Which material is the best for injection mold tooling?


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Thread: Which material is the best for injection mold tooling?

  1. #1
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    Default Re: Which material is the best for injection mold tooling?

    I think the key to injection molding is temperature control and humidity changes.
    To produce high-quality silicone.
    These need attention.
    I can add more information, I am happy to advise you

    You can check this blow molding expert?
    https://www.tigerkj.com/en/product-s...troller-series



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    Default Re: Which material is the best for injection mold tooling?

    I design injection molded parts and injection molds (tooling) for a living. I also establish molding machine injection / temperature parameters when I prove out (do the initial test run) of a new mold. I'm an M.E. by training, but have specialized training within the injection molding industry.

    Its not clear from your post if you are asking a question or if you are offering advice.

    If I assume you are asking a question, here is my reply:

    There are multiple considerations to creating a successful production run of injection molded parts. I would not say any particular consider is "key", as all are important.

    1) Which material is the part intended to be made of? Different materials require different machine parameters (settings) to run, and to some extent, influence tool design (mold design). When I am asked to design a part and mold around a material with high viscosity, I will design larger runners, sprues, and gates. If the material has a tendency to form voids in thicker areas, I might add overflow cavities to push these defects into. These become sacrificial molded "pieces" that are picked off the part after its molded.

    2) Part design along with Molding simulations to optimize part design for material flow within the cavity, as well as gate location, injection speed, gate location, etc. I typically use Autodesk Moldflow for simulations. Part design must consider how the tool will be designed to mold the part. For example, are there undercuts on the part design. Will a side action (slide) be needed for these undercuts? Are there any inserts that need to be placed in the mold before the mold is closed that will become part of the molded part?

    3) Machine limitations: Available clamp force (tonnage of the platen clamp), injection speed, and pressure limits. Generally, injecting faster is better for part quality, but the machine can only inject so fast and has a limit on clamp tonnage. If molding simulations show that you cannot get good molded parts at the available injection speeds, the part must be re-designed (for example, for 2 step molding) or the machine must be upgraded with a second injection unit to double the cavity filling speed. Pressure = Force x Area. If the cavity pressure x the "silhouette" area of the part = force greater than available clamp (platen) force, the mold will get "blown" open. note: The silhouette is the area of the molded part projected onto the parting line of the mold and must include any other molded parts that are at parting line such as runners.


    Regarding materials molds are made from:
    I typically use 7075-T6 for prototype "soft" tooling meant for very short production (ie prototype) runs.
    For production molds, P20 or A2 tool steel is typically what I spec. Sometimes I spec a type of Stainless (I don't recall which one off the top of my head), but this is very rare and is very unusual.

    P20 can also be heat treated to harden it for even higher production run volumes.
    -------------
    Chris, M.E. Low Pressure Molding Expert, Molded Part and Mold tooling design
    Also: Machine design, CNC metal part design, Sheet metal design

    Last edited by 3DBotic; 02-11-2021 at 03:17 PM. Reason: adding sig


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    Default Re: Which material is the best for injection mold tooling?

    Regarding temperatures: I'm not sure if you are referring to the ambient temps where the molding machine is located, the temperatures of the plastics the machine is injecting, or the temperatures of the mold itself.

    In my typical applications, the molding machine is set to temperatures that are optimal for the material being injected. We typically get this temperature range from the material manufacturer. We then adjust the machine temperatures within the manufacturer's supplied range, while doing a test run of the mold as needed. If we need the material to flow easier (lower viscosity), we will turn up the temperature. If we need it to be more viscous, we will lower the temp. Generally, lower temps degrade plastics less. Also the time the material is at the melted temperature is a factor where material degradation is concerned - the longer its at temperature, the more it degrades.

    Chillers - ie closed loop water/glycol refrigeration or heater units are typically attached to the mold to control the mold temperature. The goal is usually to keep the mold at a constant temperature, as the act of molding parts keeps adding more heat to the mold. Some molds need to be pre-heated and run at a much higher temperature than ambient, and the temperature held constant at that elevated temp.

    Ambient humidity is a factor where the material itself is concerned. Some plastics absorb moisture from the air, and this can produce part defects. If you think about it, you can see why: Water boils at 100 C or 212 F. Plastics are often run above 200 C (above 350 F) so any water in the plastic would flash to steam but this would happen within the heated section of an injection molding machine, and create pockets of water vapor or essentially, hot air. This would show up as voids in the molded parts.

    We typically store materials in containers that prevent moisture absorption. Some molders might go so far as to pre-dry material before running it through an injection molding machine.
    -----------
    Chris, M.E. Low Pressure Molding Expert, Molded Part and Mold tooling design
    Also: Machine design, CNC metal part design, Sheet metal design

    Last edited by 3DBotic; 02-11-2021 at 03:17 PM.


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Which material is the best for injection mold tooling?

Which material is the best for injection mold tooling?

Which material is the best for injection mold tooling?