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Technical support Trouble shooting guide

-01- Black Specks
-02- Brittleness
-03- Burn Marks
-04- Discoloration
-05- Gloss
-06- Jetting / Worming
-07- Sink Marks
-08- Weld lines (Knit lines)
-09- Splay marks(Silver Streaks)
-10- Sticking in cavity/core
-11- Stress in part
-12- Voids
-13- Warpage / part distortion

Black Specks

If previously molding other types of polymers, purge other polymer out of barrel completely
Always purge when not running for extended periods of time
Decrease nozzle temperature
Check temperature at feed section, low temperatures may cause mechanical degradation especially
with a high screw speed or high back pressure
Check heater band and thermocouple location. The heater band may be heating to a higher temperature than the thermocouple is measuring

Brittleness

Dry resin properly (moisture greater than o.o2% can cause loss of properties)
Improve weld-line strength
Decrease nozzle temperature
Check melt temperature with pyrometer
If material degradation is suspect, lower material temperature by:
a. Lowering cylinder temperature
b. Decreasing screw speed
c. Lowering the back pressure

Burn Marks

Decrease injection speed Decrease booster time
Decrease injection pressure
Check venting channels for dirt
Improve venting of tool (Add vents at burn locations)
Alter position of gate and/or increase gate size

Discoloration

Purge heating cylinder
Check melt temperature with pyrometer
Lower material temperature by:
a. Lowering cylinder temperature
b. Decreasing screw speed
c. Lowering the back pressure
Increase back pressure to improve melt homogeneity
Lower nozzle temperature
Shorten overall cycle
Check hopper and feed zones for contaminants
Cheek for proper cooling of ram and feed zone
Provide additional vents in mold
Move mold to a smaller short size press to reduce residence time
Check hot manifold for dead spots

Gloss

Increase mold temperature
Increase melt temperature
Increase injection speed
Increase injection pressure
Check surface of the mold for polish
Clean vents
Increase venting

Jetting / Worming

Decrease injection speed
Increase melt temperature
a. Increase cylinder and nozzle temperature
b. Increase screw speed
c. Increase back pressure
Increase gate size and decrease gate land length
Modify gate location or angle : directly into wall or pin
Avoid gating at thick section

Sink Marks

Follow rib design guidelines
Increase injection speed and pressure
Increase injection hold time
Reduce melt temperature
Reduce mold temperature
Enlarge and/or add vents to mold parting line
Increase size of sprue and/or runners
Increase gate size and decrease gate land length
Relocate gate next to heavy or thicker areas

Weld lines (Knit lines)

Increase injection speed and pressure
Increase injection hold time
Raise mold temperature
Raise melt temperature by increasing cylinder temperature
Vent cavity in the weld area
Change gate location to alter flow pattern

Splay marks(Silver Streaks)

Dry resin properly
Lower nozzle temperature
Lower melt temperature by :
a. Lowering cylinder temperature
b. Decreasing screw speed
c. Lowering back pressure
Decreasing injection speed
Shorten or eliminate screw decompression
Shorten overall cycle
Increase sprue and runner size

Sticking in cavity/core

Decrease injection pressure
Decrease hold time and pressure
Lower mold temperature
Increase mold closed time

Stress in part

Increase mold and melt temperature
Decrease injection speed and pressure
Increase gate size
Add gates, relocate gates

Voids

Decrease injection speed
Increase injection hold time
Reduce melt temperature
Increase mold temperature
Increase gate size and reduce gate land length
Increase nozzle size and/or runner
Redesign part to obtain equal wall section

Warpage / part distortion

Increase injection hold time
Increase mold closed time
Increase mold temperature
Check gate locations and total number of gates to reduce orientation
Redesign part to equalize wall variation in molded part thick and thin walls
Check cooling line layout, unbalanced cooling promotes warpage
Increase gate size

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