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injection molding troubleshooting
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Co-Sponsors:
Paulson Training Programs
Orbital Plastics Consulting
Injection Molding
Troubleshooting:
Flash & Burn Marks
Contact Information
Orbital Plastics Consulting
www.orbitalplastics.com
(770) 390 - 0949
Paulson Training Programs
www.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
Orbital Plastics Consulting
www.orbitalplastics.com
