Eject Deflection Temp
Sensitivity | Availability | Datasheet Category | Cool Time Relationship |
|---|
High | Medium | Thermal Properties | Direct Variation |
The Eject Deflection Temp of a part’s material is the temperature at which the part can be safety ejected from the mold tool without causing deformation. This is the temperature to which the part is cooled before the mold tool is opened and the part ejected. As Eject Deflection Temp moves closer to Melting Temp, cooling time typically decreases; the delta between the two properties is the amount of heat the material must dissipate before ejection.
Note: Accurate cost estimates depend crucially on accurate values for Eject Deflection Temp; costs are extremely sensitive to changes in value for this property.
The value of Eject Deflection Temp is typically provided in the Thermal Properties category of the material specification, and it is obtained through experimentation using standard tests. Values in aPriori starting point Digital Factories are typically obtained from the ASTM D648 heat deflection temperature test using 0.46Mpa outer fiber stress. (ISO 75 specifies a similar test.)
Values for this property may appear in material specifications under Heat Deflection Temperature, Heat Distortion Temperature, HDT, or Deflection Temperature.
Estimating Eject Deflection Temp
If you want to add a new material to your Digital Factory, and you cannot obtain
Eject Deflection Temp from a material’s specification, you may be able to estimate the value based on
Eject Deflection Temp for a similar base polymer (but see
Note in
Eject Deflection Temp). The following considerations may help you formulate your estimate:
• Semi-crystalline materials typically have higher
Eject Deflection Temp than amorphous materials. (For information on which materials are semi-crystalline, see
https://www.iapd.org/Documents/Members%20Only/iapd_rectangle.pdf. Note that URLs may change.)
• Glass fiber fill typically (but not always) increases Eject Deflection Temp.
o Thermo-plastic elastomers (TPE), particularly soft TPEs, are an exception; for them, glass fill has no impact on ejection deflection temperature.
o Glass fiber fill typically increases Eject Deflection Temp more for semi-crystalline materials than amorphous materials.
If you cannot find a value for a similar base polymer, you can base an estimate on Vicat temperature, as a last resort. For most raw polymers, Eject Deflection Temp is less than Vicat temp by 10-40°C. (Vicat temp is obtained from a test that identifies the temperature at which a needle of specified dimensions, under a given load, penetrates a specified distance into a plastic specimen.)