Causes and preventive measures of bolt breakage of tube mill
Date：2019-06-28 13:46 Source：未知Views:
First, the cause and prevention of the fracture of the lining bolt
There are many reasons for the breakage of the grinding bolts. There are several main reasons for this.
The first is the quality problem. When the bolt is in machining, there are defects such as the thread is too deep, the screw has the knives, the head and the screw are not perpendicular, and the cross-section stress increases when the thread is too deep; the tool marks cause stress concentration; the screw Non-perpendicular to the end face will cause the bolt to be stressed on one side, increase the local stress, etc. These defects will inevitably overload the bolt locally. When it exceeds its strength limit, the bolt will crack.
Secondly, improper installation will also cause bolt breakage.If the bolt head and the lining pit are not in good contact and are not compact, the bolt will be stressed on one side or part, and the local stress will increase, which will easily break the bolt; If the contact with the grinding body is not good, the bolt will be forced on one side and cause breakage. Of course, the uneven thickness of the mat is also the same.
Third, excessive preload will also promote bolt breakage, especially when the bolt is partially stressed.Fourth, the lining hole and the bolt hole of the grinding body are not concentric, and the deviation is severe. When the bolt is hit hard, the cylinder or the lining will cause damage to the screw, such as scratching, abrasion, etc., making the bolt easy. fracture.
In order to avoid or reduce the breakage of the grinding bolt, it can be prevented from the following aspects:
First of all, we must strictly control the quality of the bolts found in the inspection, such as the wrong material, rough processing, crack irregularities, bolt head irregularities and other defective bolts are stored separately, it is strictly prohibited to enter the production line.
Secondly, the nut must be ensured to be solid with the cylinder as a whole; the bolt head and the lining of the lining are true, and the affected parts are trimmed, and the hammer and the bolt head are ensured by hammering. At the same time, pay attention to the coincidence degree between the screw hole and the screw hole of the lining to prevent damage to the bolt; pre-tighten the bolt according to the standard requirements to prevent over-tightening.
Second, the cause and prevention of bolt breakage at the end of the cylinder
The end bolt of the cylinder has an end lining bolt and a hollow shaft and an end cap connecting bolt, and the reason for the breaking of the end lining bolt is substantially the same. The following mainly analyzes the cause and prevention of the breakage of the hollow shaft connecting bolt.
First, the connecting bolts of the hollow shaft and the end cover generally have high strength, high processing precision, and some have positioning functions, and need to be matched with the reaming holes, so the requirement is high. There are several main reasons for its fracture. The first is the improper selection of materials and insufficient strength.
Second, the processing precision is insufficient, and there are defects, such as rough processing, insufficient size, and the screw and the bolt head are not perpendicular, etc., and stress concentration tends to occur during operation, causing fracture.
Thirdly, the reason for the installation is that the bolt head or nut and the end cap or the hollow shaft are not solid when installed, and the bolt is on one side, causing excessive local stress and cracking.
Fourthly, the end face of the hollow shaft end or the end face of the end cover is not perpendicular to the bolt hole, so that the end faces of the nut and the bolt head are not compacted, and the bolt is partially stressed excessively.
Fifthly, the end cover and the hollow shaft have poor processing precision, and cannot be compacted by themselves, and the bolt is subjected to an increased force during operation.
Sixth, the pre-tightening force during installation is too large. When the bolt is pulled during operation, the excessive pre-tightening force and the tensile force coincide, and the bolt strength limit is exceeded, and breakage occurs. The above-mentioned unfavorable conditions will cause the local stress of the bolt to be too large, and it is easy to cause cracks and then break.
1. Check the materials at the time of acceptance to see if the materials meet the drawing requirements. Check for machining defects and prohibit unqualified parts from entering the production line.
2. When installing, ensure that the nut and bolt head are tightly fitted with the hollow shaft and the end cap. If there is any problem, it should be properly repaired and the pre-tightening force is moderate.
3. The hollow shaft and the end cap must be tightly fitted, and if necessary, can be processed to achieve a perfect fitting condition, and the partial gap is less than 0.05 mm.
Third, the conclusion
There are many reasons for the breakage of the mill bolts. This article only talks about some main reasons and preventive measures based on personal experience. Please pay attention to the corrections. In addition, it must be stated that the new bolts of the mill must be inspected and tightened every day until it is not loose. It is necessary to prevent breakage caused by loose bolts. The pre-tightening force of the bolt can be carried out according to the instructions or manual requirements.
If you still want to know more grinding equipment information, you can contact the online customer service, jiangsu LVSSN for your answer.