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Molded Foam-Rubber Dies???

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  • Molded Foam-Rubber Dies???

    Molded foam-rubber, soft, like 2-3 lb. density......Anyone know anything about this process?

    Are the dies like injection-mold dies, or since they are not high pressure, are they made out of fiberglass or plastic?

    Are these products a simple 2-part mix/ expand to fill, or are they heat/pressure activated, or some combination?

    Any info would be appreciated,


    NRA Lifetime Member
    NRA Lifetime Member

  • #2
    Had two customers with foam processes:
    One was RIM -reaction injection molding The two chemicals, I can't remember exactly what they were, were mixed in a fancy hydraulic mixing head just before being injected into the mold. The proportions could be adjusted to produce a product that ranged from rock hard to a hard skin with porous interior to rubber-like, the latter being the material that automobile bumper covers are made of. The mold, depending on the product, was made from steel or aluminum or could be epoxy or wood or a combination of all of the above. The mold could be heated or not, as injection pressures varied widely according to the product. For a crude process the chemicals could be poured in a bucket, stirred and quickly dumped into a mold and the lid slammed shut.

    The other customer bought big foam rubber "buns" about 3x4x8 feet. They had a big band saw with a murderously sharp razor edged blade (continuously sharpened during operation). The saw blade was oriented horizontally and the foam lay on a big table that was passed under the blade. The blade would sever off a layer on one pass then index down for the next cut.
    The sheets of foam rubber would then be ran through a press with a steel rule die. Imagine a steel rule or similar material set on edge and sunk into a slot in a sheet of plywood the face of the plywood pressed down on the foam to cookie-cutter out the shapes.
    The foam part can be further shaped by compressing in a heated forming tool for a period of time.

    This nearly exhausts my nutshell knowledge on the topic, perhaps there are others out there that can fill in gaps.

    Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
    ~Practitioner of the Electromechanical Arts~


    • #3
      Wes--I am familiar with the 2nd process you describe, I call this "converting".....but was unaware of the heated die treatment to finish form the part.

      The 1st process (or something similar) you describe is what I am looking for more info on.....I need the harder abrasion resistant "skin" you describe, possibly with a hard backing plate molded into the part.

      Thank you for the info, I now at least know the proper terminology to search for.

      Others--Any other info will be appreciated.

      NRA Lifetime Member