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Elevated Temperature Operation
Prototyping Situation
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Many plastic parts while lightly loaded must operate at well above room temperatures. Examples include housings for under hood components in automotive applications, appliance components and lighting components. The objective in this prototyping situation is to verify the performance of the component in the rated temperature range. It is not to determine maximum temperatures or life information.
Key Material Properties
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The primary material property that controls performance in this situation is heat deflection temperature (HDT)– that temperature at which the material softens enough to allow excessive deflection. (To see a comparison of heat deflection temperatures for common rapid prototyping materials, click here)
The second key material property is the coefficient of thermal expansion (CTE). All materials expand with heat. If the prototyping material expands significantly more or less than the proposed plastic, it may be dimensionally out of spec by the time it gets to operating temperature. (To see a comparison of CTE of common rapid prototyping materials, click here)
Approximation Requirements
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How close must we approximate the material properties of an injection-molded plastic to be able to simulate them?
We believe that the HDT of the SLA resin must be greater than the HDT of the proposed plastic minus 30°C. Parts designed for high temperature applications will include some factor of safety so that the component will not fail in temporary over-temperature conditions. The over-temperature design will often be in the range of 30°C. Since the prototyping will stay within rated temperature conditions, it is not necessary to include that factor of safety.
We believe that the CTE of the SLA resin must be within 50 mm/mm/°C of the proposed plastic. That way, dimensional errors resulting from the difference in CTE should be no greater than the change in dimension due to the change in temperature.
Selection Chart
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The chart below plots HDT against CTE. Each of the SLA resins is plotted as a point on that chart. A shaded rectangle surrounds each point, which represents the range of material properties that that resin can approximate as determined by the approximation requirements above.
The chart also includes several common injection molded plastics. If a plastic falls within a shaded rectangle, that resin for this prototyping situation can then adequately approximate it.
Most common plastics can be simulated by one of the four resin families we run in house.
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If you would like a chart like the one above with the plastics that you use in your products plotted on it, contact Tom Mueller