Thermoset Processing Manual Compression Molding

3/10/2010 Chemiplastica 1

Thermoset Processing ManualCompression Molding

3/10/2010 2Chemiplastica

General Overview


Description

Urochem-Compounded from Urea Formaldehyde Resin, Cellulose Filler, Pigments, Flow Promoters ,lubricants

Melochem- Compounded from Melamine Formaldehyde Resin, Cellulose Filler, Pigments, Flow Promoters ,lubricants

Fenochem- Compounded from Phenolic Resin, organic and inorganic fillers, Pigments, Flow promoters, Lubricants


Material Properties

Flow-Measures how fluid and soft material is. Lower Number= Easier Flow.

Cure Value- Measures how fast material is formed into a Blister Free Part .

Density- Measurement of weight per volume. Good data for charge weight considerations. Typical Urochem range 64 +/- 4 grams/100 cc.


SAFETY FIRST

Guide to Safety Around The Press

And Machinery


Ten Commandments of Safety Safety Glasses & Ear Protection

No Loose clothing, Neckties/Necklace outside clothing

Turn off all electrical switches when investigating malfunction

Never use Compressed air Gunto clean hands or clothing


Ten Commandments of Safety Know Location of Fire Extinguisher

Do not tie down or Block Safety Switch

Do not reach around or remove safety guards

Before starting press Make sure all people are clear of moving parts

Maintain good housekeeping and avoid dust collection


Thermoset Molding TermsCompression

Molding


Terms & DefinitionsBlister Raised Section in molded part

Gas TrapUnder cure or overcure

Breathe (Degassing) Opening and closing of mold to allow escape of gas

Cavity Part of mold which forms outer surface of molded part

Charge Amount of material required to fill cavity

Charging The Mold Placing required amount in mold. Only automatic at CWD.


Terms & DefinitionsCure Time required to polymerize to a

hard blister free surface under heat and pressure

Cycle Time it takes to complete one operationLoading and close of moldBreathe cycleOpen and discharge of parts

Draft Amount of taper on side of mold/molded part for easy removal

Ejector Pins Steel pins in cavity or force for removal of parts


Terms & DefinitionsFamily Mold A multi-cavity mold containing

several cavities of different sizes and shapes

Flash The excess material that flows out of the mold cavity under pressure

Guide Pins Pin or bars in mold to assure proper alignment of mold halves

Parting Line Part of mold which provides the cut-off of the flash from molded part

Plasticity/Flow Term to describe degree that material flow under heat and pressure


Terms & DefinitionsPlatens Top and bottom plates on press to

which mold halves are bolted

Polymerization Chemical reaction that starts with closing of mold and ends with cure of part

Pressure Pads Steel blocks outside cavity which meet during mold closure to prevent tooling contact at parting line

Vent Small channels of groves to allow air and gas to escape during molding


Material Handling

Storage and Rotation


Material Handling

Store material in cool, dry place First in first out (limited shelf life) Verify material before loading Use single batch at a time Avoid mixing batches Avoid contamination Avoid pressurized air for cleaning Maintain good housekeeping Shield presses running light colors from dark colors


Compression Molding

General Overview


Compression Molding Molding of thermoset plastic using a compression

press Two halves of mold brought together under high

pressure Mold is heated at 290-350°F depending on material Application of required breathe cycle Temperature and pressure cause material to melt and

flow into spaces between cavity and force Material is set and ejected after appropriate cure time


Compression Press

Molding press consisting of hydraulic ram housed in large cylinder

Cylinder located at bottom for upward acting press and in the top for downward

Hydraulic pressure drives ram with platen and mold halves attached

Force is applied depending on size of mold and output size of press


Molding Temperatures

Urea molding compound, Urochem 290 to 310°F

Melamine molding compound, Melochem 310 to 350°F

Phenolic molding compound, Fenochem 325 to 350°F


Press Controls

Understand function of all controls, buttons, switches prior to operating press

Always be aware of the location of emergency button/controls

Never touch any unfamiliar controls Always use safety devices


Compression Molding Process

Step-By-Step Start Up Guide


STEP ONE

Verify double load safeties are functional& Properly set. This ensures molding process remains in low pressure until the mold closes to the proper position. If there is a part or foreign object stuck in the mold, the press cannot close to safety position and go into high pressure. These safeties are actually part of the molding process


Step TWO

Check mold temperature with pyrometer290 to 310°F for urea5 to 10 degrees lower in cavity part

Check that temperature is even across cavities and make adjustments.

If temperature is not correct, contact supervisor to ensure thermocouples are properly working

Maintaining correct temperature is essential to quality and workmanship


STEP THREE

CLOSE MOLD EMPTY AND CHECK TO ENSURE PSI IS WITHIN ACCEPTABLE LIMITS.

25 Ton: 90 PSI Minimum 75 Ton: 2500 PSI Max and

lower on some operations

150-300 Ton: 1000 PSI Maximum


STEP FOUR

Check standards for cure time specified for part

Charge Material Close Press and hold closed at specified

cure time No Breath


STEP FIVE

Open Mold and Check Molding for uniform Flash If Heavy, Reduce weight If Short, add weight

Repeat Steps Three and Four until you are satisfied visually and based on experience that you have correct weight


STEP SIX Finalize Weight by referring to standard weight specified for

each part using accurate scale to weigh parts Allowable limit of +/- 7%

Make adjustments based on loading board capability Bolt and screw Insert

Check all cavities for uniformity If flash heavy but weight is correct recheck temperature &

pressure If still heavy try softer batch Correct weights are key to quality and waste control


STEP SEVEN

Adjust cycle for good densified, bright, gas free, blister free parts

Know your material and choose settings based on experience

Traditional setting Initial closing of press followed by one or two breath.

Optimal breath spacing based on set up trial Stop & Go setting

Initial STOP for preheating of various duration followed by press closing and perhaps short early breath.


STEP EIGHT

Finalize cure by referring again to part standard as a guide

Adjust until you have blister free part Add five to ten seconds to insure continuous

blister free operation. Beware that over curing can cause warpage,

brittleness and discoloration Maintaining optimal cycle is key to productivity

and profitability


Common Quality Defects

Blister Short Shots Porous Parts Orange peel or

wrinkly surface Gas Burns Gas Blush Low Gloss

Warped Parts Contamination Molded in Flash Heavy or thick Flash Broken parts Off Color Parts Excess flash


Trouble Shooting Techniques Temperature uniformity is Key. Always check with a

pyrometer Note cycles, cavity layout and settings prior to

trouble shooting Watch out for any unusual and erratic occurrences One change at a time Choose type of cycle and stick to process guidelines Use the trouble shooting guide Check all possible causes including material, tooling,

equipment and operator set up.

Documents

Thermoset Processing Manual Compression Molding