The quality problem of the cutting piece and its harm
|1.11.2018||Posted by xzbbvfvbh under Advertising & Marketing|
1. Main quality problems and their hazards
1) Unsatisfactory rotation strength
Rotational strength refers to the ability of the China cutting disc for metal to resist cracking under the action of centrifugal force in rotation, reflecting the tensile stress of the cutting piece, which is a very important indicator for the manufacture and use of the cutting piece. In order to ensure the safe use of the cutting piece, the standard classifies the unsatisfactory rotation strength as a „fatal defect“, that is, „a defect that is dangerous or unsafe to the user or the device“. The sampling inspection scheme is that the number of samples is n=10, the number of receptions is Ac=0, and the number of rejections is Rc=1; that is, the rotation strength of 10 pieces of cutting pieces must be all qualified, and if one piece fails, it is judged to be unqualified. Through years of quality inspection, it has been found that the slewing strength of the fiber reinforced resin sheet cutting blade and the 切割-shaped cutting piece is not ideal, and some are lower than the maximum working speed, and some rupture when the slewing test speed is not reached; some also reach the test speed. But it can’t be broken for 30s. The unsatisfactory ratio of the rotation strength is 7.1% to 18.7%.
When the fiber-reinforced resin sheet cutting blade and the 切割-shaped cutting piece are used, most of them are hand-held cutting and grinding, and the distance between the operator and the cutting piece is relatively close. Therefore, once the rotating strength is poor, the cutting piece is broken during the cutting or grinding process, which is easy to cause. Personal injury or death.
2) Static balance is unqualified
The cutting piece is an inhomogeneous object. When the cutting piece rotates, the center of mass does not coincide with the center of rotation to cause vibration. This state is called the imbalance of the cutting piece. Unbalanced cutting blades can cause a lot of harm:
Acting on the grinding machine bearing, causing the main shaft to vibrate and accelerate the wear of the grinding machine spindle;
It additionally increases the rotational stress experienced by the cutting piece, reduces its rotational strength, and may even cause it to rupture upon rotation;
The vibration of the cutting piece and the workpiece system is intensified, which is manifested by the occurrence of vibration marks on the surface of the workpiece to be processed, and the processing precision and surface roughness are deteriorated;
Affect the uniformity of the self-sharpness of the cutting piece, so that the cutting piece wears unevenly.
The static balance of the cutting piece is also one of the main quality indicators reflecting the intrinsic characteristics and performance of the cutting piece. The static balance failure is classified as “heavy defect” in the standard, that is, “seriously reduce the product performance and have the performance of the machined part. Seriously affected defects.“ In the spot check, the static balance is not qualified as shown in Table 2, one of which
A fiber-reinforced resin sheet cutting sheet having a diameter of 400 mm and a linear velocity of 70 m/s has a standard static imbalance value of ≤13 g, but the actual measurement exceeds 18 g, and the vibration of such a cutting piece at the time of use is conceivable.
3) Unqualified hardness
The hardness of the cutting piece refers to the resistance of the bonding agent to resist the detachment of the abrasive particles from the surface of the cutting piece under the action of an external force, or the ease with which the abrasive particles are detached from the surface of the cutting piece. Hardness can accurately reflect the grinding performance of the cutting piece, which is one of the important indicators to measure the quality of the cutting piece. There are two requirements for the hardness of the cutting piece:
Uniformity of hardness (the difference between the maximum and minimum values of the hardness values of each point measured) shall comply with the standards;
The compliance requirement of the hardness, that is, the average value of the hardness (the arithmetic mean of the measured values of the hardness of each measuring point) is within the allowable range specified by the standard. The proportion of unqualified hardness is also quite high. For example, the hardness of the flat cutting piece is unacceptable in excess of 20% of the total number of unqualified parts.
4) The aperture is unqualified
The inner hole of the cutting piece is the mounting reference, and the hole diameter of the cutting piece is unqualified and listed as „heavy defect“ in the standard. The aperture is large, and the eccentricity is generated after the cutting piece is installed, so that the cutting piece is unbalanced, the vibration is aggravated when rotating at a high speed, the quality of the grinding process is affected, and even the cutting piece is broken, and the equipment is damaged. If the aperture is too small, the cutting piece cannot be installed and cannot be used. If it is forcibly installed, the spindle can be scratched, and the cutting piece can be caused to be dark, causing the cutting piece to break during operation and easily causing an accident. As shown in Table 2, the case where the aperture is unqualified is the most serious in the spot check. 2%。 The total number of unqualified slabs of the slabs of the slabs of the total number of unsatisfied.
5) Flag error
The resin EN12413 cutting discs mark indicates the basic performance of the cutting piece and plays an important role in guiding the user’s use and cannot be ignored. Flag errors are listed as „heavy defects“ in the standard. There are many problems in the logo, some of the logos are incomplete; some of the logos are wrong; even deliberately shoddy, fake, and fraudulent use of trademarks, causing confusion, affecting the use of users, harming their interests, and may lead to major accidents.
6) End face runout, radial runout failed
If the end face is bouncing and the radial runout is unqualified, the yaw and the balance performance will be generated when the cutting piece rotates, which will adversely affect the machine tool and the workpiece, so it should be controlled within the allowable range.