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What are the conventional technical requirements for workpieces in machining

May 5, 2023

There are many types of workpieces in machining, and there are many processing methods. Different types of workpieces have different processing methods and technical requirements. Let's talk about what is there.

 

1) Requirements for processing cutting parts
1. Parts should be inspected and accepted according to the processing procedure, and can only be transferred to the next procedure after passing the inspection of the previous procedure.

2. The processed parts are not allowed to have burrs.

3. The finished parts should not be placed directly on the ground, and necessary support and protection measures should be taken. Defects such as rust, moth, bumps and scratches that affect performance, life, or appearance are not allowed on the processed surface.

4. Roll the finished surface, and there must be no peeling after rolling.

5. There should be no scale on the surface of the parts after heat treatment in the final process. Finished mating surfaces and tooth surfaces should not be annealed

6. The surface of the processed thread is not allowed to have defects such as black skin, bumps, chaotic buckles and burrs.

 

2) Requirements for processing forgings
1. The nozzle and riser of the forging should have enough removal to ensure that the forging has no shrinkage cavity and serious deflection.

2. Forgings should be forged on a forging press with sufficient capacity to ensure that the inside of the forging is fully forged.

3. Forgings are not allowed to have cracks, folds and other appearance defects that affect the use that are visible to the naked eye. Local defects can be removed, but the cleaning depth should not exceed 75% of the machining allowance, and the defects on the non-machined surface of the forging should be cleaned up and transitioned smoothly.

4. Forgings are not allowed to have white spots, internal cracks and residual shrinkage cavities.

 

3) Requirements for welding parts processing
1. Defects must be completely removed before welding, and the groove surface should be smooth and smooth without sharp corners.

2. The defect area of the weldment can be removed by shoveling, grinding, carbon arc gouging, gas cutting or mechanical processing.

3. Dirt such as sticky sand, oil, water and rust within 20mm around the welding area and the groove must be thoroughly cleaned.

4. During the whole process of welding, the temperature in the preheating zone shall not be lower than 350°C.

5. When conditions permit, weld in a horizontal position as much as possible.

6. When repairing welding, the electrode should not swing too much laterally.

7. During surface surfacing welding, the overlap between weld beads shall not be less than 1/3 of the weld bead width. The weld meat is full, and the welding surface has no burns, cracks and obvious nodules.

8. The appearance of the welding seam is beautiful, without defects such as meat biting, slag addition, pores, cracks, and splashes; the welding wave is uniform.

 

Fourth, casting processing requirements
1. Cold shuts, cracks, shrinkage cavities, penetrating defects and serious incomplete defects (such as under-casting, mechanical damage, etc.) are not allowed on the surface of the casting.

2. The castings should be cleaned without burrs and flashes, and the risers on the non-processing surface should be cleaned flush with the surface of the castings.

3. The characters and signs on the non-processed surface of the casting should be clearly identifiable, and the position and font should meet the requirements of the drawing.

4. The roughness of the non-machined surface of the casting, sand casting R, is not greater than 50μm.

5. Castings should be cleared of pouring risers, flying spurs, etc. The residual amount of the gate riser on the non-processed surface should be leveled and polished to meet the surface quality requirements.

6. The molding sand, core sand and core bone on the casting should be cleaned.

7. For castings with inclined parts, the dimensional tolerance zone should be arranged symmetrically along the inclined plane.

8. The molding sand, core sand, core bone, succulent, sticky sand, etc. on the casting should be smoothed and cleaned.

9. The right and wrong type, the casting deviation of the boss, etc. should be corrected to achieve a smooth transition and ensure the appearance quality.

10. Wrinkles on the non-machined surface of the casting, the depth is less than 2mm, and the spacing should be greater than 100mm.

11. The non-processed surface of the machine product castings needs to be shot blasted or roller treated to meet the requirements of cleanliness Sa2 1/2 level.

12. Castings must be water toughened.

13. The surface of the casting should be flat, and the gate, burr, sticky sand, etc. should be cleaned.

14. Castings are not allowed to have casting defects such as cold shuts, cracks, and holes that are harmful to use.