How to Calculate Ovality?

Ovality is a metric used to describe the degree to which the shape of an elliptical object deviates from a perfect circle.

 

Ovality is a metric used to describe the degree to which the shape of an elliptical object deviates from a perfect circle.

 

Simply put, it reflects the degree of difference between the long and short axes of an ellipse. The greater the ovality, the flatter the ellipse is; the smaller the ovality, the closer it is to a circle.

 

The value of ovality is usually derived by measuring the lengths of the long and short axes of an ellipse and calculating it according to a specific formula.

 

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How to calculate ovality?

 

There are a number of ways to calculate ovality, the following is one of the common ways:

 

Ovality = (max. diameter - min. diameter) / nominal diameter × 100 per cent

Where the maximum and minimum diameters are the lengths of the long and short axes obtained when measuring the ellipse, and the nominal diameter is generally the theoretical or specified standard diameter.

 

How to measure ovality?

 

Measuring ovality can be done by the following common methods:

 

1. Direct Measurement: Use calipers, micrometers and other measuring tools to measure the long axis (maximum diameter) and short axis (minimum diameter) of the ellipse, and then calculate according to the formula for calculating ovality.

2. Projection measurement method: project the ellipsoid object onto the plane, and calculate the ovality by measuring the long and short axes of the projected image.

3. Coordinate Measurement Method: Use coordinate measuring machine to measure the ellipsoid object at multiple points, obtain a large number of data points, and then analyse and calculate the long and short axes of the ellipse through the software, and then derive the degree of ovality.

4. Optical measurement method: for example, using a laser measuring instrument or other optical measurement equipment, non-contact measurement of the ellipsoidal object, to obtain the relevant dimensional data to calculate the degree of ovality.

 

Whichever method is used, it is necessary to ensure the accuracy and precision of the measurement to obtain reliable results of ovality.

 

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How to calculate ovality of pipe?

 

The measurement of ovality basically belongs to the diameter method, that is, the maximum diameter and the minimum diameter of the pipe cross-section were measured, and then find the difference between the two, that is, the value of ovality.

 

The formula for calculating ovality is: ovality = (maximum diameter - minimum diameter) ÷ nominal outside diameter × 100%

 

For example, a pipe nominal outside diameter of 60mm, after bending the maximum diameter of 61mm, the minimum diameter of 59.5mm, the pipeline ovality is: 2.5 per cent

 

How to calculate the ovality of cylinder?

 

How to calculate ovality of cylinder is similar to the pipe.

 

First of all, you need to measure the maximum diameter and minimum diameter of the cylinder cross-section.

The formula for calculating ovality is: ovality = (maximum diameter - minimum diameter) ÷ average diameter × 100%. Here the average diameter = (maximum diameter + minimum diameter) ÷ 2.

 

For example, a cylinder has a cross-section with a maximum diameter of 10.2cm and a minimum diameter of 9.8cm. Then mean diameter = (10.2 + 9.8) ÷ 2 = 10cm. Ovality = (10.2 - 9.8) ÷ 10 × 100% = 4%.

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What is the instrument used in measuring external diameter?

 

There are many kinds of instruments for measuring external diameter, the following are some common ones for you:

 

1. Vernier calipers: This is a common measuring tool to measure the external diameter by the scale on the main ruler and the vernier. It is suitable for measuring precision requirements are not particularly high.

 

For example, when measuring the outer diameter of a small cylinder, you can directly use the vernier caliper to snap the cylinder for measurement.

 

2. Outside micrometer: also known as spiral micrometer, can provide higher measurement accuracy, usually can be accurate to 0.01mm or even higher.

For example, in machining, the outer diameter of the part of the high-precision measurement will be used micrometer.

 

3. Laser O.D. Measuring Instrument: Non-contact measurement using laser technology, suitable for fast, high-precision measurement, and can measure the outer diameter of objects in motion.

 

In some production lines, the continuous production of pipe diameter of real-time monitoring, laser OD gauge plays an important role.

 

4. Image measuring instrument: through optical imaging and image processing technology to measure the outer diameter, can measure multiple size parameters at the same time, and provide intuitive images and data.

 

Commonly used in the complex shape of the object's outer diameter measurement and size analysis.

 

5. Coordinate Measuring Machine (CMM): a high-precision spatial measuring device that can accurately measure the three-dimensional dimensions of an object, including the outer diameter.

 

In the mould manufacturing, aerospace and other fields, the high-precision measurement of parts often use three coordinate measuring machine.