Production and manufacturing of pressing and forming molds in powder metallurgy parts processing

Powder forming is one of the main processes in the production of powder metallurgy parts. In this process, the single axis rigid closed mold is the most commonly used and important mold. Therefore, the design, manufacturing, and use of molds have important impacts on the quality, cost, safety, productivity, and automation of powder metallurgy mechanical parts production.

In order to meet the accuracy and strength requirements of powder metallurgy parts, as well as the forming characteristics of powders, the forming mold assembly and its main components need to meet the following requirements.

Ⅰ. Requirements for forming mold assembly:

1. There is a reliable demolding method to ensure that the blank can be demoulded reasonably without cracks.

2. A compact that can ensure the density, geometric shape and dimensional accuracy, surface roughness, etc. required by the composite technology.

3. A compact that can ensure the density, geometric shape and dimensional accuracy, surface roughness, etc. required by the composite technology.

4. For compacts with changes in cross-section along the pressing direction, in order to ensure that the density of the non cross-sectional part of the compacts is uniform after pressing, a powder loading mechanism should be transferred to obtain basically the same compression ratio. The adjustment of the powder loading structure should be fine tuned and the operation should be as convenient as possible.

Ⅱ. Requirements for main parts of the mold:

1. Requirements for female molds：

1. Demagnetization is required after flat grinding.

   
   

2. Able to ensure the intact detachment of the billet.

   
   

3. The roughness of the working surface Ra ≤ 0.016Um.

   
   

4. It should have sufficient strength and rigidity under working pressure.

   
   

5. The working surface should have high hardness and good wear resistance.

   
   

6. Capable of ensuring the geometric shape and dimensional accuracy of the billet shape.

   
   

7. Select the appropriate mold material based on the batch size and complexity of the product.

   
   

8. Structurally, it should be easy to manufacture and maintain, safe to use, and easy to operate.

   
   

9. The height of the female mold should be able to accommodate the loose powder required for pressing, and ensure good positioning and guidance for the upper and lower mold punches.

2. Requirements for core rods:

1. Demagnetization is required after flat grinding.

1. The roughness of the working surface Ra ≤ 0.016Um.

   
   

2. Ensure the geometric shape and dimensional accuracy of the inner cavity of the billet.

   
   

3. There should be good coordination, positioning, and guidance with the upper and lower die punches.

   
   

4. The core rod structure for forming irregular holes should ensure that the blank can be removed from the core rod, and the structure should be convenient for operation and processing.

   
   

5. The working section should have high hardness, and the connection or fixed end of the mobile core rod should have sufficient rigidity and toughness. The hardness after heat treatment should be appropriately reduced compared to the working section.

3. Requirements for die stamping:

1. Demagnetization is required after flat grinding.

   
   

2. The relevant parts can ensure technical requirements such as verticality, parallelism, and coaxiality.

   
   

3. The working surface should have sufficient hardness and wear resistance, and the selection and treatment of materials should consider appropriate toughness.

   
   

4. The upper and lower die punches should have a good fit, positioning, and guidance for the female mold and core rod, with reasonable fit gaps. The composite die punches (i.e. when there is a pressing sleeve) should be able to release the blank.

   
   

5. The roughness of the working surface and mating surface of the upper and lower punching dies Ra ≤ 0.025Um. The outer diameter of the non working section can be appropriately reduced, and the inner diameter can be appropriately enlarged to reduce the amount of precision machining and friction with the female mold and core rod.