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  • Surface finish for Injection Mould tooling.

    Discussion in 'Surface finishes' started by Lee_G, Jan 28, 2019.

    1. Lee_G

      Lee_G New Member

      Jan 2019
      Likes Received:

      I have a received a drawing for an Injection moulded part that requires a surface finish of 'E8' to all A-side surfaces.

      Personally I am only familiar with the SPI fininishes i.e. A-1, A-2, etc through to D-3, Would someone be able to tell me what E8 is equivalent to or direct me to where I could find relevant information on such grades?

      Thanks in advance,

    3. Bill Toulas

      Bill Toulas Well-Known Member EngineeringClicks Expert

      Sep 2017
      Likes Received:
      Ok, here’s what I’ve found: E8 corresponds to 6A, so it should have a surface roughness (Ra) of 2.914 μm. I have even found EDM settings to achieve this result, so if you need them, let me know.

      E8 as a term is used for tension testing, so maybe they have given you the wrong information because of a mistake? That is always a possibility as a mistyped word or even letter is enough to cause us engineers confusion. First, ask again, clarify. If you are not asking the client because you don’t want to give the impression that you’re clueless, do not follow this practice. :)
    4. GoodCat

      GoodCat Well-Known Member EngineeringClicks Expert

      Nov 2018
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      I did not quite understand the question, correct me if I am wrong. On some plastic parts, the size is indicated with the letter E8. What's the question? What is the tolerance for this size or what is the maximum surface roughness or what is the recommended roughness for this surface?

      E8 is the size tolerance with guaranteed gap.

      What is your Internet light?

      What is the maximum allowable surface roughness for this tolerance?

      What is the recommended surface roughness for this tolerance?

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