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Thread: Injection Molding BMC queries

  1. #1
    Join Date
    Nov 2019
    Location
    Ireland
    Posts
    3

    Injection Molding BMC queries

    Hi guys,
    I'm currently working for a company which manufactures electrical switch gear. We manufacture almost all parts for our gear in-house including plastics. Our plastic products are mostly made through granular fed injection moulding and compression moulding but we are now expanding and have bought a BMC injection moulding machine.

    Although we have an experienced team of moulders we have none with any experience in BMC so don't want to take anything for granted so i'm asking for your help.

    would any of you guys have previous experience working with BMC and have any general tips that you think might help? is there any massive differences that we should be looking out for that some of you may now take as second nature from long experience?
    for example we purge our machines at the end of every shift to clean them out, should this also be done with BMC and is it the same process and granules?
    where we insert the material into the hopper (ours has a screw crusher) how should this be cleaned after?
    Material shelf life, is it a guide or is it essential to follow?
    Any typical problems that occur or assumptions that people make that should be avoided?
    is there any products (greases/release sprays etc) that you have found work differently on BMC moulding?

    I know this all sounds very beginner like but like i said we do not want to take anything for granted because of experience in different fields.
    When we first started our journey into compression moulding we approached it with the same per-cautions, we now have 6 machines operating on 3 shifts 5 days per week so the advice definitely helps lol.

    I appreciate all the help.

    D.

  2. #2
    Join Date
    Oct 2018
    Posts
    22

    Re: Injection Molding BMC queries

    Hello D,
    I have molded millions of lbs of BMC. If you're team has thermoset knowledge, then that is good. Otherwise, I'd recommend you out source it.
    Who will be your material supplier. Depending on who it is will determine how much help they will give. There aren't that many in North America, and it
    is a tight knit club, so to speak.
    The beauty of bmc is that it is "customizable" They can and usually will fine tune the formulas to help them work and also to work around some tooling short comings.
    Again, it depends on the supplier.
    The shelf life is variable depending on the formula. Some are good for a few months, some are ok for a year or more.
    Depending on your location, you will probably need to keep the material in a "cold room", especially in the summer. The material supplier will recommend this.
    Stoner has a variety of thermoset mold releases. Others do as well, but I like Stoner.

    What brand press did you buy?

    Please feel free to message me and I will help all I can.

    Doug...in KY.

  3. #3
    Join Date
    Nov 2019
    Location
    Ireland
    Posts
    3

    Re: Injection Molding BMC queries

    Hi Dough,

    Thanks for the reply. we have a few recommended suppliers who are Plenco (USA), Mahindra (India) and Menzolit (UK).

    That's good to hear it would be a worthwhile question for us to put towards them.
    We are in Ireland so temperatures don't ever get too hot but when you say a cold room what temperatures are you talking?

    Thanks i will definetley have a look at some stoner products. As for the press we have bought a Krauss Maffei KM 350-3000 CX POL, this is the same brand as our 3 other Inj Molding machines so it made sense.

    D.

  4. #4
    Join Date
    Oct 2018
    Posts
    22

    Re: Injection Molding BMC queries

    Well, you did good with the KM. They and Arburg are about the only suppliers still supporting BMC.
    Check out BMCI, they are now a division of A. Shulman.
    As you know, the material cannot be reprocessed (regrind), so scrap is always the enemy.
    BMC lends itself to cold manifolds and fluid temp controlled extension nozzles, which can reduce waste.
    Your KM will have gate cutter capabilities, so research that with your material suppliers. It is a a sequence in which large blades are attached to another plate behind the ejector plate.
    After switch to hold, prior to the material completely curing, the press moves the plate forward and cuts off the gate at the parting line.
    It can reduce secondary operations, as well as improve part strength by having a large flow channel to the parts. (reduce glass degradation)
    Your KM should also have venting. A process in which the material is partially injected into tool, injection stops, tool decompresses and/or opens slightly to evacuate volatiles,
    recloses and finishes injection. Venting is more critical with bmc than it is for phenolics or granular polyesters if you run them.

    In addition, the hot strength for bmc is not near as good as phenolics, so the parts are very susceptible to chipping and/or breakage until they cool a bit. This can make parts handling
    more important than usual. Robotics can really help with this, especially with heavier parts and multiple cavities... parts falling on each other on a conveyor.

    Surface finish (gloss) may not be important with your parts, but the hotter the tool, the higher the gloss...right up to the point that
    you run out of flow life. Just remember that the resin will follow the heat.

    Hope this helps

  5. #5
    Join Date
    Nov 2019
    Location
    Ireland
    Posts
    3

    Re: Injection Molding BMC queries

    Hi,

    Thanks for taking the time to go over all them points they all make sense and some are news to us. We will be getting help in to help with the set up of the machine based on each part so we should be covered from that sense but the point you made about parts chipping/breaking is very interesting and is something we probably wouldn't of known until we learned the hard way lol, we will now be able to better prepare before we go in to production.

    Again thanks for your help and i look forward to getting into production.

  6. #6

    Re: Injection Molding BMC queries

    Hello Dylan,
    I am working for IDI Composites, we produce BMC in UK, US, France and China. We are able to support you for the BMC and moulding. Contact me and we can discuss about your project.

    As a reminder, since more than 50 years IDI Composites is committed to its customers and the industry. We are proposed innovative composites solutions to make your products better.

  7. #7
    Join Date
    Apr 2020
    Location
    Traverse City, MI
    Posts
    14

    Re: Injection Molding BMC queries

    I have a lot of experience with BMC as well.
    KM is a great machine for molding BMC (as @douginky mentioned). The venting and gate cutting is very useful for manufacturing operations. BMCI is a great company to work with for your raw material needs. Stoner mold release is great.

    Things that weren't mentioned yet...
    Nitride mold components and surface treatments will be your friend. Progressive mold components now make mold black nitride components that work wonderfully. Otherwise Marvel Mystery Oil and standard steel components seems to do ok.
    I always had great experiences when using Chicago Mold to build my molds.
    Always wear gloves and hot work sleeves when handling BMC raw material and molded parts. Always wash your hands as well to ensure that you will not be itching.
    mold preheat stations will definitely aid in manufacturing up time.
    Design your molds with flash pockets/overflow grooves.

    If you have any further questions feel free to private message me.

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