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The measuring tools in the mechanical factory are all senior engineers!

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Time of issue:2020-02-13 10:09
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(Summary description)I.Classificationofmeasuringinstruments Ameasuringdeviceisadevicethathasafixedshapetoreproduceorprovideoneormoreknownquantities.Accordingtodifferentpurposes,themeasuringtoolscanbedividedintothefollowingcategories: 1.Singlevaluemeasuringtool Agagethatcanonlyreflectasinglevalue.Itcanbeusedtocalibrateandadjustothermeasuringinstrumentsordirectlycomparewiththemeasuredobjectasastandardquantity,suchasgaugeblocks,anglegaugeblocks,etc. 2.Multi-valuemeasuringtools Asetofmeasuringtoolsthatcanreflectasetofsimilarmeasurements.Itisalsopossibletocalibrateandadjustothermeasuringinstrumentsordirectlycomparewiththemeasuredasastandardquantity,suchaslineruler. 3.Specialmeasuringtools Agagedesignedtotestaspecificparameter.Thecommononesare:threadgaugesforcheckingthesmoothlimitofsmoothcylindricalholesorshafts,threadgaugesforjudgingthequalificationofinternalorexternalthreads,testtemplatesforjudgingtheconformityofsurfacecontourswithcomplexshapes,andthefunctionofverifyingassemblyaccuracybysimulatingassemblypassabilityGaugesandmore. 4,universalmeasuringtools Inourcountry,themeasuringinstrumentwithrelativelysimplestructureiscalledauniversalmeasuringtool.Suchasverniercalipers,outsidemicrometers,dialindicatorsandsoon. Second,thetechnicalperformanceindicatorsofmeasuringinstruments Nominalvalueofmeasuringtool Thevaluemarkedonthegagetoindicateitscharacteristicsorguideitsuse.Suchasthesizemarkedonthegaugeblock,thesizemarkedontheruler,theanglemarkedontheanglegaugeblock,andsoon. Divisionvalue Onthescaleofthemeasuringinstrument,thedifferencebetweenthemagnitudesrepresentedbytwoadjacentgraticules(thesmallestunitmagnitude).Ifthedifferencebetweenthetworepresentativelinesonamicrometertubewithanouterdiametermicrometeris0.01mm,thegraduationvalueofthemeasuringinstrumentis0.01mm.Thedivisionvalueisthesmallestunitquantitythatcanbereaddirectlybyameasuringinstrument.Itreflectstheaccuracyofthereading,andalsoexplainsthemeasuringaccuracyofthemeasuringinstrument. Measuringrange Withintheallowableuncertainty,therangefromthelowerlimitvaluetotheupperlimitvalueofthemeasuredvaluethatcanbemeasuredbythemeasuringinstrument.Forexample,themeasurementrangeoftheoutsidemicrometeris0-25mm,25-50mm,etc.,andthemeasurementrangeofthemechanicalcomparatoris0-180mm. Measuringforce Duringcontactmeasurement,thecontactpressurebetweenthemeasuringinstrument'sprobeandthesurfacetobemeasured.Toomuchmeasuringforcewillcauseelasticdeformation,andtoolittlemeasuringforcewillaffectcontactstability. 5.Indicationerror Thedifferencebetweentheindicationofthemeasuringinstrumentandthetruevaluebeingmeasured.Theindicationerrorisacomprehensivereflectionofvariouserrorsofthemeasuringinstrumentitself.Therefore,theerroroftheindicatedvalueisdifferentatdifferentoperatingpointswithintheindicatedrangeoftheinstrument.Generally,agaugeblockorothermeasuringstandardwithappropriateaccuracycanbeusedtoverifytheindicationerrorofthemeasuringinstrument. Selectionofmeasurementtools Beforeeachmeasurement,youneedtoselectameasurementtoolaccordingtothespecialcharacteristicsofthepartbeingmeasured.Forexample,calipers,heightgauges,micrometers,anddepthgaugescanbeselectedforlength,width,height,depth,outerdiameter,andstepdifference;micrometerscanbeusedforshaftdiameterCalipers;pluggauges,blockgauges,andfeelergaugescanbeusedforholesandgrooves;usesquaregaugesformeasuringtherightangleofparts;useRgaugesformeasuringRvalues;smallmeasurementtolerances,highaccuracyrequirements,orcalculationofformandpositiontolerancesareavailableThree-dimensionalandtwo-dimensionalelementsareused;ahardnesstesterisusedtomeasurethehardnessofsteel. Caliperapplication Caliperscanmeasuretheinnerdiameter,outerdiameter,length,width,thickness,step,height,anddepthofobjects;calipersarethemostcommonlyusedandmostconvenientmeasuringtools,andthemostfrequentlyusedmeasuringtoolsareusedattheprocessingsite. Digitalcaliper:0.01mmresolution,usedfordimensionalmeasurementwithsmalltolerances(highaccuracy). Tablecard:resolution0.02mm,forregularsizemeasurement. Verniercaliper:Resolution0.02mm,forroughingmeasurement. Beforeusingthecaliper,useacleanwhitepapertoremovethedustanddirt(thewhitepaperisstuckwiththemeasuringsurfaceoutsidethecaliperandthenpulledoutnaturally,repeat2-3times) Whenusingacaliperformeasurement,themeasurementsurfaceofthecalipershouldbeasparallelorperpendiculartothemeasurementsurfaceofthemeasuredobjectaspossible; Whenusingdepthmeasurement,ifthemeasuredobjecthasanRangle,avoidtheRanglebutbeclosetotheRangle,andkeepthedepthruleandthemeasuredheightasverticalaspossible; Whenthecalipermeasuresacylinder,itneedstoberotatedandthemaximumvalueismeasuredinsections; Duetothehighfrequencyofcalipers,maintenanceneedstobedonebest.Afterdailyuse,wipethemcleanandputtheminthebox.Beforeusing,youneedtouseablocktochecktheaccuracyofthecalipers. 2.Applicationofmicrometer Beforeusingthemicrometer,useacleanwhitepapertoremovethedustanddirt.(Usethemicrometertomeasurethecontactsurfaceandthescrewsurfacetojamthewhitepaperandpullitoutnaturally.Repeatfor2-3times.)Thenturntheknobtomeasurethecontact.Whenthesur

The measuring tools in the mechanical factory are all senior engineers!

2016年中国机床行业将向高端化方向发展

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The measuring tools in the mechanical factory are all senior engineers!

Categories:Industry news
Author:
Origin:
Time of issue:2020-02-13 10:09
Views:

Information

I. Classification of measuring instruments

A measuring device is a device that has a fixed shape to reproduce or provide one or more known quantities. According to different purposes, the measuring tools can be divided into the following categories:

1.Single value measuring tool

A gage that can only reflect a single value. It can be used to calibrate and adjust other measuring instruments or directly compare with the measured object as a standard quantity, such as gauge blocks, angle gauge blocks, etc.

2.Multi-value measuring tools

A set of measuring tools that can reflect a set of similar measurements. It is also possible to calibrate and adjust other measuring instruments or directly compare with the measured as a standard quantity, such as line ruler.

3. Special measuring tools

A gage designed to test a specific parameter. The common ones are: thread gauges for checking the smooth limit of smooth cylindrical holes or shafts, thread gauges for judging the qualification of internal or external threads, test templates for judging the conformity of surface contours with complex shapes, and the function of verifying assembly accuracy by simulating assembly passability Gauges and more.

4, universal measuring tools

In our country, the measuring instrument with relatively simple structure is called a universal measuring tool. Such as vernier calipers, outside micrometers, dial indicators and so on.

Second, the technical performance indicators of measuring instruments

Nominal value of measuring tool

The value marked on the gage to indicate its characteristics or guide its use. Such as the size marked on the gauge block, the size marked on the ruler, the angle marked on the angle gauge block, and so on.

Division value

On the scale of the measuring instrument, the difference between the magnitudes represented by two adjacent graticules (the smallest unit magnitude). If the difference between the two representative lines on a micrometer tube with an outer diameter micrometer is 0.01 mm, the graduation value of the measuring instrument is 0.01 mm. The division value is the smallest unit quantity that can be read directly by a measuring instrument. It reflects the accuracy of the reading, and also explains the measuring accuracy of the measuring instrument.

Measuring range

Within the allowable uncertainty, the range from the lower limit value to the upper limit value of the measured value that can be measured by the measuring instrument. For example, the measurement range of the outside micrometer is 0-25mm, 25-50mm, etc., and the measurement range of the mechanical comparator is 0-180mm.

Measuring force

During contact measurement, the contact pressure between the measuring instrument's probe and the surface to be measured. Too much measuring force will cause elastic deformation, and too little measuring force will affect contact stability.

5. Indication error

The difference between the indication of the measuring instrument and the true value being measured. The indication error is a comprehensive reflection of various errors of the measuring instrument itself. Therefore, the error of the indicated value is different at different operating points within the indicated range of the instrument. Generally, a gauge block or other measuring standard with appropriate accuracy can be used to verify the indication error of the measuring instrument.

Selection of measurement tools

Before each measurement, you need to select a measurement tool according to the special characteristics of the part being measured. For example, calipers, height gauges, micrometers, and depth gauges can be selected for length, width, height, depth, outer diameter, and step difference; micrometers can be used for shaft diameter Calipers; plug gauges, block gauges, and feeler gauges can be used for holes and grooves; use square gauges for measuring the right angle of parts; use R gauges for measuring R values; small measurement tolerances, high accuracy requirements, or calculation of form and position tolerances are available Three-dimensional and two-dimensional elements are used; a hardness tester is used to measure the hardness of steel.

Caliper application

Calipers can measure the inner diameter, outer diameter, length, width, thickness, step, height, and depth of objects; calipers are the most commonly used and most convenient measuring tools, and the most frequently used measuring tools are used at the processing site.

Digital caliper: 0.01mm resolution, used for dimensional measurement with small tolerances (high accuracy).

Table card: resolution 0.02mm, for regular size measurement.

Vernier caliper: Resolution 0.02mm, for roughing measurement.

Before using the caliper, use a clean white paper to remove the dust and dirt (the white paper is stuck with the measuring surface outside the caliper and then pulled out naturally, repeat 2-3 times)

When using a caliper for measurement, the measurement surface of the caliper should be as parallel or perpendicular to the measurement surface of the measured object as possible;

When using depth measurement, if the measured object has an R angle, avoid the R angle but be close to the R angle, and keep the depth rule and the measured height as vertical as possible;

When the caliper measures a cylinder, it needs to be rotated and the maximum value is measured in sections;

Due to the high frequency of calipers, maintenance needs to be done best. After daily use, wipe them clean and put them in the box. Before using, you need to use a block to check the accuracy of the calipers.

2. Application of micrometer

Before using the micrometer, use a clean white paper to remove the dust and dirt. (Use the micrometer to measure the contact surface and the screw surface to jam the white paper and pull it out naturally. Repeat for 2-3 times.) Then turn the knob to measure the contact. When the surface is in quick contact with the screw surface, use fine adjustment instead. When the two surfaces are completely in contact with each other, adjust to zero to measure.

When measuring the hardware with a micrometer, turn the knob. When it comes into contact with the workpiece, use the fine adjustment knob to turn it in. When you hear three clicks, stop, read the data from the display or scale.

When measuring plastic products, the measuring contact surface and the screw lightly touch the product.

When the micrometer measures the diameter of the shaft, at least two directions are measured and the micrometer in the maximum measurement is measured in sections. The two contact surfaces should be kept clean at all times to reduce measurement errors.

3. Application of height ruler

The altimeter is mainly used to measure the height, depth, flatness, perpendicularity, concentricity, coaxiality, surface vibration, tooth vibration, depth, and altimeter measurement. First, check the probe and the connection parts for looseness.

4. Application of feeler

The feeler gauge is suitable for the measurement of flatness, curvature and straightness

Flatness measurement:

Place the part on the platform and use a feeler gauge to measure the gap between the part and the platform (note: the feeler and the platform should be kept in a tight state without gap during measurement)

Straightness measurement:

Place the part on the platform for one revolution, and use a feeler gauge to measure the gap between the part and the platform.

Bend measurement:

Place the part on the platform and select the corresponding feeler gauge to measure the gap between the sides or middle of the part and the platform.

Verticality measurement:

Place one side of the zero angle of the measured zero on the platform, and make the square ruler close to it, and use a feeler gauge to measure the maximum gap between the part and the square ruler.

5. Application of plug gauge (rod):

It is suitable for measuring the inner diameter, slot width and gap of a hole.

The diameter of the part is large. When there is no suitable needle gauge, the two plug gauges can be overlapped, and the plug gauge is fixed on the magnetic V-shaped block according to the 360-degree measurement to prevent loosening and easy measurement.

Aperture measurement

Inner hole measurement: When the hole diameter is measured, the penetration is qualified, as shown in the figure below.

Note: When measuring the plug gauge, insert it vertically, not obliquely.

6. Precision measuring instrument: two-dimensional

The second element is a non-contact measuring instrument with high performance and high precision. The sensing element of the measuring instrument is not in direct contact with the surface of the measured part, so there is no measuring force of mechanical action; the image captured by the two-dimensional element is transmitted to the data acquisition card of the computer through the data line, and then Software imaging on a computer monitor; various geometric elements (points, lines, circles, arcs, ellipses, rectangles), distances, angles, intersections, shape and position tolerances (roundness, straightness, parallelism, verticality) (Degrees, inclination, position, concentricity, symmetry), and CAD output for 2D drawing of outlines. Not only the contour of the workpiece can be observed, but also the surface shape of the opaque workpiece can be measured.

Conventional geometric element measurement: The inner circle in the part below is a sharp angle, which can only be measured by projection.

Observation of electrode processing surface: The two-dimensional lens has a magnification function to check the roughness of the electrode after processing (magnified 100 times image).

Small size deep groove measurement

Gate detection: During mold processing, there are often some gates hidden in the groove, and various detection instruments cannot measure. At this time, you can use rubber paste on the glue gate, and the shape of the glue gate will be printed on the glue. On the other hand, the size of the glue print is measured by the second element to obtain the gate size.

Note: Because there is no mechanical force during the two-dimensional measurement, it is best to use the two-dimensional measurement for thinner and softer products.

7. Precision measuring instrument: three-dimensional

The characteristics of the three-dimensional element are high accuracy (up to μm level); universality (can replace a variety of length measuring instruments); can be used to measure geometric elements (in addition to the elements that can be measured by the two-dimensional element, can also measure cylinders, cones) , Shape and position tolerance (in addition to the shape and position tolerance that can be measured by the second element, it also includes cylindricality, flatness, line profile, surface profile, coaxiality), complex surfaces, as long as the three-dimensional probe Where it can be touched, its geometric size, mutual position, and surface profile can be measured; and data processing is completed by means of a computer; with its high precision and flexibility and excellent digital capabilities, it has become important for modern mold processing and manufacturing and quality assurance Means, effective tools.

In the modification of some molds, there is no 3D drawing file, which can measure the coordinate values of various elements and the contours of irregular surfaces, and then use drawing software to export and make 3D graphics based on the measured elements, which can be processed and modified quickly and without errors. (After the coordinates are set, the coordinates can be measured at any point).

3D digital model comparison measurement: In order to confirm the consistency with the design or find an abnormal fit during the assembly of the fit mold, when some surface contours are neither circular arcs nor parabolic, but some irregular surfaces When geometric element measurement cannot be performed, a 3D model and part comparison measurement can be imported to understand the processing error; because the measurement value is a point-to-point deviation value, it can be easily and quickly corrected and improved (the data shown in the figure below is the measured value) Deviation from the theoretical value).

8. Application of Hardness Tester

The commonly used hardness testers are Rockwell hardness tester (desktop) and Leeb hardness tester (portable). The commonly used hardness units are Rockwell HRC, Brinell HB, and Vickers HV.

Rockwell Hardness Tester HR (Desktop Hardness Tester)

The Rockwell hardness test method is to use a diamond cone with a vertex angle of 120 degrees or a steel ball with a diameter of 1.59 / 3.18mm to press the surface of the material under a certain load, and determine the material hardness from the depth of the indentation. According to the hardness of the material, it can be divided into three different scales to represent HRA, HRB, HRC.

HRA is a kind of hardness obtained with 60Kg load and diamond cone indenter, which is used for extremely hard materials. For example: cemented carbide.

HRB is a hardness obtained with a 100Kg load and a hardened steel ball with a diameter of 1.58mm. It is used for materials with lower hardness. For example: annealed steel, cast iron, etc., alloy copper.

HRC is a hardness obtained with a 150Kg load and a diamond cone indenter, and is used for very hard materials. For example: hardened steel, tempered steel, quenched and tempered steel and some stainless steel.

Vickers hardness HV (mainly for surface hardness measurement)

Suitable for microscope analysis. With a load of less than 120kg and a diamond square cone indenter with an apex angle of 136 °, the material is pressed into the surface, and the diagonal length of the indentation is measured. It is suitable for the hardness measurement of larger workpieces and deeper surface layers.

Leeb hardness HL (portable hardness tester)

Leeb hardness is a dynamic hardness test method. During the impact process of the impact body of the hardness sensor with the measured workpiece, the ratio of the rebound speed to the impact speed at a distance of 1 mm from the workpiece surface is multiplied by 1000, which is defined as the Leeb hardness value.

Advantages: The Leeb hardness tester manufactured by Leeb hardness theory changes the traditional hardness test method. Because the hardness sensor is as small as a pen, it can be used to directly carry out hardness testing in various directions on the workpiece at the production site, which is difficult for other bench hardness testers.

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