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General technical requirements for machining workpieces of various CNC machines

Jun 10, 2019

There are many machining methods, and the types of machined workpieces are also various. Different kinds of workpieces have different machining methods. Different kinds of workpieces also have different mechanical processing technical requirements. ALLES CNC will now share with you the general technical requirements of all kinds of CNC machined workpieces collected and sorted out by itself.

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First, the conventional technical requirements for mechanical processing of castings


1. Cold isolation, cracks, shrinkage and penetration defects and serious defects (such as undercasting, mechanical damage, etc.) are not allowed on the surface of castings.  

2. Castings should be cleaned up without burrs or flying edges. Non-processing indicates that the riser should be cleaned up and the surface of the castings should be level.  

3. The characters and marks on the non-machined surface of the castings should be clearly distinguishable, and the positions and fonts should meet the requirements of the patterns.  

4. Roughness of non-machined surface of castings, R of sand casting, is less than 50 micron.  

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

6. The moulding sand, core sand and core bone on the castings should be cleaned.  

7. Castings with inclined parts and tolerance zones should be symmetrically arranged along the inclined surface.  

8. The moulding sand, core sand, core bone, multi-flesh and viscous sand on castings should be shoveled and ground smoothly and cleaned up.  

9. Corrections should be made to correct the misalignment and the casting deviation of the boss so as to achieve a smooth transition and ensure the appearance quality.  

10. The wrinkles on the non-machined surface of castings should be less than 2 mm in depth and more than 100 mm in spacing.  

11. The non-machined surface of machine castings needs shot peening or drum treatment to meet the requirements of cleanliness Sa2 1/2.  

12. Castings must be treated with water toughening.  

13. The surface of the castings should be smooth and the gate, burr and sticky sand should be cleaned up.  

14. Castings are not allowed to have casting defects such as cold insulation, cracks and holes which are harmful to the use.  


Secondly, the conventional technical requirements of forging machining


1. The nozzle and riser of forgings should be removed sufficiently to ensure that there are no shrinkage holes and serious deflection in forgings.  

2. Forging should be forged on a forging press with sufficient capacity to ensure full penetration within the forging.  

3. Forgings are not allowed to have visible cracks, folding and other appearance defects affecting their use. Local defects can be removed, but the cleaning depth should not exceed 75% of the processing allowance. Defects on the non-machined surface of forgings should be cleaned up and smooth transition.  

4. No white spots, internal cracks and residual shrinkage holes are allowed in forgings.  

Thirdly, the conventional technical requirements of weldment machining.

1. Defects must be thoroughly removed before welding. The groove surface should be repaired smoothly and without sharp corners.  

2. Welding defects can be removed by shoveling, grinding, carbon arc air gouging, gas cutting or mechanical processing.  

3. Clay, oil, water, rust and other dirt within 20 mm around the welding zone and groove must be thoroughly cleaned.  

4. During the whole welding process, the temperature of the preheating zone should not be lower than 350 degree C.  

5. Welding in horizontal position as far as possible, if conditions permit.  

6. When repairing welding, the electrodes should not oscillate transversely.  

7. When surfacing, the overlap between beads should not be less than 1/3 of the width of beads. The welded meat is full and there are no burns, cracks and obvious nodules on the welded surface.  

8. Beautiful appearance of the weld, no defects such as biting, slagging, pore, crack, spatter and so on; uniform welding wave.  


Fourth, the conventional technical requirements for the mechanical processing of cutting parts


1. Parts shall be inspected and checked according to the processing procedure. After the previous procedure has been checked and qualified, they can be transferred to the next procedure.  

2. Burrs are not allowed on machined parts.  

3. After finishing, the parts should not be placed directly on the ground. Necessary support and protection measures should be taken. No rust and other defects affecting performance, life or appearance are allowed on the machined surface.  

4. No peeling shall occur on the surface after rolling.  

5. There should be no oxide skin on the surface of the parts after heat treatment in the final process. There should be no annealing on the finished mating surfaces and tooth surfaces.

6. No defects such as black skin, bump, chaos and burr are allowed on the surface of the processed thread.

Different workpieces have different technical requirements for mechanical processing. We have to follow the conventional technical requirements for mechanical processing, in order to better ensure the quality of the workpiece.

General technical requirements for machining workpieces of various CNC machines

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