SARATH BABU MADDUKURI

Index
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Product Design Environment

Product Design & Development Steps
1 End Use Requirement a) Anticipated Structural Requirement
Loads- Stresses a material will be subjected
Rate of Loading
Duration of Loading
Impact Forces
Vibration
Foreseeable Misuse b) Anticipated Environment
Temp Extremes c) Assembly and Secondary Operation d) Cost Limits e) Regulation Standards compliances

Product Design & Development Steps
1 Establish Preliminary Design( Preliminary Concept Sketch and Sections)
2 Select the material( Expected End Use Requirement, Material Data Sheets) a) Mechanical Properties used for essential component design calculations b) Other Relevant Properties
3 Modify Design as per the calculations results and desired function a) Specific property balance of selected grade b) Processing Limitation c) Assembly Method d) Cost of Modification

Product Design & Development Steps
4 CAD/CAE
1 Flow Analysis
2 Stress Analysis
5 Prototype and Testing
6 End Use Testing

Polymer Fundamentals

Polymer Fundamentals

Polymer Fundamentals

INTRODUCTION
Plastics were considered as “Replacing Materials”
Today’s world plastics are unreplacable materials on the same level as the classic materials:
- Primarily due to special combination of properties (profiles & material combinations)
- Plastics offers solutions, that are not possible with classic materials (Electronics,
Medical care, Automotive industries etc.)
- Low weight, allows high accelerations & decelerations.
- Weather resistance (Corrosion) is better than resistance of metallic materials.
- Good Electrical Isolation properties (Housings of Electrical devices)
- Low manufacturing costs, especially with injection moulding technology.

CLASSIFICATION :
MATERIALS
High-Molecular
(Makromolecular) materails
Organic
Thermoplastics
Synthetic resp.
Modified material
Thermosets
Metals
(as Ores)
Inorganic e.g. Glasses
Natural e.g. Wood
Elastomers
Thermoplastic elastomers
PLASTICS
Crosslinkable
(vulcanisible) elastomers
Crosslinked:rubber

They are thread-like molecules (Linear & Branched)
They are always Deformable – Fusible – Soluble.
As degree of polymerisation (molecule length) increases strength & toughness increases, but flowability decreases.
They are further classified as
Ø
Amorphous thermoplastics &
Ø
Crystalline (Partially crystalline) thermoplastics

Ø
Bulky thread-like molecules, with unarranged interconnected macromolecular structures, similar to that of staples in a cotton pad.
Ø
Transparent (Exception) : Styrol – copolymers with Butatein like
ABS.
Ø
Lower degree of Shrinkage & high precision can be achieved with less cost.
Ø
High elastic properties between melt & freezing (Glass transition) temperature makes it to be produced at low holding pressure to avoid demoulding problems & high internal stress.
Ø
They are more sensitive against solvents & the parts are more suspectable to stress cracking .
Examples:
Polycarbonate (PC) , Polyvinylchloride (PVC),
Acrylonitrile – Butadiene – Styrene – Copolymer (ABS), etc.

Acrylonitrile – Butadiene – Styrene – Copolymer (ABS) :
Structure : amorphous Density : 1,03 – 1,07 g/cm³ Elastic-Modulus : ~ 2400 N/mm²
Properties :
High rigidity & toughness also at low temperature to
– 40º C,
High Scratch resistance, High impact resistance, High suspectability to stress cracking
Temperature limits:
Short-Term ~ 100
°C, Long Term ~ 85°C
Surface Quality :
High gloss surface can be achieved.
Natural colour: opaque, non-transperant
Manufacturing related properties :
Low shrinkage & low tendency to wrap,
Good Paintability & electroplatability.
Applications :
Automotive panels - (Interior & Exterior parts), etc.

Acrylonitrile – Butadiene – Styrene – Copolymer (ABS) : Applications

Polycarbonate (PC) :
Structure : amorphous Density : 1,20 – 1,24 g/cm³ Elastic-Modulus : ~ 2200 N/mm²
Properties :
High strength & Hardness, Toughness at low temperature.
High impact resistance, High suspectability to stress cracking
Temperature limits:
Short-Term ~ 135
°C, Long Term ~ 100°C
Surface Quality :
High gloss surface can be achieved.
Natural colour: Transperant
Manufacturing related properties :
Low shrinkage & low tendency to wrap,
Good Paintability & electroplatability.
Applications :
Automotive panels - (Interior & Exterior parts), Headlights, Helmets, etc.

Polycarbonate (PC) : Applications

Polyvinylchloride (PVC) :
Structure : amorphous Density : 1,38
– 1,55 g/cm³
Elastic-Modulus
: ~ 3000 N/mm²
Properties :
High hardness & stiffness.
High impact resistance at low temperature till -5 °C, below this brittleness increases.
High suspectability to notch failure.
Temperature limits:
Short-Term ~ 70 °C, Long Term ~ 60°C
Surface Quality :
High gloss surface can be achieved.
Natural colour: Transperant till Opaque
Manufacturing related properties :
Low shrinkage
High chemical resistance
Applications :
Ducts, Ventilation Channels, tubes, etc.

Polyvinylchloride (PVC) : Applications

Ø
Bulky thread-like slim molecules, which are alligned or with each other.
Ø
Non transparent (translucent), naturally coloured good slip properties.
Ø
Higher degree of Shrinkage due to higher package of molecules.
Ø
Are less compressible than amorphous during hardening & freezing temperatures, hardly faces any demoulding problems.
Ø
Due to higher shrinkage may form voids during cooling.
Examples:
Polyethylene (PE), Polypropylene
(PP), Polyamide (PA), Polyacetal
(POM) etc.

Polyethylene (PE) :
Structure : Semi crystalline
N/mm²
Density : 0.91
– 0.96 g/cm³
Elastic-Modulus : ~ 1200
Properties :
High stiffness & Hardness. Good elastic properties.
Practically unbreakable, ductile till -60
°C
Temperature limits:
Short-Term ~ 135 °C, Long Term ~ 80°C
Surface Quality :
High gloss surface can be achieved.
Natural colour: milky white
Manufacturing related properties :
No water absorption, High Shrinkage & tendency to warpage
High chemical resistance
Applications :
HR inserts, Ducts, Channels, etc.

Polyethylene (PE) : Applications

Polypropylene (PP) :
Structure : Semi crystalline
N/mm²
Density : 0.90
– 0.92 g/cm³
Elastic-Modulus : ~ 1450
Properties :
High stiffness & Hardness. Stability higher than PE.
High flexural fatigue strength. Low impact strength at low temperature.
Temperature limits:
Short-Term ~ 140 °C, Long Term ~ 100°C
Surface Quality :
High gloss surface can be achieved.
Natural colour: Colourless shining through
Manufacturing related properties :
No water absorption, High Shrinkage & tendency to warpage
High chemical resistance
Applications :
Car – Coverparts (Interior & Exteriors), etc.

Polypropylene (PP) : Applications

Polyamide (PA) :
Structure : Semi crystalline Density : 1.02
– 1.15 g/cm³
Elastic-Modulus : ~ 1300 -
2800 N/mm²
Properties :
High stiffness & impact strength.
Good friction & wear resistance
Temperature limits:
Short-Term ~ 170 °C, Long Term ~ 110°C
Surface Quality :
High gloss surface can be achieved.
Natural colour: Translucent white-yellow
Manufacturing related properties :
Good flow properties & chemical resistance,
Not so good shrinkage. Tendency to warpage.
Applications :
Car – (Inner, Outer), Bearings, Gear wheels, etc.

Polyamide (PA) : Applications

They are closely crosslinked, that is the reason they are non – thermoplastic.
They are always Non - deformable – Infusible – Insoluble.
Examples:
Epoxy (EP), Phenol-formaldehyde (PF), etc.

They are loosely crosslinked, highly elastic & show very low plastic deformation.
They are highly deformable –Insoluble.
Examples:
Natural Rubber (NR), Ethylen-Propylen rubber (EOM, EPDM), etc.

Design Guidelines
REQUIREMENT (For what ?, strength, assy)
MATERIAL
SELECTION
PACKAGING DATA &
KINEMATICS
(Cost , Manuf Prosess,Temp conds,
Strength, Safety)
DECIDING SNAP & SCREW FIXING LOCATIONS
( From customer)
(Locking 6 deg. Of freedom, DFA
)
FIX TOOLING DIRECTION (Die-Draw direction, Minimum silder’s and aesthetic requirement
)
DECIDING STRENGTHING RIBS,LOCATIONS & GEOMETRY
(Packaging data, strength requirement)
DRAFT ANGLES,RIBS WALL THICKNESS RATIO (As per design guidelines)

Design Guidelines
TOOLING FEASIBILITY
( Minimum core thickness, Slider ejection space, Sharp corners etc.)
DRAFT ANALYSIS A & B SURFACES
SECTIONS WITH PACKAGING THROUGH SNAP & RIBS
( Tolerance issues)

Design Guidelines
The wide variety of injection moldable thermoplastics often makes material selection a difficult task.
Factors governing material selection
Ø
Cost
Ø
Functionality
Ø
Assembly (Typically when bonded)
Ø
Temperature
Ø
Strength
Ø
Government Regulations.
Ø
Surface finish/aesthetic etc.

Design Guidelines
Proper wall thickness determines success or demise of a product.
Like metals injection molded plastics also have normal working ranges of wall thickness. This can be taken into consideration while deciding wall thickness.
Factors to be considered while deciding wall thickness.
Ø
Structural strength of the part to be designed plays important role in deciding wall thickness.
Ø
Normal working ranges of wall from chart for particular material selected.
Ø
As a thumb rule 2.5mm.
Ø
Prior experience or bench mark parts can also be referred while deciding on wall thickness.

Design Guidelines
Once nominal wall thickness is decided, following are some design rules which should be followed.
Ø
Maintain uniform wall thickness wherever possible which helps in material flow in mold, reduces risk of sink marks, Induced stresses & consideration of different shrinkage
Ø
For non-uniform wall thickness change in thickness should not exceed
15% of nominal thickness & should transition gradually.
Ø
At corner areas minimum fillet at inner side should be 50% of wall thickness.

Design Guidelines
It is always recommended first to decide upon the core-cavity direction.
Generally core-cavity direction & parting line depends upon following parameters
Ø
The shape & function of the component. Shape in turn is governed by A-
Surface, packaging/environment data.
Ø
Core-cavity & slider directions should be considered such that they do not appear on A-Surfaces, unless otherwise specified & accepted by the customer.

Design Guidelines
Draft is necessary for ejection of part from the mold
& are always Tooling (Die-Draw) & Slider direction.
Recommended draft angle is minimum 1deg .
Factors governing draft angle.
Ø
Surface finish – Highly polished mold requires less draft than an unpolished mold.
Ø
Surface Texture (Graining) – Draft increases with texture depth,normally 1 deg draft for every
0.025mm
depth recommended.
Ø
Draw depth – To keep the draft angle to minimum as thumb rule draft angle – draw depth charts are followed & often design engineer should discuss with tool maker.

Design Guidelines
Ribs should be used when needed for stiffness & strength or to assist in filling difficult areas.
For structural parts where sink marks are no concerns
-Rib base thickness can be 75%-80% of adjoining wall thickness
For appearance parts where sink marks are objectionable: With texture (Graining) - Rib base thickness should not exceed 50% of adjoining wall thickness for part . Without texture
(Graining) - Rib base thickness should not exceed 30% of adjoining wall thickness.
Some important points to consider while rib design.
Ø
Draft angle on ribs should be minimum 0.5 deg per side
Ø
Rib height should be 2.5 to 3 times of wall thickness for effective strength. Recommended to add multiple ribs instead of single large rib, Spacing between multiple ribs should be at least 2 times that of rib thickness.
Ø
Fillets at base of ribs should be 0.5mm Minimum.

Design Guidelines
Usually designed to accept inserts, self tapping screws, drive pins etc for use in assembling or mounting parts.
Some important points to consider while Boss design:
Ø
The O.D of the boss should be ideally 2.5 times of screw diameter for self tapping screw applications.
Ø
If O.D exceeds 50% of adjoining wall thickness, thinner wall boss of
O.D 2 times or less of screw diameter can be considered with supported by ribs.
Ø
Bosses should be attached to walls with ribs. Thickness at base of rib should not exceed 50% of adjoining wall thickness.
Ø
Boss inside & outside diameters should have 0.5 deg draft per side.

Design Guidelines

Design Guidelines
Coring in injection molding terms to addition of steel to mold for the purpose of removing plastic material in that area
Coring is necessary to create Pocket or, Opening in the part or to reduce heavily walled section.

Design Guidelines
Openings are desired in a part to eliminate sliders, cams, pullers, etc. to accommodate features like snaps.
As general thumb rule 5deg angle in the area of mating of core & cavity is required.

Design Guidelines
Types of assemblies :
Ø
Molded-in assembly
Ø
Chemical bonding assembly
Ø
Thermal welding assembly
Ø
Assembly with fasteners.
Molded-in Assembly : (Snap fit, Press fit, molded in threads etc.)
This is generally the most economical method of assembly.
Assembly is fast, inexpensive & does not require any additional part or substance. Minimizes changes of improper assembly.
Some times tooling becomes complex & expensive.

Design Guidelines

Design Guidelines
Y = Deflection
Important points to remember :
Ø
Design for given assembly force or overlap length & material.
Ø
Deflection required to assemble the part should always be less than maximum deflection(strain) for safe design.
Ø
Snaps increase possibility of sliders wherever possible try to eliminate sliders by providing slot below snap or moving snap to outer edge of the part, if design permits.
Q values to be referred from
Material graphs

Design Guidelines
Ø
Press fit design is more critical in plastics (Thermoplastics as they creep (Stress or Relax).
Ø
Good design should minimize stress on the plastic,by considering assembly tolerance between assembled parts & clamping force due to creep relaxation.

Design Guidelines
Ø
Two similar or dissimilar plastics can be assembled in a strong leak-tight bond by using adhesives.
Ø
The choice of adhesive depends upon the application & the environment to which the part would be subjected.
Ø
Some of adhesives are Polyurethanes, Epoxies, Cyanoacrylates, Silicones etc.

Design Guidelines
Ø
Certain precaution must be taken while designing to reduce excessive compressive stress on the plastic.
Ø
Larger head screw or larger washer is preferred as that contact area increases & stress reduces.

Design Guidelines
Ø
Coarse threads are preferred due to higher strength & torque limits.
Ø
Generally 0.8 – 0.9 mm relief should be provided to prevent high stress at the end of the threads.
Ø
To reduce the stress concentration minimum 0.25mm radius should be applied to the threads roots.
Ø
External threads should be as far as possible located on parting lines to avoid need of unscrewing mechanism.
Ø
Internal threads are usually formed by an unscrewing or collapse core.

Design Guidelines
Further classified in 2 types Thread cutting & Thread forming
Ø
Thread cutting screw is most used on brittle plastics such as thermosets & filled (50%) thermoplastics.
They should not be reinstalled
Ø
Thread forming screws is mostly used on thermoplastics. They can be reinstalled for 3 to 5 times.
General Guidelines while using self-tapping fasteners :
1.
Thread engagement length 2.5 times screw diameter
2.
Boss diameter minimum 2 times of pilot hole diameter.
3.
Cored hole should have 0.25 ° to 0.5° draft.
4.
Holes should be counterbored or chamfered to a depth of 0.5mm to aid alignment & avoid cracking of boss.
5.
Sufficient clearance to be kept between screw end
& bottom of the hole.

TOLERANCE RANGE TO BE GIVEN ON DWGS:

SLIDER FOR UNDERCUT :
Horn Pin
Molded Part
Slide
Undercut

SLIDER FOR UNDERCUT :

SLIDER FOR UNDERCUT :

SLIDER FOR UNDERCUT :
Cover tool
Horn Pin
Locking Block
Slide core
Molded part
Undercut
Spring

SLIDER FOR UNDERCUT :

SLIDER FOR UNDERCUT :

SLIDER FOR UNDERCUT :

LIFTER FOR UNDERCUT :
Lifter
Undercut
Angled pin

LIFTER FOR UNDERCUT :

LIFTER FOR UNDERCUT :

LIFTER FOR UNDERCUT :
Lifter
Undercut
Horn pin
Lose core
Molded part

LIFTER FOR UNDERCUT :

LIFTER FOR UNDERCUT :

LIFTER FOR UNDERCUT :

HYDRAULIC CYLINDER FOR UNDERCUT :
Core pin Undercut
Hydraulic Cylinder

HYDRAULIC CYLINDER FOR UNDERCUT :

HYDRAULIC CYLINDER FOR UNDERCUT :

FORCED EJECTION :

FORCED EJECTION :

FORCED EJECTION :

FORCED EJECTION :

FORCED EJECTION :

MULTIPLE UNDERCUTS
Molded Part
Hydraulic Cylinder
Slide

MULTIPLE UNDERCUTS

MULTIPLE UNDERCUTS

MULTIPLE UNDERCUTS

MULTIPLE SLIDERS:
Locking Block
Core Pin
Horn Pin
Slide
Molded part
Undercut
Spring

MULTIPLE SLIDERS:

MULTIPLE SLIDERS:

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Product Design & Development Steps
1 Design For Stiffness
Relation between load and deflection of the part is Stiffness
Determined by material and geometry of the part
Material Stress Strain Curves ( Young's Modulus)
2 Design For Strength
Max Load that can be applied to a part without resulting into part failure
Determined by Tensile stress strain curves( Tensile Strength etc)
3 Design for Behavior overtime
Creep : Time dependent Increasing Strain under constant stress
Stress Relaxation: Reduction of stress under constant strain

Product Design & Development Steps
3 Design for Impact Performance
Ability of material to withstand impulsive loading
Factors: type of material, geometry, wall thickness, size of component, operating temp, rate of loading etc
3 Design for appearance
Sink Marks, weld lines, air traps, voids, streaks, delamination, jetting, gate marks etc
4 Design for precision
5 Design for moldability
6 Design for Recyclability
7 Design for automation

Part Application Requirement

Material Selection Process

Material Selection Process

Design Based Material Selection

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Guidelines for Injection Molded Design

Plastic Processing

Plastic Processing

Plastic Processing-Injection Molding

Plastic Processing-Injection Molding

Plastic Processing-IMD

Plastic Processing-Injection Molding

Assembly Techniques for Plastic parts

Assembly Techniques –Snap Fits
Snap fit cantilever beam type
Snap fit cylindrical Type

Assembly Techniques –Snap Fits
Factors for calculating cantilever beam for Snap fit

Assembly Techniques –Snap Fits
Mold Design For Snap Fits

Assembly Techniques –Spin Welding

Assembly Techniques –Ultrasonic Welding

Assembly Techniques –Hot Plate Welding

Assembly Techniques –Adhesive Bonding

Assembly Techniques –Ultrasonic Insertion

Assembly Techniques –Screw and Bosses

Assembly Techniques for Plastic parts

Injection Mold

Injection Mold

Injection Mold- Slider and Stripper Plate

Injection Mold- Stripper Plate

Injection Mold- Stripper Plate

Injection Mold-Hot Runner System

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2. Utilize the appropriate radii where applicable:
3. Strive to use snap fit and thread forming screws whenever possible to eliminate hardware, maximize design for assembly (DFA), and achieve the lowest cost.
4. Draft is mandatory. 1.5 degrees per side, plus 1 degree per 0.001 depth of texture.
5. Eliminate side draws (slides) and undercuts (lifters) whenever possible. Use through wall openings.
6. Use the general tolerance box - tight tolerances drive up part and tooling cost.
7. Do not put datum on flexible walls or points in space.

Typical Rules for Rib Thickness
Conventional Thermoplastics - 0.7T some sink mark will come
- 0.4T for part which is visible.
Structural Foam - 1.0T

It is important to use uniform walls to minimize warp age and maximize manufacturability potential.
Injection Molding : 2 to 4mm
Structural Foam : 5 mm
No thin areas less than 1.5mm
No thick areas - core for uniform sections.
Always try to core from the ejector side of part.

Draft is needed to facilitate release of part from mold.
The draft to use, unless otherwise specified, is 1.5 degrees per side.
Indicate if draft is to be added or subtracted from nominal dimension.
Show draft on part whenever possible to avoid confusion as to direction.
The "No Draft Allowed" is not to be used. Even on critical areas allow 0.5 degrees.

Eliminate undercuts by alternative redesign.
A minimum of 5 degree shut-off is required for all areas around a through opening. A 7 degree angle is even better.
See "Bad" steel conditions for steel limitations

Generally, "Bad" steel conditions can be avoided if all standing steel has a height to width ratio of 1:1 or better.

Slide Core
Horn Pin
Molded Part
Slide
Undercut

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core
Cover tool
Horn Pin
Locking Block
Slide core
Molded part
Undercut
Spring

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core
Locking Block Core pin
Horn Pin
Slide core
Molded part
Undercut
Spring

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Slide Core

Accelerated Lifter
Lifter
Undercut
Angled pin

Accelerated Lifter

Accelerated Lifter

Accelerated Lifter

Accelerated Lifter

Accelerated Lifter

Accelerated Lifter

Accelerated Lifter

Hydraulic cylinder
Core pin Undercut
Hydraulic Cylinder

Hydraulic cylinder

Hydraulic pin

Ejecting molded part

Ejecting molded part

Actuating Core pin

Ejection of undercut part
Undercut
Hydraulic Cylinder
Slide Core

Ejection of undercut part

Ejection of undercut part

Ejection of undercut part

Ejection of undercut part

Ejection of undercut part

Ejection of undercut part

Ejection of undercut part

Ejection of undercut part

Ejection of undercut part

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Pendulum Core
Pin

Center Rib with Undercut
Undercut

Center Rib with Undercut

Center Rib with Undercut

Center Rib with Undercut

Center Rib with Undercut

Center Rib with Undercut

Center Rib with Undercut

Forced Ejection

Forced Ejection

Forced Ejection

Forced Ejection

Forced Ejection

Multiple Undercut
Molded Part
Hydraulic Cylinder
Slide

Die Opening

Die Opening

Lifter Ejection

Part Ejection

Lifter Return

Slide Return

Die Closing

Multiple External Slides
Locking Block Core Pin
Horn Pin
Slide
Molded part
Undercut
Spring

Multiple External Slides

Multiple External Slide s

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple Undercuts

Multiple External Slides
Locking block Core pin
Horn Pin
Slide
Molded part
Under
Spring

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Multiple External Slides

Lifter
Angled Lifter
Undercut
Horn pin
Lose core
Molded part

Angled Lifter

Ejection

Ejection

Ejection

Ejection

Die closing

Die closing

Die closing

A B

Injection Mold-Hot Runner System