3. Recompression. Calibration

After sintering, the dimensions of the parts are not very precise and their surface finish is poor. This is why most of them are calibrated.

To increase their density and thus their mechanical properties, they are recompressed. They can also be re-sintered and then calibrated.

The distinction between recompression and calibration has not been clearly defined by powder metallurgists. Hereafter, the operation will be considered as calibration when the vertical recompression is less than 5% of the height. In this case, the only aim is to improve surface finish and dimensional accuracy.

Both recompression and calibration tools are simpler. Dies are lower, as the compression ratio is lower. As for punches, they are generally monobloc, since there is no risk of powder movement as in compression.