Deep drawing and redrawing - National Institute of ...
Transcript of Deep drawing and redrawing - National Institute of ...
Deep drawing and redrawing
Dr. Dinesh Kumar
PIE, NITJSR
Deep drawing• Deep drawing or cup drawing is
a process of forming hollow shaped components from flat pieces of sheet metal of from already drawn components.
• Examples: kitchen wares, boxes of various shapes, car bodies, domestic gas cylinder, etc.
Retaining metal in draw dies
With rigid blank holder
With spring pressure pad
Metal Flow during deep drawing
Factors affecting the metal flow during deep drawing• Radius on punch
• Draw radius on die
• Friction
• Material to be drawn
• Percentage reduction
• Drawing speed
• Die clearence
Factors affecting…… :Radius on punch• Punch corner radius=(4-10)thickness of sheet
• For single draw: Punch corner radius=as per the product design
• For multiple draws: Punch corner radius reduces after each draw
Factors affecting…… :Draw radius on die
• Draw radius on die=4*sheet thickness
• Too large radius will tend to release the sheet by the blank holder very soon thus the wrinkling may take place
• Too small radius will tend to thinning and tearing the sheet at the corners
• Friction plays an important role
• Too less friction: wrinkling
• Large friction: thinning and tearing of the sheet
Factors affecting…… :Friction
Factors affecting…… :Material to be drawn
• Large ductile material should be avoided
Factors affecting…… :Percentage reduction
h/d ratio Number of draws
Up to 0.7 1
0.7-1.5 2
1.5-3 3
3-7 4
• Low carbon steel:9-15m/min
• Non ferrous sheet: 45-60m/min
• Harder and less ductile material: low speed
Factors affecting…… :Drawing Speed
Factors affecting…… :Die Clearence
Blank Size (D) Calculation
Drawing Force
Blank Holding Force