Plastic products are mostly produced by injection molding machine. With the injection molding method, there are often defects occurred in plastic products, such as jetting, flow marks, short shot and many more. Therefore, it is important for us to know the defects as to ensure a high quality product.
Most commonly, defects happen when there are errors in materials used for the product, mold itself or the machine setting.
Some of the common defects and solutions are:
Defects name
|
Descriptions
|
Possible
solutions
|
Bubble
|
It is referred to the phenomenon where bubble or
blister occur within the plastic product.
|
- Increasing the
back pressure
- Dry the
material properly
- Decrease the
material temperature
- Reduce the
injection speed
|
Drag marks
|
It is referred to the phenomenon where scratches
occur when it is ejected from the mold.
|
- Maintenance of
the mold itself
|
Flash
|
It is referred to the phenomenon where excess
plastic overflow and penetrate out of the mold gap.
|
- Reduce the
injection speed
- Reduce the
injection pressure
- Reduce the material
temperature
- Increase the
clamping pressure
|
Flow marks
|
It is referred to the phenomenon where wave
pattern is formed around the gate.
|
- Increase the
mold temperature
- Raise the gate
and runner.
|
Jetting
|
It is referred to the phenomenon where a snake
line of material formed on the surface of the molded product.
|
- Reduce the
injection speed
- Increase the
mold temperature
|
Short shot
|
It is referred to the phenomenon where the
plastic does not reach certain portions of the mold.
|
- Increase the
injection speed
- Increase the
pressure
- Increase
ventilation lines
|
Silver streaks
|
- It is referred to the phenomenon where circular
marks appear at the molding surface.
|
- Proper drying
of material before use
- Increase back
pressure
|
Sink mark
|
It is referred to the phenomenon where indentation occurs on the surface of the plastic product.
|
- Increase
injection speed
- Increase back
pressure
- Reduce
material temperature
|
Warping
|
It is referred to the phenomenon where
deformation caused by difference in the degree of shrinkage.
|
- Increase
injection pressure
- Increase
barrel temperature
|
Weld Line
|
It is referred to the phenomenon where the two
different flow fronts meet and formed a narrow V-shaped line.
|
- Increase
injection speed
- Increase mold
temperature
- Increase
material temperature
|
The following information is provided for reference
only, without guarantee of any kind. It is encouraged to verify all information
with experienced plastic experts, as there are always specific conditions that
cannot be anticipated.
Please feel free to contact YHK design for more
plastic advices or new product development.
