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Hassas kesme ve kalıpları

Başlık çevirisi mevcut değil.

  1. Tez No: 75585
  2. Yazar: Ü.BAHAR DARICI
  3. Danışmanlar: DOÇ. DR. MEHMET DEMİRKOL
  4. Tez Türü: Yüksek Lisans
  5. Konular: Makine Mühendisliği, Mechanical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1998
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: İmalat Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 133

Özet

HASSAS KESME ve KALIPLARI ÖZET Özel bir kesme yöntemi olan hassas kesme, parçaların doğru bir geometri, çatlak veya yırtılma içermeyen ve pürüzsüz kesilmiş kenarlarla herhangi bir ana ikincil operasyona gerek duyulmadan kalıplarla üretildiği ileri ve hassas bir sac şekillendirme yöntemidir. Hassas kesme, kısa üretim süreleri, aynı makinada sürekli bir üretim ve son nihai parça üretimine tam güvenilirlikle ve hassasiyetle olanak verme, karmaşık şekillerin üretimi, normal pres işleriyle karşılaştırıldığında daha düşük kalıp ve üretim maliyetleri gibi nedenlerle günümüz endüstrisinde yerini almıştır. Uçak endüsrisinden, hidroliğe, tıbbi teçhizatlardan, elektroniğe, otomotiv endüstrisinden tekstil sektörüne kadar geniş bir spektrum çeşitliliğine sahiptir. Özellikle ikincil operasyonların elimine edilmesiyle presten çıktıktan ve hemen sonrasında çapak alma işlemi uygulandıktan sonra toplanmaya hazır parçaların elde edilmesi parça üretim maliyetlerini ve sürelerini düşürmekte, aynı zamanda yüzey ve boyut hassasiyeti çok yüksek olan parçalar elde edilmektedir. Hassas kesme ile kesme, delme kabartma, ezme, çevresel ezme ile basamak oluşturma, havsa başı açma, yan delme, bükme, ekstrüzyon, form verme gibi operasyonlar tek bir pres stroğunda elde edilebilmektedir. Kullanılan kalıp sistemleri bileşik, progresiv ve modülerdir. 1980'lerden sonra modüler kalıpların gelişimiyle üç boyutlu, derin parçaların üretimi de mümkün olmuştur. Hassas kesmede birbirinden bağımsız olarak çalışan üç ayrı kuvvet vardır. Kesme kuvveti parçayı keserken, batma çeneleri malzeye batarak baskı kuvveti uygulamakta ve malzemenin kalıplardan kaçışını engellemekte, karşı ıstampa kuvveti ise baskı kuvveti ile birlikte etkiyerek parçada meydana gelebilecek eğilmeleri engelleyerek tamamen düz parçaların üretimini sağlamaktadır. Konvansiyonel kesmedeki malzeme kalınlığının 1/3 'ü olan parlak kesme şeridi hassas kesmede tüm malzeme kalınlığı boyuncadır. Konvansiyonel kesmede elde edilen minimum delik çapı malzeme kalınlığına eşit iken, hassas kesmede bu değer malzeme kalınlığının 0.6 katı olmaktadır. Maksimum verilebilecek kesme aralığı değeri malzeme kalınlığının % l'idir, genellikle ise bu değer % 0.5 olmaktadır. Daha büyük değerlerde yüzey kalitesi bozulmaktadır. Ancak bu yöntemde de diğer sac şekillendirme yöntemlerindeki gibi çapak oluşumu kaçınılmazdır ve işlemin sonunda mutlaka çapak alma işlemi uygulanmalıdır. X111

Özet (Çeviri)

FINE BLANKING and TOOL SYSTEMS SUMMARY In metal working industry, for the manufacture of ready to assemble functioning parts with smoothly sheared edges as well as close dimensional and form tolerances, fine blanking is a higly economical production method. Fine blanking originated in 1923 in Germany. The process came into more general use in 1950's. In 1980 the number of presses came up to 2800. Today many industries take advantage of this technology. The foremost market is automative industry. Because it requires precision components in a wide variety of shapes, sizes and qualities. Industries that typically take advantage of fine blanking are as follows: -Automative (door locks, brake shoes, seat belt assemblies, etc.) -Aircraft -Firearm -Precision optics -Home appliance -Hardware -Textile parts -Office-eqipment -Hydraulics -Agricultural machine -Medical -Electronic equipment -Precision optics Fine blanking is a method of punctioning parts without die break. The metal flow is controlled in the shearing area through the use of an impingement ring (usually in knife-edge form) which is pressed into the metal outside the cutting with a great force to restrain the metal. The metal outside the impingement ring can not move inward. This results as clean cut and % 100 free of tearing and perpendicular, ( 90° angle to the surface) edges. The advantageous of fine blanking are as follows: -With fine blanking close dimensional tolerances can be optained. Parts requiring surface finishes on sheared edges down to 16 rms are possible in fine blanking. Dimensional tolerances down to +/- 0.013 mm (+/- 0.0005“) can be obtained. -The surface of edges cut by fine blanking have an finish of R, 0.4 - 1.5 u,. If tungsten carbide is used as the die material this value can go down to R* 0. 1 u, So no subsequent polishing or grinding is necessary. XIV-The dimensional range is 25x25 - 250x250 mm and external dimensions can go up to approximately 1000 mm. The metal thickness that can be worked with is 0.8 to 16 mm. Fine blanking can also handle complex parts than convantional blanking. -Secondary operations such as drilling, boring, reaming, broaching, gear hobbing, countersinking, grinding and more can be eliminated. A ready to install part is produced with each stroke. -When fineblanked parts are compared with cast and sintered components they weigh substantially less. -The time for each press stroke in fine blanking is less than convantional blanking. So JIT (just in time) is possible in fine blanking. -As a result of short production times and elimination of secondary operations the production costs are reduced. The price is 50 to 70 percent less than what you may currently be paying. -Fine blanking can also handle smaller holes and thicker materials than can convantional stamping. Parts with holes and/or slots, thinner webs, closser spacings between holes are smaller than material thickness is possible. The min. hole diameter is 0.6 times the material thickness while it is equal to material thikness in convantional blanking. -Impact noise and vibration are eliminated, so the noise in the workplace and shock to the tooling are reduced. -With fine blanking many operations such as cutting, forming, elbowing, countersinking, coining, bending, extruding, semi piercing etc. can be successfully achieved. -Fine blanking technology offers favorable conditions for producing ”near net shape“ and even ready to assemble sheet metal parts. Fine blanking involves three press motions. In the first motion, lower half of the tool is lift and the material is raised and clamped against the upper half of the tool. At the same time, the V - ring bites into the material so that it can not flow away fom the punch during the blanking operation. In the next motion, the ram speed is reduced as the blanking punch sheraes the workpiece into the die opening and against the counter punch-ejector. In the third motion, the ram reverses direction just when the workpiece is fully sheared. Then the counter punch pushes the finished part out of the die opening as the tool opens and the workpiece is blown on a conveyor or catch bin. Heavy workpieces are swept out mechanically. Fine blanking requires three forces which can be seperately and independently applied. They are blanking or cutting force, holddown or blankholding force or V-ring force, and counter and ejection force. The principal element is counter force. An addition xvdie element is added which mirrors the shape of the punch. Pressure is applied to this element througout the process. Counter force isn't so effective as blankholding force to improve the sheared surface quality. Without counter force fine blanking can be often done successfully. The inner surface of pierced hole depends on the counter force. In convantional stamping the material will bend away from the punch, causing the part to fracture. But in fine blanking counter force keeps the part from bowing away from the punch resulting in an extremely flat piece. Blankholding force compresses directly the material close to the cutting edge of die. The increase of blankholding force decreases the fracture zone. Some of the fine fine blanking parametres are cutting edge radius of punch and die, projection types, clearance, the distance between the peak of knife-edge type projection and the shearing line. In fine blanking small cutting edge radius of die makes the sheraed surface quality better, but the cutting edge radius of punch is harmfull. Also flat-topped, conical and flat projections can be used. For optimum conditions flat-topped and flat projections have almost the same performanse of knife-edge type projection. So at this situation flat-topped projection leaving no grooves on the waste strip, has the advantage to be produced easily. Clearance has a great effect in fine blanking on the sheared surface quality. In convantional stamping clearances are % 10-20 of the material thickness. In fine blanking the clearance is % 0.5 of the material thickness and over clearance reduces the surface quality. Using the short distance projection by blankholding force, causes large bending moment. To prevent this bending, the projection must be employ both on die and on blankholder relative to one another not to cause bending moment. With long distance projection blankholding force doesn't effective, because most of it escapes to the die space. And it is also said that for materials more than 4 mm thickness, the projection must be on both the blankholder and die. There are two different fine blanking press systems: the fully hydraulic press and the mechanical fine blanking press with hydraulically actuated V-ring and counter force. The mechanical and the hydraulic presses are 250 kN - 2500 kN and 2500 kN - 25000 kN in range respectivelly. These two types are used for moving punch tools, for fixed punch tools or for presses which are convertible to both tool systems. The die elements are blanking punch, guide plate, die plate, counter punch, centering pin and the die set. The strip loader, coil cradles, straigteners, tool fitting aids, slug and parts seperatmg drum are the peripheral equipment. The strip loader can automatically feed strip material to the fine blanking system. Tool set up rails can be used to allow placing the tool by crane or fork lift in front of the die space. The tool is then manually pushed along the rails into the tool clamping zone. The finished parts are removed by special automatic handling systemsor air jets. The seperating drum sorts parts from waste slugs. In the early days of fine blanking, simple parts were usually produced with compound tools. Coining and forming operations can be performed at the same time the part is blanked. When compound tools weren't adequate for part design in a single station tool, progressive tools were used. Today modular transfer tooling systems allow the combination of forming, fine blanking and convantional blanking. The most XVIsignificant characteristic of modular tooling is that it consists of single tool sets, arranged in sequence and unlike progressive tools, provides complete seperation of each operation. The parts are transported from one tool set to the next with a tranfer system. The modular tooling system completely seperates the various fine blanking, convantional blanking and forming steps. With each press stroke these are performed simultaneously on the work pieces in various stages of completition on the press table. This simplifies timing and adjustment of the tooling during set - up, and reduces long - term maintenance. It even allows empty tooling stations. The expansion of fine blanking tooling technology is indicated on Table SI. The development of a new tool follows the steps listed below: -Preliminary sketch -Intensive discussion -Trials, simulation -Part drawing -Fine blanking layout -Tool design -Tool manufacture -Testing, optimizing, training -Ready - to - operate handover -First production batch Table SI Expansion of fine blanking tooling technology [1] xviiAs % 95 of componenets produced by fine blanking are steels. Carbon steels, stainless steel, low carbon steels, high carbon steels, alloyed steels, nickel and cobalt alloys, brass, aluminium, copper alloys are suitable for fine blanking. 16 MnCr 5, 42 CrMo 4, Ck 45, Ck 55, Ck 60, 100 Cr 6, 20 CrMo 5, 25 CrMo 4, Ck 70, 13 NiCr 6, C 10, Ck 10, C 15, Ck 22, 15 NiCr 6, 17 CrNiMo 6, 30 NiCr 11, are some examples of these materials that can be possesed easily. The most favourable material is ”Martin" steel strip with a tensile strength of 40-50 kgf/mm2. With aluminium clean cut edges are obtained if the tensile strength is not more than 25 kgf/mm2. Copper must be used with a suitable lubricant because it tends to stick both to the punch and to die. Also brass can be cut easilly by fine blanking. Materials in fine blanking are placed in different fineblanking grades, according to the difficulty of forming and/or cutting them, and their compositions. Materials in grade I are sıubject to no conditions concerning metallurgical structure; grade II corresponds to structure G, % 90 carbide spherodizing and grade III corresponds to GKZ, a structure with % 100 carbide spherodizing or GKZ-EW, an exteremly soft annealed condition. In the materials area, there is wider variaty of hot rolled and cold rolled steels in coil and strip up to 12 mm thick. Coiled material is usually preferred, because it permits continuous processing. Hot-rolled sheets of all qualities except DIN 17400 stainless steels and DIN 46400 magnetic steels are available to DIN 1016 in thickness from 10 to 2000 mm. Hot rolled sheets are used in pickled and annealed conditions. Cold rolled sheets are used in G, GKZ or GKZ-EW conditions. The cold-rolled sheets can have a moderate extra cold-rolling. This process after annealing makes cold-rolled sheet flatter and gives better surface finish. Today, fine blanking is world wide. All modern industries utilize this technology as an economic resource for quality. Fine blanking is especially benefical due to short production times, reduced operations and lowered production costs. It is used in all over the world as a high qualified and a challenging technology for all other sheet metal industries. For small and complex parts as it is told, fine blanking is used instead of many sheet metal works. And also it must be noted that the tool and the press costs are higher than convantional stamping. But for optimum production number, part cost will compansate the tool cost. One of the leading companies of feinblanking in the world is Feintoll AG Lyss. Feintool AG Lyss was founded in 1959 in Switzerland. With its group companies in the world, it is the world leader in fine blanking technology and dominates % 64 of world market in 1963. It is expert on design, work materials, hardening and coating techniques, lubrication, process, technology and fine blanking systems and ensures full service abaut these subjects to all its customers on all over the world. The head quarter is in Switzerland and there are many many divisions in Germany, USA, China, Great Britain, Japan, France and etc. in the world. In Turkey only 3 suppliers take adventage of fine blanking. These are Teknik 20, Toksan and Beşer Balata. They have one or two Feintool presses and they are bought from Feintool AG Lyss as second hand after revision. They produce their xviiiown tools. Vanadis 4, 90 MnCrV 8, X 155 CrVMol2 1 are used as tool materials and Erdemir 3237, 3010 and Ck 75 as fine blanking materials. Both of them produces parts for automative industry such as door locks and shoe plates. Fine blanking technology still has an important problem to solve. This is the need for deburring after the press. This operation must be carried out with great care in order to preserve the edge quality and the required precision. This work explains fine blanking technology, tools and the peripheral equipment, fine blanking materials, forces, presses and the parametres of fine blanking. At the end many examples are given from the automotive industry. And also the market of this sector is investigated in the world and Turkey. XIX

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