This document describes various defects that can occur during the metal deep drawing process, their causes, and recommended corrective actions. It lists different types of defects like cracking, tears, wrinkles, and earing. The causes of the defects include issues with tooling like incorrect die curvature, drawing clearance being too narrow/wide, and blank holder pressure being too high/low. It also lists causes related to the metal stock like flaws, holes, and incorrect blank sizing. The document provides solutions for correcting the defects such as annealing stock, grinding tooling, adjusting pressures and speeds, ensuring proper tool alignment, and selecting appropriate stock quality.

1. Appearance Type of defect Cause of defect Corrective action
Material flaw …..
Irregular cracking
from the edge of the
wall down Cracks of
this type often only
develop days or weeks
after drawing
Too high stresses
Anneal the stock
directly
Deep crack on one
side of the wall, crack
is a curved shape.
Clean edge to crack.
Transverse crack on
one side
Flaw in the sheet
caused by thicker
nodules or foreign
bodies pressed in, e.g.
metal chips.
Short transverse
cracks in the wall.
Black spots with
flattened areas directly
above and below them
Fine holes in the
material, porous sheet
Defects in the tooling ….
Bottom is torn off on
all sides with no wall
forming.
The drawing tooling is
acting as a cutter, as
1. die edge curvature
too low and sharp-
edged or
2. drawing clearance
too narrow
3. too high blank
holder pressure
4. too high drawing
speed.
Raise the die edge
radius, generally by
grinding the punch or
drawing ring. Reduce
the blank holder
pressure. Reduce the
number of press
strokes per minute.
Bright compression
mark at height p on the
upper part of the wall,
externally.
Drawing clearance too
narrow.
Grind drawing ring or
punch.

2. Drawing successful
except for frayed wall
edge and flattened
wrinkles.
1. Mostly drawing
clearance too wide
or
2. die edge curvature
too large.
Replace tooling to
reduce clearance.
Draw almost successful
except very wrinkled
extra flange with
horizontal cracks
beneath it.
Too high die edge
curvature, too low
blank holder pressure.
Grind down the
surface
of the drawing ring
and
reduce edge radius. Set
blank holder pressure
higher.
Blistering at the bottom
edges. Bottom bulges
as shown by the dashed
line.
1. Bad punch
ventilation,
2. occasionally also
heavily-worn die radius
Install or widen vents.
Polish the die radius.
Wrong blank size or wrong step difference….
Only a short wall stub
is formed, at about the
height of the die edge
curvature, then the
bottom tears off.
Too great a difference
between steps
considering the drawing
quality of the sheet.
Punch off-center to the
drawing ring.
Determine value (=
highest permissible
D/d
ratio) using the cup
test
procedure.
Perhaps make steps
smaller or select sheet
of
higher drawing
quality.
Adjust tooling
correctly.
Tearing in the corners
of rectangles, starting
out at the edge and
moving down towards
the bottom corners.
1. Lack of material in
the corners due to
incorrect blank sizing.
2. Drawing clearance
too narrow
Change blank.
Rectangular draws
require a greater
drawing clearance
in the corners than
at the sides.
Cracks starting in the
bottom corners of
rectangular draws,
then moving out
diagonally.
1. Excess material in
the corners.
2. Differences between
steps too great in the
corners.
Change the blank.
Make steps smaller or
use higher-quality
deep
drawing sheet.

3. Earing on one side of
the wall edge or on the
sheet flange.
1. Blank inserted off-
center.
2. Irregular blank
holder pressure.
3. Off-center
positioning of the
punch in the drawing
ring (rarely).
4. Irregular sheet
Use guide pins. Align
tooling.
Operating errors ….
Sheet flange too wide
on one side near the
web.
Blank inserted off-
center.
Fit stop pins.