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How is it Done ? Pebble grain on molded plastic .

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  • How is it Done ? Pebble grain on molded plastic .

    I always wondered how they get the patterns onto the mold surface...it can look like leather.
    Or simply pebble grain. Is it a random pattern or oft repeating ?
    I always look at it and go what the hell ..?
    Anyone here work in that industry ?

  • #2
    Look here:
    http://www.mold-tech.com

    Those are the finishes we often use.

    Sid

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    • #3
      I did my apprenticeship as a toolmaker for a firm that under licence produced plastic products called rubbermaid or sealatainer. I think it was an american product made under licence by our south african company. I never saw how they did it because it was sent out to an outside company. I was told it was an acid etching process. I liked it because as an apprentice our moulds were polished by the apprentices, a soul destroying job that I hated. This process saved us from the horrible job of polishing the moulds

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      • #4
        The website does not seem to explain how they do it. I have often wondered the same when sitting in the car and looking at the dash board texture.

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        • #5
          Photo resist etching.

          The tricks are in getting the pattern to go nicely around corners.
          1601

          Keep eye on ball.
          Hashim Khan

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          • #6
            Edm seemed a popular mould finish to get patterns, bead blasting and such also, I saw self adhesive hexagon sticky sheet applied as a mask then etch a few times, mask and blast too, a lot of companies keep their mould surfacing tech secret, there was a firm who did the rolls in work, surface technology I think, they had their own little factory in the steelworks where they surfaced rolls, no one got in there, the rolls went in through a double door "airlock" to ward of the curious, primarily they were edm surfacing, but how was not known.
            Mark

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            • #7
              Yup, photo resist etching is the usual method, but nowadays lasers are becoming dominant in texturing the surface as it is fast and doesn't require the resistive mask on the part.
              Amount of experience is in direct proportion to the value of broken equipment.

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              • #8
                Originally posted by plunger View Post
                . I liked it because as an apprentice our moulds were polished by the apprentices, a soul destroying job that I hated.
                Funny enough, when I worked for Newell-Rubbermaid, I traveled to several of our overseas mold shops to view tool progress. I was always shocked to find workers squatting on the floor next to a mold cavity, polishing it with what looked like a popsicle stick with some polishing compound on the end. Not SA, however - it was Guangdong province, China.

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                • #9
                  Visiting places is an education, on the blast furnace floor in India, while the furnace is tapping and there are women in saris, barefoot taking samples, health and safety doesn't apply to poor people I discovered.
                  Mark
                  (I had a packet of polishing sticks once, different grades like a hard plastic stuff.)

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                  • #10
                    I had a look inside a place that made many of the plastic armrests and similar parts for the auto industry. It was in interesting process. They made a wax master with the leather pattern, stitching etc, then painted it with a conductive paint. That was then electroplated with copper to a sufficient thickness for a durable mold. The wax was melted out and they then had a mold with all the requisite features and texture in one piece. There would be a hole in the back side for loading and pulling the part. Vinyl powder was put in, the mold closed, then mounted in a rack that would rotate it in every direction as it went through the heating chamber. The plastic coated the interior, cooled and was then pulled out through the back opening. Since this was just the skin of the part, a second operation filled it with foam.
                    .
                    "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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                    • #11
                      Most all of our molds are acid etched. I have repaired dozens of them over the last 17 years where I work. We use screens that have the patterns on them. Place them on the cavity or core, mask them off and build a clay dam around them, then fill them with acid, agitate the acid for a specific time and then remove and rinse. Most of our surfaces are then glass beaded with very fine glass to give them a satin finish over the acid etching.

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