中英文翻译-机床床主轴轴承的监控-英文版

Int J Adv Manuf Technol 2006 28 993 1005 DOI 10 1007 s00170 004 2449 0 S Saravanan 9 G S Yadava 9 P V Rao Condition monitoring studies on spindle bearing of a lathe Received 10 June 2004 Accepted 18 October 2004 Published online 16 November 2005 9 Springer Verlag London Limited 2005 Abstract In modern industry machinery must become increas ingly flexible and automatic In order to increase productivity enhance quality and reduce cost machine tools have to work free of any failure When a failure occurs in a machine tool it is necessary to identify the causes as early as possible Machine tool condition monitoring is very important to achieve this goal Condition monitoring is generally used on the critical subsystem of any machine tool This paper endeavors to focus on the con dition monitoring aspects on the machine tool element In the present study a critical subsystem has been identified based on the failure data analysis Condition monitoring techniques like vibration monitoring acoustic emission Shock Pulse Method SPM and surface roughness have been successfully used for fault identification Keywords Acoustic emission 9 Bearing Lathe 9 Shock pulse method 9 Surface roughness 9 Vibration Abbreviation SPM Shock Pulse Method 1 Introduction Machine tool technology the backbone of the world s manufac turing industry is developing faster than ever Despite these rapid advances developments in the strategy and techniques of ma chine tool maintenance have fallen behind in the general pattern of progress This is of serious concern since it can be argued that present maintenance techniques will be unable to cope with new demands In the modern automated manufacturing process ma S Saravanan 9 G S Yadava Industrial Tribology Machine Dynamics and grease mixtures with 90 Ixm size silica particle with 5 10 and 15 concen tration by weight are identified as B 1 B2 and B3 respectively The details of grease mixtures are given in Table 2 Table 2 Details of grease mixture used for experimentation Grease Concentration of Particle size of mixture contamination contamination identification wt lxm Remarks HG A 1 5 53 A 2 10 53 A 3 15 53 B 1 5 90 B 2 10 90 B 3 15 90 Sample taken from bearing under healthy condition Delibeartely prepared Delibeartely prepared Delibeartely prepared Delibeartely prepared Delibeartely prepared Delibeartely prepared 3 3 Experimental procedure Accelerometers were mounted at locations 1 and 2 to receive the spindle bearing vibration The overall vibration levels and vibration spectrums were recorded in FFF Analyser ONO SOKKI for all the cutting conditions as shown in Table 1 The acoustic emission hydrophone SEH receives the acoustic waves through a jet of cooling lubricant which is connected directly to cutting zone as shown in Fig 4 The measuring jet was made as short as possible since this has better charac teristics with respect to ground noise and damping The flow quantity was also kept as low as possible to minimize the impact noise The shock pulse measurements were carried out on test bear ings to ensure that the bearing fault due to contaminated lu brication condition existed Surface roughness measurements of a turned workpiece was carried out as an offline monitoring method Talysurf 6 Taylor Hobson was used for this purpose To minimise the effect of cutting tool wear and breakage on acoustic emission and surface roughness care was taken to en sure cutting tool sharpness For each set of experiments a fresh cutting tool insert was used i e the tool was not allowed to wear more than a standard specification 28 3 4 Signal acquisition for healthy condition Turning operations were performed with the combinations of three independent cutting parameters namely cutting speed feed rate and depth of cut Three different cutting speeds i e 78 98 and 125 m rain were used Feed rate values of 0 304 mm rev 0 384 mm rev 0 480 mm rev and 0 528 mm rev were kept for the entire experiment Depth of cut varied from 0 2 mm to 0 8 mm While varying one parameter the value of all other parameters were kept constant In the first stage machining op erations were performed on a defect free healthy lathe The overall vibration level rms velocity and frequency spectrum were recorded at both the headstock beating locations The over all vibration levels for a healthy condition lathe was monitored at locations 1 and 2 as shown in Figs 5 8 respectively The fre quency spectrums of the defect free lathe are shown in Figs 9 and 10 for monitoring locations 1 and 2 respectively The AE values for the healthy condition are shown in Fig 11 The AE smoothed signal for healthy conditions is given in Fig 12 Sur face roughness measurements in txm on the turned workpieces 997 are shown in Figs 13 and 14 for a defect free lathe The grease sample was taken from the taper roller bearing after complet ing the experimentation Flame atomic absorption spectrometry FAAS analysis was carried out at Department of Chemistry on the used healthy grease HG sample this is shown in Fig 15 3 5 Signal acquisition for faulty bearing conditions The next stage of experimental investigations considers defective taper roller bearings In our study a new set of taper roller bear ings were used for each step In the first step the test bearings were filled with a particular contaminated grease mixture The amount of grease added can be obtained from 29 G 0 005D B where G grease quantity g D bearing outside diameter mm B beating width mm The taper roller bearing was lubricated with deliberately con taminated grease mixture A1 The lathe operated for 8 hours Fig 5 Overall vibration levels for 1 8 healthy and faulty bearing condi tions at location 1 for a speed of 125 m min a feed of 0 528 mm rev and a contamination particle size of 53 ltm at various wt 1 6 O v 1 4 1 2 0 8 0 6 0 4 0 2 OIQIQIQDNeDmNDQimD OtOli i I i O i g O 6 9 g J Feed 0 0 584 mm rev o 0 480 mm rev A 0 384 mm rev x 0 304 mm rev O Healthy J J 9 5 silica AI 10 silica A2 S 9 mD 15 silica A3 9176 O 9 l I 9149149 j t n l S o 9 o J o 9 I 12 J 9 s j 9 9 149149176176176176 l 11 o 9 o e or o 9 r 9149 9 x x o c Lr 9 9 K s t 9 No Cut 0 2 0 4 0 6 0 8 Depth of Cut mm 4 3 8 3 6 3 4 3 2 3 2 8 2 6 2 4 2 2 2 1 8 1 6 IA 1 2 1 0 8 0 6 0 4 998 Fig 6 Overall vibration levels for healthy and faulty bearing condi tions at location 1 for a speed of 125 m rain a feed of 0 528 mm rev and a contamination particle size of size 90 Ixm at various wt 2 75 2 5 2 25 2 75 a5 1 25 re 1 0 75 0 5 0 25 0 Feed O 0 584 mm rev c 0 480 mm rev A 0 384 mm rev x 0 304 mm rev Healthy 5 silica AI 10 silica A2 4 411 B r r 0 5 without cutting For every 30 minutes of run a 15 minute in terval was provided to avoid overheating the motor and bearing elements It was regularly observed from the shock pulse meas urement SPM that the test bearing had entered the faulty zone A turning operation was performed and parameters were meas ured as for the healthy condition The overall vibration levels for faulty bearing conditions at locations 1 and 2 are shown in Figs 5 8 respectively The frequency spectrums of faulty bearing conditions A1 and B1 at locations 1 and 2 are shown in Figs 16 19 respectively The AE values in decibels for various feed and depth of cut conditions at a constant spindle speed 125 m min tinder faulty bearing conditions are shown in Figs 11 and 20 The AE smoothed signal for faulty bearing con dition A1 is given in Fig 12 Surface roughness measurements Fig 8 Overall vibration levels for healthy and faulty bearing conditions at location 2 at a speed of 125m rain a feed of 0 528 mm rev and a contamination par tic e size 90 Ixm at arious wt I g 1 6 1 4 I 1 2 1 0 g 0 8 0 6 0 4 0 2 0 Feed 0 0 584 mm rev 0 480 mm rev A 0 384 mm rev x 0 304 mrrdrev Healthy 5 silica AI El o silica n 9 15 siLica A3 A Ce 0 0 02 0 01 0 0 57 5 425 75 9 9 T 50 100 150 200 250 300 350 400 450 500 Frequency Hz 28 75 Fig 10 Frequency spectrum for healthy condition at location 2 at a speed of 125m min a feed of 0 528 mm rev and a depth of cut of 0 8 mm 0 35 o 3 o 25 0 1 0 05 I O 0 56 25 50 1 O0 150 200 260 300 350 400 450 500 Frequency Hz 1000 Fig 11 Acoustic emission levels of healthy and faulty bearing conditions at a speed of 125m min a feed of 0 528mm rev and a contamination particle size of 53 I tm at vari ous wt 41 39 37 A 111 35 o m E 33 tu o o 29 27 25 Feed 0 0 584 mm rev o 0 480 mm rev A 0 384 mm rev x 0 304 mm rev Healthy 5 silica AI NNmm 10 silica A2 15 silica A3 o e S S a O I B 4t r S o r Q 4r s 3 If 9 9 O e a r r r 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 Depth of Cut mm in Itm were carried out on the turned workpiece for defective bearing condition A1 and are shown in Figs 13 and 14 The experiments were repeated for other grease mixtures for all the cutting conditions shown in Table 1 FAAS analysis was also car ried out for contaminated grease mixtures and the proportions of iron content is shown in Fig 15 Fig 12 Acoustic emission smoothed signals for healthy and faulty bearing conditions 4 Results and discussion 4 1 Vibration monitoring 4 1 1 Overall vibration The graph of overall vibration levels at locations 1 and 2 for defect free lathe conditions Figs 5 and 6 shows continuous lines This indicates that vibration levels increase with an in crease in the depth of cut at a constant feed With an increase in feed keeping depth of cut constant the overall vibration level shows an increasing trend The values of overall vibration level are higher at location 2 than at location 1 This is because at lo cation 2 the headstock spindle is supported on a bush bearing whereas a pair of taper roller bearings are used at location 1 A study of the overall vibration levels at location 1 for various faulty bearing conditions of 53 Ixm silica contamination A1 A2 and A3 grease mixtures of the bearings in Figs 5 and 6 shows that overall vibration levels are higher than those recorded in the healthy condition The rate of increase with the depth of cut is also more than that in measured under defect free conditions With an increase in feed keeping depth of cut constant the in crease in overall vibration level is more in the case of healthy conditions At location 2 the overall vibration level values show Fig 13 Surface roughness of healthy and faulty bearing conditions at a speed of 125 m rain a feed of 0 528 mm rev and a contamination particle size of 53 txm at various wt 5 5 4 5 4 35 lao r 2 5 1 5 Feed 0 0 584 mm rev 0 480 mm rev A 0 384 mm rev x 0 304 mm rev Healthy 5 silica A O 10 silica A2 41 rt 15 silica A3 J3 e 4 1 r d W o X r 4X 176 176 i i i 0 2 0 4 0 6 0 8 Depth of Cut mrn 1001 Fig 14 Surface roughness of healthy and faulty bearing conditions at a speed of 125 m min a feed of 0 528 mm rev and a contamination particle size of 90 ttm size at various wt 5 5 4 5 3 5 2 5 1 5 Feed 0 0 584 mm rev 0 480 mm rev A 0 384 mm rev x 0 304 mm rev Healthy 5 siliea Al 4 2SS 15 siliea A3 o D O S 2 9 J I 4 1 dr 0 2 0 4 0 6 0 8 Depth of Cut mm a similar trend but the increase in the vibration level is much lower than that at location 1 This is because the taper roller bear ings in location 1 were lubricated with deliberately contaminated grease mixtures Figures 7 and 8 show the overall vibration lev els at locations 1 and 2 for faulty bearing conditions of 90 Ixm sized silica contamination B 1 B2 and B3 grease mixtures of the lathe The increase in vibration level is much greater as com pared to the 53 Ixm sized silica contamination for all cutting t002 Fig 15 Amount of iron content ppm on different grease mixtures according to FAAS study Fig 16 Frequency spectrum for defective bearing condition at location 1 at a speed of 125 m min a feed of 0 528 mm rev a depth of cut of 0 8 mm and a 53 txm silica contamination 5 wt Fig 17 Frequency spectrum for defective beating condition at location 2 at a speed of 125 m min a feed of 0 528 mm rev a depth of cut of 0 8 mm and a 53 1Lm silica contamination 5 wt Fig 18 Frequency spectrum for defective bearing condition at location 1 at a speed of 125 m min a feed of 0 528mm rev a depth of cut of 0 8mm and a 90 1 m silica contamination 5 wt 0 4 0 35 0 3 0 25 0 2 0 15 o o 1 tn 0 05 28 75 7 5 k 1003 218 75 56 75 270 50 1 O0 150 200 250 300 350 400 450 500 Frequency Hz Fig 19 Frequency spectrum for defective bearing condition at location 2 at a speed of 125 m min a feed of 0 528mm rev a depth of cut of 0 8mm and a 90 1tm silica contamination 5wt E C o 0 0 35 0 3 0 25 0 2 0 15 0 1 0 05 0 28 75 218 75 0 50 100 150 200 Frequency Hz 250 300 350 400 450 500 Fig 20 Acoustic emission levels of various faulty bearing condi 40 tions at a speed of 125 m min a feed of 0 528mm rev and 5 wt at various contamination sizes 38 36 34 r 1 32 30 28 Feed 0 0 584 mm rev 0 480 mm rev A 0 384 mm rev x 0 304 mm rev 53 t m silica A1 4 90 lm silica B 1 A i i i i i 0 2 0 4 0 6 0 8 1 Depth of Cut ram 1004 conditions The surface waviness created due to the bigger par ticle may be responsible for higher vibrations 30 4 1 2 Frequency spectrum Figures 9 and 10 show the frequency spectrums of the defect free lathe at a spindle speed of 125 m rain a feed of 0 528 mm rev and a depth of cut of 0 8 mm at locations 1 and 2 respectively Significant peaks can be observed at frequencies of 28 75 Hz 57 5 Hz and 451 25 Hz for location 1 Location 2 Fig 10 has significant peaks at 28 75 Hz and 56 25 Hz frequencies IX com ponent i e 28 75 Hz is predominant at both locations This indicates that there may be certain amount of residual imbalance in the headstock spindle Figures 16 and 17 show the frequency spectrums of faulty bearing condition A1 at a spindle speed of 125 m min a feed of 0 528 mm rev and a depth of cut of 0 8 mm for locations 1 and 2 respectively The bearing defect frequencies are given as follows 31 Defect on ball roller Defect on inner race Defect on outer race t21 N Fb d 1 cos Fi 1 cos 1 n d cos 3 N n Fo 1 b 1 d N Defect on cage Fc 1 cos 3 120 In the present case the values of Fb Fi Fo and Fc are found to be 5 36 268 23 211 76 and 11 76 Hz respectively The corres ponding bearing defect frequencies for the inner race 265 Hz the roller 7 5 Hz the cage 13 75 Hz and some higher frequen cies can be observed in Figs 16 and 17 The frequency spectrums of faulty bearing condition B 1 at locations 1 and 2 are shown in Figs 18 and 19 respectively The corresponding peaks of roller 7 5 Hz outer 218 75 Hz and inner 218 Hz defect frequen cies were observed with higher amplitudes than was the case in faulty bearing condition A1 The increase in amplitude of bear ing defect frequencies were observed from Figs 16 19 as the size of the silica particle increases Thus it can be concluded that there is certain residual im balance in the spindle because the 1X component i e 27 5 Hz is predominant in all the cases healthy and faulty bearing con ditions Significant peaks are observed at the bearing defect frequencies Also an increase in amplitude was observed as par ticle size of the contamination increased 4 2 Acoustic emission monitoring Figure 11 shows that AE values for a defect free lathe increase continuously with an increase in the depth of cut at a constant feed With an increase in feed for the same depth of cut the AE level shows an increasing trend The AE smoothed signals for healthy and faulty bearing conditions are shown in Fig 12 The AE levels for defective bearing A1 as shown in Figs 11 and 20 demonstrates that AE levels are higher here as compared to healthy conditions The rate of increase with the depth of cut is also more than the case of healthy conditions With an increase in feed with the same depth of cut the increase in AE level is more than that under healthy conditions The study of AE lev els for defective bearing condition A1 Fig 11 shows a higher AE level compared to a defect free lathe But at higher feed and higher depth of cut the increase in AE level is much more as compared to healthy bearing conditions and is shown in Fig 11 Figure 20 depicts the relationship between the particle size of the contaminants and AE level With larger particle sizes there is a considerable increase in the AE level irrespective of depth of cut But in earlier research 19 AE pulse count measurements on a deep groove ball bearing indicated that the AE pulse count decreased with an increase in particle size It may be that a large number of smaller particles can agglomerate more easily in the vicinity of the contact zone 4 3 Surface roughness monitoring Surface roughness increases with an increase in the depth of cut for constant feed in both healthy and faulty bearing conditions as shown in Figs 13 and 14 For the same depth of cut the sur face roughness level shows an increasing trend with an increase in feed rate At higher feeds and depth of cuts the surface rough ness value increases rapidly The bigger size of contamination particles may increase the surface waviness rather than surface roughness and this could be the cause of higher vibrations as discussed in Sect 4 1 1 30 In defective bearing conditions the relative increase in surface roughness values for a given increase in feed rate is higher than in healthy conditions 4 4 Flame atomic absorption spectrometry FAAS study According to FAAS study the grease sample under healthy con ditions had an atomic iron content of 285 ppm With the contam inants the atomic iron content was found to be more than that in healthy conditions However with an increase in the size of silica contaminant particles the atomic iron content shows a de creasing trend Fig 15 This may because smaller particles of the same quantity could stimulate the wear rate of the bearing components 5 Conclusion In this study critical subsystems and components have been identified for lathes using failure data The application of con dition monitoring techniques like vibration acoustic emission AE and surface roughness monitoring have been successfully implemented for diagnosing faulty bearings in a lathe We have reached the following conclusions 9 Headstock subsystem i