Extruders: defects and troubleshooting.pptxAbhijithKS36
The slide contains details of most common defects and troubleshooting(reason, causes, remedy) of polymer extruders used in industries for various types of polymer product manufacturing.
Extruders: defects and troubleshooting.pptxAbhijithKS36
The slide contains details of most common defects and troubleshooting(reason, causes, remedy) of polymer extruders used in industries for various types of polymer product manufacturing.
Pultrusion is a continuous process for manufacture of composite materials with constant cross-section.
It is more widely used in industries where there is a continuous demand of the product
http://www.spiratex.com/ : Understand the complete process of custom plastic extrusion with step by step details of the process through this presentation. It also explains the various specialized forms of plastic extrusions.
This PPT contains information about basic operations of Powder Metallurgy(PM). it is consist of manufacturing techniques of powder, and manufacturing of products by the powder.
My presentation on resin transfer molding. Not much description included. For reference i would recommend
" Composite manufacturing by Sanjay Mazumdar".
Pultrusion is a continuous process for manufacture of composite materials with constant cross-section.
It is more widely used in industries where there is a continuous demand of the product
http://www.spiratex.com/ : Understand the complete process of custom plastic extrusion with step by step details of the process through this presentation. It also explains the various specialized forms of plastic extrusions.
This PPT contains information about basic operations of Powder Metallurgy(PM). it is consist of manufacturing techniques of powder, and manufacturing of products by the powder.
My presentation on resin transfer molding. Not much description included. For reference i would recommend
" Composite manufacturing by Sanjay Mazumdar".
Ekeeda Provides Online Engineering Subjects Video Lectures and Tutorials of Mumbai University (MU) Courses. Visit us: https://ekeeda.com/streamdetails/University/Mumbai-University
Ekeeda Provides Online Engineering Subjects Video Lectures and Tutorials of Mumbai University (MU) Courses. Visit us: https://ekeeda.com/streamdetails/University/Mumbai-University
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Laser beam manufacturing is used for manufacturing difficult parts that cant be done using conventional machining methods.
This ppt covers the advantages and disadvantages of using LBM.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
2. The profile of extruded material grows in size, reflecting its tendency to
return to its previously larger cross section in the extruder barrel immediately
before being squeezed through the smaller die opening.
Shape memory: Extruded polymer remembers its previous shape when it
was in the larger cross section of the bar.
Die swell
3. Die swell
Die swell occurs because the sudden release of pressure causes the polymer
chains to relax
Polymers are viscoelastic Time dependent stress relaxation
Die swell =
𝐷2−𝐷1
𝐷1
, where 𝐷1 is the inner diameter of the die and 𝐷2 is the
average outer diameter of the extruded part.
Die swell can vary from 10% to over 100% increase in dimensions depending on:
1. Material
2. Melt temperature
3. Extrusion speed
4. Die geometry
4. Die swell
Notes:
1. Short-land dies leads to greater swell.
2. Long-land dies leads to less swell.
3. Higher output rate leads to viscous heat generation (frictional heat).
4. Higher output rate leads to greater swell.
5. Die swell
How to avoid ?
1. Decrease the extrusion rate (screw speed).
2. Increase the length of the die end (land).
3. Increase the drawdown ratio by improving design factors.
6. Die swell
Drawdown: The size of the designed die dimensions relative to the final part
dimensions. The dimensional ratio of the die to final part is used to offset the
“swell” of the thermoplastic as it exits the die.
Land length: The length of the steel (of die) that runs parallel to the polymer
flow. The land-length ratio is the ratio of the land length to the die gap (wall
thickness).
13. Causes
Moisture Absorption
Trapped Air
Polymer Degradation
Depolymerization of the Polymer
Incompatible additive
14. Causes: Moisture Absorption
Polymers have high moisture absorption. Some
plastics, such as PET, the nylons, and
polycarbonate, can degrade and weaken if even a
tiny amount of moisture is present
When the polymer pellets are heated, the absorbed
moisture is also heated and turned into steam. It
passes through the extruder and boils when the
pressure is relieved at the die lips.
The result is a pattern of long bubbles, and pits.
15. Causes: Moisture Absorption
Remedies:
To remove moisture, the material must be pre-dry in a hot over
before loading into the hopper.
Dehumidifying dryers are used to get moisture down to 0.01% or
less which is enough to avoid problems.
A vent must be used in the extruder to remove the trapped
steam.
16. Causes: Trapped Air
This is more common if the starting material is powder and not pellets.
This is not common in pelletized material used with long extruder
barrels. However, some old machines have short barrels, and even a
long machine can be pushed so fast that the air is carried forward into
the product.
A trapped-air surface shows bubbles and pits.
17. Causes: Trapped Air
Remedies:
Such a surface will improve if run more slowly if moisture is not
the problem, so we need to avoid the over-speed of extrusion.
Vents and vacuum hoppers will eliminate trapped air and are
essential for powders, where passages between the particles are
much smaller; the air cannot escape back through these passages
and is carried forward instead.
18. Causes: Degradation of Polymer
Overheating may produce degradation of the polymer material that is used.
The degradation varies from one polymer to the other.
For example, PVC is the most susceptible to degradation as its processing
temperature is always close to its decomposition temperature.
This degradation might cause the polymer to produce gases that might
become trapped inside the material.
19. Causes: Degradation of Polymer
Remedies:
Avoid overheating and make sure that the temperature we heat the polymer is safe
and causes no degradation.
Very accurate temperature control is needed for materials susceptible to
degradation.
20. Causes: Depolymerization of Polymer
It is the process of converting a polymer into a monomer or a mixture of
monomers. All polymers depolymerize at high temperatures driven by
increase in entropy.
Some of the products of the depolymerization could be volatile monomers,
that could be entrapped inside the material.
Remedies:
Avoid overheating and make sure that the temperature we heat the polymer is safe
and causes no degradation.
21. Blistering:
Blistering may be caused by water either absorbed into the granules or lying on
the surface. The amount of steam produced to give blisters will depend on:
the amount of water present
the extrusion temperature.
Polymers are hygroscopic and /or require a high process temperature are
normally carefully dried and stored in sealed tins.
22. SCREW ROTATION TOO FAST
“A screw rotation speed that is too high will tend to ``whip'' air into the molten
plastic. This excessive air may not be drawn out of the material during the
molding process and pockets of the air may be forced to the surface of the
molded part, forming blisters.”
LOW BACK PRESSURE
“The back pressure setting controls the density of the melt. A low setting results
in a melt that is not dense enough to push out excessive gases.”
USING A FLATTER TEMPERATURE PROFILE ALONG THE BARREL.
Blistering: Reasons
23. Relation:
“When there are problem handling fluid polymers it is often advisable to change
to a higher molecular weight grade of polymer”
24. PVC :
Polymer degrade on subjection to continual heating but some are
more resistant than others.
Among the important commercial thermoplastics PVC is probably the
most susceptible to degradation since it is processed at temperature
close to its decomposition temperature; Therefore, when extruding
PVC very accurate temperature control will be necessary;
25. Lumpiness :
Some extrudate may have a glossy finish but are lumpy
and very irregular. This is usually the result of poor mixing
of the melt. Good mixing is necessary temperatures and
also subjected to different shear conditions and will thus
have different viscosity .
Decreasing the melt temperature in the die will increase
melt viscosity and increase the back pressure. Hence
decreasing the die head temperature may help to reduce
lumpiness
27. Shark-Skin : Pressure Plateau
Through the lower region of the curve, melt flow is steady and bottle surfaces are
smooth
As melt pressure continues to increase, suddenly sharkskin occurs.
if extrusion pressure is raised still further, the sharkskin disappears. Actually, neither
the parison nor the bottle is quite as smooth as one produced in the steady-flow
region.
28. Melt Fracture:
Pseudoplastic materials become less viscous with increase in shear rate.
Thermoplastic melts almost invariably show pseudoplastic behavior.
Above some critical shear rate most thermoplastics exhibit a phenomenon
variably known as elastic turbulence or melt fracture. It is characterized by
various type of distortion which have a helical form .
Increase the melt temperature increases the critical shear rate for onset of
melt fracture. The effect may therefore be reduced and perhaps even
eliminated by reducing the shear rate and /or decreasing the temperature.
The critical shear rate for onset of melt fracture is reduced by increasing
molecular weight. Therefore, melt fracture is more likely to occur with high
molecular weight grades than low molecular weight grade
30. Five pictures of a of molten polyethylene flowing out of a pipe, visible at the
top. The flow rate increases from left to right.
Note that in the two leftmost photographs the extrudates are nice and
smooth, while in the middle one undulations start to develop. As the flow rate
increases even further towards the right, the amplitude of the undulations
gets stronger. When the flow rate is enhanced even more, the extrudate can
break. Hence the name "melt fracture".
Melt Fracture:
32. Melt Fracture : Remedy
The melt fracture effect can be reduced by:
lowering the shear rate
Raisingthe temperature
using the material of lower molecular weight
33. Black Lumps:
The extruder may show black lumps or flecks.
These may be due to polymer stagnate some points in the machine and
decomposing. Pieces of decomposed material are then swept away by molten
polymer at irregular intervals.
The problems may be avoided by :
lowering extrusion temperature
regularly cleaning dies
avoiding dead spots. The black particles may occur due to contaminated
compound also.
34. Knitting Error :
When polymer melts pass round a spider leg and or through a breaker plate
the molten material is separated. unless there is a high pressure on the side
of the spider and /or breaker plate the separated melt will not fully knit
together and lines or planes of weakness willoccur.
The head pressure may be increased by:
Increased the die land reducing the cross sectional area at the die
lowering the die temperatur
35. Plate-Out :
When extruding polymers, additives are sometimes deposited from the melt
onto the forward part of the screw and onto the extruder head and die. This
effect is know as plate- out and is most frequently met within PVC. Deposition
occur s most frequently in regions of high temperature and high shear.
Formulation also has an important influence.
This can be reduced by:
lowering the die head temperature
reducing extrusion speed
change the formulation