Today's KNOWLEDGE Share : Packing Phase

-

Today's KNOWLEDGE Share

Understanding Shrinkage in Injection Molding: The Role of the Packing Phase

In injection molding, shrinkage is fundamentally linked to thermal expansion.


However, this relationship can become complex, especially when we factor in the "Packing Phase."


During this phase, we apply significant pressure to the molten material, allowing us to inject more grams of material into a predefined mold volume, assuming we disregard mold deformation for now.

As a result, the final shrinkage can vary widely—ranging from high shrinkage, dictated by the room pressure PvT curve (in cases where no packing is applied), to even negative shrinkage in situations of overpacking.


While the basic principles of shrinkage are driven by Coefficient of Thermal Expansion (CTE), the reality is much more nuanced.


For instance, with glass-filled polymers, increased packing pressure can influence the anisotropy-driven warpage of the material; it may even suppress warpage without affecting the CTE anisotropy itself.


source:Vito leo

Comments

Post a Comment

Popular posts from this blog

Today's KNOWLEDGE Share:PLA BOTTLE

-
Image
Today's KNOWLEDGE Share Ever wondered how we can reduce plastic pollution in India? The Mysuru-based Defence Food Research Laboratory (DFRL), affiliated with the DRDO, has launched an eco-friendly remedy with the introduction of biodegradable water bottles. Crafted from sustainable Polylactic acid (PLA) material, these bottles not only combat plastic waste but also contribute to reducing the overall carbon footprint. The best thing about this bottle is its all-encompassing sustainability approach – the bottle, cap, and label are all compostable. This innovation, derived from 100% bio-based and renewable sources, sets us on a path towards environmental conservation and fosters a greener and more sustainable future. Source:The Better India #polymers #bioplastics #pla   #compostable   #ecofriendly   #sustainability
Read more

Today's KNOWLEDGE Share:High and low shear rate changes in Rheology

-
Image
Today's KNOWLEDGE Share If a relatively high Mw grade flows from thin to thick, as shown in the picture, and if the time needed to fill the thick section is way shorter than the average polymer relaxation time, the polymer will not be able to reach its higher viscosity (corresponding to higher thickness/lower shear-rate). I am assuming here the polymer reached equilibrium low viscosity in the thin section, say for instance because it is much longer. Any pressure prediction not accounting for transient rheology would then overpredict the pressure to fill.Of course the diverging flow will further complicate the situation and mess with the molecular orientation created in the thin section, but to what extent ? Since this is more of a reasonable "conjecture", don't take this for granted, and discuss or share your opinion in the comments. There are hundreds of Rheology papers on the "4:1 contraction flow". Not sure I have ever seen any on the..."1:4 expansio
Read more

Bibby Marine Orders First Battery and Methanol Powered eCSOV

-
Image
  A shipbuilding contract has been completed for what is being called the “world’s first truly zero-emission, electric Commission Service Operation Vessel,” which is being built as part of UK sponsored demonstration project. The ship is expected to enter service in the UK in 2026 using a combination of a powerful battery system along with dual-fuel methanol engines. A coalition of leading maritime companies led by Bibby Marine proposed the project as part of the UK’s Zero Emission Vessels and Infrastructure (ZEVI) project staged by the UK Department of Transportation. A total of £80 million was awarded to 10 projects in the 2022 round with the Bibby effort being   awarded   $25 million. They estimated the cost of the project for the vessel at $37.5 million total. Bibby Marine reports that it completed a tender process and has selected Gondan to build the vessel. The Asturias shipyard in Spain won out of a variety of yards in the UK and internationally. Bibby cites the timeline, budget,
Read more