Excessive dimensional shrinkage/dimension out of tolerance

After sintering, the dimensional shrinkage of the product exceeds the allowable tolerance range. This type of defect mostly occurs in the thick-wall transition areas of the product and at the far end of the gate, and gradually appears in the cooling and shaping stage. This problem causes the product dimensions to exceed the tolerance range, affecting assembly accuracy and product function.

(1) Temperature parameter aspect: Excessively high sintering temperature or excessively long holding time may cause thermal degradation of the material or loss of control of the reaction rate, destroying the internal structure of the product. (2) Pressure parameter aspect: Insufficient preforming pressure leads to excessively low blank density, causing the material to fail to fully fill or to be insufficiently densified, and the product density and bonding strength decrease. (3) Raw material characteristic aspect: Improper material particle size/morphology; the physical characteristics of the powder directly affect the preforming and sintering quality.

(1) Process control: Strictly control the sintering temperature and time, establish an online monitoring mechanism, set upper and lower parameter limits and implement alarm management. (2) Implementation measure: Ensure that the preforming pressure keeps the blank density within a reasonable range, formulate specific operation plans in combination with actual production conditions, and verify the implementation effect. (3) Material selection: Select a suitable powder particle size distribution., establish material selection evaluation standards, and determine the optimal plan through comparative tests. (4) Preventive measure: Establish a shrinkage rate database, preset shrinkage compensation amounts according to product structure and material type, and regularly calibrate mold dimensions.

The core of shrinkage defects lies in the contradiction between the volume change of material curing and insufficient process compensation, which needs to be comprehensively controlled through formulation optimization and process adjustment.