Weld Line & its Troubleshooting

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Weld line are some unwanted lines formed over the surface of product thus causing some serious defects and lose in the strength of the manufacturing product.


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weld line on a product



HOW WELD LINES ARE FORMED ON A PRODUCT ?

it is mainly caused when two flow fronts meet together inside a closed mold, let me explain it in a brief ;
what happen when the molten material that is your melted plastic is transferred from barrel to the mold by the help of nozzle during injection process the molten material runs inside the cavities of the mold with a high pressure what happen at a certain place these upflowing molten materials meets at a particular point and if meeting point have certain cuts undercuts or any other obstruction few  more issues are discussed below then  there is a certain disturbance occur in the meeting of these flowing molten material then a line is beeing formed where these molten material meets thus forming weld lines.


FEW MAJOR CAUSES FOR WELD LINES ARE :

  1.  Molten plastic is too cold.
  2. Use of excessive lubrication on mold surface.
  3. Trapping of air in mold.
  4. Mold is too cold.
  5. Insufficient amount of injection pressure.
  6. injection speed is slow.
  7. Too low barrel temperature.
  8. Unequal distribution of heat.

TROUBLESHOOTING & ITS PROCEDURES

  • INCRESE SCREW RPM.
  • INCREASE BARREL TEMPERATURE.
  • INCREASE INJECTION PRESSURE.
  • CREASE MOLD TEMPERATURE 
  • CHECK PROPER MOLD VENTING.
  • INCREASE GATE&RUNNER SYSTEM .
  • INCREASE SPRUE OPENING.
  • CHECK NOZZLE OPENING.
  • GATE POINT TOO FROM FROM WELD POINT.
  • INTERRUPTED MOLD FILLING CHECK THAT.
  • CHECK THE PLASTICIZING CAPACITY OF MACHINE.
  • MATERIAL SHOULD BE PROPERLY PURIFIED.
  • POOR MATERIAL FLOW FOR THAT LUBRICATE MATERIAL .

 

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