What are the Techniques for Boring Machining? And the Main Problem of Boring Machining Technology
The precision of boring machining is very high, it can reach IT8~IT7, and the aperture can be controlled within the dimensional accuracy of 0.01MM. For precision boring, the machining accuracy can reach TT7- IT6, and the surface quality is good. For general boring, the value of surface roughness is Ra 1.6 to 0.8μm. Let's take a look at how to process boring.
Requirement of boring hole
1. Carefully check the positioning of the tool and workpiece before boring, and ensure that the positioning components are stable and reliable.
2. The caliper is used to measure the diameter of the hole. The reserved processing allowance should be calculated.
3. Before processing, check the accuracy of resetting and dynamic balance of the equipment (principal axis) and ensure that the requirements of processing are met.
4. In the process of boring, the dynamic runout value of the boring bar must be checked, and the cutting parameters should be corrected reasonably to reduce the influence of centrifugal shearing vibration. Reasonably correct cutting parameters and reduce the impact of centrifugal shear vibration.
5. The allowance for boring should be reasonably allocated according to the steps of rough boring, semi precision boring and fine boring. The allowance for rough boring is about 0.5mm. And the allowance for semi-fine boring and fine balance is about 0.15mm. We should avoid that the semi-fine boring may cause the knife phenomenon due to the excessive margin, which affects the precision adjustment accuracy.
6. The use of processing materials, high-precision boring (tolerance≤ 0.02mm) can add the processing steps of fine boring. The allowance for boring should be no less than 0.05mm, avoiding the flexibility of the machined surface.
7. In the process of cutting the boring tool, we should pay attention to avoid the collisions between the boring tool part (blade and cutter holder) and the cutter block. We also shouid avoid damaging the blade and changing the adjustment value of the boring cutter which may affect the machining accuracy of the hole.
8. During the boring process, we should maintain fully cooling and strengthen the lubricating effect of the processing parts to reduce cutting force.
9. In each processing step, chip removal should be strictly carried out to prevent chip from participating in the second cutting process, and affecting the machining accuracy and the surface quality.
10. We should check the degree of wear of the tool (blade) at any time and chnage the tool in time to ensure the quality of the hole machining.
11. It is strictly forbidden to replace the blade during the process of fine boring to prevent errors. After each step, the requirements of quality control must be strictly carried out, and the actual processing aperture should be carefully detected and recorded to facilitate analysis, adjustment and perfection of the boring process.
Main problems of boring
Tool wear
In the boring process, the tool is continuously used which is easy to wear and breakage. It may lead to the reduction of dimensional accuracy and the increase the value of surface roughness. At the same time, the calibration of micro feed unit is abnormal, and it leads to errors, causes deviation of processing aperture and even leads to lower quality of products.
Wear change of blade edge ▼
Machining error
The machining errors of boring mainly appear in the size, shape and surface quality of holes after machining, and the main influencing factors are:
1. The draw ratio of the cutter bar is too large or too long.
2. The mismatch between the blade material and the workpiece material.
3. The amount of boring is not reasonable.
4. The adjustment and distribution of allowance is unreasonable.
5. The deviation of the initial hole makes a change in the periodicity of the allowance.
6. Workpiece material is high rigidity or inductile, tool or material presents the trend of relieving cutter.
Surface quality
It is a common surface quality phenomenonon to cut the fish scale and screw thread on the machined surface:
It is mainly caused by the mismatch of tool feed and speed. ▼
It is mainly caused by rigid vibration and tool wear in the process of boring. ▼
Adjustment errors
In the process of boring, it is necessary for the operator to adjust the amount of cutter relieving in the distributing layer. In the process of adjusting the allowance, the error of accuracy of the machining dimension is easily caused by improper operation.
Adjustment errors
In the process of boring, it is necessary for the operator to adjust the amount of cutter relieving in the distributing layer. In the process of adjusting the allowance, the error of accuracy of the machining dimension is easily caused by improper operation.
Measuring errors
In the process of boring, using improper measuring tools and wrong measuring methods are common quality problems.
1. Errors of measuring tools
2. Errors of measuring methods
Analysis of the quality problems of typical boring machining ▼
The step of boring hole and some matters needing attention
Install boring tool
It is very important to install the boring tool, especially for work adjustment which based on eccentric principle. After installing the boring tool, we must pay attention to observe whether the plane on the blade edge is on the same level with the feed direction of the head of boring tool? Installing on the same level can ensure that several cutting edges are at normal machining cutting angles.
Test the boring with boring tool
The boring tool is adjusted according to the requirements of the process manufacturing to reserve a margin of 0.3~0.5mm. It is necessary to ensure that the allowance for rough boring is less than 0.5mm by adjusting the initial hole allowance.
After the boring tool is installed and loaned, the test is required to verify whether the boring tool meets the requirements of rough boring.
Requirement of boring hole
1. Carefully check the positioning of the tool and workpiece before boring, and ensure that the positioning components are stable and reliable.
2. The caliper is used to measure the diameter of the hole. The reserved processing allowance should be calculated.
3. Before processing, check the accuracy of resetting and dynamic balance of the equipment (principal axis) and ensure that the requirements of processing are met.
4. In the process of boring, the dynamic runout value of the boring bar must be checked, and the cutting parameters should be corrected reasonably to reduce the influence of centrifugal shearing vibration. Reasonably correct cutting parameters and reduce the impact of centrifugal shear vibration.
5. The allowance for boring should be reasonably allocated according to the steps of rough boring, semi precision boring and fine boring. The allowance for rough boring is about 0.5mm. And the allowance for semi-fine boring and fine balance is about 0.15mm. We should avoid that the semi-fine boring may cause the knife phenomenon due to the excessive margin, which affects the precision adjustment accuracy.
6. The use of processing materials, high-precision boring (tolerance≤ 0.02mm) can add the processing steps of fine boring. The allowance for boring should be no less than 0.05mm, avoiding the flexibility of the machined surface.
7. In the process of cutting the boring tool, we should pay attention to avoid the collisions between the boring tool part (blade and cutter holder) and the cutter block. We also shouid avoid damaging the blade and changing the adjustment value of the boring cutter which may affect the machining accuracy of the hole.
8. During the boring process, we should maintain fully cooling and strengthen the lubricating effect of the processing parts to reduce cutting force.
9. In each processing step, chip removal should be strictly carried out to prevent chip from participating in the second cutting process, and affecting the machining accuracy and the surface quality.
10. We should check the degree of wear of the tool (blade) at any time and chnage the tool in time to ensure the quality of the hole machining.
11. It is strictly forbidden to replace the blade during the process of fine boring to prevent errors. After each step, the requirements of quality control must be strictly carried out, and the actual processing aperture should be carefully detected and recorded to facilitate analysis, adjustment and perfection of the boring process.
Main problems of boring
Tool wear
In the boring process, the tool is continuously used which is easy to wear and breakage. It may lead to the reduction of dimensional accuracy and the increase the value of surface roughness. At the same time, the calibration of micro feed unit is abnormal, and it leads to errors, causes deviation of processing aperture and even leads to lower quality of products.
Wear change of blade edge ▼
The machining errors of boring mainly appear in the size, shape and surface quality of holes after machining, and the main influencing factors are:
1. The draw ratio of the cutter bar is too large or too long.
2. The mismatch between the blade material and the workpiece material.
3. The amount of boring is not reasonable.
4. The adjustment and distribution of allowance is unreasonable.
5. The deviation of the initial hole makes a change in the periodicity of the allowance.
6. Workpiece material is high rigidity or inductile, tool or material presents the trend of relieving cutter.
Surface quality
It is a common surface quality phenomenonon to cut the fish scale and screw thread on the machined surface:
It is mainly caused by the mismatch of tool feed and speed. ▼
It is mainly caused by rigid vibration and tool wear in the process of boring. ▼
Adjustment errors
In the process of boring, it is necessary for the operator to adjust the amount of cutter relieving in the distributing layer. In the process of adjusting the allowance, the error of accuracy of the machining dimension is easily caused by improper operation.
Adjustment errors
In the process of boring, it is necessary for the operator to adjust the amount of cutter relieving in the distributing layer. In the process of adjusting the allowance, the error of accuracy of the machining dimension is easily caused by improper operation.
Measuring errors
In the process of boring, using improper measuring tools and wrong measuring methods are common quality problems.
1. Errors of measuring tools
2. Errors of measuring methods
Analysis of the quality problems of typical boring machining ▼
| Quality Problem | Cause | Solution |
| Error of dimensional accuracy | The excessive margin of rough boring affects the accuracy of the margin of fine boring. | Adjusting the allowance ofsemi precision and fine boring and keep the boring state stable. |
| The cutting depth of fine boring is not big enough. | Recheck the cutting depth of the tool. | |
| Change in the size of the blade wear. | Change the tool. | |
| The rigidity of boring bar is not enough and it produces a cutting edge | Use a rigid rod or reduce the amount of boring. | |
| The runout amplitude of the radial circle of the spindle of the machine tool is too large | Before fine boring, we should keep the margin well-distributed, determine the stable difference, compensate for the fine adjustment or feed back to the equipment department to adjust. | |
| The draw ratio of boring tool (boring bar) is too large so its rihidity is not enough. | Reduce the draw ratio, increase cutting rigidity or adjust cutting parameters. | |
| The allowance of fine tuning feed is fault. | We can find someone to check and record carefully. | |
| The measuring method is not correct or the proofreading is not careful. | Learning the process of standard measurement. |
Ningbo Hewcho Industrial was established in 1999, is an experienced manufacturer ,exporter and supplier of precision custom machining parts.
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