 mm; z= 8 dinţi; = 0,68 mm were is te mier widt, is te mier eigt, t 1 is te contact engt, f z is te toot feeding, D is te mier diameter, z is te numer of te teet. If we insert te reations () and (6) in Mae we otain te next rocedure: 16 Fiaiitate si Duraiitate - Fiaiity & Duraiity No 1/ 01

5 Te stress variation in function of te mier teet ange (for eica miers) and of te secific ciing ressure is resented in fig... CONCLUSIONS In tis aer I ave made a strengt cacuus for te miing toos teet. I ave considered for te strengt cacuus, te first toot tat removes te tooing aowance from te manufactured iece, ecause it is te most oaded one. I ave aso resented a te oading scemes for te mier toot. In te next art of te aer, I ave resented te strengt cacuus mode. I ave considered tat te toot is oaded y: - F r force (comression); - F t force (ending in vertica ane); - F a force (ending and tangentia trust in side ane). I ave determined te equivaent stresses in te oints of te toot section, were tese stresses were susected to e te igest. In te ast art of te aer I ave determined te stress variation in function of te mier teet ange (for eica miers) and of te secific ciing ressure. a. rad. c. rad rad Fig.. Te stress variation in function of te mier geometry and ciing ressure; 16 Fiaiitate si Duraiitate - Fiaiity & Duraiity No 1/ 01

6 a. σ ecb ;. σ ecb1 ; c. σ ecb From fig. we can extract te foowing genera tendencies: - te stress vaue was determined in te emedding oint, ecause tat is were te stress is maximum; - te stress increase wit te secific ciing ressure increase; - te stress is ow for soft materias (wit HB< 00) and ig for ard materias (wit HB 00); - te stress increase wit te increase of te toot tit ange (for miers wit eica teet).. ACKNOWLEDGEMENT Tis work was artiay suorted y te strategic grant POSDRU/88/1.5/S/5078 (009), co-financed y te Euroean Socia Fund Investing in Peoe, witin te Sectora Oerationa Programme Human Resources Deveoment REFERENCES [1].Aexandru, I., R., (011) Studiu comortamentuui dinamic a sistemuui ort-scuă scua aşcietoare Piesa în cazu oeraţiei de frezare cu viteze înate, Teză de Doctorat, Universitatea «Transivania» din Braşov, Facutatea de Inginerie Tenoogică, Catedra «Tenoogia construcţiior de maşini, Brasov [].Beju, L., D., Brîndaşu, P., D., (011) A Generaized Aroac of te Hoder Systems for Cutting Toos, Academic Journa of Manufacturing Engineering, 9 (), 1-18 [].Buzatu, V., s.a., (1975) Îndrumător entru ridicarea caificării frezorior, Editura Tenică, Bucureşti [].Cernăianu, A., (005) Maşini-unete. Eemente de roiectare, organoogie şi Cinematică, Editura Universitaria, Craiova [5].Frăţiă, D., s.a., (011) Tenoogii de Faricaţie. Îndrumător Pentru Lucrări de Laorator, Cuj Naoca [6.]Freudenerger, J., s.a., (010) Sringer Handook of Mecanica Engineering. Voume 10. Materias Science and Engineering, , Sringer [7].Iincioiu, D., s.a., (010) Rezistenţa Materiaeor, Vo. 1, Editura Universitaria, Craiova [8].Iincioiu, D., s.a., (011) Rezistenţa Materiaeor, Vo., Editura Universitaria, Craiova [9].Miriţoiu, C., M.,Iincioiu, D., (01) Rezistenţa Materiaeor. Aicaţii, Vo. 1, Editura SITECH [10].Păuşan, N., A., (00) Studii Mecano-Cimice asura fuideor de răcire-ungere în rocesee de reucrare mecanică a comonenteor rumenţior, Teză de Doctorat, Universitatea Transivania din Braşov, Facutatea de Inginerie Tenoogică, Catedra Design de Produs şi Rootică, Braşov [11].Picoş, C., s.a., (197) Cacuu adaosurior de reucrare şi a regimurior de aşciere, Editura Tenică, Bucureşti [1].Picoş, C., (198) s.a., Normarea Tenică Pentru Preucrări Prin Aşciere, Editura Tenică, Bucureşti [1].Roşca, V., Iincioiu, D., s.a., (007) Rezistenţa Materiaeor. Încercări fundamentae, Editura Universitaria, Craiova 16 Fiaiitate si Duraiitate - Fiaiity & Duraiity No 1/ 01