Role of Lubrication.

Role of Lubrication.
A major loss of compaction. energy takes place became of friction which affects :
(i) the density and-density distribution within the compact
(ii) the strength of the compact
(iii) the ease of ejection after pressing, and
(iv) the wear of the die
During compaction several types of friction occurs as follows.
(a) friction between moving punches and die wall which is relatively small and the pressure loss caused by the practically negligible
(b) friction between adjacent particle which is insignificant and plays a minor part in compaction
(c) Internal friction within the powder particles during deform
(d) friction between powder particles and the die wall, ( the one of the most important factors which after the uniformed density throughout the compacted part this is the primary source of pressure loss during pressure and the magnitude of effect is dependent upon powder material, particle size and the distribution, particle shape and surface condition and the inter particle pressure)and
(e) friction between the green compaction the die wall during ejection this type of friction depends upon the powder material, die finish and tolerance and the compaction pressure.
When a compact is obtained by pressing from one sid.0 only the greatest density exists in the top layer just below the movable
Punch and nearest the die wall. The density drops with the increase of disunite from the punch face. Thus the lowest density occurs in the bottom layer nearest the die wall density variation is also found in the horizontal plane due to the decreasing pressure loss away from the die wall arising from the frictional effect. The total effect of density distribution is shown in fig. 23,