Before the CNC machined parts are delivered to the customer, the inspection of the parts is an indispensable link in the CNC machining, and it is also an important link to ensure product quality.
What is CNC Part Inspection?
Through the professional CNC inspection equipment to test the tolerance range, surface finish, performance and other links of the parts is the CNC parts inspection.
Our CNC part inspection services include:
- Detect the shaft diameter of the part. In single-piece and small-batch production, the actual size of medium and low-precision shaft diameters is usually tested with ordinary measuring instruments such as calipers, micrometers, and special gauges; in mass production, smooth limit gauges are often used to judge the actual size and shape error of the shaft Whether it is qualified or not; high-precision shaft diameters are often compared and measured with mechanical micrometers, electric micrometers or optical instruments. Measuring shaft diameters with a vertical optical meter is the most commonly used measurement method.
- Test the aperture of the parts. Common measuring tools and general measuring instruments such as calipers, inner diameter micrometers, inner diameter gauges, inner diameter shakers, and internal measuring calipers are usually used for single-piece and small-batch production; smooth limit gauges are often used for mass production; high-precision deep holes and precision holes are commonly used for measurement 3 Micron-level testing equipment such as coordinate measuring machines.
- Detect the length and thickness of parts. Calipers, micrometers, special gauges, length measuring instruments, comparators, altimeters, pneumatic measuring instruments, etc. are generally used for length dimensions; feeler gauges, gap plates combined with calipers, micrometers, height gauges, and gauges are generally used for thickness dimensions; wall thickness dimensions Ultrasonic thickness gauges or wall thickness micrometers can be used to detect the thickness of pipes and thin-walled parts, and film thickness gauges and coating thickness gauges can be used to detect the thickness of coatings on blades or other parts; eccentricity values can be detected with eccentricity checkers , Use a radius gauge to detect the radius value of the arc corner, use a pitch gauge to detect the pitch size value, and use a hole distance caliper to measure the hole distance size.
- Inspect the surface roughness of parts. Use a magnifying glass, a comparison microscope, etc. to compare directly with surface roughness comparison samples; use a light section microscope (also known as a double-tube microscope) to measure the metal plane or outer circular surface completed by processing methods such as turning, milling, and planing; use an interference microscope (such as double-beam interference microscope, multi-beam interference microscope) to measure the surface with high surface roughness requirements; the electric profiler can directly display the value of Ra0.025～6.3μm; On the surface of large and bulky parts and surfaces that are difficult to measure directly with instruments or to compare samples (such as deep holes, blind holes, grooves, internal threads, etc.), print the surface contour of the part on the impression, and then measure the impression, Obtain the roughness parameter value (the measured surface roughness parameter value of the die is smaller than the actual parameter value of the part, so the roughness measurement result needs to be corrected empirically); use the laser micrometer laser to combine the atlas method and laser light energy Measure the surface roughness of Ra0.01～0.32μm by method.
- Check the angle. Relative measurement: use angle gauge blocks to directly detect high-precision workpieces; use squares to check right angles; use polyhedral prisms to measure indexing errors of precision gears and turbines on indexing plates. Direct measurement: use goniometers, electronic angle gauges to measure the working angles of angle blocks, polyhedral prisms, prisms, etc. with reflective surfaces; use optical dividing heads to measure the circumference of workpieces; Angle parts that do not require high measurement accuracy. Indirect measurement: Commonly used measuring devices include sine gauges, rollers and steel balls, etc., and three-coordinate measuring machines are also used. Small angle measurement: The measuring device has a level, an autocollimator, a laser small angle measuring instrument, etc.
- Check the straightness of parts. Use a ruler (or knife-edge ruler) to measure the straightness with a gap of 0.5 μm (0.5-3 μm is colored light, and 3 μm or more is white light). If the gap is too large, you can use a feeler gauge to measure it; Measure the straightness error with a dial indicator or a dial indicator; tighten with a steel wire with a diameter of 0.1-0.2mm, and check the straightness with a reading microscope installed vertically on a V-shaped iron; use optical instruments such as a level, autocollimator, and collimating telescope Measure the straightness error; measure the straightness with a square level and bridge plate; use the optical flat crystal segment indicator to detect the straightness error with high precision.
- Inspect parts for flatness. Use an indicator (such as a dial indicator); use a flat ruler to combine the indicator; use a plane scanner, level, autocollimator, collimating telescope, flat crystal and other optical instruments to measure the plane error of the workpiece; use a standard flat or flat The ruler is painted with paint and rubbed against the measured plane ruler, and the flatness error is represented by the number of bright spots per 25.4×25.4mm area.
- Check the roundness of the part. Use a roundness meter to measure. During the measurement, the instrument can record the outline on paper, and use the concentric circle template or compare the ideal circle given by the instrument to find the roundness error. The roundness meter has two measuring methods: rotary shaft type and rotary table type; Use calipers, micrometers, etc. to measure the cross-sectional diameter of several workpieces, and take 1/2 of the maximum value minus the minimum value of the same cross-section as the roundness error of the workpiece; place the workpiece on the V-shaped iron and use the indicator to measure several cross-sections , take 1/2 of the maximum difference as the roundness error value, take the maximum error value as the roundness error of the workpiece; use the optical dividing head and the indexing table of the universal tool microscope as the rotary indexing mechanism for measuring the roundness error, Use the indicating mechanism of the electric micrometer and the torsion spring comparator to measure the roundness and cylindricity error; Read a value, and then draw the error curve on the polar coordinate chart to obtain the roundness or cylindricity error; place the measured workpiece on an instrument with a coordinate device (three-coordinate measuring machine or a universal tool microscope with two coordinates, etc.) On the workbench, adjust the axis of the measured piece to be perpendicular to the working surface of the instrument and basically coaxial, measure the coordinate values of each point in equal parts on the measured circle of the selected section, and take the largest error value as the roundness error for evaluation .
- Check the cylindricity of the part. Measure the roundness of several cross-sections with the roundness meter method, and give the cylindricity error according to the minimum condition. You can also use the transparent concentric circle template to calculate the cylindricity error by recording the roundness error graph of each section, and you can also take several sections. The maximum value of the roundness error is the cylindricity error; put the workpiece on the flat plate and close to the square box, measure the maximum and minimum readings of several sections with a dial gauge, and take half of the difference between the maximum and minimum readings among all readings as the The cylindricity error of the workpiece; place the workpiece in the V-shaped block (the length of the V-shaped block should be greater than the length of the measured workpiece), and use a dial gauge to measure the maximum and minimum readings of several sections when the workpiece rotates, and take all the readings of each section Half of the maximum and minimum readings is the cylindricity error of the workpiece; adjust the axis of the workpiece to be parallel to the axis of the three-coordinate measuring device, measure the coordinate values of each point on the outer circle of the workpiece, and calculate the cylindricity error according to the minimum condition by the computer; use the indicator Position the part on the two top axes of the instrument, measure several cross-sectional profiles on the entire length of the measured cylindrical surface, select several equal points on each profile, and obtain the radius difference of each point on the entire cylindrical surface value.
- Check the line profile of the part. Using the profiling (profiling) machine tool to detect the line profile error requires that the shape of the profiling probe should be the same as that of the dial gauge probe; use an accurate inspection template to detect the workpiece, and measure the gap between the template and the workpiece to determine the workpiece line profile Degree error; use a universal tool microscope, use a turntable with an indexing device or a precision boring machine to measure the coordinate value of the workpiece contour, and find the line contour error; put the workpiece on the projector and enlarge the workpiece according to the multiple of the magnified image Compared with the theoretical contour of the contour projection, check whether the workpiece contour exceeds the limit contour, this method is suitable for smaller thin workpieces.
- Check the parallelism of parts. Put the reference surface of the workpiece on the flat plate, measure the surface to be tested with a dial gauge, and read the difference between the maximum and minimum values as the parallelism error. The measured data should be converted to the actual length of the workpiece; put the workpiece on the flat plate , to level the datum plane, use the spirit level to measure the straightness of the datum plane and the measured plane respectively to obtain the parallelism error.
- Verify the perpendicularity of the part. Use a square or a standard cylinder on a flat plate (or directly on the reference surface of the workpiece), check the gap between the other side of the square and the measured surface of the workpiece, check the size of the gap with a feeler gauge, and convert the measured data to the workpiece In terms of actual length; fix the workpiece reference plane on a right-angle seat or a square box, and measure the verticality error by measuring the parallelism on the flat plate; for the verticality measurement of some large workpieces, an autocollimator or collimating telescope can be used Check the verticality error with the right-angled edge, or use a square level to check the verticality error of a large workpiece. When using this method to measure the verticality error, the datum plane should be leveled first, and the shape of the workpiece datum plane should be excluded when processing the measurement result data. Error: Install the measured mandrel and the reference mandrel on the workpiece, rotate the reference mandrel, measure the readings at two positions with 2 dial gauges fixed on the reference mandrel, and calculate the line-to-line perpendicularity.
- Check the slope of the part. Generally, the elements to be measured are converted into a state parallel to the measurement datum through standard angle blocks, sine rulers, and tilting tables, and then the inclination error is measured by measuring the parallelism. The tilt error measurement method is similar to the small angle measurement method.
- Check the concentricity of the parts. Align the workpiece on the roundness meter according to the reference elements, measure the roundness of several sections of the element to be measured and draw a record graph, and calculate the coaxiality error according to the definition according to the graph. This method is more suitable for measuring small parts at the same time Axis error; align the workpiece on the measuring table, measure the coordinates of several cross-sectional contour points on the surface of the measured cylinder (the instrument used has the same contour degree), and find the position of the actual axis of the measured cylinder, and the maximum distance between the actual axis and the reference axis Twice of the thickness difference is the coaxiality error; the amount used (see the thickness of the instrument used) can directly measure the uniformity of the wall thickness, and take 1/2 of the maximum thickness difference as the coaxiality error. This method is suitable for plate-shaped and cylindrical workpieces Measuring the coaxiality of the inner and outer circles; use the self-collimating telescope, place the target in the center of the hole (the bull’s eye) with the bracket, and after aligning the reference hole with an optical instrument, measure the offset of the bull’s eye relative to the optical axis to evaluate the measured The coaxiality error of the axis, this method is suitable for the measurement of the coaxiality of the hole system of workpieces such as large boxes; put the workpiece reference cylinder on the equal-height cutting-edge V-shaped frame, rotate the workpiece, and read the value indicated by the pointer of the dial gauge. 1/2 of the difference between the maximum and minimum readings is the coaxiality error. If the reference is designated as the center hole, the center hole should be measured on the steady rest during measurement. This method is suitable for measuring workpieces with small roundness errors;
There are many kinds of detection methods and equipment for CNC parts. But the ultimate goal is to ensure that the quality of the parts is qualified. As a professional CNC machining parts manufacturer, we will ensure that each delivered part is a qualified and high-quality product. Want to get a quote for CNC machining parts inspection services? Contact us now.