DROOLING IN INJECTION MOLDING

-

  DROOLING




Drooling is a continuous flow of plasticized / melted material from the nozzle tip of injection molding machine during the time of refilling or dosing of raw material for another cycle.

Drooling mostly comes when we  make certain products where we have to give high back pressure products where we have to mix colorant , pigments , master-batch etc.

* Damage of NRV ( NON-RETURN VALVE ) or shut off valve is also one of the major cause of drooling.


EFFECTS OF DROOLING

1. Defects on the products are been observed like surface detoriation, patchy or rough surfaces, improper finishing over the product .

2. Wastage of raw material thus increasing cost of production.

3.  Sometimes product becomes short at next cycle.

4. it also causes problem like sticking of runner on the mold.


HOW TO TROUBLESHOOT THE PROBLEM OF DROOLING


1. Increase Suckback ( after plasticisizing )

2. Decrease Back-pressure

3. Use Sprue Break

4. Decrease Nozzle and Barrel temperature

5. Decrease Injection Pressure 

6. Decrease radius of Bore/Hole of nozzle keep it according to product only.

7. Material should be properly predried

8. Mixing of additives should be in proper amount.



Comments

Post a Comment

Popular posts from this blog

Weld Line & its Troubleshooting

-
Image
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 . . 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 :   Molten plastic is too col...
Read more

Maintenance and cleaning of plasticising cylinder

-
Image
  Maintenance and cleaning of plasticising cylinder  Clean when it is absolutely necessary to clean  If it is desired to change from one plastic to another, it is advisable to observe the correct sequence for colour change or material change. This saves a great deal of cleaning work.  A decision whether to clean partially or totally depend on the type of contamination.  In most cases, contamination due to material entrapment results if there is a gap between plane sealing surfaces of the injection unit – especially near the surfaces of nozzle and cylinder head or near the cylinder head and barrel. Partial cleaning It is frequently found that the screw tip and the conical surface of the bore in the cylinder head are the areas where remnants of material get entrapped and adhere. Streaks which occur regularly at the same point in the moldings are most likely due to such entrapped material. If the remainder of the melt is in other aspects completely free from defects, it is suffici...
Read more