This article is about precision CNC machining shop, the classification of measuring instruments, measuring instruments, measuring instruments, technical performance indicators, the selection of three major parts of the measuring tool, after reading this, do you have anything else to add?
Classification of measuring instruments in the CNC machining shop
Measuring instrument is a fixed form, used to reproduce or provide one or more known quantitative value of the instrument. According to the different uses of the gauge can be divided into the following categories:
Single-value gage
Gauges that can only represent a single value. To calibrate and adjust other measuring instruments or as a standard amount of direct comparison with the measured, such as blocks, angle blocks.
Multi-value gage
Can reflect a group of similar values of the gage. The same can be calibrated and adjusted to other measuring instruments or as a standard amount of direct comparison with the measured, such as line ruler.
Specialized gage
Used to test a particular parameter of the gauge. Commonly used: test smooth cylindrical holes or shafts smooth limit gauge, to determine the qualification of internal or external threads thread gauge, to determine the qualification of complex shapes of the surface contour of the test template, with the simulation of the assembly through the test of the assembly accuracy of the function of the gauge and so on.
General Gauge
Vernier calipers, external micrometers, percentage tables, etc.
Technical performance indicators of measuring instruments
Nominal value of a gauge
Marked on the gauge to indicate its characteristics or guide its use of the value of the quantity. Such as marked on the size of the block, marked on the size of the scale, marked on the angle of the angle of the block.
Graduated value
Measuring instruments on the scale, two adjacent lines (the smallest unit of measurement) represented by the difference between the quantitative value. Outside the micrometer micrometer tube on the two adjacent lines represented by the difference between the quantitative value of 0.01mm, the measuring instrument of the index value of 0.01mm. index value is a measuring instrument, can be read directly out of the smallest unit of value, which reflects the accuracy of the readings of the high and low, but also explains the measurement of the measuring instrument of the measurement of high and low precision.
Measuring range
Measuring instruments can measure the measured value of the lower limit value to the upper limit value of the range. For example, the measuring range of the external micrometer 0 ~ 25mm, 25 ~ 50mm, etc., the mechanical comparator measuring range of 0 ~ 180mm.
Measuring force
In the process of contact measurement, the contact pressure between the measuring instrument probe and the measured surface. Measuring force too large will cause elastic deformation, measuring force too small will affect the stability of the contact.
Oscillometric Error
The difference between the indicated value of the measuring instrument and the true value of the measurement. Oscillometric error is a comprehensive reflection of the various errors of the measuring instrument itself. Therefore, different working points within the range of the instrument’s indication, the indication error is not the same. Generally available with the appropriate accuracy of the block or other measurement standards, to check the measuring instrument of the error of the display value.
Selection of measuring tools
According to the characteristics of the measured parts to choose the appropriate measuring tool, for example, length, width, height, outside diameter, inside diameter, such as calipers, height gauge, micrometers, depth gauge; shaft diameter can be used micrometers, calipers; holes, slots can be used to choose the plug gauge, block gauge, plug gauge; measurement of the parts of the right angle of the choice of the right-angled ruler; measurement of R-value of the choice of the R-rule; measurement of the coordination of the tolerance is small, the precision requirements of the high requirements or requirements of the calculation of the shape and location tolerance can be Choose three yuan, two yuan; measurement of steel hardness selection of hardness tester.
Caliper application
Calipers can measure the object’s inner diameter, outer diameter, length, width, thickness, section difference, height, depth; calipers are the most commonly used, the most convenient gauge, the highest frequency of use in the processing site gauge.
Digital calipers: resolution 0.01mm, used to match the small tolerance (high precision) size measurement.
Calipers with table: resolution of 0.02mm, for routine size measurement.
Vernier calipers: resolution 0.02mm, for roughing measurement.
Calipers should be used with clean white paper to remove dust and dirt before use; when measuring, the measuring surface of the caliper should be parallel or perpendicular to the measuring surface of the object to be measured.
When using depth measurement, when the object to be measured has an R angle, it is necessary to avoid the R angle but close to the R angle, the depth gauge and the measured height to maintain vertical
When calipers are used to measure cylinders, they need to be rotated and measured in sections to take the maximum value;
Because of the high frequency of use of calipers, maintenance work needs to do the best, every day after use need to be wiped clean and put into the box, before use need to use the measurement block to check the accuracy of the caliper.
Micrometer applications
Remove the dust and dirt before use, then twist the knob, measure the contact surface and screw surface fast contact, change to micro-adjustment, when the two surfaces are completely in contact with the zero, you can measure.
Micrometer measuring hardware, mobilize the knob, fast contact with the workpiece, switch to fine-tuning knob screwed in, when you hear the click, click, click three sound stop, read the data from the display or scale.
Measurement of plastic products, measuring the contact surface and screw gently touch the product can be.
Micrometer to measure the diameter of shafts, the need to measure more than two directions and segments to measure the maximum value of the micrometer in the measurement, the two contact surfaces should be kept clean at all times to reduce the measurement error.
Application of height gauge
Height ruler is mainly used to measure the height, depth, flatness, perpendicularity, concentricity, coaxiality, face vibration, tooth vibration, depth, height ruler measurements, the first thing to check the probe, the connecting parts of the loosening phenomenon.
Application of plug ruler
Suitable for flatness, curvature, straightness measurement
Flatness Measurement
Place the part on the platform and measure the gap between the part and the platform with a plug ruler (Note: Keep the plug ruler and the platform in a gap-free compressed state during the measurement).
Straightness Measurement
Place the part on the platform and rotate it for one week, and measure the clearance between the part and the platform with a plug rule.
Bend Measurement
Place the part on the platform and select the appropriate plug gauge to measure the clearance between the sides or center of the part and the platform.
Verticality Measurement
Place one side of the right angle of the zero to be measured on the platform, and on the other side, let the right-angle ruler lean against it, and measure the maximum clearance between the part and the right-angle ruler with a plug ruler.
2D CMM
The secondary element is a non-contact measuring instrument with high performance and high precision characteristics. The sensing element of the measuring instrument is not in direct contact with the surface of the measured part, and there is no mechanical action of the measuring force.
Secondary element through the projection of the way will be able to capture the image transmitted to the computer’s data acquisition card, imaging in the computer monitor; can be carried out on the part of a variety of geometric elements of measurement, but also for the shape of the outline 2D depiction with CAD output. Not only can the contour of the part be observed, but the surface shape of opaque parts can also be measured.
CMM
CMM is characterized by high accuracy (up to μm level); versatility (can replace a variety of length measuring instruments); can be used to measure geometric elements (in addition to measuring the elements that can be measured by the secondary element, but also can measure cylindrical, conical), form and positional tolerance (in addition to measuring the form and positional tolerance that can be measured by the secondary element, but also includes cylindricity, flatness, line contouring, surface contouring, coaxiality), and complex shaped surfaces.
As long as the CMM probe can reach the place, it can measure its geometric size and mutual position, surface profile; and with the help of the computer to complete the data processing; with its high precision and high flexibility as well as excellent digital capabilities, become an important means of modern mold processing and manufacturing and quality assurance, an effective tool.
The use of these gauges is critical to ensure machining accuracy and product quality in CNC machine shops. At the same time, the personnel who operate these gauges need to be professionally trained to ensure the accuracy and reliability of the measurements.
