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What are the requirements for precision machinery parts processing?

Time: 2019-04-11 Source: Site views: 1924

What are the requirements for the processing of precision mechanical parts? In such an era of a hundred schools of contention, Mo Zi once said: sweet melons are bitter, there is nothing in the world. Although Baiye Xing has its shortcomings. Plum is not as white as snow, and snow has no plum fragrance, just like people have their own strengths and weaknesses, they are not perfect. Taking advantage of others and supplementing one's weaknesses is the truth. In the modern era, the current CNC machining can not escape the fate of the industry. What are the requirements for precision mechanical parts processing in the processing process, the following editors tell you.


1. Error of processing principle



The principle error of CNC machining is the error caused by the use of approximate machining movement methods or approximate tool contours. There is an error in the machining principle, so it is called a machining principle error. As long as the principle error is within the allowable range, this processing method is still feasible.


2. Geometric error of machine tool


The manufacturing error, installation error and wear of the machine tool directly affect the machining accuracy of the workpiece. Among them are the rotary motion of the machine tool spindle, the linear motion of the machine tool guide rail, and the error of the machine tool transmission chain.


3. Manufacturing error and wear of cutting tools


Manufacturing errors, installation errors, and wear during use of CNC-machined tools all affect the machining accuracy of the workpiece. During the cutting process of the tool, the cutting edge, the cutting surface and the workpiece and the chip produce strong friction, which makes the tool wear. When the tool wear reaches a certain value, the surface roughness value of the workpiece increases, the chip color and shape change, and it is accompanied by vibration. Tool wear will directly affect cutting productivity, machining quality and cost.


4. Fixture error


CNC machining fixture errors include positioning errors, clamping errors, fixture installation errors, and tool setting errors. These errors are mainly related to the manufacturing and assembly accuracy of the fixture.


CNC machining accuracy cannot be perfect, as long as the error is controlled within a certain range, it will not matter. Tool manufacturing errors and wear.


5.Positioning error


Positioning errors mainly include reference misalignment errors and inaccurate positioning manufacturing errors. When machining a workpiece on a machine tool, several geometric elements on the workpiece must be selected as the positioning reference during processing. If the selected positioning reference and design reference (the reference used to determine the size and position of a surface on the part drawing) ) If they do not coincide, a reference misalignment error will occur. The workpiece positioning surface and the fixture positioning element together form a positioning pair. Due to the inaccurate manufacturing of the positioning pair and the gap between the positioning pairs, the larger position variation of the workpiece is called positioning. Inaccurate manufacturing errors. The inaccuracy of the positioning sub-manufacturing will only occur when the adjustment method is used for processing and will not occur during the trial cutting method.


6.Adjustment error


In each step of the machining process, the process system must be adjusted in one way or another. Since adjustment is impossible to be accurate, adjustment errors occur. In the process system, the mutual position accuracy of the workpiece and tool on the machine tool is guaranteed by adjusting the machine tool, tool, fixture or workpiece. When the original accuracy of the machine tools, tools, fixtures and workpiece blanks meets the process requirements without considering dynamic factors, adjustment errors play a decisive role in machining errors.


7.Measurement error


When the part is measured during or after processing, the measurement accuracy, the accuracy of the measuring tool, and the workpiece and subjective and objective factors directly affect the measurement accuracy.


Part contour processing:


1. The unspecified shape tolerance should meet the requirements of GB1184-80.

2. The allowable deviation of the length without dimension is ± 0.5mm.

3. The corner radius R5 is not noted.

4. The unfilled chamfers are C2.

5. Acute angles are dull.

6. The sharp edges are dulled to remove burrs and flashes.


Surface treatment of parts:


1. There should be no scratches, abrasions and other defects on the surface of the parts that damage the part surface.

2. The surface of the processed thread must not have defects such as black leather, bumps, random buckles and burrs. Before painting the surface of all steel products, rust, scale, grease, dust, dirt, salt and dirt must be removed before painting.

3. Before removing rust, first use organic solvents, lye, emulsifier, steam, etc. to remove grease and dirt on the surface of iron and steel parts.

4. The time interval between the surface to be coated and the primer after shot peening or manual rust removal is not more than 6h.

5. The surfaces of the riveting parts that are in contact with each other must be coated with antirust paint with a thickness of 30 ~ 40μm before connection. Overlap edges should be closed with paint, putty or adhesive. Primers that have been damaged due to processing or welding must be repainted.


Heat treatment of parts:


1. After quenching and tempering treatment, HRC50 ~ 55.

2. Medium carbon steel: 45 or 40Cr parts are subjected to high frequency quenching, tempered at 350 ~ 370 ℃, HRC 40 ~ 45.

3. Carburizing depth is 0.3mm.

4. Perform high temperature aging treatment.


Technical requirements after finishing:


1. The finished parts should not be placed directly on the ground when placed, and necessary support and protection measures should be taken.

2. The processed surface must not have defects such as rust, bumps, scratches that affect performance, life or appearance.

3. After rolling, the surface must not peel after rolling.

4. The surface of the parts after heat treatment in the final process should be free of oxide scale. Finished mating surfaces and tooth surfaces should not be annealed


Sealing of parts:


1. Each seal must be soaked with oil before assembly.

2. Strictly check and remove the remaining acute angles, burrs and foreign matter during processing before assembly. Ensure that the seals are not scratched when installed.

3. After the bonding, the excess adhesive should be removed.


Gear technical requirements:


1. After the gear is assembled, the contact spots and backlash of the tooth surface should meet the requirements of GB10095 and GB11365.

2. The reference end face of the gear (worm gear) and the shaft shoulder (or end face of the positioning sleeve) should fit together, and cannot be checked with a 0.05mm feeler. The perpendicularity of the reference end face of the gear and the axis should be guaranteed.

3. The joint surface of the gear box and the cover should be in good contact.


Bearing technical requirements:


1. Assembly rolling bearings are allowed to be heated by oil heating. The temperature of the oil must not exceed 100 ° C.

2. The semi-circular hole of the bearing outer ring, the open bearing seat and the bearing cover must not be stuck.

3. The outer ring of the bearing should be in good contact with the semi-circular hole of the open bearing housing and bearing cover. When inspected by coloring, it should be within 120 ° symmetrical to the centerline and 90 ° symmetrical to the centerline. Even contact. When checking with a feeler gauge within the above range, a feeler of 0.03mm must not be inserted into 1/3 of the outer ring width.

4. After the outer ring of the bearing is assembled, it should contact the end surface of the bearing cap of the positioning end evenly.

5. After the rolling bearing is installed, it should be flexible and stable to rotate by hand.

6. The joint surfaces of the upper and lower bearing pads should be closely attached, and cannot be checked with a 0.05mm feeler.

7. When fixing the bearing pads with positioning pins, drill the hinges and distribute the pins while ensuring that the tile mouth and end faces are flush with the opening and closing faces and ends of the relevant bearing holes. Do not loosen the pins after they are inserted.

8. The bearing body of the spherical bearing and the bearing seat should be in uniform contact. Check by coloring method, and the contact should not be less than 70%.

9. The surface of the alloy bearing lining is not allowed to use when it is yellow, and no nuclear separation is allowed within the specified contact angle. The area outside the contact angle should not be greater than 10% of the total area of the non-contact area.


螺母技术要求: Technical requirements for screws, bolts and nuts:


1. When tightening screws, bolts and nuts, it is strictly forbidden to hit or use inappropriate screwdrivers and wrenches. After tightening, the screw slot, nut, screw, and bolt head must not be damaged.

2. Fasteners with specified tightening torque must be tightened with a torque wrench and tightened with the specified tightening torque.

3. When the same part is fastened with multiple screws (bolts), each screw (bolt) should be tightened crosswise, symmetrically, gradually and evenly.

4. The flat keys and the two sides of the keyway on the shaft should evenly contact, and there should be no gaps in their mating surfaces.


Technical requirements for repair welding:


1. Defects must be completely removed before repair welding. The groove surface should be smooth and smooth without sharp corners.

2. According to the defects of the cast steel, the defects in the repair welding area can be removed by shovel, grinding, carbon arc gouging, gas cutting or mechanical processing.

3. Adhesive sand, oil, water, rust and other dirt within 20mm around the repair welding area and the groove must be thoroughly cleaned.

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

5. Where possible, apply welding in a horizontal position as much as possible.

6. When repair welding, the electrode should not make excessive lateral swing.

7. When surfacing welding on the surface of cast steel, the overlap between welding beads shall not be less than 1/3 of the width of the welding beads.


Technical requirements for castings:


1. The tolerance zone of the casting is symmetrical to the basic size configuration of the blank casting.

2. Cold insulation, cracks, shrinkage holes and penetrative defects and serious incomplete defects (such as under casting, mechanical damage, etc.) are not allowed on the casting surface.

3. The castings should be cleaned without burrs and flashes. The non-processing indicates that the pouring riser on the castings should be flush with the surface of the castings.

4. The cast and logo on the non-machined surface of the casting shall be clear and legible, and the position and font shall meet the requirements of the drawing.

5. The roughness of the non-machined surface of the casting, sand casting R, not more than 50 μm.

6. Castings should be cleared of sprue and fly thorn. The remaining amount of the sprue on the non-machined surface should be leveled and polished to meet the surface quality requirements.

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

8. Castings have inclined parts, and their dimensional tolerance zone should be symmetrically arranged along the inclined surface.

9. The molding sand, core sand, core bone, fleshy, and sticky sand on the casting should be ground and cleaned.

10. The right and wrong type and the cast deviation of the boss should be corrected to achieve a smooth transition and ensure the appearance quality.

11. The wrinkles on the non-machined surface of the casting should be less than 2mm in depth and the distance should be greater than 100mm.

12. The non-machined surfaces of machine product castings need to be shot blasted or drum treated to meet the requirements of cleanliness Sa2 1/2.

13. Castings must be water-toughened.

14. The surface of the casting should be flat, and the gates, burrs, and sticky sand should be removed.

15. Casting defects such as cold insulation, cracks, holes, etc. that are detrimental to the use are not allowed.


Technical requirements of forgings:


1. The sprue and riser of each steel ingot should have sufficient resection amount, one to ensure that the forgings have no shrinkage and serious deflection.

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

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

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


Assembly technical requirements:


1. Sealing packing or sealant is allowed when assembling the hydraulic system, but it should be prevented from entering the system.

2. The parts and components (including purchased parts and outsourced parts) that have been assembled must have a certificate from the inspection department before assembly.

3. The parts must be cleaned and cleaned before assembly, and there must be no burrs, flashes, scale, rust, chips, oil, colorants and dust.

4. Prior to assembly, review the main fit dimensions of the parts and components, especially the interference fit dimensions and related accuracy.

5. The parts must not be scratched, bumped, scratched or rusted during assembly.

6. When assembling the conical pin, it should be painted and inspected with the hole. Its contact rate should not be less than 60% of the mating length, and it should be evenly distributed.

7. The number of tooth surfaces that the spline assembly contacts at the same time is not less than 2/3, and the contact rate must not be less than 50% in the direction of the length and height of the key teeth.

8. After assembling the flat key (or spline) with sliding fit, the parts can move freely without unevenness.

9. All the pipes before assembly should be removed with burrs, burrs and chamfers. Use compressed air or other methods to clear debris and rust on the inner wall of the pipe.

10. Before assembly, all steel pipes (including prefabricated pipes) should be degreased, pickled, neutralized, washed and anti-rusted.

11. When assembling, tighten the pipe clamps, supports, flanges and joints with threaded connections to prevent loosening.


是可以避免的,因此需要进行机械加工的操作人员在加工时对这六个容易造成机械加工误差的加工流程能更认真仔细的进行检测及各方位的验证后再进行机械加工操作,这样就能更好的减少机械加工误差造成的影响。 What are the requirements for the processing of precision mechanical parts? The processing errors can be avoided to a certain extent. Therefore, the operators who need to perform machining process the six processing processes that are likely to cause machining errors. The machining operation can be carried out after more careful and careful inspection and verification of various positions, so that the impact caused by machining errors can be better reduced.

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Address: Building 2, No. 5, Shijing Industrial Park, Pingshan District, Shenzhen Tel: + 86-755-8992 4285-611 + 86-755-8992 4486
Mobile phone: +86 13823281286 (Chen Sheng), +86 13686803292 (Lilian)
Website: http://www.china-rfc.com Email: [email protected]
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