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PLASTICS PRODUCT DESIGN
PLASTICS PRODUCT DESIGN PART DESIGN MAIN FACTORS – 1. END USE 2. MATERIAL PROPERY 3. MANUFACTURING PROCESS
PLASTICS PRODUCT DESIGN PRIME CONSIDERATION OF A PART DESIGN – BASED ON END USE i. SHAPE – SIMPLE/COMPLEX, HOLLOW/ SOLID, FLAT/ROUND ii. SIZE – LARGE / SMALL , THICK / THIN & iii. PART FEATURES
PLASTICS PRODUCT DESIGN PART FEATURES DETAILS TO BE CONSIDERED IN A PART 1. WALL THICKNESS 2. CORNERS 3. RIBS 4. BOSSES 5. WELD LINES 6. DRAFT 7. PARTING PLANE 8. UNDERCUT 9. INSERTS 10. TOLERANCES 11. LOAD & STRENGTH 12. HINGES & SNAP FIT 13. THREAD
PLASTICS PRODUCT DESIGN WALL THICKNESS PLASTIC MATERIAL PROPERTIES GOVERNING WALL THICKNESS OF PLASTICS PART – 1. MATERIAL STRUCTURE – PARTLY AMOURPHOS, PARTLY CRYSTALLINE & VISCOSITY. 2. PROCESS – THE NATURE OF PLASTIC PRODUCT MANUFACTURING IS MATERIAL ADDITION. 3. THERMAL CONDUCTION – PLASTICS IS BAD CONDUCTOR OF HEAT , HENCE SOLIDIFICATION PROCESS VARIES WITH THICKNESS. 4. THERMAL EXPANSION / SHRINKAGE – ABOVE FACTORS INDICATE , WALL THICKNESS SHOULD BE UNIFORM AND THIN.
PLASTICS PRODUCT DESIGN WALL THICKNESS SHOULD BE AS UNIFORM AS POSSIBLE TO ELIMINATE INTERNAL STRESSES, PART DISTORTION, AND CRACKING.
PLASTICS PRODUCT DESIGN WALL THICKNESS If two different wall thickness is join , blending should be Gradual
PLASTICS PRODUCT DESIGN
PLASTICS PRODUCT DESIGN WALL THICKNESS
PLASTICS PRODUCT DESIGN WALL THICKNESS GOOD DESIGN BAD DESIGN UNIFORM WALL THICKNESS IS DESIRABLE
PLASTICS PRODUCT DESIGN CORNERS GOOD DESIGN BAD DESIGN SHARP CORNERS SHOULD BE AVOIDED
PLASTICS PRODUCT DESIGN RIBS – PURPOSE – IT HAS TWO PURPOSE A) B) TO IMPROVE MELT FLOW IN THE SECTION TO INCREASE FLEXURAL STIFFNESS
If a part has wall thickness W, and thickness W is added as follows – Case (a) Parallel Along thickness & Case (b) perpendicular to wall , then Comparing Case (a) and Case (b) Section Modulus - is proportional to Square of thickness. Weight - is proportional to thickness Cooling Time - is proportional to Square of thickness Increasing Stiffness – Reduce Deflection Reduce Creep Strain Natural Frequency Impact Resistance
PLASTICS PRODUCT DESIGN RIBS - The Rib design and proportions used in most thermoplastic materials Note : If thickness “C” is more than 0. 8 A, Sink mark will appear.
PLASTICS PRODUCT DESIGN RIBS - A uniform wall thickness can be maintained in a rib if it is hollowed or cored out from the back
PLASTICS PRODUCT DESIGN RIBS - A Rib should be located in the corner or side of a moled part. This will lower the mold cost and allow easier filling of the plastic part
PLASTICS PRODUCT DESIGN RIBS - IF THE RIB IS TO BE EXTREMELY THIN AND AWAY FROM SIDES OF PART, FILLING MAY BE HELPED BY ADDING INTERMITTENT HEAVY SECTION ON WHICH VENT PIN CAN BE PLACED.
PLASTICS PRODUCT DESIGN BOSSES – It is protruding studs on a part that assist in assembly of the plastic parts and also bear stress and strain therein.
PLASTICS PRODUCT DESIGN BOSSES Design and proportions of boss at a wall, it is used in most thermoplastic materials
PLASTICS PRODUCT DESIGN BOSSES Design and proportions of boss away from a wall, it is used in most thermoplastic materials Note : If thickness “C” is more than 0. 8
PLASTICS PRODUCT DESIGN BOSSES Ribs on the side of long bosses will aid in filling them
PLASTICS PRODUCT DESIGN BOSSES Recommended proportions for Boss on the outside of a moulded part B = A or 2 A max.
PLASTICS PRODUCT DESIGN Gusset Design RIM DESIGN – It is an undercut in the part and is used to give added strength and support. GUSSETS – These are supporting arrangements for an edge. For additional support, two or more gussets do the job better than increasing height or width.
PLASTICS PRODUCT DESIGN DRAFT – TAPER IS PROVIDED IN A MOLD WALL TO FACILITATE EASY EJECTION. Also HELPS IN STACKING
PLASTICS PRODUCT DESIGN MOULDED HOLE i) Holes should be Parallel to Draw of mold as it opens. Oblique angle hole are expensive to manufacture. ii) Strength of PIN forming the moulded hole is influenced by ratio of Diameter to Length called Slenderness Ratio.
PLASTICS PRODUCT DESIGN MOULDED HOLE -
PLASTICS PRODUCT DESIGN MOULDED HOLES OF VERY SMALL DIAMETER IN CASE OF COMPRESSION MOLDING
PLASTICS PRODUCT DESIGN UNDERCUTS
PLASTICS PRODUCT DESIGN THREADS -
PLASTICS PRODUCT DESIGN Metal INSERTS FACTORS TO BE CONSIDERED WITH MOLDED IN INSERTS I) It should provide required mechanical strength. Sufficient anchorage must be provided to prevent insert from pulling out of the plastic. II) Some plastic material will crack around the insert as it ages. III) Flow of plastic material should not dislodge the insert. IV) Plastics has higher co efficient of thermal expansion and contraction than metal. V) Insert may be pre heated prior to molding to avoid cracks around insert.
PLASTICS PRODUCT DESIGN INSERT - A ROUND SHOULDER ON THE TOP PART OF A HEXAGONAL INSERT ELIMINATETHE NECESSITY TO MACHINE A HEXAGONAL HOLE IN THE METAL MOLD.
PLASTICS PRODUCT DESIGN NOT PREFERRED WHEN STRESSES ARE ENCOUNTERED , INSERT AND NOT PLASTIC SHOULD BEAR THE LOAD
PLASTICS PRODUCT DESIGN INSERT - INCORRECT METAL INSERT IN BOSSES SHOULD EXTEND TO WITHIN ONE MATERIAL THICKNESS OF OPPOSITE WALL AND RIBS CAN BE ADDED FOR ADDITIONAL SUPPORT
PLASTICS PRODUCT DESIGN INSERT MALE INSERT SHOULD HAVE SHOULDER IN ORDER TO SEAL OUT PLASTIC MATERIAL THAT MIGHT BE FORCED AROUND THE INSERT POOR DESIGN NO SHOULDER OR SEAL GOOD DESIGN HORIZONTAL SEAL BETTER DESIGN HORIZONTAL & VERTICAL SEAL BEST DESIGN HORIZONTAL & VERTICAL SEAL
PLASTICS PRODUCT DESIGN HINGES IN PLASTICS PRODUCT TYPES OF HINGE – A) RATHBUN HINGE – IT USES ELLIPTICAL SHAPED STEEL SPRING B) C) D) E) F) G) CLIPS TO HOLD A BOX LID TIGHTLY CLOSED OR WIDE OPEN. CLIP ARE PLACED IN SMALL UNDERCUTS OR SLOT. PROVIDES STURDY SPRING ACTION AND HOLDS COVER TIGHTLY PIANO HINGE – MADE OF METAL , SAME AS USED FOR HINGE COVER OF PIANO. HINGE RIVETTED OR FIX BY SELF TAPPING SCREW. LUG & PIN HINGE – LEAST EXPESIVE. RECESS DRILLED IN SIDE OF BOX & COVER IS PROVIDE. METAL PIN IS DRIVEN THRO’ HOLE STANDARD PIN HINGE – Molded HOLES ARE EXPENSIVE FOR CAM OPERATION IN MOLD. INEXPENSIVE PIN HINGE – ELIMINATES DRILLING OR CAM OPERATION HEAT SEALED HINGE – VERY STRONG AND DURABLE. AFTER ASSEMBLY, TWO TABS ARE HEATED AND BENT PERMANENTLY AROUND TWO PINS. BALL GRIP HINGE – USED IN SMALL BOXES. BALL SNAPS INTO TWO DEPRESSION.
PLASTICS PRODUCT DESIGN HINGES IN PLASTICS PRODUCT STANDARD PIN HINGE INEXPENSIVE PIN
PLASTICS PRODUCT DESIGN HINGES IN PLASTICS PRODUCT RATHBUN HINGE PIANO HINGE - LUG & PIN HINGE
PLASTICS PRODUCT DESIGN HINGES IN PLASTICS PRODUCT - HEAT SEALED HINGE – VERY STRONG AND DURABLE. AFTER ASSEMBLY, TWO TABS ARE HEATED AND BENT PERMANENTLY AROUND TWO PINS.
PLASTICS PRODUCT DESIGN CLASPS – MOSTLY WORKS ON FRICTION HOOK PRINCIPLE
PLASTICS PRODUCT DESIGN SNAP ON FIT SNAP IN FIT
PLASTICS PRODUCT DESIGN SNAP FITS
PLASTICS PRODUCT DESIGN SNAP ON FIT & SNAP IN FIT