Moulding Problems- Mould, Machine And Material Related _ (table 17-02)
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6.2.2017
MOULDING PROBLEMS Mould, Machine and Material related : (Table 1702)
In case, you do not see blue navigation panel at left, please click here and then locate this page on the blue navigation panel at left.
MOULDING PROBLEMS Mould, Machine and Material related MOULDING PROBLEMS
MOULD related
MACHINE related
IN CONSISTENT CRITICAL DIMENSIONS
Unequal shrinkage due Holdon pressure and to variation in mould holdon time surface temperature. influences the shrinkage. High Cooling circuit design pressure and time related. reduces the shrinkage. Lower pressure and Core and cavity time increases the dimension related. shrinkage of the part. Correct shrinkage is not considered for shrinkage in the core / cavity direction of orientation dimension. is more. dimensions could be controlled by controlling cooling rate in different areas of the mould when wall thickness is not constant. Cooling rate could be increased by using BaCu insert in the mould.
SINK MARKS
WARP
http://www.pitfallsinmolding.com/problems.html
Part design related non uniformity of wall thickness.
Use technique to improve part stiffness with part design.
Injection speed profile and hold on pressure profile can minimise to some extent. Gas injection Moulding technique can be considered. ...
1/3
6.2.2017
MOULDING PROBLEMS Mould, Machine and Material related : (Table 1702)
Random distribution of mould surface temperature. Cooling circuit design related. WEAK WELD LINES
Part design related.
Injection speed can influence.
DEGRADATION Check dimensions of runner Excessive Residence system for excessive time due to use of shearing. oversized injection unit. Lowering barrel temperature and injection speed can have some influence EJECTION DIFFICULTY
Part design related ... Unbalanced melt flow. Use flow leader to reduce unbalance in flow.
POOR IMPACT strength
Radius at projections and sharp corners as it act like notch from where crack propagates.
...
IN CONSISTENT WEIGHT.
...
% age utilisation of shot capacity is closer to 90% resulting in inconsistent melt quality if metering stroke is more than 3 times screw diameter. Borderline case for shot weight.
IN CONSISTENT FILLING
Increase gate size to reduce pressure drop across the gate.
Available maximum injection rate is not adequate for flow ratio of part being moulded. Borderline case for injection rate.
STRESS CRACKING
Melt flow is unbalanced. Part design related.
Over packed part. Set correct pressure profile during pressure phase.
...
MATERIAL RELATED PROBLEMS
SINK MARKS
Filled polymer can reduce sink mark.
http://www.pitfallsinmolding.com/problems.html
2/3
6.2.2017
SINK MARKS MOULDING PROBLEMS Mould, Machine and Material related : (Table 1702) Filled polymer can reduce sink mark. POOR MECHANICAL STRENGTH
Consider high molecular weight polymers.
DIMENSIONAL VARIATION
Check shrinkage characteristics of material.
Consider filled polymers. Pre heat polymer in dehumidifier if required for polymer as recommended for polymer.
DEGRADATION Check thermal stability of polymer as well as OF MELT pigments and other additives if any used with material. DIFFICULTY IN Consider polymer of higher MFI FILLING Click here to see Understanding QUALITY Let us understand the factors influencing quality consistency in processing and quality in performance Let us understand moulding problems. HOME
Contactto buy this book
Things to know Process
Things to know Polymers
Things to know Part Design
Things to know Machine
Injection Moulding Process
Screw Plasticating
Moulding
Key factors influencing Shear strain proces curve
pvt diagram
Thermal stability
Balancing melt Flow
Balancing Heat
Freezing
Quality Problems
Three Balances
Mouldedin Stress
Shrinkage
Inconsistent Dimension
Sinkmark
Weldlines
Moulding Problems
CYCLE TIME
Plastics Part Design
Flow Analysis
..
..
Myth
Understanding Mould Cooling Channels
Ideal Moulding Shop
Engineering Glossary of technical Glossary of technical Basics in Machine terms Physics terms Polymer process
http://www.pitfallsinmolding.com/problems.html
Things to know Mould
3/3
MOULDING PROBLEMS Mould, Machine and Material related : (Table 1702)
In case, you do not see blue navigation panel at left, please click here and then locate this page on the blue navigation panel at left.
MOULDING PROBLEMS Mould, Machine and Material related MOULDING PROBLEMS
MOULD related
MACHINE related
IN CONSISTENT CRITICAL DIMENSIONS
Unequal shrinkage due Holdon pressure and to variation in mould holdon time surface temperature. influences the shrinkage. High Cooling circuit design pressure and time related. reduces the shrinkage. Lower pressure and Core and cavity time increases the dimension related. shrinkage of the part. Correct shrinkage is not considered for shrinkage in the core / cavity direction of orientation dimension. is more. dimensions could be controlled by controlling cooling rate in different areas of the mould when wall thickness is not constant. Cooling rate could be increased by using BaCu insert in the mould.
SINK MARKS
WARP
http://www.pitfallsinmolding.com/problems.html
Part design related non uniformity of wall thickness.
Use technique to improve part stiffness with part design.
Injection speed profile and hold on pressure profile can minimise to some extent. Gas injection Moulding technique can be considered. ...
1/3
6.2.2017
MOULDING PROBLEMS Mould, Machine and Material related : (Table 1702)
Random distribution of mould surface temperature. Cooling circuit design related. WEAK WELD LINES
Part design related.
Injection speed can influence.
DEGRADATION Check dimensions of runner Excessive Residence system for excessive time due to use of shearing. oversized injection unit. Lowering barrel temperature and injection speed can have some influence EJECTION DIFFICULTY
Part design related ... Unbalanced melt flow. Use flow leader to reduce unbalance in flow.
POOR IMPACT strength
Radius at projections and sharp corners as it act like notch from where crack propagates.
...
IN CONSISTENT WEIGHT.
...
% age utilisation of shot capacity is closer to 90% resulting in inconsistent melt quality if metering stroke is more than 3 times screw diameter. Borderline case for shot weight.
IN CONSISTENT FILLING
Increase gate size to reduce pressure drop across the gate.
Available maximum injection rate is not adequate for flow ratio of part being moulded. Borderline case for injection rate.
STRESS CRACKING
Melt flow is unbalanced. Part design related.
Over packed part. Set correct pressure profile during pressure phase.
...
MATERIAL RELATED PROBLEMS
SINK MARKS
Filled polymer can reduce sink mark.
http://www.pitfallsinmolding.com/problems.html
2/3
6.2.2017
SINK MARKS MOULDING PROBLEMS Mould, Machine and Material related : (Table 1702) Filled polymer can reduce sink mark. POOR MECHANICAL STRENGTH
Consider high molecular weight polymers.
DIMENSIONAL VARIATION
Check shrinkage characteristics of material.
Consider filled polymers. Pre heat polymer in dehumidifier if required for polymer as recommended for polymer.
DEGRADATION Check thermal stability of polymer as well as OF MELT pigments and other additives if any used with material. DIFFICULTY IN Consider polymer of higher MFI FILLING Click here to see Understanding QUALITY Let us understand the factors influencing quality consistency in processing and quality in performance Let us understand moulding problems. HOME
Contactto buy this book
Things to know Process
Things to know Polymers
Things to know Part Design
Things to know Machine
Injection Moulding Process
Screw Plasticating
Moulding
Key factors influencing Shear strain proces curve
pvt diagram
Thermal stability
Balancing melt Flow
Balancing Heat
Freezing
Quality Problems
Three Balances
Mouldedin Stress
Shrinkage
Inconsistent Dimension
Sinkmark
Weldlines
Moulding Problems
CYCLE TIME
Plastics Part Design
Flow Analysis
..
..
Myth
Understanding Mould Cooling Channels
Ideal Moulding Shop
Engineering Glossary of technical Glossary of technical Basics in Machine terms Physics terms Polymer process
http://www.pitfallsinmolding.com/problems.html
Things to know Mould
3/3
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