1、STD-AGMA 77FTML-ENGL 1777 m b87575 0005L9b 723 W 97FTM1 Calibration of Gear Measuring instruments and Their Application to the Inspection of Product Gears by: B.L. Cox, Lockheed Martin Energy Systems, Inc., and R.E. Smith, R.E. Smith yaw and pitch variations are rotations about two mutually perpendi
2、cular transverse axes (e.g. on a horizontal slide, yaw is a rotation about the vertical axis). Slide straightness variations: Slide straightness variations are undesirable lateral motions of a point on a linear slide carriage as. it moves over a defined length. Straightness variation is defined as t
3、he largest deviation from the least squares fit mean line of the slide. Squareness variations: Squareness variabons are angular variations defined by the least squares fit mean line of two nominally mutually perpendicular axes. Squareness variations are commonly defined in pmlm. Systematic variation
4、: Systematic variation is the component of the measuring variation which does not vary in the course of a large number of repeated measurements of the same quantity X under nominally identical measuring conditions. Tooth Alignment Artifact An artifact having a certified helix form. True position pit
5、ch: The true position pitch is the circumference of the datum circle divided by the number of teeth. This can be determined by the average of all pitch measurements of the entire gear taken on successive pairs of teeth, or between corresponding points of adjacent teeth generated by an angular positi
6、oning device. True value: The actual value of the quantity X which is to be measured. (This can never be precisely determined in practice.) Verified measuring volume: The verified measuring volume-is defined by: (a) Maximum / minimum diameter: The maximum and minimum diameter is 1.25 times the large
7、st diameter of a gear artifact used for the tests to 0.5 times the smallest artifact diameter used for the tests. COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services- STD-AGMA 97FTML-ENGL 1997 D Ob87575 0005204 b2T m (b) Maximum facewidth: The maximum fac
8、ewidth is equal to the length of the calibrated parallel mandrel, which is used for alignment and straightness measurements on the vertical axis. (c) Maximum helix angle: The maximum helix angle is the largest helix angle tested on the gear artifacts. (d) Maximum module: The maximum module is the la
9、rgest module tested on the gear artifacts. (e) Maximum weight The maximum weight is 1.5 times the heaviest gear artifact used for the verification tests. 8 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesSvmbol Measurement diameter Facew i dth Helix an
10、gle Length between datum surfaces Pitch variation, allowable Pitch, cumulative Radial runout tolerance Tooth alignment tolerance True position pitch Profile tolerance Tenns 4 Instrument condition The calibration engineer and the client should agree on the accuracy requirements, verified measuring vo
11、lume size, and parameters that are to be tested before starting the verification work. Much of the general information in this information sheet comes from the British Gear Association codes of practice DUCOP.03, “Involute Gear Measurement? DUCOP.04, “Checking the Reproducibiltty of Gear Measuring M
12、achines“2, DUCOP.0511, Verifying the Accuracy of Gear Measuring Machines: Part l“3, and DUCOP.0512, “Verifying the Accuracy of Gear Measuring Machines: Part 2“*. 4.1 Instrument checking procedure (a) Carry out a brief, preliminary visual inspection of the instrument, venfying that the centers, drive
13、rs, and stylus are in good condition. Check that the environmental conditions meet the requirements in section 6.2. (b) Mount each traceably calibrated tooth alignment, profile, and pitch artifact between centers and measure and record the runout of the reference bands and of the instrument centers.
14、 Verify that these runout values are within the limits specified in Table 5. (c) For instruments checking ANSllAGMA-2000-A88 accuracy grade Q13 and higher only: Measure and record the alignment variation on the top center relative to the bottom spindle axis. This should be checked as shown in Figure
15、s 1-3. Measure the alignment variation by probing the master or the spindle with the indicator and rotating the whole assembly. Record the total runout (TIR) over one revolution. Verify that the resuits are within the limits specified in Table 2, column 3. (d) Instruments with tooth alignment master
16、s, which are less than 1 O0 mm facewidth, should be checked for alignment with a parallel mandrel. Permissible variations are specified in Table 5. 9 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services - STD-AGMA 77FTML-ENGL L977 E Ob87575 000520b 4T2 D A
17、ccuracy Runout of Spindle Gradeto be Top Center Tested i% Base Disc AN SIIAGMA (Y Q15 1.5 2000-A88 J Measure each gear artifact for a sufficient time period (4 weeks) to verify that the measured variation is within statistical control (see Appendix A). The results must satisfy the requirements in Ta
18、ble 4. If they do not, further testing is pointless. Investigate the cause of any variabons, which are outside these limits before the instrument is used for measuring gears. Z-axis Alignment and Alignment of Straightness with a over 200 mm A B Top Center with the Parallel Mandrel Spindle Axis (TIR)
19、 2.0 2.5 2 pmll50 mm Determine the measurement uncertainty of each gear artifact as specified in section 6. If the measurement uncertainty of the instrument exceeds the values in Table 4, conduct further checks outlined in this section. Once the measurement uncertainty of the instrument is determine
20、d, periodic tests of the gear artifacts should be conducted to verify that the instrument uncertainty has not changed. The variation values in Table 2 can be adjusted by a factor of 42 for each successive change in accuracy grade. 10 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by
21、 Information Handling ServicesBETWEEN CENTERS AXIS 4: 1- SPINDLE AXIS I A I I V rl I II I I I I i Figure 2 Measurement method 11 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesTAILSTOCK m- R ECHA NI CAL INDICATOR RESOLUTION DRIVER PIN (CLEARANCE IN HO
22、LE) L WORK SPINDLE Figure 3 Tailstock center alignment fixture for horizontal or vertical work spindles 4.2 Probe system Check the condition of the stylus that is to be used to measure the artifacts and record its size and geometry. Verify the position of the probe on the instrument by re-datuming (
23、re-qualifying) or use the manufacturers setting fixture. For each probe axis that is used to measure gear variations, use a traceably calibrated probe tester to carry out the following tests: (a) Check the magnification of the probe system over a I50 pm range and verify that it satisfies the require
24、ments specified in Table 3. (b) Check the resolution and lost motion of the probe system at 3 positions in the probe range and verify that it satisfies the requirements in Table 3. Note: Most probe systems are bi-directional (SO that they can measure left and right flanks of teeth). it is important
25、that the probe is tested in both directions. Aso note that the dynamic characteristics are not verified with this test procedure. 12 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesAccuracy Grade Probe Magnification to be Tested Deviation ANSIIAGMA (Em
26、) 2000-A881 (% of Measured Variation) I Q15 I 32% I 0.2 I 0.3 I Resolution Lost Motion VI WI The variation values in Table 3 can be adjusted by a factor of 42 for each successive change in accuracy grade. To enable the static tests of the probe to be carried out, a traceably calibrated probe test sy
27、stem with the following characteristics is required: Range +50 pm Resolution O. 1 pm over +i O pm Resolution 0.3 pm over k50 pm Measurement uncertainty (U,) range 1t10 Fm U, = k0.3 pm range 150 pm USS = k0.8 pm The test system must be capable of being mounted on the instrument and aligned parallel t
28、o the probe axis being tested. 4.2.1 Readout condition This section provides an explanation and general guidelines for determining critical probe measurement errors, including the calibratton of the readout electronics. 4.2.1.1 Gain Evaluation of a gaging system gain involves comparing the actual pr
29、obe deflection to the amount of deflection indicated by the final output device (see Figure 4). Gain accuracy is dependent upon the performance of the Linear Variable Differential Transformer (LVDT) measuring probe, and the supporting electronics which convert an analog signal representing probe def
30、lection into a numerical value or travel of the strip chart pen. Gain can be tested either by using gage blocks or a pin master. A pin master is preferred since it produces two reversals when checked as an involute profile. 13 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Inform
31、ation Handling ServicesProbe Amplifier I 0 +/- 10 volts 8 4. -i analog signal - I . I ,I *- Analog to Digit: Converter Final Readout Device DIGITAL Final Readout Device STRIP CHART Figure 4 Gaging system gain 4.2.1.2 Linearity Gaging system linearity can be evaluated observing the pattern of a chang
32、e in the error in magnification as the actual deflection of the probe vanes along its measurement range. A typical LVDT accuracy characteristic shown in Figure 5 demonstrates the increase in measurement error as the probe deflection increases significantly plus or minus from electrical zero. This ca
33、n easily be evaluated by caiibrating the magnification at varying probe deflections. It is recommended to evaluate probe linearity within the range of deviations that exists in the production gears being measured on the instrument Some modern CNC measuring instruments may provide software correction
34、s for LVDT non-linearity . 14 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services STD-ALMA 97FTML-ENGL L997 Ob87575 0005211 BbT -.l O0 O +.loo PROBE DEFLECTION (MM) Figure 5 Gaging system linearity 4.2.1.3 Lost motion Lost motion is the amount of differen
35、ce the readout displays after the probe has been deflected in one direction and then is reversed to return to the previous position (see Figure 6). Lost motion can be checked by tracing along a calibrated drop in an involute profile or a lead surface, by measuring a flank master, or by measuring a p
36、in master. 15 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services STD-AGMA 77FTML-ENGL 1977 D Ob87575 0005212 7Tb 4.2.2 Filtering There are two types of filtering related to the probing system, mechanical and electronic. Mechanical filtering occurs by nat
37、ure of the probe tip diameter used in the gear measuring instrument. Spherical probe tips also have an averaging effect by not allowing the probe tip to fall into the small valleys on the surface. Since the lower frequency surface irregularities, i. e. waviness and form error, may be of greater impo
38、rtance to the part function than the higher frequency irregularities, an electrical signal filter is commonly used for the suppression of the representation of high frequency deviations. This tends to smooth the data and eliminate the surface texture effects. It is important to know the type of filt
39、ering used and if possible to be able to view the data with different filters or no filter applied. 4.3 Mechanical elements Tooth surface with depression Lost motion Readout displayed deviation Figure 6 Gaging system lost motion Ail equipment used for gear measuring instrument uncertainty tests shou
40、ld be traceably calibrated to national standards. The function of all equipment should be verified before use on site. Laser interferometer equipment used for straightness variation, angular variation, and length measurement should be re-calibrated within every 18 months period. 16 COPYRIGHT America
41、n Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesPrecision levels should be re-calibrated within every 12 month period. The accuracy requirements for straig htness measurement are as follows: US = a.6 pm on slides up to 300mm over 21 O pm range US = M.8 pm on slides ove
42、r 300mm over trl O pm range The accuracy requirement for angular measurement is as follows: uS = +1 .O pm/m for all slides over i20 pmlm range The accuracy requirement for length measurement is as follows: Us = +1 .O pmm over any specified slide length 4.3.1 Spindle runout Check that the center is f
43、ree from damage and corrosion. Measure runout over several revolutions on the center and verify that it meets the requirements in Table 2. Mechanical or electronic indicators are used to measure runout and alignment during tests. They require the following characteristics: Measurement uncertainty (U
44、S) Resolution 0.5 um i25 pm range U% = +1 .O pm k5 pm range US = rto.5 pm The function of the indicator should be tested before use and the indicator should be traceably calibrated. 4.3.2 Centers Check that the center is free from damage and corrosion. If the instrument has a live center, measure ru
45、nout over several revolutions of the center while the center is supporting a mandrel and verify that it meets the requirements in Table 2. Check the alignment of the axis between centers with the spindle axis by measuring runout of the tailstock center relave to the spindle axis (see Figure 2) with
46、a mandrel between centers. Venfy it meets the requirements specified in Table 2 at 3 different heights over 80% of the tailstock range. Check the alignment of the axis between centers with the main vertical (Z) axis and venfy that the mean alignment and straightness variations of the vertical axis m
47、eet the requirements specified in Table 2. 17 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesA parallel mandrel which will normally be mounted between centers should be calibrated for straightness using the reversal method. The calibrated length of th
48、e mandrel should be over 250 mm long. The mandrel should be straight within 1 .O pmll OOmm length with a calibrated uncertainty of kl .O pm. 4.3.3 Ways, slides, columns Some CMMs and gear measuring instruments use variation correction software which should compensate for systematic variations in sli
49、des of the instrument This may mean that variations measured when testing the individual slides may be correctly compensated by the instrument sohare. In these cases the tests on the individual slide variations should be camed out but the test results should not be treated as variations if: (a) the variation correction method and data are disclosed by the instrument manufacturer, and is considered to be valid by the calibrabon engineer or (b) the accuracy of the variation compensation method can be verified by independent measurement tests which are agreed between the client
