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PLASTICS ENGINEERING COMPANY |
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3518 LAKESHORE |
Injection Molding Guidelines
PLENCO Single Stage Phenolic
Molding Compound
|
Parameter |
Suggested
Press Settings |
|
Mold Temperatures |
165° - 182°C (330° - 360ºF) |
|
Front Barrel Temperatures Rear Barrel Temperatures |
82° - 99°C (180° - 210ºF) 66° - 82°C (150° - 180ºF) |
|
Stock Temperature |
104° - 115°C (220° - 240ºF) |
|
Injection Time |
3 - 8 Seconds |
|
Clamp Tonnage |
27.6 - 41.4 MPa
(2 - 3 Tons/in2) Of Projected Part Area |
|
Screw Back Pressure |
0.21 - 0.69 MPa
(30 - 100 psi) |
|
Screw |
30 - 60 |
Additional Technical Information
·
A clean, highly polished, chrome plated mold is recommended.
Use a mold release such as Carnauba Wax, being careful to coat the entire
surface including the sprue bushing.
After several shots wipe off the excessive mold release using a clean,
soft cloth.
·
Each time a mold using a Single Stage compound has sat idle,
it is highly recommended that the mold is started with a Two Stage general
purpose product for the first several shots and then switched to the Single
Stage compound. This is done to minimize
sprue, runner, part and flash sticking.
·
The orifice size of the nozzle should be 1 mm (1/32”) less
than the sprue bushing orifice. This
will allow material to be pulled from the nozzle, which helps minimize nozzle
freeze off. The nozzle and sprue orifice
should be the same radius, to provide a leak free shut off. In some cases, it may be necessary to have a
smaller radius on the nozzle, to reduce the heat transfer from the sprue, which
may be causing nozzle freeze off.
·
A tapered, highly
polished, D2 steel, sprue bushing, will provide easy release of the sprue from
the sprue bushing.
·
The shot weight (part & runner volume) should be between
20% and 80% of the barrel capacity of the injection press. A Thermoset
injection screw and barrel provides optimum performance when molding these
materials. A Thermoset screw is one with
a 12:1 L/D (length/diameter) Ratio, a 1:1 Compression Ratio and a 40° included
angle on the tip.
·
A soft bulb of material on the end of the sprue, ensures
that the nozzle is being evacuated of material every shot, which minimizes
nozzle freeze off.
·
Adding a cushion of 3 mm (1/8”) and switching to secondary
or holding pressure at 6 mm – 10 mm (1/4” - 3/8”) before the screw bottoms out,
will help maintain a part density that maximizes physical and electrical
properties.
|
Common
Molding Problems |
Potential
Solutions |
|
Blistering |
Increase mold temperature Increase
stock temperature Increase
cure time |
|
Gas Burns |
Slow injection time Check for
blocked vent(s) Lower stock
temperature |
|
Short Parts |
Increase
shot length Increase
back pressure Lower mold
temperature |
|
Sticking Parts |
Increase
mold temperature Increase
cure time |
The listed parameters
are suggested for use as a guide when setting up an injection molding machine
for molding