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Quality tool Training ppt

1. 44650 Helm Court
Plymouth, MI 48170
[phone]
Plastic Molding Seminar
Basic Plastic Molding Technology
An MMI customized seminar on industry
standard practices for injection molded plastic
part design, tooling, materials and
applications.

2. Seminar Objective
•An understanding of injection molding processing, mold
tooling, and part design.
•Familiarity with plastic terminology and concepts.
•A grasp of plastic molding’s strengths and limitations.
•Basic design guidelines for injection molded parts.
•Knowledge of the available array of plastic materials,
their key properties, and potential applications.
•The ability to recognize injection molded applications.
The main objective of this seminar is to provide
you with additional resources that can be readily
applied to current and future projects and improve
your overall effectiveness. We hope you to leave
with the following:

3. Agend
a
1.Processing
2.Injection Mold Design
3.Part Design
4.Design and Analysis Tools
5.Materials and Applications
Appendices: Part Design Guide (GE)
Material Data Sheets
We find that the following topics build off each other best in the
following order. We start with describing the overall process
and work our way down to mold design, then the actual part.
The design/analysis tools and materials/applications sections
tie in with each of the previous sections.

4. 44650 Helm Court
Plymouth, MI 48170
[phone]
Processing
Injection Machine Layout
Injection Stages

5. Injection Press

6. Injection Press Operation
Stage 1: Startup
Stage 2: Barrel Fill

7. Injection Press Operation
Stage 3: Injection
Stage 4: Cooling

8. Injection Press Operation
Stage 5: Opening
Stage 6: Eject

9. Injection Press Operation
Stage 7: Close
Stage 8: Reset

10. 44650 Helm Court
Plymouth, MI 48170
[phone]
Injection Mold Design
Basic Mold Components
Runner Systems
Hot Manifold Systems
Cylinders/Slides/Lifters

11. Injection Mold Assembly
The injection mold assembly includes A/B Plates, the Eject
System, and any Hot Runner System (not shown). The assembly
is fitted into the press between the Nozzle and Knockout Pins.
Cavity: Open area shaped to
create the part geometry.
Sprue: Removed in secondary
operation.
Parting Line: Contact surface
between A & B Plates.
Return Pins: Push back eject
plate upon mold closure.
Cooling Lines: Used to regulate
mold temperature.
Nozzle & Knockouts: Included
on the press - not part of
the mold assembly.

12. Mold
Components
Basic Features of a (2-Plate) Injection Mold Assembly

13. Cold Runner System
Runner Systems are employed to distribute the material from the
nozzle to different gate locations. A common situation that requires
this feature is a Multiple Cavity Mold.
•Gates are positioned at the material
entrance point of the part cavity. Their
size and geometry vary based upon
material, flow length, and other factors.
•The Sprue and Runners are removed
from the part after molding in a
secondary operation.
•The runner system should be balanced
in order to create consistent parts from
different cavitities.

14. Hot Runner System
Hot Runner Systems are employed to keep the material hot up until
the point of entry at multiple locations.
•The Hot Manifold and Hot
Sprue Bushings contain
heaters that keep the melted
plastic from hardening until
reaching the mold cavities.
•Saves part material (no cold
sprue/runners to remove).
•Increases tooling cost.
•Increases setup time.

15. Example: Hot Runner System
4 Drop Hot Manifold System. This is a Cross-sectional view
taken through 2 of the manifold legs to show the material
chambers.
Cross-Sectional Cutout

16. Die-Lock
Mold designers must consider the method of
removing the formed part from the mold. Often the
part geometry requires that the mold open in more than the
standard 2 directions.
This section of the tool must
be pulled in this direction in
order to release the part.
Note that the formed part is
‘trapped’ in the A-Plate due to the
additional geometry on the top end.
This unwanted condition is called a
Trap or Die-Lock.
Die-Lock requires
a Side-Pull. The
three common
methods are:
•Cylinders
•Slides
•Lifters

17. Side-Action: Cylinders
The most straightforward method of incorporating
side-action is by attaching a core block (red) to a
cylinder mounted to the side of the mold
Event Sequence:
1.Part forms in cavity.
2.Mold opens.
3.Cylinder pulls back core block.
4.Part Ejects.
5.Eject and Cylinder move back
to original positions.
6.Mold Closes.

18. Side-Action: Slides
Another more common method of side-action uses a slide that is
activated automatically by the opening of the mold. A horn pin
attached to the A-Plate acts as a guide.
Event Sequence:
1.Part forms in cavity.
2.Slide is pushed back by the horn
pin and springs as mold opens
3.Part Ejects.
4.Slide is pulled back into place
by horn-pin as mold closes.

19. Side-Action: Lifters
A third less common technique actually ejects the part with the core
block. At this point the part can be pulled out by the operator. In
this scenario, the core block is called a lifter.
Event Sequence:
1.Part forms in cavity.
2.Mold opens.
3.Eject system pushes out part
with core block attached.
4.Part is removed.
5.Mold closes.

20. Example: Side-Action

21. 44650 Helm Court
Plymouth, MI 48170
[phone]
Part Design
Wall
Thicknesses
Draft
Radii
Rib/Boss Design
Undercuts

22. Wall Thickness - Coring
Typical injection molded parts should have a uniform wall
thickness to allow even flow and cooling.
•Nominal wall thickness normally falls between 1/16” and 1/4”
depending upon material, desired strength, and necessary flow
length.
•Thicker sections require longer processing times for cooling.
•Sharp transitions in wall thicknesses can cause uneven shrinkage that
leads to molded-in stress and warpage.
•Coring is the process of
removing thick sections
from a part design.

23. Rib Design
Ribs are added to give part strength, but
introduce the following problem in
maintaining even wall thicknesses. The
intersection point automatically creates a thick
section.
The thicker the section  the slower the cooling  increased
shrink
This phenomenon results in sink marks on the outside wall.
To avoid sink ribs should be constructed at
50% to 75% of the nominal wall thickness.

24. Boss Design
Bosses, used to reinforce
holes, also introduce thick
sections and follow the
same design guidelines as
ribs. There are many
methods available to
optimize the plastic design
of these features.

25. Draf
t
Draft is required on surfaces perpendicular to the
parting line (or side-action features as applicable).
Benefits
•Aids in part ejection.
•Prevents marks on side
walls from tool separation.
•Reduces tool wear.
Issues
•Often results in thicker
sections – especially on
tall ribs.
•Tooling more complex.

26. Corner Radii
Sharp, inside corners have a dramatic
weakening effect upon part strength. Radii
should be employed wherever possible.
Benefits
•Avoids stress concentrations.
•Aids in flow of material during processing.
•Reduces molded-in stress points.
Issues
•Often creates thick sections – especially on
ribs.
•Design clearances restrict use.
Note: Unlike machining a
solid, when building a
mold cavity it is usually
easier to put a radius on
an outside part corner due
to the cylindrical shape of
the cutter.

27. Undercut
s
Undercuts are features in the part that require a
lifter, slide, or a through core. A through core
is a is a telescoping finger that requires a
window in the part.
Undercuts require shutoff areas in
which the tool plates must be able to
open and close cleanly. This requires
the following conditions:
•Draft on both sides of shutoff.
•Exact matching of tool geometry.
The potential effects of shutoff
considerations on part design.
•Widened holes in part to allow for
tooling draft.
•Draft of some sidewalls.
•Necessity of some sharp part edges.
In cases where the shutoff is not sufficient, plastic will slip
between the mold plates creating a condition called flash.

28. Other
Considerations
Understanding the mold layout will help identify issues that
do not typically appear on the part prints. The following
mold features do appear on every injection molded part and
should be moved away from critical surfaces.
•Gates/Hot Sprue Points
•Eject Pins
•Parting Lines
•Knit Lines
(defined below)
When material flows around a feature such as
a hole, it must rejoin on the other side. This
creates a knit line, which will be somewhat
weaker than the surrounding plastic.
Gate

29. 44650 Helm Court
Plymouth, MI 48170
[phone]
Design and Analysis Tools
CAD Solid Modeling
CAM Machining
Mold Flow Analysis
FEA
Dynamic Analysis

30. CAD – Solid Modeling
CAD Solid Modeling has provided great benefits for
plastic part and mold design that go well beyond
advanced visualization abilities.
•Obtain quick and accurate part mass and volume
properties for costing purposes.
•Models can be directly imported into FEA and
dynamic simulation programs.
•Provides ability to conduct Mold Flow Analysis.
•Part model can be cut directly from the mold model
to quickly create cavities for mold design.
•CNC machining of mold can be programmed
directly to the solid model of the mold.

31. Computer Aided Machining (CAM)
Computer Aided Machining allows tool engineers to
program the entire machining process on a computer
before cutting the first chip.
•Identify issues before machining begins.
•Full planning before the physical material is available.
•Machines can operate with minimal supervision – even
after hours.

32. Mold Flow Analysis
Mold Flow Analysis simulates how the mold will fill
from the solid model. This allows optimization of
the following mold and processing characteristics.
•Cavity Layout
•Runner Systems
•Gate Design
•Injection Pressures
•Material Selection
•Processing Times
•Clamp Pressures

33. Finite Element/Dynamic Analysis
Finite Element Analysis is becoming more accurate,
more robust, quicker, and easier to apply year-by-year.
It has become an invaluable tool to engineering
companies that depend upon strong design capabilities.
•Load-Deflection Analysis
•Static Stress Analysis
•Dynamic Loading Analysis
•Motion Simulation
•Noise, Vibration, Harshness
Studies (NVH)

34. 44650 Helm Court
Plymouth, MI 48170
[phone]
Advanced Techniques
Molded-In Inserts
Overmolding
Snap Design
Living Hinges

35. 44650 Helm Court
Plymouth, MI 48170
[phone]
Plastic Materials & Properties
•History of Plastics and Polymers
•The Structure of Polymers
•Types of Polymers
•Material Selection
•The Thermoplastic Selection Tree
•Some Examples

36. The History of Plastics
•Polymers have been with us since the
start of time
•Natural Polymers
–Tar
–Shellac
–Tortoise Shell and Horns
–Tree Sap
•Chemically modified in 1800’s
–Vulcanized rubber
–Gun Cotton
–Celluloid
•First Synthetic Polymers
–Bakelite in 1909
–Rayon fibers in 1911

37. The Structure of Plastics

•A Monomer is a single link in a chain
•By joining these links together, materials
are built with useful properties
•Building monomers together forms a
Polymer.

38. The Structure of Plastics
•Plastics are
Polymers
•Polymer is from
the Greek words
“Poly” meaning
many and “Mer”
meaning parts
•The most simple
type of polymer is
a hydrocarbon – a
polymer created
from a single
monomer

39. The Structure of Plastics
•Copolymers are
created when the
polymer is built
from multiple
monomer links
•ICP – PP with a
rubber phase
•Acrylonitrile –
Butadiene –
Styrene (ABS)

40. The Structure of Plastics
•Blending two or more polymers together
without a chemical reaction results in the
creation of an Alloy
•The benefit of creating an alloy is to
achieve properties better than either of
the individual materials
•Common examples of alloys frequently
used are:
–Polycarbonate/ABS (Dow Pulse, GE Cycoloy)
–Polycarbonate/PBT (Xenoy)
–PPO/PA, PPE/PA (Noryl, Noryl GTX)

41. The Structure of Plastics
•Some polymers pack
together tightly in a
regular pattern
•These polymers have
a characteristic called
SEMI-CRYSTALLINE
•Materials that do not
crystallize upon
turning solid are
called AMORPHOUS

42. Semi Crystalline
•Exhibit a very sharp melting point
•With a small increase in temperature
they become liquid or melt
•Melting behavior similar to a household
candle
•Provide superior properties, but exhibit
high shrink as they cool and reharden
•Common examples of semi crystalline
materials are:
–Nylon
–Polyethylene
–Polypropylene

43. Amorphou
s
•Do not crystallize upon solidifying
•Demonstrate a gradual softening as the
temperature is increased
•No specific melting temperature
•Usually not as easily processed as a
crystalline material
•Most commonly processed just above
the Tg – Glass Transition Temperature
•Common examples of amorphous
materials are:
–ABS
–Polycarbonate
–Acrylics

44. Semi Crystalline vs. Amorphous

45. Types of Polymers
•Thermoset
polymers are like
concrete
•One chance to
liquify and shape
•“Cured” using heat
and pressure or a
chemical initiator
•Common examples
–Phenolics
–Epoxies
–Cast urethanes
•Thermoplastic
polymers are like
wax
•Can melt and shape
multiple times
•Processed by
heating and cooling
•Common examples
–Polypropylene
–Nylon
–ABS
Generally speaking, there are two types of
polymers

46. Material
Selection
•Material selection should be made
based upon an applications’ need
for specific key properties
–Temperature
–Load Carrying Capability
•Tensile Strength
•Flexural Strength
•Modulus or Stiffness
–Impact Resistance
–Chemical Resistance
•Wash solutions
•Chemical dip
–Wear Resistance
–Cost

47. Steps in Material Selection
•Using an injection molded dunnage tray
as our example
•Carefully define the application
–What load will the tray carry
–Will the tray undergo shaking or impact
–What temperature will the tray see
–Will the tray be exposed to chemicals or moisture
–Will the tray be used with electrical components
–What about wear resistance against the parts
–Is dimensional stability an issue
–Will the tray be used and/or stored outdoors
–Cost allocated to the project

48. Steps in Material Selection
•Identify the importance of each
requirement
–Cost is not always the most important !
•Match the defined requirements to the
best available material
•Design the application with the defined
material in mind
–Plastic is not designed the same as metal !

49. II









HIGH PERFORMANCE

Materials
Polyetherimide (PEI): Ultem

Key Characteristics
High cost
High temperature
High strength and good stiffness
Hot water and steam resistance
HIGH PERFORMANCE

Materials
Polyphenylene Sulfide (PPS): Ryton

Key Characteristics
High cost
High temperature and strength
Good chemical resistance
Good electrical properties

ENGINEERING

Materials
Polycarbonate (PC): Lexan
Polyphenylene Oxide (PPO): Noryl
Thermoplastic Polyurethane (TPU)

Key Characteristics
Moderate Cost
Moderate Temperature Resistance
Moderate Strength / Impact
ENGINEERING

Materials
Polyamide (PA): Nylon
Polybutylene Terephthalate (PBT)
Polyethylene Terephthalate (PET)

Key Characteristics
Moderate Cost
Moderate Temperature Resistance
Moderate Strength
COMMODITY

Materials
Polystyrene (PS)
Polyvinyl Chloride (PVC)

Key Characteristics
Low Cost
Low Temperature Resistance
Low Strength
COMMODITY

Materials
Polypropylene (PP)
High Density Polyethylene (HDPE)

Key Characteristics
Low Cost
Low Temperature Resistance
Low Strength
AMORPHOUS PLASTICS SEMI – CRYSTALLINE PLASTICS
IMIDIZED

Materials
Polyamide-Imide (PAI): Torlon
Polyimide (PI): Vespel

Key Characteristics
Very High Cost per Pound
Excellent Physical Properties Above 400 F
Excellent Dimensional Stability
Low Coefficient of Friction

Higher Cost,
Temperature
And Strength
The Thermoplastic Selection Tree