Talaş kaldırma belirli boyut, şekil ve yüzey kalitesine sahip bir parça meydana getirmek için ucu keskin bir takımla ve güç kullanarak, iş parçası (hammadde, taslak) üzerinden tabaka şeklinde malzeme kaldırma işlemidir. Ayrılan malzeme tabakasına talaş denir. Fiziksel bakımdan Talaş kaldırma işlemi, elastik ve plastik şekil değiştirmeye dayanan, sürtünme, ısı oluşumu, talaşın kırılması ve büzülmesi, işlenen parçanın yüzeyinin sertleşmesi, takım ucunun (ağzının) aşınması gibi olaylar meydana gelen, karmaşık bir fiziksel olaydır.
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· Assuming that the cutting action is continuous we can develop a continuous model of cutting conditions.
· Orthogonal Cutting - assumes that the cutting edge of the tool is set in a position that is perpendicular to the direction of relative work or tool motion. This allows us to deal with forces that act only in one plane.
· We can obtain orthogonal cutting by turning a thin walled tube, and setting the lath bit cutting edge perpendicular to the tube axis.
· Next, we can begin to consider cutting forces, chip thicknesses, etc.
· First, consider the physical geometry of cutting,
· Next, we assume that we are also measuring two perpendicular cutting forces that are horizontal, and perpendicular to the figure above. This then allows us to examine specific forces involved with the cutting. The cutting forces in the figure below (Fc and Ft) are measured using a tool force dynamometer mounted on the lathe.
Talaş Tipleri
Discontinuous chips
-Typically associated with brittle metals like Cast Iron
-As feed is increased, some compression takes place
-As the chip starts up the chip-tool interference zone, increased stress occurs until the metal reaches a saturation point and fractures off the work-piece.
Conditions which favor a discontinuous type of chip:
o Brittle work material
o Small rake angles on cutting tools
o Coarse machining feeds
o Low cutting speeds
o Major disadvantage—could result in poor surface finish
Continuous Chips
-Continuous “ribbon” of metal that flows up the chip/tool zone.
-Usually considered the ideal condition for efficient cutting action.
Conditions which favor a continuous type of chip:
o Ductile work
o Fine feeds
o Sharp cutting tools
o Larger rake angles
o Proper cutting speeds
o Proper coolant
Continuous chips with a built-up edge (BUE)
-Same process as continuous, but as the metal begins to flow up the chip-tool zone, small particles of the metal begin to adhere or weld themselves to the edge of the cutting tool
-As the particles continue to weld to the tool it effects the cutting action of the tool including the beginning of gauling
Conditions which favor a BUE type of chip:
o This type of chip is common in softer non-ferrous metals and low carbon steel
o BUE chip formation increases as the tool begins to dull
Problems associated with BUE chip formation
o Welded edges break off and can become embedded in work-piece
o Decreases tool life
o Can result in poor surface finishes
Talaş Formasyonu
