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J. Eur. Opt. Society-Rapid Publ. 21, 37( 2025)
Fig
. 2.( a) Shape adaptive grinding( SAG) process,( b) standard SAG tool shapes.
Fig. 3.( a) Tungsten carbide channel and optical micrograph of the surface and( b) measured 3D shape of the channel.
3D measurement of the surface was carried out using a form talysurf( Make: Taylor Hobson, Model: PGI1240). Form error of the surface was determined by mapping the measured 3D profile against the design, by using Metrology Toolkit software( Make: Zeeko). Measured 3D shape of the channel is shown in Figure 3b. Initial roughness Ra on the channel surface was approximately ~ 1.5 lm.
2.2 Process and tooling
Shape adaptive grinding was carried out on 7-axis ultraprecision finishing machine( Make: Zeeko Ltd., Model-IRP 200). The machine provides travel range of 200 mm 200 mm 120 mm and positioning resolution of 10 lm. A thin wheel type finishing tool is designed which can rotate along an axis perpendicular to the surface normal, shown in Figure 4a. The wheel has a recess on periphery to accommodate a rubber ring. A strip of SAG abrasive pad is attached on top of the ring using superglue. The diameter of the wheel is 20 mm and the width of the attached SAG pad is 1 mm. The finishing wheel is fixed to a 3D printed jig( Material: ABS) by using screw and bearings, to ensure free rotation. The assembled tooling system attached to the
machine is shown in Figure 4a. A driving wheel with a thick rubber disk on top of it is inserted inside the machine spindle( H-axis). The finishing wheel( driven wheel) is in contact with the driving wheel at an eccentricity of 15 mm, and their axis are perpendicular to each other. When the spindle with driving wheel rotates with rotation n 1 rpm, the friction between driving wheel rubber disk and finishing wheel abrasive pad leads to rotation of the finishing wheel at n 2 rpm. The driving wheel and the driven finishing wheel are in contact with a preset load. H-axis( spindle) of the machine is equipped with a load cell which can be used to read the load at the interface of driving and driven wheels. The simplified H-axis configurations mounted with standard SAG tool and the new wheel tool are shown in Figure 4b. In case of standard SAG tools directly inserted into the H-axis, the diaphragm is pressed in backward direction and the floating bas presses the load cell. This gives the positive load value on the load reading bar available on the machine interface. In case of the new proposed tooling system, the ABS jig is mounted on outside of the H-axis. When there is any load on the finishing wheel, the load is transferred on the outside of the H-axis though the ABS jig. This load tries to push the diaphragm in