·Table of Contents ·General | Examinations of Sliding Burnishing Using for Improving the Surface Quality of External Cylindrical SurfacesDr. Gyula Varga, Prof. Illés Dudás,Department of Production Engineering, University of Miskolc, H - 3515 Miskolc - Egyetemváros, Hungary Contact |
Advantege of this method: simple tool, does not require special machine tool, suitable both hardened and low-carbon steel, etc. Because of the plastic deformatin the surface roughness of the turned (or grinded) surface is reducing. Generally the dimension and shape accuracy is improving, favourable change the feature of the surface layer determining the surface quality: hardness is increasing, developing of compressive (negative) stresses, etc. In this way the endurance limit, abrasive resistance, and resistance against other loads/stresses is increasing, which results the increase of the tool life of the part.
3. 1. Adjustments of parameters and experimental background
The preparing manufacturing of the weared piston pins was grinding, and the smooth sliding burhishing was done on a centre lathe type E400/1000. The clamping of the workpiece was done according to Fig. 1.b. The burnihing force was guaranteed by a calibrated burnishing tool having spring, which was clamped into the toolholder.
Input data:
| F_{vmin} = 125 N, | F_{vmax} = 150 N, |
| f_{vmin} = 0,0203 mm/rev, | f_{vmax} = 0,05 mm/rev, |
| v_{vmin} = 60 m/min, | v_{vmax} = 83 m/min. |
| HRC @ 55, |
| Æ24,9 x 100mm, |
| |
| a @0°. |
Surface roughness after grinding | Adjusted parameters | Measured surface roughness values after burnishing | ||||
R_{max,g} | R_{a,g} | f_{v} | v_{v} | F_{v} | R_{max,v} | R_{a.v} |
mm | mm/ford | m/min | N | mm | ||
2,66 | 0,33 | 0,0203 | 60 | 1,03 | 0,112 | |
3,32 | 0,33 | 0,0500 | 125 | 1,92 | 0,260 | |
3,39 | 0,37 | 0,0203 | 83 | 0,70 | 0,096 | |
3,32 | 0,37 | 0,0500 | 1,40 | 0,180 | ||
2,79 | 0,37 | 0,0203 | 60 | 0,75 | 0,100 | |
3,89 | 0,42 | 0,0500 | 150 | 1,18 | 0,160 | |
3,53 | 0,43 | 0,,0203 | 83 | 0,97 | 0,130 | |
2,95 | 0,34 | 0,0500 | 1,20 | 0,150 | ||
Table 1: |
Beyond the measurements mentioned above we measured roundness error as well. The measurements were done by passameter, 3D measuring machine, Pert-o-meter, and Talyrund (for measurement of roundness error).
3.2 Examination of microgeometrical features
The selection of the input paramteres, making them into right order by the use of Factorial Experiment Design can be done actively [4]. Output parameters the R_{max.v} and the R_{a.v}.
We write empirical functions to these paramteres, as response function as followes:
(1) | |
(2) |
Applying the steps of the method to this concrete case, the contants C_{vm} and C_{va}, the a _{m}, g _{m}, d _{m}, and the a _{a}, g _{a}, d_{a} exponents were determined. The constants and exponents of R_{max,v} can be found as follows:
formula (1) |
C_{vm} = e^{218,152} |
a _{m} = (11,5073 - 0,2899 ln_{ }v_{v} - 1,9766 ln F_{v}) |
g_{m} = - (41,9107 - 8,2493 ln F_{v}) |
d_{m} = - 42,7924 |
These formulas are a little bit sophisticated ones, but describe the results of the burnishing. However if we take into account, that the value of the surface roughnesses weren't the same, maybe we can accept these calculations with reservations.
Remark: the constants and exponents of R_{a,v} easily can be calculated, however we do not publish them here.
We can tell more about the improvement of the surface quality if we examine only the improvement/difference between the before and after burnishing surface roughness. So introduce the following inner parameters:
(3) | |
(4) |
(5) | |
(6) |
formula (5) |
C_{r m} = e^{-230,5053} |
a_{ r m} = 0,4515 |
g _{r m} = (52,8366 - 10,6419 ln F_{v}) |
d _{r m} = 46.34 |
Fig 1: Smooth sliding burnishing of external cylindrical surfaces on manufacturing centre (a) and on centre lathe. Workpiece (1), burnishing tool (2), burnishing insert (3), active element of tip (A). |
Fig 2: Characterisation of the r_{Rmax } relative feature of surface roughness as the function of the technological paramteres f_{v}, v_{v} and burnishing force F_{v} |
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