VARIETY of DEFECTIVE MOLD and CAUSE

Condition FILLING MISS

Cause Molding Machine :

1.Low material temperature

2. Low injection pressure

3. Material feed shortage

4. Too small nozzle hole diameter

5. Cylinder nozzle clogging

Cause Mold :

1. Small gate or runner

2. Inadequate gate position

3. Inadequate position of or no air vent

4. Low mold temperature

5. Cold slag clogging in runner or gate

Cause Material :

1. Low fluidity

2. Low lubricity

Condition F I N

Cause Molding Machine :

1. Weak clamping force

2. High injection pressure

3. Material over feed

4. High material temperature

Cause Mold :

1. Flaw or foreign body on parting plane

2. Wide project area to the machine

3. High mold temperature

Cause Material :

1. Excessive fluidity

Condition SHRINKAGE CAVITY

Cause Molding Machine :

1. Low injection pressure

2. Slow injection

3. High material temperature

4. Short pressure retaining

5. Material feed shortage

Cause Mold :

1. High mold temperature

2. Products thickness uneven

3. Small gate

4. Cooling time shortage

5. Inadequate ejection

Cause Material :

1. Material too supple

2. High contraction coefficient

Condition WELD LINE

Cause Molding Machine :

1. Low material temperature

2. Low injection pressure

3. Slow injection

Cause Mold :

1. Small gate or runner

2. Low mold temperature

3. Inadequate gate position

4. Inadequate air vent

Cause Material :

1. Rapid curring

2. Insufficient drying

3. Low lubricity

Condition NO GOOD LUSTER/HAZE

Cause Molding Machine :

1. Nozzle clogging or small diameter

2. Material feed shortage

Cause Mold :

1. Inadequate air vent

2. Small gate or runner

3. Insufficient measures for corrosion

4. Excessive mold release agent

Cause Material :

1. Insufficient drying

2. High volatility

3. A foreign body mixed

Condition FLOW MARK

Cause Molding Machine :

1. Low material temperature

2. Low injection pressure

3. Slow injection

4. Too small nozzle diameter

Cause Mold :

1. Low mold temperature

2. Products thickness uneven

3. Small gate or runner

4. Small or no slag well

Cause Material :

1. Low fluidity

2. Low lubricity

Condition SILVER STREK/BUBLE

Cause Molding Machine :

1. Fast injection

2. Low injection pressure

3. Small injection capacity

4. Short pressure retaining

5. High material temperature

Cause Mold :

1. Inadequate air vent

2. Small gate or runner

3. Products thickness uneven

4. Small or no slag well

Cause Material ;

1. Insufficient drying

2. High volaticity

Condition BLACK STREAK/BURNED

Cause Molding Machine :

1. High material temperature

2. Long stay inside cylinder

3. Flaw inside cylinder

Cause Mold :

1. Inadequate position of of no air vent

2. Small slag well

3. Oil or something inside cavity

Cause Material :

1. Excessive lubricant

2. Insufficient drying

Condition BAD RELEASE of SPUE or PRODUCTs

Cause Molding Machine :

1. High injection pressure

2. Material overfeed

Cause Mold ;

1. Dislocation of nozzle hole and sprue hole

2. High mold temperature

3. Low sprue gradient

4. Undercut on or low gradient of cavity

Cause Material :

1. Insufficient lubricant

Condition WARPAGE/DEFORMATION

Cause Molding Machine :

1. High injection pressure

2. Long pressure retaining

3. Insufficient annealing

Cause Mold ;

1. No good ejection mechanism

2. High mold temoperature

3. Big gate

4. Uneven cooling

Cause Material :

1. Low fluidity

2. High contraction coefficient

3. Low material rigidity.

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Electric Heating Elements for Mold Plastic

The most common electric heating elements are circular heater band,catridge heaters,tube heaters,flexible flat tube heaters and spiral heater.The heater band generally have a surface capacity of about 5 W/cm2 and are manufactured to customer specifications.The most frequently used cartridge heater are hight performance with surface capacity means that outside dimensions of the heaters can be small,an advantage for mold making.
Standard cartridge heater have capacities of about 5 W/cm2.The dimensions of hight performance cartriedge heater range from about 6.5x30mm to about 20x300mm in diameter.Various connection types and voltages are available.Some configurations include built in thermocouples.
The sensitivy of the hight performance cartridge heaters depends on their specific surface capacity(W/cm2).The higher this value is,the better the contact must be between the location hole and the cartridge.In any case it is recommended to use several cartridge of lower surface capacity to ensure ideal installation conditions.This will also produce better heat distribution within the mold.
Tube heater are used whenever components in molds and other equipment are to be hated externally in very limited space.The heat capacity in is directed inward,the sizes range from about ID 18/OD35 to about ID 60 and the capacities from abouth 200 to 1500watt.
If properly used,flat tube heater will achieve uniform temperatures over large surface areas.These heaters can be bent into any shape to fit into grooves,thermally conductive cement is used conductive cement is used as the embedding compound.
The spiral cartridge heater is made of flexible tubing,which is available in a variety of diameter.These heating elements have a surface capacity of approximately 6W/cm2,are available in length of up to approximately 1000mm and can be bent by the user in accordance with requirements.Thee effectiveness and the service life of electric heating elements depend to the mold.The tapered hight performance cartridge heaters illustrated in fig fit in the location hole and easily removed.
The cartridge with standard 1:50 taper is fitted and removed with sleeve nut via the circlip.This heating element will fit tightly,even in awkward installation position,the location bore can be machined with standard tools.

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Basic Molds

Basic mold as swown in fig are assembled as ready made mold base,available in relatively small range only.Their application is far more limited because the designed is confined by being kept to the assembled mold base.
Basically,two types are available as standart elements;assembled mold base,referred to basic mold,and the modular systems for individual combinations.

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Mold and Dies EXPERTS

Apart from the actual machinery,almost all the processes used for the manufacture of plastics,allumunium part also require o mold.This applies,for example,to injection molding,blowmolding,strength molding,transfer and compression molding, die casting and generally to foaming as well.The sullution is somewhat different in case of punching tools,extrusion,where the die determines only two of the three possible dimension.
Mold are often designed and built by plastics processors them selves,in many cases,the availability of a processor's own mold making facilities is an important precondition for the production of high quality moldings.

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