Injection Molding Troubleshooting: Flash & Burn Marks
Co-Sponsors: Paulson Training Programs Orbital Plastics Consulting
Contact Information Orbital Plastics Consulting www.orbitalplastics.com
[email protected] (770) (77 0) 390 390 - 094 0949 9
Paulson Training Programs
www.paulsontraining.com
[email protected]
About Orbital Plastics Consulting, Inc.
Co-founder & Partner in Paulson School of Molding
Injection molding processing & troubleshooting
Injection molding training – 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 Fla sh - Pro Proble blem m Ana Analy lysis sis
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
Flash - Mold Design Solutions
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 - Material 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 - 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
Vent Depths for Various Resins Resin ABS Acet al Acry lic Nylon PPO/PS (Noryl) Polycarbonate P ET, PBT, Poly es ters Polysulfone Polyethylene Polypropylene Polystyrene T/P Elastomer
Depth (inches) 0.0010 - 0.0015 0.0005 - 0.0010 0.0015 - 0.0020 0.0003 - 0.0005 0.0010 - 0.0020 0.0015 - 0.0025 0. 0005 - 0. 0007 0.0010 - 0.0020 0.0005 - 0.0012 0.0005 - 0.0012 0.0007 - 0.0010 0.0005 - 0.0007
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
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
