structural foam molding 1
Post on 13-Jan-2017
63 Views
Preview:
TRANSCRIPT
STRUCTURAL FOAM MOLDING
AND SANDWICH MOLDING
INJECTION MOLDING
To produce the parts by injecting a material.
Performed with metals, , thermoplastic and thermosetting polymer.
STRUCTURAL FOAM MOULDING
Definition.
Process
WHAT IS STRUCTURAL FOAM MOLDING? Low pressure injection moulding process. Inert gas is introduced into molten polymer for reducing
density and weight. Used in mass production of large parts or multiple parts
produced in single machine. It requires less pressure than other moulding process so
parts are likely to have thicker wall section.
PROCESS Molten resin is injected with Nitrogen gas or chemical
blowing agent. The mixture is injected into the mould. The gas expands and fills the mold with foam. As the foam flows through the mould ,the surface cells
collapse. Solid skins are formed against the walls of mold while
core remains structurally foamed.
PROCESS. The outer skin is solid and the centre of the wall is foam. The part weight is reduced upto 20%. Part densities are as low as 40% of density of solid
plastic. Thermoplastic material used in structural foam
applications include polycarbonate,ABS.
APPLICATIONS
•Tool boxes•Trash cans•Commercial laundry bins•Pallets•Replace wood,concrete,metals,fiberglass
ADVANTAGES OF STRUCTURAL FOAM MOLDING
ADVANTAGES Low cost tooling Different materials can be run simultaneously Low pressure process for optimum product quality Large parts can be produced Superior design flexibility High strength to weight (specific strength) ratio Reduced part weight with high stiffness to weight
(specific modulus) ratio
ADVANTAGES Can achieve between 10% to 30% weight reduction
without affecting structural integrity Finished products is glossier than other low pressure
methods Less energy and materials are used , resulting in energy
savings Superior impact resistance Dimensional accuracy over the entire production run
STRUCTURAL FOAM MOLDING
DISADVANTAGES OF STRUCTURAL FOAM MOLDING
DISADVANTAGES Air trapped in mold causing the burning Bubbles are showing in the finished part due to the
moisture Shrinkage occurs due to not enough plastic for molding In the product surface , there are some marks due to
unbalanced flow of mold in the gates and runners
SANDWICH MOLDING
SANDWICH MOULDING
Two or more polymers are injected one after another through the same gate in one or more cavities.Core and skin material different or same.Also called as co-injection molding
PROCESS
INJECTION 1-FORM THE SKIN MATERIAL
INJECTION 2- FORM THE CORE
INJECTON 3-TO SEAL THE GATE AND FINISH THE PART
PROPERTIES OF SKIN MATERIAL
Will be thin Surface structure of the material.Transparent materialPaintable surfaceE.g.: glass, thermoplastics,
thermosets , sheet material , plywood
PROPERTIES OF CORE MATERIAL
Thick but will be lightweight.Low density materialHigh bending stiffness.Recycled material.E.g. :PVC, polyethylene ,polystyrene ,
metal foams.
METHODS:
Autoclave molding Adhesive bonding Liquid molding Continuous lamination Compression molding
APPLICATIONS OF SANDWICH MOLDING
APPLICATIONS
Door handles in car industryElectronic housingsDecks in shipsIn aerospace, making doors in
airplaneAntennas
ADVANTAGES AND DISADVANTAGES OF
SANDWICH MOLDING
BENEFITS OF CO INJECTION MOULDINGRECYCLED CORE REDUCES COSTS RECYCLED CORE REUSES WASTE
ENGINEERING CORE STRUCTURE.EG.FIBER FOAMING,ENHANCES PRODUCT STRENGTH OR PERFORMANCE.
VIRGIN SKIN PROVIDES QUALITY AESTHETIC FINISH FOR RECYCLED OR ENGINEERING CORE.
ELASTOMER SKIN IMPROVES SURFACE TOUCH.
STRUCTURAL PRODUCT:
CO INJECTION IS PREFERRED TO CONVENTIONAL STRUCTURAL FOAM OR FIBER REINFORCED PLASTICS BECAUSE OF ITS SUPERIOR SURFACE FINISH.
A SOLID SKIN COMBINED WITH A STRUCTURAL FOAM CORE PROVIDES THE ADVANTAGES SUCH AS LOW MOLDED IN STRESS,SKIN FREE PARTS WITHOUT THE SKIN SURFACE DEFECTS.
QUALITY SURFACE IS OBTAINED IN FIBER REINFORCED PLASTICS SINCE THE FIBER LOADED MATERIAL IS RESTRICTED IN THE CORE OF THE PART.
EXCELLENT BONDING between components.
DESIGN (colour combinations,information brokerage,marketing possibilities)
SOFT TOUCH or NON SLIP COVERAGE (to obtain certain grip control or for ergonomical reasons)
SEALING FUNCTIONS (closens against dust and condensation water).
RIGIDE/FLEXIBLE COMPOSITES ( with good damping characteristics).
LESS PRODUCTION STEPS
Shorter period between order and delivery of parts
Higher reproducibility and increased productivity
High reliability of production process
Simplified logistics
VISCOSITIES
LESS
HIGH
VISCOSITY LIMITATION OF 2 MATERIALS
TWO MATERIALS CAN ONLY BE PROCESSED SUCCESSFULLY BY CO INJECTION MOULDING IF THEIR PROCESSING PROPERTIES MATCH.
THAT IS THE VISCOSITY RATIO OF CORE/SKIN SHOULD BE BETWEEN 0.5 AND 5.
LOWER VISCOSITY RATIOS WOULD LEAD TO BREAK THROUGH OF CORE MATERIAL.
HIGHER VISCOSITY RATIOS WOULD LEAD TO POOR MOLD FILLING, FINGER LIKE DEFECTS AND VARIABLE CORE THICKNESS THROUGH THE PART
ADVANTAGES DISADVANTAGES
MATERIALS COST SAVING AND LIGHTER WEIGHT PARTS
MACHINE COSTS ARE 25 TO 30 % HIGHER THAN FOR STANDARD INJECTION EQUIPMENT
2 DIFFERENT OR ALIKE MATERIALS CAN BE SHOT SIMULTANEOUSLY INTO MOULD
GOOD TOOL MAKERS FAMILIAR WITH TOOLING REQUIREMENTS ARE DIFFICULT TO FIND IN SOME AREAS.
SOME CO INJECTION MACHINES CAN BE ADAPTED FOR GAS ASSIST,WHICH ALLOWS THE MACHINE TO PERFORM DUAL FUNCTIONS
MATERIAL VISCOSITIES MUST BE VERY SIMILAR OR PART CAN EASILY BE CORE RICH OR SKIN POOR.
ALLOW AN OUTLET FOR REGRIND USAGE ON INTERNAL CORE
SOMETIMES DIFFICULT TO OBTAIN TECHNICAL SUPPORT FOR EQUIPMENT PROBLEMS.
top related