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1/6 Page No.: 104

Title: Venting System

Rev.: A

Created by: **** Approved by: **** Last Modified: 3.25.05

1.The burn marks ,underfilled areas or other cosmetics defects,which

resulted from the compressed air between the flow front in the knit-lines or at the

end of flow(the last filled area), become visible on the part surface when the

mold has been poor vented or the vents have not been designed properly. Two

major types vents used:

Individual Vents Perimeter Venting

Kwik-Mold Inc. Moldmaking Guide

TOP

Gate & Runner

Perimeter vents run around the entire parting line, which then vents to open air.

SECTION B-B

Vent land 0.060-inch length.

Vent channel 0.040-inch deep.

Vent depth per material specifications.

Cavity Mold edge.

Gate & Runner

TOP

SECTION A-A

Gate & Runner

Part

Draw polish vent lands to SPI A-1 in direction of airflow.

Secondary relief channel

Air Flow AA

B

B

Vent 0.040-inch land to 0.040-inch deep channel to atmosphere.

Individual part vents are placed around the cavity.


X

2/6 Page No.: 105


Rev.: A


2. Vent depth Easy Flow

Stiff Flow or Glass Filled Polymer

Depth of vent (inches) ABS SAN HIPS 0.002 0.003

Acetyl 0.001 0.0015 Acrylic 0.002 0.003

Cellulose/acetate/butyrate 0.001 0.0015 Nylon 6/6 0.0005 --

Nylon 6/6, 13% glass 0.0015 Polyallomers 0.0005 0.001 Polycarbonate 0.0015 0.003 Polyethylene 0.001 0.002

Polypropylene 0.001 0.002 Polyphenylene oxide 0.001 0.003 Polyphenylene sulfide 0.0005 --

Polysulfone 0.001 -- Crystalline Polystyrene 0.001 0.002

Polyvinylchloride (rigid) 0.001 0.003 Polyvinylchloride (plasticized) 0.001 0.002

3.Runner venting

Runner venting is needed

for all the resins,especially stiff

flow and filled material.

MATERIAL X(Max.) PE 0.0005” POM, ACETATE, CAB, EVA,PA, PS, PP, SAN,Urethane, PVC 0.001” PMMA, ABS, PC 0.002 Foamed PE,PS 0.008



3/6 Page No.: 106


Rev.: A


3.Vent the core pins and ejector sleeve

Vent to atmosphere.


Vent depth per material specifications

1/64”(Min.) Core Pin

Clearance: 1/32”(Min.)

Vent depth per material specifications


0.5”(Min.)

Lower this face by 0.005”-0.01”

4/6 Page No.: 107


Rev.: A


4. Vent the ejector pins

5.Decrease the fitting area between A and B half


Vent per material specifications per side. Vent (4) places equally spaced around periphery of pin.

Vent length to be 1.5 times the distance over 2 parallel vent flats.

Draw polish vent lands to SPI A-1 in airflow direction.

Air flow

Use 0.060-inch wide radial groove by 0.010-inch per side deeper than the distance over 2 parallel primary vent flats.

Vent channel width 0.05 times the distance over 2 parallel vent flats. Vent channel depth maximum of 0.010- inch deep. Continue length to open air.

The actual fitting area

The molded part


A

A

Porous Mold Steel

Vent to atmosphere.

Porous Mold Steel

Support

Vent to atmosphere.

30-50mm

Design I

Design II

5/6 Page No.: 108


Rev.: A


6. Porous Mold Steel

Refer to steel supplier’s guide for other design items.



6/6 Page No.: 109


Rev.: A


7. other venting design


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