Plastics Engineering Company

PLASTICS ENGINEERING COMPANY
SHEBOYGAN, WISCONSIN 53082-0758 U.S.A.


 

3518 LAKESHORE ROAD
POST OFFICE
BOX 758
PHONE
920-458-2121
FAX
920-458-1923

Injection Molding Guidelines

PLENCO Single Stage Phenolic Molding Compound

 

Parameter

Suggested Press Settings

Mold Temperatures

165 - 182C (330 - 360F)

Front Barrel Temperatures

Rear Barrel Temperatures

82 - 99C (180 - 210F)

66 - 82C (150 - 180F)

Stock Temperature

104 - 115C (220 - 240F)

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 RPM

30 - 60 RPM

 

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 Plenco Thermoset materials. These parameters are for your evaluation and may or may not be compatible for all mold designs, runner systems, press configurations, and material rheology. Please feel free to call Plenco and a Plenco Technical Service Representative will be happy to assist you. Revised 4-30-03