vladfranjo 2010 wtc mold engineering nrc
TRANSCRIPT
Injection Mold Engineering using FEA and CFD
International Special Tooling & Machining Association World Conference
Windsor, Ontario, Canada
June 23, 2010Vladimir Franjo, NRC-IRAPIndustrial Technology Advisor,Windsor, Ontario
NRC-IRAP?
NRC -- National Research Council of Canada
IRAP -- Industrial Research Assistance Program
What is IRAP?
• A federal R&D assistance program for SMEs
• Financial Support
• Customized Technical & Business Advice
– 240 IRAP Advisors across Canada
– Links
– Working on-site with clients
What is an Injection Mold?
• An arrangement, in one assembly, of one (or a
number of) hollow cavity spaces built to shape of
the desired product, with the purpose of
producing (usually large numbers of) plastic
parts, or products.
Source ‘Mold Engineering’ 1995 by Herbert Rees
• Basic Injection Mold Assembly:– Core half
• Core block– Guide Pins
• Ejection Box– Rails– Pillar Supports– Ejector Plate & Ejector Pins– Retainer Plate & Retainer Pins
• Clamping Plate– Stop Buttons
– Cavity Half• Cavity Block
– Guide Bushing• Manifold Plate & Manifold• Injection Sprue(s)
Larger Injection Mold assemblies could have over 500 components!
What is an Injection Mold?
Use of FEA and CFD in Injection Molding Simulation
• Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) commonly used for:– Injection Simulation
• Sizing and positioning of gates & runners
• Injection process simulation & optimization
• Pressure and temperature analysis
• Shrinkage and warpage simulation
– Mold Cooling Analysis
Use of FEA and CFD in Mold Engineering
• Not used for sizing and optimizing of mold components
• The first screw injection machine built in 1946 by American inventor James Watson Hendry
• Molds are traditionally designed using empirical rules or ‘rules of thumb’ often incorporated in individual mold standards
• Mold making ‘myths’:
– Adding steel is the simplest and lowest cost solution for mold design
– It is very difficult to calculate the exact deflection of a plate supported in several locations
Injection Molding Conditions
• Injection pressure (internal forces similar to a pressure vessel)– Bursting– Stretching (below the yield strength of steel)– Lateral forces depending on part geometry
• Injection molding temperature• Clamping pressure• Ejection Forces
– Forces resulting from plastic shrinkage (geometry dependant)• Fatigue
– Load cycle from 0 back to full to 0– The yield strength can not be used for calculations as it is for one load
only – Need safety factor from 5 to 10
Structural Analysis I/Os
• Inputs:– Injection pressure and temperature (could use injection
simulation outputs for complete cycle)– Clamping pressure– Material properties
• Young’s Modulus of Elasticity • Poisson’s ratio
• Outputs:– Deflection or displacement distribution– Stresses and strains distribution
Common FEA application with proven reliability
Fatigue Analysis
• More complex, but engineering software tools available• Need additional material properties (stress-strain curve,
compressive and tensile strength, shear and torsional properties, fatigue life curves)
• Critical factors:– Load fluctuation, Size and Direction– Temperature fluctuation– Material selection and characterization– Finish & Hardness– Geometry– Stress concentrations and stress risers (sharp corners)– Tool marks– Fretting– Engraving– Grain structure
Is it Sci-Fi?
– Not at all
– It is the best practice state-of-the-art
manufacturing engineering
• Optimize the Process
• Maximal displacement reduced by 33% (“Morph Improved” Die)
• Die weight reduced by 19%
Example:Die/Mould Stress Analysis and Structural Optimization
Courtesy of Altair Engineering Inc.
Die Stress Analysis and Optimization based approach
2. Design Space and Loads definition
1. Original Die Design with traditional patterns
4. Optimized structural ribs
Geometry Extraction (CAD)
3. Topology Optimization
Results layoutCourtesy of Altair Engineering Inc.
Analysis Process ; Transient Heat Transfer Set Up
Example of Die Cast Mould Analysis
Temperature Contours
Courtesy of Altair Engineering Canada Ltd
Example of Die Cast Mould Analysis
Stress Contours
Courtesy of Altair Engineering Canada Ltd
Analysis Process ; Thermal Stress Set Up:
Example: Mold Optimization
Courtesy of WIDL –Windsor industrial Development Laboratory Inc
Mold Core and Cavity Blocks Boundary conditions and Loads on the Core Block
Example: Mold Optimization
Stress distribution for initial design Proposed reduced size block, weight reduced by 58%
Courtesy of WIDL –Windsor industrial Development Laboratory Inc
Example: Mold Optimization
Stress distribution for initial design Stress distribution for new design, weight reduced by 58%
Courtesy of WIDL –Windsor industrial Development Laboratory Inc
Mold Cost Benefits
• Material cost savings– Assumed $2/Lb, removed volume 12,741 in3– Approx. $7,400
• Roughing cost & time savings– Assumed removal rate 400 Lb/hr, cost $75/hr,
50% of removed volume– Approx. $330 and 4.5hrs
• Gun-drilling cost savings– Assumed 40 WL, 34 EP, ½” dia, removal 3”/min
$75/hr– Approx. $180 and 2.5hrs
• Drilling cost savings– Assumed 4 GP, single drop, removal 2”/min– Approx $70 and 1hr
Assumed Mold Size: 24in x 60in x 30in
TOTAL: $7,980 and 8hrs
Mold Cost Benefits
Other potential savings:• Optimize number of pillar supports
– Assumed reducing the number from 14 to 6, $100 and 1hr per pillar support– Approx. $1,000 and 8hrs
• Optimize number of screws– Assumed reducing the number from 100 to 70, $15 and 15min per screw– Approx. $450 and 7.5hrs
• Optimize number of stop buttons– Assumed reducing the number from 30 to 20, $15 and 15min per button– Approx. $150 and 2.5hrs
• Optimize number of ejector pins– Assumed reducing the number from 30 to 20, $60 and 1hr per pin– Approx $600 and 10hr
TOTAL: $2,200 and 28hrs
Other Benefits of Engineered Molds
• Optimally sized injection mold may fit into smaller injection molding machine– Easier handling– Less energy consumption and lower operating costs– Cycle time improvements– More options for production scheduling
• Customized components like slides, lifters, rockers, collapsible cores can be optimized individually
• FEA and CFD analysis can be applied to families of molds (like automotive door panels, instruments panels etc.) in order to generate better standards and reduce the cost of FEA and CFD analyses
• New and alternative mold materials can be simulated without the need for trial & error– Aluminum injection molds are becoming more popular and may result in up to
30% cycle time reduction– Historical data not available for alternative materials, making it perfect
candidates for FEA and CFD engineering tools
FEA and CFD Service Providers
Windsor Industrial Development Laboratory Inc.Ben Chouchaoui, Ph.D.3310 Longfellow AveWindsor, Ontario, Canada,N9E 2L6Tel: (519) 966-4479Fax: (519) [email protected]
Altair Engineering CanadaJean-Pierre (JP) Roux (Toronto area)Bob Little (Windsor area) 170 The Donway West, Suite 301Toronto, ON M3C 2G3 Canada Tel: (416) 447-6463 E-mails: [email protected]
Special Thank You
• Cornerstone Intelligent Software Corp. www.corintsoft.com
• Genesis Mold Inc www.genesismold.com
• Standard Tool & Mold Inc. www.standard-mold.com
• Windsor Mold Group www.windsormoldgroup.com
References
• Mold Engineering, 1995 by Herbert Rees
• Solutions for Mold Designer, 2004 Moldflow Corporation
• Optimizing Plastic Injection Mold Materials with FEA, by Dr. BenChouchaoui, presented in Cutting Tool Engineering (Northbrook, IL), Mold Making Technology (Cincinnati, OH), and Society of Manufacturing Engineers (Dearborn, MI) in 2008 using ROI Engineering (Simultech Group) software ANSYS
• Dies Structures Optimization, July 2008 by Altair Corporation
ANY QUESTIONS!
Vladimir Franjo, B.Sc., P.Eng.Industrial Technology Advisor, Windsor, [email protected]://www.irap.nrc.gc.caWindsor office (519) 971-2015Regional toll-free 1-877-994-4727