INDUSTRIAL TRAINING

Footwear Manufacturing by Injection Moulding

Presented By:NASEEL IBNU AZEEZ.M.PM-Tech Machine Design3rd SemesterRoll No:12AJCE-Kanjirapally

Company Layout Product Design Footwear Upper

Manufacturing

Footwear Sole Production by Injection Moulding

Chemical Handling

Quality Control

Heat Treatment

Packing & Despatch

Raw Materials

Footwear Upper Materials• Cotton• Leather• Rubber

Footwear Sole Materials• Polyurethane

Polyol Isocyanate

Polyurethane

60-65% 35-40%

Production Of Polyurethane

Hydrolysis resistanceMicrobial stabilityAdhesion strengthThermo-oxidative resistanceLow temperature flexibilityOil and grease resistanceInjectability

Production Line

Releasing Agent

Injection Moulding

Heat Treatment

Demoulding

Cleaning

Packing Unit

Production TimeFull Cycle=180 sec.Heating Camber=90sec.

Setting Upper

Injection Moulding• Moulding material is injected into a cold mould where it solidifies and takes the

shape of the mould cavity

• Polyurethane expands on phase changing ,so the amount of polyurethane injected is calculated based on this expansion ratio

• Polyurethane phase change starts within 10 sec.• Polyurethane mixing occur at specially designed nozzle tip

Polyurethane pouring method

Direct Injection Process (DIP)

Nozzle For Injection Moulding

Filter

Rotating MixerStatic Mixer

Injection Tip CNC

Problems in Injection MouldingProblem Cause SolutionBrittleness Wet-material

OverheatingMolded-in-stressesPoor part design

Review drying procedure Eliminate sharp corners Increase injection pres. Increase melt temp.

Warped parts Orientation of materialPoor part designEjection problemPart temperature differential

Increase part packing Change gate locationAdd ribs or part thickness to improve stiffnessCheck for uniform wall thickness

Flashing Inadequate clampingHigh Injection Pres.Misaligned platenExcessive vent depth

Reduce injection pressureAlign platenReview mould venting

Burn marks Air trapped in cavityBarrel or nozzle overheatingHang-up in molding machine

Improve mould ventingCheck heater controlsClean hopper dryer• Remove and clean screw

Problem Cause Solution

Sticking in mold Over packingMold design

Reduce injection pressure Reduce injection speedCheck for undercutsInspect ejector systemIncrease draft

Surface imperfections (frosty surface or white marks)

Injection speed too lowWet material

Increase injection speed Increase barrel temps

Sinks or voids Insufficient feedGate freezing off or located improperly

Increase shot sizeCheck gate dimension and location

Gate blush Shot to Shot variationInadequate packing

Reduce injection speed• Increase gate sizeAdd radius to gate

Dimensional inconsistency Shot to Shot variationMelt temperature variationInadequate packing

Increase hold timeEnlarge gate to prevent premature freeze-off

PU sticks on Nozzle Time delay in injection Use special designed nozzle

Re-design for nozzle to improve Injection

Air Supply

• Hot air will remove the PU residuals from nozzle tip• Hence it reduce material waste (5Kg of PU/Day)

Sharp Tip

Contour Tip • Increasing degree of mixing• Reduce centrifugal effect on of mixture , hence reduce premature solidification• Reduce Shot-to-Shot Variation

Design For Injection Mould• The basic wall of the part should be kept uniform *

• Coring should be employed where possible to reduce uniform model and avoid sink marks*

• Provide gradual thickness transformation *

• For deep ribs and protrusions, provide knockouts *

• Provide draft angle *

• Raised or recessed letter on appearance surface should have 0.254 mm *

• Spacing between two parallel ribs should be a minimum of 2x wall thickness *

• The fillet radius should be 20-60% of wall thickness

• The outside corner thickness should be equal to inside radii plus wall thickness *

Improving efficiency of Heating Chamber

Working• Heating chamber requires heating track• Blower placed at the centre of heating chamber• Air is heated by heating coil placed under to blower out let & heated air

propagated towards bot ends Problems• Unequal temperature distribution: High temperature at centre and low temperature at both ends• For best result in PU phase change , it should keep at 50 about 60-90 sec.• Surface imperfection in products , sticking on de-moulding etc.

• Provide multiple inlet for hot air• Provide fins to improve the thermal efficiency of heating duct

Conclusions

1. Carried out a detailed Study about design considerations for Injection mould design and solution for identified problems are suggested

2. Identified the problem related to injection mould nozzle design and possible solutions are suggested

3. Identified the common manufacturing defects in the products and found solutions to reduce manufacturing defects

4. Possible design changes are suggested to increase the efficiency of heating chamber

References 1. Friedrich Johannaber ,Injection Molding Machines ISBN-10: 3-446-22581-1

2. Gasper Gantar ,Andrej Glojek,Mitja Mori ,Resource Efficient Injection Moulding Journal of Mechanical Engineering 59(2013)3,193-200

3. Weigang Hu , Syed Masood ,An Intelligent Cavity Layout Design System for Injection Moulds International Journal of CAD/CAM Vol. 2, No. 1, pp. 69~75 (2002)

4. E. Bociga, T. Jaruga,K. Lubczyñska, A. Gnatowski,Warpage of injection moulded parts as the result of mould temperature difference International Scientific Journal -Volume 44 Issue 1-July 2010 5. David O. Kazmer, Russell G. Speight,Polymer Injection Molding Technology for the Next Millennium Journal of Injection Molding Technology-University of Massachusetts