Issues with the inspection of the outer diameter of EHB end caps
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As the title suggests, when checking whether the outer diameter of EHB heads meets the tolerance requirements, should one use a ruler to measure two points on the cut edge of the straight section of the head, or should the outer perimeter of the head be measured and then converted into a diameter?
After measuring the perimeter of the head, converting it to a diameter can yield only one result (one value). By using a ruler to directly measure two points on the cut of the straight edge section of the head, many values can be obtained. Use this method.
The EHB type end caps are based on their outer diameter and are used in conjunction with steel pipes to form the cylinder body; they are all devices of small diameter, and the diameter tolerance must be determined by two points passing through the center at the side ports.
For end caps based on outer diameter, the measurement method is to measure the perimeter. It is specified in GB/T25198 6.3.5.1. The perimeter is more accurate for measurement than the inner diameter.
The measurement of the outer diameter has two purposes. 1. The average diameter value is determined based on the perimeter of the upper edge, from which the actual average diameter at that point of the head is calculated. To determine whether the head diameter meets the standard requirements and is consistent with the cylinder diameter? 2. Measure the outer diameter of the head at multiple points. It is generally divided into approximately 8 equal parts for measurement; if the diameter of the head is large, more measurement points can be used. For shapes that are significantly elliptical, it is necessary to select representative points for measurement. The value of the ellipticity of the outer diameter of the head can be determined. To determine whether the ellipticity of the head exceeds the tolerance.
There’s a problem with the roundness of the head; it’s quite large. . So, measurements are generally taken based on the perimeter. When joining the cylinder to the head, a pull plate can be used to align the head with the cylinder, ensuring an appropriate amount of misalignment ； If the end cap is connected by flanges, it is more convenient to use the diameter as the reference.