INJECTION MOLDING

1
INJECTION MOLDING TECHNIQUE
2
OBJECTIVES
3

• INJECTION MOLDING I/P CHILD PARTS,BUMPERS,
  PILLAR TRIMS.
• EXTRUSION SEALING SYSTEMS OF AUTOMOBILE, PIPE
  (PLASTIC RUBBER)
• BOLW MOLDING DUCTS , BOTTLES, TOYS.
• THERMO/ VACUUM FORMING DISPOSABLE CUP TRAY,
• EXPANDED FOAM MOLDING STEERING WHEEL,
• ROTATIONAL MOLDING WATER TANK,SPEARS.

4
(No Transcript)
5
MAJOR PARTS OF MOLDING MACHINE
6
DETAIL PARTS OF INJECTION MOLDING MACHINE THEIR
FUNCTION
7
(No Transcript)
8
TYPES OF MOLD

• BASED ON FEEDING SYSTEM
• COLD RUNNER MOLD
• HOT SPRUE MOLD
• HOT RUNNER MOLD

• BASED ON NUMBER OF PARTS
• SINGLE CAVITY MOLD
• MULTY CAVITY MOLD

• BASED ON TYPE OF COMPONENT
• SINGEL PART MOLD
• FAMILY MOLD

• BASED MOLD OPENING
• 2 PLATE MOLD
• 3 PLATE MOLD

• BASED ON SPECALITY
• COINJECTION MOLD
• INSERT MOLD

9
BASED ON MOLD OPENING
2 PLATE MOLD
ADVANTAGE 1)MOLD WILL BE SIMPLE CHEAP 2)
VARIOUS TYPE OF GATES CAN BE ADOPTED.
SINGLE OPENING
DISADVANTAGE 1)MOLD WIDTH AND LENGTH WILL BE MORE
THAN 3 PLATE MOLD 2) AUTO DEGATING WILL BE
POSSIBLE ONLY IN SUBMARRINE GATE
3 PLATE MOLD
ADVANTAGE 1) MOLD SIZE WILL BE LESSER AS THE
FEEDING SYSTEM WILL BE ON UPPER PLATE 2) AUTO
DEGATING POSSIBLE
DISADVANTAGE 1) MORE COSTLY 2) SLOWER PRODUCTION
RATE 3) MOLD HEIGHT WILL BE MORE
10
BASED ON FEEDING SYSTEM

• Hot Runner Benefits
• Faster Cycles
• - 15-20 Faster
• Eliminates Material Waste
• - No Sprue or Runners(IN HOT RUNNER SYSTEM)
• Improves Part Quality
• - Less Stress
• - Better Appearance

HOT RUNNER MOLD
11
SPRUE BUSH
MOLD PARTS
TOP PLATE
GUIDE BUSH
GUIDE PIN
CAVITY PLATE
SLIDER ASSLY
COMPONENT
CORE PLATE
CORE BACK PLATE
RETURN PIN
GUIDE BUSH
EJECTOR GUIDE PIN
SPACER BLOCK
BOTTOM PLATE
12
FEEDING SYSTEM
13

• SPRUE
• -It is the connecting path between machine
  nozzle runner system.
• RUNNER
• -It is the connecting path between sprue
  gate.
• GATE
• -It is the connecting path between runner and
  component.

14
SPRUE

• Sprue is the beginning of the melt delivery
  system within the mold
• The interface between the nozzle the mold
• Taper shape has been made for avoiding the back
  flow of material.

15
SPRUE PULLER
REVERSE TAPER BEST
Z PULLER GOOD
GROOVE TROUBLE- SOME
16
RUNNER SYSTEM

• A runner system that has been designed correctly
  will
• Achieve the optimal number of cavities
• Deliver melt to the cavities
• Balance filling of multiple cavities
• Balance filling of multi-gate cavities
• Minimize scrap
• Eject easily
• Maximize efficiency in energy consumption
• Control the filling/packing/cycle time.

17
RUNNER BALANCING -FOR UNIFORM FILLING OF
COMPONENT -FOR MAINTAINING UNIFORM PRESSURE
INSIDE MOLD -REDUCE FILLING TIME
UNBALANCED RUNNER SYSTEM
BALANCED RUNNER SYSTEM (CHANGING RUNNER DIA)
BALANCED RUNNER SYSTEM (CHANGING RUNNER LAYOUT)
18
COLD SLUG WELL
Flow Direction
Cold SlugWell
-Plastic looses its temp during flow through
runner. -Cold slug well is provided to
accommodate the initial cold material and release
behind hot material into cavity.
Cold SlugWell
19
GATING
Manually Trimmed
Auto-Ejection Trimmed

• Direct (sprue) gate
• Tab gate
• Edge (standard) gate
• Disc/Diaphragm gate
• Spoke gate
• Fan gate
• Film(Flash) gate
• Ring gate

• Pin gate
• Submarine (tunnel, chisel) gate
• Hot-runner (hot-probe) gate
• Valve gate

The shape of gate will be decided based no the
shape appearance requirement of component.
20
DIRECT SPRUE GATE
Suitable for single cavity large components.
21
TAB/OVERLAP GATE
Suitable for stress free and high optical clarity
components.
Single Tab Gate
Multiple Tab Gate
6 in. Max
12 in. Max
Tab
Tab
Gate
Sprue
Gate
Sprue
Gate
Tab
22
EDGE GATE
Most commonly used.
Land Length
0.030 Inches Maximum
23
DISC/DIAPHARGM GATE
Runner
Runner
Part
Sprue
24
FAN GATE
Suitable for larger area with thin wall
components.
RUNNER
RUNNER
PART
GATE
LAND
25
FILM /FLASH GATE
Suitable for thin walled flat comopnents. Used
for the components required with stress and
warpage free. Used for transparent components
where flow mark is not allowed.
Parallel Runner
Gate
Parallel Runner
Runner
26
RING GATE
Gate
Runner Disk
Gate
Part
27
PIN POINT GATE
0.050
0.020 Land Length
900
28
SUBMARRINE GATE
Molded Part
Sprue
Parting Line
Zero Land Length
Grind Flat on Gate Side, Min. 20
Tunnel
Gate
Knock Out Pin
Fasten Pin Head To Prevent Turning
29
SUBMARRINE GATE
R
R
Gate
30
(No Transcript)
31
(No Transcript)
32
UNDERCUTS ARE THE SHAPES -WHOSE ORIENTATION ARE
NOT ALLONG WITH MODLING DIRECTION OF THE ENTIRE
PART -LOCATION OF THESE SHPAES WILL BE BELOW
PARTING LINE.

• TYPES OF UNDERCUT
• INTERNAL UNDERCUT
• EXTERNAL UNDERCUT

33
TYPES OF UNDERCUT

• INTERNAL UNDERCUT
• It can be removed by
• Force ejection
• Use of collapsible core
• Use of lifters
• Use of unscrewing mechanism(for threads)

INTERNAL THREAD
SNAP LID
34
TYPES OF UNDERCUT

• EXTERNAL UNDERCUT
• It can be removed by
• Side core actuated by
• mechanical pins,
• Hydrolic Phumatic cylinders

Detail on Side
External Thread
35
TECHNIQUES FOR UNDERCUT REMOVAL
CORE CAVITY MATCHING AREA FOR HOLE
CORE CAVITY MATCHING
36
SLIDER MECHANISM
37
SIDE CORE MOVEMENT BY HYDRAULIC CYLINDER
Cavity
Core Pin
Hydraulic Cylinder
Plastic
MOLDING DIRECTION
Cored Hole
Core
38
LIFTER MECHANISM
39
(No Transcript)
40
BASIC DESIGN CONSIDERATIONS

• The first requirement is to have a properly
  modeled part that is fully moldable
• Sufficiently drafted faces to easily eject the
  part.
• No undercuts (will require lifters or sliders)
• Wall thickness should be uniform(if changing then
  it has to be gradually for avoiding shrink mark)
• When creating internal ribs, they should be no
  greater than 1/3t of the parts wall thickness to
  avoid sink marks on the outside of the part.

No draft difficult to eject
Drafted faces
41
(No Transcript)
42
(No Transcript)
43

• Short Shot
• Flash
• Weld Lines
• Ejector Pin Marks
• Sink Marks

44
Short Shot
Cold material, cold mold, insufficient pressure,
non uniform mold temperature, insufficient feed,
entrapped air, insufficient external lubrication,
insufficient plunger forward time, small gates.
Short defect
45
Flash
Material too hot, Inj Pressure too high, High
packing pressure, Less clamping force, Poor
parting lines or mating surfaces
Part w/ Moderate-Heavy Flash
Flash
46
Weld Lines
Weld lines is the meeting face of 2 flows coming
in opposite direction. Part is weak at Weld line.
Can result from poor gate placement
Unavoidable areas
Weld lines occurs if material temperature is
low, mold temperature will be improper, improper
gate position, improper runner balancing.
47
Ejector Pin Marks
Marks are often left on the part in the area
where the ejector pins pushed. Four possible
cause
1) Pin above flush
2) Pin below flush
3) Clearance around pin
4) Improper cooling time 5) Ejection force
more. 6) Part sticking.
48
Sink Marks
Sink mark occurs due to abrupt change of
thickness. Thickness to be considered for every
shape(Rib, Boss, Clip mountings) Minor sink marks
can be removed by texturing
Improved Design
49

• Sink mark removed by optimizing the rib thickness
  to 1/3 t.

Result after redesigning the Internal Ribs to be
1/3t or less of the nominal wall thickness
Sink due to ribs
50

• THANK YOU