PTFE sintering is an elevated temperature process in which powder metal is caused to coalesce into essentially solid form, with properties similar or nearly identical to those of the material in wrought form.
The sintering process can be used to fabricate high-performance and complex shape parts. It can be used in aerospace, automotive, chemical, electronics, marine and other industries.
Sintering is known to have a significant effect on the dimensional tolerances of article sizes, especially for complex shape parts. This is because the shrinkage during sintering provides a densification from 0.5 to 0.9 g/cc, which adversely affects the dimensional tolerances.
As a result, there is a need for a simple yet reliable way to control sintered part geometry, improving tolerances and eliminating secondary operations and scrap without unnecessarily increasing cost. Moreover, there is also a need for a method of controlling the sintering process to eliminate residual stress, improve the tensile strength of the final product and minimize deformation and cracking.
Temperature and velocity of heat flow in the sintering furnace are influenced by the sinter rod geometry. To investigate this problem, a finite element thermal model was established, and the internal and external heat flow were simulated in the thermal model.
Depending on the gas and thermal characteristics settings, a temperature distribution and flow field were simulated for the heating furnace and the sinter, as shown in Fig. 7.
To test the accuracy of the temperature analysis, temperature measuring probes were installed inside and on the surface of a PTFE rod and the temperature distribution was measured. The results showed that the holding time at the melting point and crystallization point depended on the rod geometry, as shown in Fig. 5.