Announcement

Collapse
No announcement yet.

Reparing A Injection Runner Nozzle *WARNING ACTUAL MACHINING QUESTION WARNING*

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Reparing A Injection Runner Nozzle *WARNING ACTUAL MACHINING QUESTION WARNING*

    Ok, the material flows through the injection system, into the cold runner manifold and the flow splits eight times and fills six cavities.

    Due to a combination of factors, some material bypasses the nozzle and ends up "stuck" where it should not be! This causes the sprue to stick, and the part to tear.

    I think at this point it's a question of wear on the original set of nozzles, so I am going to have a toolmaker make a new set... eventually.

    I got a couple of spares to play with... I have two ideas.

    1: Build up a bead of weld around the outside and grind it into final shape. Only thing I'm not sure of... thermal expansion of dissimilar materials... I'd have to find a wire/rod that matches my tool-steel fairly close.

    2: Machine a groove into the nozzle and fit some kind of ring there... I see various fiber, non-fiber, and metallic options for doing this.

    Of the two options I think #2 would be best right now because I can do that on my lathe in about an hour. Question is... I'm thinking a brass ring. However, again I'm not sure how much the material is going to expand when heated.

    Can anyone think of a third option? I'm open to suggestions.






    This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
    Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
    Plastic Operators Dot Com

  • #2
    I have no expierence in this area but I agree a metalic ring seal would be the fix... I vote for copper, how about a ring cut from a piece of copper tubing of the correct diameter.

    Joe B

    Comment


    • #3
      I'm not very familiar with injection molding but I would think that if the plastic is seeping out around the injector that the nozzles are not seating tightly to the mold. So it would seem that you need to look at your mold set up or the mold itself and verify that all of the nozzles seat into/onto the mold equally.

      The nozzles are threaded, are some shorter than the others or are they all the same size?
      Last edited by BillDaCatt; 12-01-2010, 02:11 PM.

      Comment


      • #4
        Mold Nozzle

        An Aluminum Bronze ring would probably wear a long time. Also, you can get A2 or D2 tig welding rod.

        Comment


        • #5
          From what I know about injection molding, rubber is very watery, making a tight seal very important. With the drop not being on the part means it does not have to look pretty, it needs to just function. A soft metal ring that can be pressed in should work.
          Mike
          Brandon MI
          2003 MINI Cooper S JCW#249
          1971 Opel GT
          1985 Ford 3910LP

          Comment


          • #6
            Well, I not sure what you are asking but if this runner system and the puck under the drop is all scrap you have an option of peening (I think that is the correct word) of the mold steel around this nozzle tip to reduce the gap between the nozzle and the mold steel. This distance should be only about .001 gap or smaller. There must be some gap since when this tip heats up it needs some room to expand. This gap is really dependent on what resin you are using since some resin flashes at a very small gap.

            The correct fix would be to either replace the nozzle tip or weld and re-cut the mold steel. Normally you check them both and see what is incorrect and fix that.

            Comment


            • #7
              Call DME in Michigan they sell dies, unit holders, sprue male and female and everything you need. Water cooling in the sprue makes a world of difference. Sprues last a long time and if one goes bad you can usually polish it with a die grinder and get a few more months of service. Then when it is time to change it, it is only a 1 hour job. I have been getting several years out of each sprue on the 11 machines that we have. Usually only the female half goes bad. The water lines sometimes plug up after 5 years on the male half run some acid through it and its as good as new.
              Last edited by gary350; 12-01-2010, 02:17 PM.

              Comment


              • #8
                This is thermoset rubber, the stock temp doesn't exceed 200 degrees F, it only flows under pressure.

                The cold runner is maintained at 190F and the mold sections are heated to 375 to cure the rubber.

                There is a thread on here where I was asking about mold insulation not that long ago.

                Anyway, these screw up into the mold into the cold runner. Heat is being conducted through them from the mold up into the body of the cold runner.

                I talked with a rubber molding expert and he agrees these nozzles need to seal tighter. He suggests that I replace them (naturally) using his company.

                They ain't no good until they are reduced to swarf on the lathe or melted into slag by my welder. Replace them.. HA!
                This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
                Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
                Plastic Operators Dot Com

                Comment


                • #9
                  Originally posted by BillDaCatt
                  I'm not very familiar with injection molding but I would think that if the plastic is seeping out around the injector that the nozzles are not seating tightly to the mold. So it would seem that you need to look at your mold set up or the mold itself and verify that all of the nozzles seat into/onto the mold equally.

                  The nozzles are threaded, are some shorter than the others or are they all the same size?
                  All the same length.

                  There is an orifice inside. I actually have 16 of them per mold (plus a few "extra"), two different orifices. Depending on how the rubber flows through the manifold I change the nozzles to balance the flow.

                  It looks like the previous owner or one of his "talented" assistants took a wire-wheel to them.

                  Tomorrow I am going to chuck one in Mr. Lathe and see what I can come up with. Going to try the copper-pipe idea first since I can get that first thing in the morning.
                  This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
                  Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
                  Plastic Operators Dot Com

                  Comment


                  • #10
                    I think you could just weld it up (Tig) and reshape. Even if you have to redo it every once in a while as it wears it will work better than anything non-ferrous. Just about any standard filler rod will work.

                    -Jerry

                    Comment


                    • #11
                      If you had asked about your cat, dog, computer, favorite lathe color, how to reside your house, or any of the normal conspiracy theories, I might have been able to offer advise. But a machining related question........what's that?

                      Comment


                      • #12
                        Questin and a couple blind thoughts

                        How much pressure are these pieces under from the injection unit pushing against them? 2 reasons I ask, 1 is because you may need to use some hard filler because these parts will tend to deform under the mechanical forces. 2 if they aren't under a great deal of pressure might it be easier to just remake them? By the time you weld and remachine you might be able to produce a new one and have the old one for a pattern/sample that is still functional.

                        Comment


                        • #13
                          Kf2QD.... it's a 600 ton press, and I wish it was 800 tons like the other one.

                          They screw into the cold runner body, full engagement. Its not the material coming down I'm worried about it's the material seeping up between the mold and the nozzle.

                          I suspect a picture of one of these in it's native habitat is in order.
                          This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
                          Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
                          Plastic Operators Dot Com

                          Comment


                          • #14
                            We micro-weld mold cavities up all the time in pilot molds - and have seen it done in molds that run hundreds of millions of cycles and hold 0.002" tolerance. This is you might not have the equipment and may want to send it out.

                            Comment


                            • #15
                              long time ago i used to patch blow moulding dies by silver soldering the nicks and dents and polishing, it worked ok
                              mark

                              Comment

                              Working...
                              X