Injection Molding Technology Material From Dr. Piyawit Khumphong (MTEC)

Injection Molding System

Tpe of Mold for Injection Molding Two-piece mold Three-piece mold

Flow Channels for Molten Plastic Sprue Runner Gate Cavity Sprue Runner Gate Cavity

Cooling System for Injection Mold

Injection Molding Cycle 1. Filling 2. Repeat Filling (Packing) and Cooling 3. Mold opening 4. Product ejecting 5. Mold closing

Temperature and Pressure Setting Unmolten Temp (T) Pressure (P) Degrade Flash Short shot T g T m + 50

Temperature Setting for Injection Molding Machine Depending on Screw (Diameter, D) 1D 1.5D3D D Shot size Viscous heat ====> shear heating

Mold Filling Fountain flow Surface Center Skin - core morphology Birefringence microscopy of HDPE

Short Shot Discoloration Air traps Burn marks, Black specks-black streaks Brittleness, Fish Eyes Flow marks, Ripples Flash, Jetting, Silver Streaks, Sink Marks Shrinkage and Warpage Weld Lines and Meld Lines Overpacking Flow into thin section Defect Problems in Injection Molded Products

Air traps >>> Burn marks Problems that arrived from poor mold design Front View Top View

Burn marks Black specks-streaks Brittleness Fish Eyes

Flash Jetting Silver Streaks Sink Marks

Flow marks Ripples

Shrinkage and Warpage

Weld Lines and Meld Lines

Sandwich-Molding Overmolding Simultaneous Sequential 1. Coinjection 2. Gas assisted 1. Monosandwich 2. Airpress III 1. Core-Back-Technique 2. Sandwich-Overmoulding 3. Insert-Moulding* 4. Outsert-Moulding* 5. Textile-Overmoulding* 6. In-Mould-Labeling* 1. Turntable 2. Transfer 3. Overmoulding-Stackmould Single Cavity Multi-Cavity Multi-component molding

Sandwich molding

Viscosity ratio Viscosity ratio = viscosity 2nd melt / viscosity 1st melt Desired structure Sandwich molding

Simultaneous Technique

Sequential Technique core material (B) skin material (A)

Monosandwich molding core material (B) skin material (A)

core material (B) Monosandwich molding

Door Handle Monosandwich molding

Compatibility ABSPA6PPPEPSPETPC ABS+?--*++ PA6?+---?* PP PE PS* PET+?---++ PC+*---++ (- ) : No adhesion, (*) : Poor adhesion, (+) : Good adhesion, (?) : N/A or Depend on Condition

Depend on Chemical bonding Inter-diffusion >>>>Time & Temp PP-PP under 110 °C >>> Poor adhesion ABS-ABS under 130 °C >>> Poor adhesion Compatibility

Corrects: Warpage Shrinkage Section change Surface aesthetics Developments: Cold Gas Injection Water Injection Gas Assisted Injection Molding

Airpress III 12 34

Bottle Crades Airpress III

OVERMOLDING

Overmolding can be...  multi colour technique (e.g. buttons for key boards)  multi material technique (hard and soft, e.g. for integrated seals)  in-mold assembling (e.g. hinges, air vents...)

Core – Back Technique

Transfer - Technique ABS Tray with anti-slip TPE material Tooth Brush with soft-feel TPE material

TurnTable Technique Tube shoulder for thoothpaste with barrier layer from PET and over-molded skin from PP

Stack-Turning-Technique process phase 1process phase 2 preform Injection unit 2 Main injection unit

Stroke 3 2nd injection unit Stroke 2 Assembling Stroke 4 Demolding Stroke 1 1st injection unit Stack-Turning-Technique

Vertical turn with the Cube-Technique Production cost reduction about 25% 4 sides of the cube usable Siemens M35 Stack-Turning-Technique