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Rigid profiles |
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Design with a regular wall thickness |
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 Always try to achieve a regular wall thickness in your design, otherwise the flow of material will be difficult to regulate and cooling will be faster in some places than others. Irregular walls will lead to difficulties in production, increased costs, and the profile may be impossible to manufacture. |
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Avoid details inside hollow profiles |
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 Unlike aluminium extrusion, thermoplastic extrusion relies upon calibrating (or forming) after the material passes through the die. This is where the definition of the profile is achieved, while being cooled and turned from liquid to solid. Because extrusion is a continuous process there is no way of getting inside hollow sections to hold details in place while the material is still liquid. The result is that anything more than the shortest of legs inside hollow sections will droop while the outside of the profile is being held to shape. |
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Avoid hollows within hollows |
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 For much the same reason as above, one hollow within another cannot be prevented from changing shape and position. Gravity will inevitably force the intended internal design out of shape and position before the thermoplastic solidifies. |
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Provide good access for internal detail |
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 So long as good access can be achieved, legs, grooves, snap-in features and other details can be incorporated internally, but there must be a way in. The outside profile cannot be a totally closed section. |
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Length tolerance |
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 Where possible design a little tolerance into your required length. Thermoplastics contract and expand with temperature, and cutting to a very critical length may add unnecessarily to cost. Typically, +/-2mm on a 500mm length is maintainable. Tighter tolerances are naturally achievable, but are generally cut out of line, adding to handling and cost. |
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Mating parts |
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 Where a profile is being designed to fit another component, we would like to have a sample of that mating part as soon as possible. This enables the intended connection detail to be considered at the tool design stage, and again when trialling your profile for the first time, to ensure correct fit. Always bear in mind that both components have tolerances that need to be accounted for. |
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Clear profiles |
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 When considering clear rigid PVC for a profile design, please note that this material is not glass clear. Generally speaking the thinner the wall the better the clarity. Also, because clear PVC is tin based (rather than calcium zinc based) its melt temperature is lower, so that swarf on cut ends has a tendency to stick, and may need additional cleaning off. In order to obtain much higher clarity we would recommend PETG or Polycarbonate, depending on your design criteria. |
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Flexible profiles |
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| Flexible profile design follows the same rules as rigid, with the following exception: |
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Wall thickness |
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 The wall of a flexible profile may vary if necessary, as the process of extruding flexible profiles is more akin to aluminium extrusion, and the profile is supported rather than formed while cooling. |
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Co-extruded profiles |
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Rigid/flexible co-extrusion |
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 To achieve a dual hardness co-extrusion, two machines are used to feed the separate materials through the same die. For the tooling to be achievable, co-ex designs should only include one or two points of a flexible material welded to a rigid main section. A variation on the theme may be where two rigid profiles are joined with a single flexible web to form a hinging profile. |
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Two-colour co-extrusion |
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 This process is typically used for epos (electronic point of sale) ticket sections. A coloured back, which attaches to the shelf edge is extruded with a thin clear cover to protect labelling. A maximum of two clear portions is advised. |
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