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  • Texture of injection moulding

    Discussion in 'Plastic moulding' started by GarethW, Mar 20, 2013.

    1. GarethW

      GarethW Chief Clicker Staff Member

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      How do you determine what texture should be on an injection moulding? I am aware of different standards, but what's the best standard to use? Basically I want to achive a very light "bead blasted" texture. A book of samples containing different textures would be handy too to make a judgement.
       
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    3. Eric Green

      Eric Green New Member

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      Gareth, the industry standard for textures is available from Mold-Tech - they can sell you individual plaques or a complete set of reference textures. You may be able to get a free set of texture plaques from Custom Etch, although they do not follow the same naming conventions and may not be a direct substitute. Another possibility is Proto Mold, who offer a free marketing sample called "Protogami" - it includes not only the various surface textures they offer but a number of materials. Mold-Tech and Custom Etch create textures in the mold tooling using a chemical etch process, while Proto Mold and many small shops use bead blasting or other mechanical means.

      If you are a SolidWorks user, you can find the Mold-Tech finishes in the Textured subset of Plastic appearances; MT11000 is the lightest texture.

      Textured finishes vary in depth, and will require suitable draft. Usually the plaques will indicate the texture depth and recommended draft angle.
       
    4. gfought

      gfought New Member

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      Good Day...
      Mold-Tech can get you any information you require on textured mold surfaces. They have a sample texture plate set that you can buy, that has actual molded surface textures with their associated Mold-Tech numbers, that you can see and touch. Tool makers normally send their mold out for texturing and the Mold-Tech number can be used to specify the texture you want. Here is their website... http://www.mold-tech.com/, and a reference sheet on how to select a texure... http://www.mold-tech.com/PDF/TEXTURETECH.pdf
       
    5. PeterB

      PeterB Member

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      Texture definition

      Injection mould tooling can be textured by different means, which may vary according to tool manufacture method, time scale, budget, material and supplier facility limitation.
      Aluminium tooling (and others) which is typically machined rapidly by a CNC process often uses bead, sand or vapour blasting to minimise budget and time. In practice, the final surface varies by supplier and can be influenced by the personal technique of the operator as well as the precise bead/abrasive material used. I've found it best to obtain moulded sample parts from the moulder/toolmaker in question, so that their specific process can be seen and approved, with their sample becoming the standard reference for all parties to abide by.

      Steel tooling, where spark erosion may be used to define final surfaces, can utilise the various textures available by the spark erosion/EDM techniques. Those are well defined and controlled by standards and applied by most suppliers. Guide plaques and reference strips are available for these and can be obtained from the machine manufacturers as well as other engineering supply houses/sources, such as: <http://www.rubert.co.uk/Comparison.htm>. Such sources can generally also supply polishing grading and gloss finish grading bars for other material finishes. These are commonly used to keep time and budgets tight. But sparking creates sharp cavities with a hardened surface. This may or may not be desirable. Sharp textures do hold dirt more than softer forms.

      Where time and budget is available, the best and widest range of textures to source are the proprietary photo-etched patterns, available from various suppliers, all of whom can provide full sample books and individual moulded plaques. <Mold-tech.com> and Akron <http://www.textureame.com/moldtexture.html>, are examples. These companies produce specific easy-clean textures with soft form cavities, developed for the vehicle industry to aid in keeping bumpers and suchlike looking good for the customer.

      With all texturing, draft angles must be allowed, dependent on the depth of surface change. Otherwise scuffing will occur during part ejection.
       
      Last edited: Mar 21, 2013
    6. RickStockton

      RickStockton Member

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      Gareth, I have found that peaks per inch is extremely critical to texture robustness, depending heavily on the plastic material used. For instance, I used MT-11000 on an ABS part, and had wonderful results, but when I used MT-11000 on a Nylon part, the relative softness of the Nylon resulted in a part which was very susceptible to marring, or abrasive smearing, where a relatively smooth object could rub a flat spot in the Nylon part — not by removing material, but by mashing all of the microscopic peaks together. I got in touch with the Mold Tech reps, and found a similar-looking Mold Tech texture, but with far fewer peak per inch, and thereby picked up a huge improvement in mar-resistance.
       
    7. GarethW

      GarethW Chief Clicker Staff Member

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      Thanks to all for the excellent advice. Has anyone heard of the Tanazawa standards? I used it whilst working for Hitach a few years agoi. Perhaps that's more of a Japanese thing rather than being in general use globally...
       
    8. Martin-s

      Martin-s New Member

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      For a quick reference to easily produced finishes, have a look at the prop labs design cube and website, they give you good advice on their website as well. Hope it helps.
       
    9. BDry

      BDry New Member

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      We use mainly Mold-Tech though some blasting or spark eroding for less handled items. I agree with all the reference info as that is what we use too.
      Rick's point on peaks per inch is interesting.
      another thing to consider for durability is that etching gives a different micro topography than either blasting or spark eroding and it is this that tends to make it more durable in general. You can think of:
      -Etching as creating little recesses in the tool, with walls between them, of relatively even depth at a certain pattern.
      --The effect of etching for the part is to have plateaus of plastic with canyons between them.
      -Spark eroding creating rounded depressions in the surface of the tool with sharp upstands between them.
      --The effect of spark eroding for the part is to have spherical topped mountains with very sharp bottomed valleys between.
      -Blasting creating an effect similar to spark erosion but with many of the tips of the upstands knocked knocked over. Blasting finish also depends on the media being used; round glass beads giving smoother rounded dents and crushed grit more jagged dents. The lightest finish that I am aware of is referred to as Vapour Honing (or at least in my neck of the woods) and this uses fine pumice so it really is for making a surface matte rather than textured. As has been pointed out the base material for the tool affects what the blasting does. Also as has been pointed out blasting is one of the more variable finishes and is very operator dependent even for the same nominal materials.
      --The effect of blasting on part finish is quite varied from what I would call a medium texture at it coarsest to matte at its finest.

      Etching gives generally a more durable handling finish as the plateaus provide more bearing area meaning the wear reduces the height rather than the area. For spark eroded and blasted finishes the tips are rounded so any wear flattens these off giving a noticeable change in appearance.

      And yes the previous comment about texture requiring more draft is well worth remembering.

      Hope this helps.
      Brent
       
    10. Franz_fladic

      Franz_fladic Member

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      in china, we are more and more like to use Yick Sang texture standard.
       
    11. Ashish

      Ashish New Member

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      Mold-tech and YS (Yick Sang) are more popular, the latter is relatively cheaper than MT. You'll also have to check the recommended draft angle for the texture you select else it will leave scoring / scratch marks on the textured surface on de-molding if adequate draft angle is not provided.

      --
      Ashish Shah
       

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