INVESTIGATION OF DENTAL LUBRICANTS

Transcription

1 Selected topics from research and dental practice No. 03 / February 01 Extract from REPORT INVESTIGATION OF DENTAL LUBRICANTS Tribology and Engineering Vienna University of Technology responsible for the order work: Univ.Prof. Dipl.-Ing. Dr. Friedrich FRANEK

2 INVESTIGATION OF DENTAL LUBRICANTS 1 GENERAL PROJECT INFORMATION 1.1 Customer Company W&H DENTALWERK GesmbH. A 5111 Bürmoos 1.2 Assignment according to W&H Dentalwerk Order of Internal project number WH O 1.4 Purpose/aim of the project Investigation of lubricants for use in dental equipment. The aim of the project is a qualitative comparison for the wear-reducing effect of the lubricants included in the project. The basis for the investigations is the application of a dental instrument under normal operating conditions with a fast-running transmission (gearing from approx. 40,000 rpm. to approx. 200,000 rpm in two stages). 1

3 2 MARGINAL FRICTION AND WEAR CONDITIONS Following an expert discussion concerning the principle possibilities for the employment of different methods of investigation to obtain comparative data relevant to practical applications, test principles were selected for the assignment largely based on standard procedures, taking into consideration the tribological systems in dental instruments and the various anticipated loads: Translatory oscillation (SRV) test (see DIN ) The translatory oscillation (SRV) test is used to test lubricants 1 in the mixed friction area in translatory oscillating movements. The wear indentation diameter W K in mm of the mating body and the coefficient of friction f are determined as the parameters. 3 TEST SPECIMENS The customer made available 7 lubricants for the investigations. For each test, these lubricants were applied in their new condition, i. e. for each individual test, the lubricants were removed with a new pipette from the delivery containers. The lubricant was applied as standard to the cleaned and degreased main and mating bodies. Test specimen Specimen 1 Specimen 2 Specimen 3 Specimen 4 Specimen 5 Specimen 6 Specimen 7 reference oil SRV test Designation W&H Service Oil KaVo oil from EU KaVo oil from USA External reference oil Phase Change oil ProForm Table 1: Overview of tested oils and dental lubricants 1 DIN

4 4 TRANSLATORY OSCILLATION (SRV) TEST The test specimens (steel disk and steel ball) with standardized geometry incorporated in the test chamber of the test equipment are wetted with the trial sample (lubricant) to be tested and placed under a mechanical dynamic load at a selected normal force F n at the selected test frequency ν and at the selected test temperature ϑ. The coefficient of friction f is determined on the basis of continuous measurements using a piezo sensor. At the end of the selected test time t, the amount of wear W K is measured at the steel ball. F f F n d 2 d 1 W k = (d 1 +d 2 )/2 Fig. 1: Test principle of the translatory oscillation (SRV) test 4.1 Test/measuring devices SRV tribometer; type: OPTIMOL Instruments Prüftechnik GmbH., Munich, Germany 4.2 Main and mating bodies Fig 2: Main and mating bodies in the translatory oscillation (SRV) test 3

5 Test slice: Provided by the customer Dimensions: D: 24,0 ± 0,5 mm H: 7,8 ± 0,1 mm according to DIN Material: No.: according to DIN Hardness: 62 ± 1 HRC Roughness: see Annex, polished Quantity: 20 off No.: (practice-relevant material) Quantity: 5 off Test ball: Provided by the customer Dimensions: D w : 10 mm according to DIN Material: No.: according to DIN Hardness: 62 ± 1 HRC Roughness: see Annex Quantity: 20 off Nr.: (practice-relevant material) Roughness: see Annex Quantity: 5 off Test and measuring conditions Test conditions and measuring conditions according to DIN All investigations into friction and wear were undertaken in the laboratory in the standard atmosphere 23/50-2 DIN Parameters recorded The following parameters were determined during the investigations: Coefficient of friction f as a function of time Wear indentation diameter W K In addition: Evaluation of wear according to the evaluation method of Klüber Lubrication München KG. This involves calculating the product of the area of the wear indentation of the ball and a representative depth of the wear track on the test disk. This wear factor is not standardized. A greater numerical differentiation of the tribological behavior of the materiallubricant combinations investigated is achieved by using the grossly 4

6 4.2.3 Testing simplified multiplication of representative wear values of the two test bodies. According to standard DIN Test disk with respect to test ball Test disk with respect to pin with end indentation 4.3 RESULTS AND EVALUATION Lubricant f min f max f 15 f 30 f 90 f 120 W k standard 0,108 0,130 0,112 0,112 0,108 0,109 0,42 0,110 0,131 0,114 0,111 0,110 0,110 0,43 W&H Service Oil 0,107 0,127 0,115 0,112 0,108 0,107 0,43 W&H Service Oil 0,134 0,146 0,141 0,140 0,136 0,135 0,48 KaVo oil, EU 0,100 0,123 0,112 0,104 0,117 0,123 0,66 KaVo oil, EU 0,098 0,115 0,110 0,102 0,110 0,115 0,64 KaVo oil, USA/Kanada 0,130 0,140 0,131 0,135 0,134 0,134 0,56 KaVo oil, USA/Kanada 0,125 0,137 0,128 0,132 0,133 0,132 0,56 External reference oil 0,106 0,200 0,111 0,113 0,132 0,135 0,95 External reference oil 0,104 0,142 0,108 0,109 0,123 0,128 0,91 Phase Change oil 0,109 0,122 0,115 0,114 0,111 0,109 0,45 Phase Change oil 0,110 0,119 0,113 0,117 0,110 0,110 0,46 Pro Form oil 0,110 0,120 0,115 0,113 0,111 0,111 0,49 Pro Form oil 0,114 0,124 0,116 0,115 0,114 0,114 0,49 0,125 0,133 0,131 0,133 0,133 0,131 0,43 0,121 0,129 0,128 0,128 0,128 0,128 0,38 Table 2: Parameters determined according to the standard (Note: The standard concerned allows for only 2 decimal places!) Lubricant f min f max f 15 f 30 f 90 f 120 W k standard 0,133 0,187 0,156 0,159 0,170 0,169 1,41 0,127 0,172 0,153 0,158 0,155 0,150 1,34 0,134 0,160 0,149 0,155 0,158 0,153 1,15 0,130 0,157 0,151 0,153 0,153 0,154 1,225 Table 3: Parameters determined according to the standard for tests with material (Note: The standard concerned allows for only 2 decimal places!) 5

7 Lubricant W&H Service Oil W&H Service Oil KaVo oil, EU KaVo oil, EU KaVo oil, USA/Kanada KaVo oil, USA/Kanada External reference oil External reference oil Phase Change oil Phase Change oil Pro Form oill Pro Form oil Remarks Wear tracks Wear tracks in the middle of the mark Wear tracks in the middle of the mark Scoring, pitting at the ball, deposits No scoring, spikes in the coefficient Light wear tracks Ball surface appearance indistinct Table 4: Notes concerning the wear zone at the end of the test Lubricant Remarks Unsteady running with the first signs of scoring Unsteady running with the first signs of scoring Table 5: Notes concerning the wear zone at the end of the test with material

8 Coefficient of friction characteristic 0,15 0,14 KaVo oil, EU External reference oil Pro Form oil W&H Service Oil KaVo oil, USA/Canada Phase Change oil Coefficient of friction f [-] 0,13 0,12 0,11 0, Test time t [min] Diagram 1: Representation of the mean values (from 1 basic test and 1 repeat test) of the coefficients of friction concerned as a function of the test time (from Table 2) Indentation diameter of friction Wk [mm] W&H Service Oil F1 W&H Service Oil F1 KaVo oil, EU KaVo oil, USA/Canada External reference oil Phase Change oil Pro Form oil SRV reference oil Diagram 2: Representation of the mean values (from basic test and 1 repeat test) of the indentation diameters from Table 2 7

9 Wear coefficient according to Klüber, material Wear factor W&H Service Oil F1 W&H Service Oil KaVo oil, EU KaVo oil, USA/Canada External. reference oil Phase Change oil Pro Form oil SRV reference oil Diagram 3: Wear evaluation using internal evaluation method from Klüber Lubrication München KG. Smaller wear factors reveal a more favorable wear protection effect of the lubricant concerned The present investigation revealed that the test specimens W&H Service Oil F1, Phase Change Oil and Pro Form Oil produced the most advantageous behavior with reference to the overall size of the coefficients of friction measured, with reference to the requirements for a coefficient of friction reducing with time as well as with reference to the width of wear. Considerable differences were found in the behavior of the External reference oil which revealed spikes in the coefficient of friction in the measurements recorded and a steeply rising characteristic of the coefficient of friction over time. This test specimen also revealed the largest wear indentation by far. A rising coefficient of friction characteristic was also found with KaVo Oil EU. 8

10 DATE / CASE WORKER: / Sworn and court-certified expert 9