Surface roughness detection of automobile engine cylinder block

The testing capabilities of the Ultra Precision Laboratory of You'erhongxin Testing include:3DMicrostructure and film thickness analysis, surface roughness detection, shaft shape and position tolerance detection, gear meshing accuracy detection. The laboratory hashigh precisionMeasuring instrument, with an accuracy of up to0.1nanometer. Applied in industrial manufacturing, electronic manufacturing, automotive industry and other scenarios, it can provide parameter optimization basis for research and development, shorten the cycle and reduce costs.

Definition of surface roughness

Surface roughness is the micro geometric shape error of small peaks and valleys on the machined surface of a component (different from macro shape error and meso waviness), caused by machining factors such as tool cutting and material plastic deformation.

The core evaluation parameters include:

1. Ra(Arithmetic mean deviation of contour): a commonly used parameter, the arithmetic mean of the distance between contour points and the reference line within the sampling length, measured in micrometersm；

2. Rz(Height of contour z): The vertical distance between the peak and valley lines of the contour within the sampling length;

3. Rz（ISO）Commonly used in Europe,5The average value of the peak valley difference of z within a continuous sampling length;

4. Rq(Root Mean Square Deviation of Contour): The square root of the sum of squared distances between contour points and the reference line within the sampling length, which is sensitive to peak values.

The practical use of surface roughness

Surface roughness directly affects product performance, reliability, lifespan, and assembly accuracy, and is a key indicator for industrial quality control. Its core applications cover multiple industries

1. Mechanical manufacturing industry

Friction and Wear Control:

Excessive roughness: increased friction coefficient and accelerated wear on the mating surface (such as crankshaft journal)Ra 0.2-0.8MmEnsure lubrication and reduce wear);

Rough and small: lubricating grease is difficult to adhere and prone to "bite" (such as precision screw)Ra 0.1-0.4MmBalancing lubrication and precision.

Sealing performance: The static sealing surface needs toRa 1.6-6.3MmForming a "maze seal" to prevent leakage, excessive smoothness actually reduces sealing performance.

Assembly accuracy: The roughness in the interference fit improves the stability of the fit, and the clearance fit needs to match the tolerance (such as machine tool guide rails)Ra≤0.8Mm）.

2. car/Aerospace industry

Surface roughness detection of automobile engine cylinder block（Ra 0.2-0.5Mm）Oil storage reduces wear and improves fuel economy;

Aircraft engine bladesRa≤0.1MmReduce airflow resistance and minimize high-temperature fatigue damage.

Method for detecting surface roughness

The detection method needs to be selected based on the sample material, accuracy requirements, etc. The core can be divided into two categories: contact and non-contact,

1. Contact detection

profilometer

Principle: The diamond stylus slides along the surface, and the displacement is converted into electrical signal calculationRaTheRzWaiting for parameters;

Advantages: High precision（0.001Mm-20Mm）Easy to operate, cost-effective, and compliant with standards;

Applicable scenarios: Solid materials such as metal and plastic, suitable for batch quality inspection and laboratory calibration;

Attention: The contact pin is prone to wear, and the sample needs to be clean and free of oil stains.

Touchpin profilometer (high-precision type)

Principle: High precision sensor+Servo control, synchronous measurement of roughness, waviness, and contour;

Applicable scenarios: high-precision requirements for precision parts, wafers, etc. (accuracy up to)0.0001Mm）.

2. Non contact detection method

Optical interference

Principle: Light interference forms fringes, and the roughness is calculated by analyzing the fringes;

Advantages: No damage, fast speed (millisecond level), can obtain3DMorphology;

Applicable scenarios: precision electronics, coatings, soft materials, suitable for automated testing;

Attention: The sample should have a certain degree of reflectivity.

Precautions

Sample preparation: Clean the surface, fix it flat;

Parameter setting: Select sample length, evaluation length, and parameters according to standards;

Multi point measurement: same surface measurement3Take the average;