Here - the ESAFORM 2008 Conference - INSA de Lyon

More documents

Recommendations

Info

eJ / 2βD pD mr pJ / 2PunchFig. 2.Geometrical parameters characteristic of blanking.The main conclusions of these studies show that thesize of burr depends mainly on the blankingclearance, the wear condition of the tool edge andproperties of the cutting materials and the toolmateriel. According to the studies carried out in [1]and [2], it appears that the wear promotes theappearance of burr and that the increase in theblanking clearance results in an increase in thefracture angle of the shear zone and the height of theburr. This is confirmed also in [3] and [4]. Withregards to the properties of blanking materials,Gréban in [5] says that the composition of cuttingalloys has a strong influence on the quantity of burrsthat is created during the blanking operation.However, the works are more on the theoreticalstudy of the conditions of burr appearance, than onan experimental metrology on the burr amount.αr mBlank-holderSheet metalDie3.1 MetrologyWe can see that in literature, there are many ways ofmeasuring burr, but fundamentally based on adestructive test of blanking pieces and therefore ofmetrology in a few positions of the cutting edge.Other methods that have been proposed formetrology burr heights were the non-contact ortactile optical profilometry [7], or the visionmetrology [8] of the cutting edge, which is aimed atpieces with straight faces. The latter allows thenaccess to the profile heights of burr over a length ofcut board of 4mm. Another example is ameasurement using the shadow of burr or a moretraditional measure, the mechanical profilometry.3.2 Crushed burrIn the case of progressive blanking, complexgeometry of the parts is produced by several pressstrokes, which has the effect of crushing burrs. Thismakes it more difficult to measure the height of theburr by traditional means.3 METROLOGY OF BURRThe possibility to estimate the burr size on the blankpieces remains of great importance in the blankingindustry, because the quality of the products isdetermined with the evaluation of the level ofacceptable burr on the parts. It is possible to study,in theory, the emergence of blanking burrs.However, if we wish to verify the theoreticalpredictions, it is necessary to be able to accuratelyand reliably measure the quantity of burrs. Tosummarize, we can return to what might be adefinition of the burr height, the main criterionmentioned here. According to [6], because the sheetcan have a residual macroscopic deformation duringthe cutting operation, the height of burr is defined as"the difference between the highest point of burr andthe surface of the sheet metal immediately adjacentto the burr". This definition seems satisfactory andwill be the basis for development of our work.Fig. 3. Crushed burr.This has prompted us to seek, in this work, a newmethod more able to give us a precise quantificationof the crushed burr. To do this, we sought to define areference plan around the cutting form, because theadjacent sheet is distorted.3.3 Establishing a means of measurementIn our approach to the burr quantification, we soughtto meet a need, which is to confront the theoreticalresults with experimental robust measurements.3.3.a Images AcquisitionThe device used is a microscope Infinitefocus ®
Alicona (Fig.4). It is based on an optical microscopecoupled to a camera. Unlike a confocal microscope,which uses a monochromatic sensor, the device usesa sensor of contrast in color. On the whole height,the microscope collects images which are thenanalysed by the software. The latter analyses eachpixel and compares it to its neighbours to see if it isfocused or not. Then, it reconstructs a threedimensionalimage from this focus. From this image,surface-, volume-, surface state- and topographydimensional measurements are possible. Inaccordance with selected lens, the image size rangesfrom 2.1x1.6mm ² to 103x83 µm² and resolution inheight from 444nm to 20nm. If the sample or area ofinterest is larger than the size of capture of theselected lens, it is possible to achieve a multi-fieldacquisition through motorized tables. We only needto identify the entire area to be analysed, and byinterconnection between image fields acquired withrecoveries, we reconstructed a joined-fie image.Profile afterstraighteningProfile beforestraighteningFig. 5 . Profiles on the surface of the sheet before and afterstraightening .• Secondly, an image processing is performed inorder to extract the profiles that we wishvertically from the contour of the blanked shape(Fig. 6).Blanked ShapeSheet metalProfile beginningProfileFig. 4. The optical device measurement: InfiniteFocus ®3.3.b MeasurementThe measurement method is developed within theLMS specifically for quantifying the burr volume.The originality of this method lies in thetransformation of the blanked shape, (here a circularshape). The main stages of this transformation are:Fig. 6. Example of obtained profile.• Thirdly, the profiles are extracted in multiples soas to build a rectangular matrix; each profilebeing the average of 100 adjacent profiles.Thereafter, the image is adjusted, outside thezone of the blunder, with a linear polynomial ofdegree 2, which assembles all the profile (Fig. 7).• First, a straightening of the image around theblanked shape (hole) is achieved (Fig. 5). This isdone in order to eliminate any imperfections inthe image rectitude. The straightening of theimage (outside the zone of burr) is made with themethod of least squares.Fig. 7. Representation of the profiles assembling.• Finally, the volume is determined only in theareas of the burr presence on the image.
Page 1 and 2: Development of a friction modelling
Page 3: The evolution of heat flux transmit
Page 6 and 7: 2.2 Toolkit and specimen geometryFi
Page 8 and 9: In general, the friction coefficien
Page 10 and 11: determining a relative movement bet
Page 12 and 13: force needed to move the pin (frict
Page 14 and 15: and specimens are parts of actual i
Page 16 and 17: 4.3 Effect of lubricant particle si
Page 18 and 19: 2 EXPERIMENTAL2.1 PSCT set-up and p
Page 20 and 21: found here only in a low strain rat
Page 22 and 23: pieces are scaled by the same scali
Page 24 and 25: the experimental one shows nearly n
Page 26 and 27: 2 NUMERICAL TOOL2.1 General descrip
Page 28 and 29: much better when rotating velocity
Page 30 and 31: transfer across the roll-strip inte
Page 32 and 33: egime, the contact behaviour is gov
Page 36 and 37: number of profiles, which has the a
Page 38 and 39: In spite of the predominance, galli
Page 40 and 41: other hand, it has not been observe
Page 42 and 43: corresponds to the minimum energy s
Page 44 and 45: 10.90.80.70.60.50.40.30.20.100 5 10
Page 46 and 47: 2 EXPERIMENTAL PROCEDURETwo lubrica
Page 48 and 49: can be described using the followin
Page 50 and 51: through an arc cathodic equipment.
Page 52 and 53: To verify the absence of coating in
Page 54 and 55: angle, and m 0 the constant frictio
Page 56 and 57: 4 NUMERICAL MODELLING4.1 Upsetting
Page 58 and 59: indenter. T-shape compression, a ne
Page 60: Tangential force / Normal force0.35

Here - the ESAFORM 2008 Conference - INSA de Lyon

Create successful ePaper yourself

Delete template?

Save as template?