Injection Molding Troubleshooting Flash Burnmarks

Co-Sponsors:

Paulson Training Programs

Orbital Plastics Consulting

Injection Molding

Troubleshooting:

Flash & Burn Marks

Contact Information

Orbital Plastics Consulting

www.orbitalplastics.com

umberto@orbitalplastics.com

(770) 390 - 0949

Paulson Training Programs

www.paulsontraining.com

spaulson@paulsontraining.com

About Orbital Plastics

Consulting, Inc.

Co-founder & Partner in Paulson School of Molding

Injection molding processing & troubleshooting

Injection molding training – processing & part design

Expertise in selecting and implementing in-mold

instrumentation.

Provides suggestions regarding material selection and

plastic part design.

About the Presenter

Umberto F. Catignani

Co-founder, Partner and Principal Instructor in Paulson

School of Molding

President of Orbital Plastics Consulting, Inc

2007-2008 President of Southern Section of SPE

Work Experience: 13 + Years Hands-On

BS Materials Engineering. University of Cincinnati.

MS Polymer Engineering. The University of Akron.

Jointly published papers in: SPE Technical Papers, The

Journal of Polymer Science and Polymer Engineering &

Science.

SPE Speaker on Injection Molding Instrumentation.

About Paulson Training

Programs

For over three decades, Paulson Training Programs has been the leading source for training in the plastics industry.

3,000+ plants and over 30,000 employees trained.

Strong training alliances with over 80 colleges and universities.

Library includes over 300 hours of interactive plastics training and 2,000+ hours of additional business and manufacturing training titles.

New SkillBuilder and SimTech products, software based injection molding machine simulation programs.

Record of innovation and quality.

Partner and co-founder in Paulson School of Molding with Orbital Plastics Consulting.

Presentation Overview

Welcome, Introductions & Overview

Flash & Burn Marks

Causes

Problem Analysis

Solutions

Conclusion, Summary & Questions

The Four Primary Plastic

Conditions

Flash

Molded Part Problems - Flash

Flash is plastic that flows beyond the mold parting lines

or between metal inserts.

Flash Locations

Flash can be on the runner.

Flash Locations

Flash can be on the part.

Molded Part Problems - Flash

Molders should avoid flashing a mold…even if the

plastic parts can be trimmed, the flash damages the

parting line of the mold.

Flash- How Problem Develops

Flash - Review: Statement of

Problem

Flash - Note

Flash Question

D

Problem Analysis

The Four Primary Plastic

Conditions

Flash - Problem Analysis

An increase in the clamp force is usually the first

adjustment.

Flash Question

B

Question Explanation

Flash - Problem Analysis

The next plastic condition that can cause flash is

plastic cavity pressure.

Flash - Problem Analysis

Plastic flow rate can also cause flash. Reduce flow

rate.

Flash - Problem Analysis

Plastic flow rate can also cause flash.

Flash Question

Flash - Problem Analysis

Raising or lowering plastic melt temperature can also

cause flash.

Flash - Problem Analysis

Lowering the melt temperature will increase the plastic viscosity

and lower the cavity pressure. The flash problem is reduced. But a

lower melt temperature may require higher injection pressures to fill

the cavity resulting in a larger pressure loss across the cavity. Higher

pressures may exist near the runner or gate area and may cause

flash in the runner or gate-end of the part.

Flash - Problem Analysis

Raising the Melt Temperature will reduce the plastic

viscosity and increase the cavity pressure. The flash

problem will be increased. However, the pressure needed

to fill and pack the cavities can then be reduced resulting in

reduced flash.

Flash - Problem Analysis

Flash - Problem Analysis

Raising or lowering melt temperature can reduce

flash…Cavity pressure is the key!!!

Flash - Problem Analysis

Plastic entering parting line cools faster…cannot flow

far.

Flash Problem Locations

Flash Problem Locations

Flash Problems on Toggle

Style Clamps

The cavities should be placed so that the plastic

pressure is taken up equally by all the machine tie

bars. The projected area that the plastic fills

should not be concentrated on one side of the

mold.

Flash - Mold Design Solutions

Very low viscosity plastics such as Nylon and

Polypropylene can flow into very small parting lines;

they flash easily. The high viscosity plastics such as

Polycarbonate do not flash easily. Most plastics fall in

between.

Flash - Material Solutions

Flash - Conclusions

All 4 primary plastic variables can affect flash.

Burn Marks

Molded Part Problems –

Burn Marks

Examples of molded parts where the plastic has

burned at its leading edge.

Molded Part Problems –

Burn Marks

This part is not completely filled out and the edge of the

part where flow stopped is charred.

Molded Part Problems –

Burn Marks

This part is filled out, but the last region of the part to

fill has a burn mark.

Molded Part Problems –

Burn Marks

This part has a dark spot surrounded by plastic. It's a

burn mark.

Functions of the Mold –

Escape of Air

Burn Marks

Burn Mark Question

C

Burn Mark Question

C

Burn Mark Question

C

Burn Mark Problem Analysis

Burn Mark - Clean Vents

Venting- Escape of Air

Venting Considerations

The critical dimension on a vent is the depth or D1. Located

at last place to fill or may cut primary vent to form a

continuous venting channel.

Vent Depths for Various Resins

Resin Depth (inches)

ABS 0.0010 - 0.0015

Acetal 0.0005 - 0.0010

Acrylic 0.0015 - 0.0020

Nylon 0.0003 - 0.0005

PPO/PS (Noryl) 0.0010 - 0.0020

Polycarbonate 0.0015 - 0.0025

PET, PBT, Polyesters 0.0005 - 0.0007

Polysulfone 0.0010 - 0.0020

Polyethylene 0.0005 - 0.0012

Polypropylene 0.0005 - 0.0012

Polystyrene 0.0007 - 0.0010

T/P Elastomer 0.0005 - 0.0007

Burn Mark Problem Analysis

If the vents are compressed, air will have difficulty

escaping.

Burn Mark Problem Analysis

Burn Question

Burn Mark Question

C

Burn Mark Design Solutions

Vent on Ejector

Burn Mark Design Solutions

Burn Mark Design Problem

Burn Mark Question - Design

Problem

B – Race tracking

Burn Mark Design Solutions

Summary

Burn Mark Conclusions

Thank You

Paulson Training Programs

www.paulsontraining.com

spaulson@paulsontraining.com

Orbital Plastics Consulting

www.orbitalplastics.com

umberto@orbitalplastics.com