China Wholesale Manufacturer of large diameter machining
Assembly error refers to the difference between the installation position of parts and the ideal position required by the assembly specification design and process. China Wholesale Manufacturer of large diameter machining
- The cause of assembly error
- Part error: the manufacturing error of the part and the additional error caused by the deformation and wear after operation and use.
- Tool and measuring tool error: tools and measuring tools have manufacturing errors, and systematic errors will occur when measuring and positioning with them.
- Operation error: Due to the hand feeling (such as tightness, flushness, sharpness, smoothness, jumping, shaking, vibration, distance, pull force, firm hand knocking, hand-pull gap and loose hand feeling, etc.), visual inspection (size, level, level, etc.) Straight, vertical, parallel, alignment and tangent, etc.), ear hearing (various abnormal noises), nose smelling (air leakage, etc.), and the errors generated by human sensory identification.
- Environmental error: Errors caused by temperature, relative humidity, light direction, air flow direction, foundation movement, etc.
- Consciousness errors: Errors caused by lack of concentration or lack of responsibility.
Rigorous work style, the spirit of technical excellence, and an extremely responsible attitude to work are the ideological basis for reducing assembly errors. In specific operations, there are several methods to directly reduce assembly errors that need attention. China Wholesale Manufacturer of large diameter machining
Second, choose a reasonable assembly benchmark
In order to make the assembly position of the parts accurate, select a certain part (point, line, surface) of the part that has been positioned as the basis for the positioning of the parts to be installed. This part is called the assembly datum. The correct selection of assembly datum is an important factor to improve assembly accuracy and reduce assembly error, which must be taken seriously. The correct selection of assembly datum should generally consider the following factors.
- Try to choose parts with higher processing precision, that is, parts with small dimensional tolerance, high shape precision, small position deviation and low roughness as the benchmark. For example, the diameter tolerance and radial runout of the groove part during roller manufacturing are lower than that of the smooth surface part, so when checking roller bending and correcting roller gauge, the groove part is used as the benchmark.
- The reference position should be as close to the assembly adjustment point as possible. For example, when the surface of the vehicle is flat, the height of the vehicle surface should be adjusted by the lifting screws of the frame, so the flat iron should be placed as close to the frame as possible. For example, place the flat iron rest far away from the frame, so that the reference point is far away from the frame. When the height of the adjacent frame is adjusted, the iron rest will be driven up and down, causing the reference to drift. The farther the flat iron rest is from the frame, the greater the height change of the reference plane will be, which will affect the assembly accuracy. China Wholesale Manufacturer of large diameter machining
- Try to reuse the same reference as much as possible to eliminate the deviation of the surface shape of the part. For example: because there is a certain degree of long-term bending and width-direction distortion on the top surface, it is necessary to place the iron on the level ruler that looks at the horizontal direction of the vehicle surface, the spirit level that looks at the horizontal horizontal direction of the vehicle surface, and the support that supports the height line of the front roller. The wire round rollers are placed in the same position to avoid additional errors caused by the uneven top surface of the vehicle.
- The convenience of flat packaging should also be considered when selecting the benchmark. For the left and right positioning of the helical gear of the spindle shaft, there are generally two methods: one is to insert the spindle, use the spindle as the reference, and use the clamping plate for positioning; the other is not to insert the spindle, and use the lower dragon tendon oil cup as the reference. Although the diameter tolerance of the spindle is smaller than that of the oil cup hole, it is more difficult to locate after inserting the spindle. Taking the oil cup hole as the reference, it can meet the left and right positioning requirements of the spindle shaft gear, and the spindle can not be inserted, so that the operation is convenient.
- Try to be consistent with the reference position of parts processing and pre-assembly in the machinery manufacturing plant.
- Avoid multiple transfers of assembly benchmarks (reduce cumulative errors) China Wholesale Manufacturer of large diameter machining
There are two ways to divide a 1m-long straight line into ten equal parts: one is to use a 150mm steel ruler, move the steel ruler once every 100mm, and measure ten times in total; the other is to use a 1m-long steel ruler. Straightedge, do not move, but take ten points sequentially according to the corresponding scale line. Obviously, the error of the latter method is relatively small. Because of the former method, due to the multiple movements of the measurement benchmark, two or more assembly errors (tools, operation errors) are superimposed together, resulting in a cumulative error. For the same reason, when measuring the gap with a specified feeler gauge, it is more accurate to use a single-page feeler gauge as much as possible, and avoid using two or more thin feeler gauges for measurement.
- Grasp the changing law of errors (eliminate systematic errors)
If the change law of the error is found and the value is found out, it is like trying to eliminate this error value in the assembly. This regular error is called a systematic error. For example, when the inner diameter measuring jaw of a vernier caliper wears out by 0.02mm, making the reading of each measurement falsely larger by 0.02mm, the reading can be automatically subtracted by 0.02mm to obtain the required real reading. Another example is when the air bubbles in the level meter are inaccurate, after positioning and turning around to check, it is found that the air bubbles are inaccurate, and after positioning, the air bubble is in a horizontal state. , to bring the part to a horizontal state. China Wholesale Manufacturer of large diameter machining
- Reasonably allocate or adjust the error value (reduce assembly error)
- Mutual loan law
When large-scale castings such as drawing frame surface, bottom plate, roving machine head and tail wallboard, frame, and vehicle surface are distorted and deformed, due to the inconvenience of orthopedic correction, it is only possible to check the verticality or levelness of multiple points, so that the readings after flat-packing are positive and negative. The maximum value in the direction is equal, or the difference after subtracting the maximum value in the positive and negative directions is not greater than the tolerance, this method is called the mutual borrowing method. - Adjustment method
When the cumulative error in assembly exceeds the tolerance, the size and shape of one of the links can be changed, or an unimportant size can be discarded and not controlled, so that the total size is within the allowable range. This link that can be changed is called the “adjustment ring”. Set the positions of the second, third, and fourth roller seats in turn, and the size between the fourth roller seat and the upper wall panel at the rear of the car can only be discarded, and it is impossible to correct. In actual work, the size, shape or position of the adjustment ring The change is often achieved by filing, padding, welding, or adjusting with adjustable parts, such as adjusting screws, adjusting washers, car foot pads, etc. Using these parts to adjust can improve the accuracy of assembly and save manual work. File repair and other work.
- Select assembly method
In order to reduce the assembly error and improve the accuracy of parts assembly, parts with certain errors can also be matched or grouped by selection, so that the upper and lower errors between parts can be properly matched to improve the accuracy, which is called selective assembly. China Wholesale Manufacturer of large diameter machining