Introduction to coaxiality and its symbolic representation
1. Coaxiality is a mechanical professional term that refers to the positioning tolerance in the form and position tolerance of a part. The relevant elements are that the shafts, holes and holes, and shafts and holes are required to be on the same straight line, or in other words, to be concentric. That is, to control the degree of deviation between the actual axis and the reference axis!
2. Its symbol is represented by two concentric circles: ◎
Adverse consequences of large coaxiality errors
Coaxiality error is reflected in the misalignment of the centers of circles on a cross-section. If parts with large coaxiality errors are installed in a machine, they may not fit properly during assembly. The assembled machine may experience vibration, shaking, periodic noise, unstable suction, damage to machine parts, and in severe cases, even safety accidents. Therefore, controlling the coaxiality of components has always been a crucial aspect of Junhua Special Plastics’ quality inspection.
The type of parts targeted by coaxiality measurement
Coaxiality measurement is only applicable to rotating parts, such as shafts, gears, and bushings.
Instruments used for testing
Coaxiality is relatively difficult to measure. We use instruments such as image analyzers, coordinate measuring machines, runout instruments, V-blocks, dial indicators, and special fixtures for measurement.
Measurement methods
Coaxiality testing is a common testing item we perform in our measurement work. Below is a brief introduction to the coaxiality testing methods for shafts and gears produced by our company.
I. Method for measuring coaxiality using an image measuring instrument
1. Turn on the computer and place the part to be tested on the worktable.
2. Open the quick test button on your computer and import the program.
3. Click on the outer circle and inner hole of the object to be measured with the mouse, and then click the “Measure” button.
4. Read the coaxiality data, record it, and fill in the inspection report!
II. Methods for measuring coaxiality using a coordinate measuring machine (CMM).
1. First, identify the drawings and find the reference.
2. Securely clamp the part to be measured onto the coordinate measuring machine platform.
3. Open the coordinate measuring machine, calibrate the side head, turn on the computer, find the corresponding measurement software, open the software, and then write the program.
4. Begin measuring the product, establish a coordinate system, and measure the outer circle.
5. Define a reference point, evaluate the measured cylinders, and then you can see the coaxiality.
6. Export the test report.
III. Method for measuring coaxiality using a runout meter
1. Wash the test piece with warm water and dry it with a dry cloth.
2. Adjust the distance between the two tips of the yaw meter to be about 8 mm shorter than the shaft part being measured. Align the center hole of one end of the part being measured with the fixed tip of the yaw meter. Hold the part with your left hand and use your right hand to compress the handle of the moving tip at the other end of the yaw meter, so that the moving tip retracts backward. Coordinate your left and right hands to push the moving tip into the center hole at the other end of the part being measured!
3. Rotate the object being tested by hand. The rotation should be smooth, but not too loose; ensure the object is properly tightened. Otherwise, the test results will be inaccurate. If adjustment is needed, please refer to point 2 above.
4. Install the dial indicator, base, and stand. Adjust the dial indicator so that the probe contacts the outer surface of the workpiece being measured, with a compression of 0.5 to 1 revolution.
5. Slowly and evenly rotate the workpiece one revolution by hand and observe the fluctuation of the dial indicator pointer. Take the difference between the reading Mmax and the reading Mimin as the coaxiality error of the cross section and record the data.
6. Move the dial indicator bracket, select an outer circle, rotate the part to be measured, and measure four different positions as described above. Take the MAX value of the difference between the reading Mmax and the reading Mimin at each position as the coaxiality error of the part.
7. Complete the test report and organize the experimental equipment.
IV. Method for checking coaxiality using V-blocks
1. Wash the test piece with warm water and dry it with a dry cloth.
2. Prepare two V-shaped blocks of the same height and with the same cutting edge. Place the prepared V-shaped blocks on a marble slab or a very flat machine workbench.
3. Place the reference of the workpiece to be measured in the V-groove of the instrument.
4. Install the dial indicator, indicator base, and indicator stand. Adjust the dial indicator so that the probe contacts the outer surface of the workpiece being measured, with a compression of 0.5 to 1 revolution.
5. Press down with your hand and slowly and evenly rotate the workpiece one revolution, and observe the fluctuation of the dial indicator pointer. Take the difference between the reading Mmax and the reading Mimin as the coaxiality error of the cross section, and record the data.
6. Then move the dial indicator base, select another point on the outer circle, rotate the part being measured, and measure four different positions using the method described above. Take the MAX value of the difference between the measured reading Mmax and the reading Mimin at each location as the coaxiality error of the part.
7. Complete the test report and organize the experimental equipment.
V. Methods for testing coaxiality using specialized tooling
Data calculation methods and report completion
1. First, calculate the coaxiality error value on a single measurement section, i.e., Δ = Mmax – Mmin.
2. Take the MAX value among the coaxiality error values measured on each cross section as the coaxiality error of the part.
3. Complete the measurement according to the above steps and fill in the relevant information of the measured part and the measurement results into the corresponding inspection report. Use this as a reference to determine whether the coaxiality error of the part is qualified.
Jiangsu Junhua also employs numerous testing methods and techniques, which will not be detailed here. Jiangsu Junhua is a fully integrated company encompassing the R&D, production, and sales of PEEK (polyetheretherketone) resin polymerization, continuous extrusion molding of sheet, rod, and tube profiles, and finished parts. PEEK, with its excellent comprehensive performance, is widely used in aerospace, defense, automotive manufacturing, electronics, and medical fields. The company’s machining equipment includes imported 5-axis CNC, 4-axis CNC, 3-axis CNC, imported milling and turning machines, CNC lathes, gear hobbing machines, and other precision machining equipment to ensure the quality of your products. We welcome inquiries and discussions; Junhua is willing to work with people from all walks of life to create a bright future for Junhua PEEK!