Linear Scale Positioning Fixture, 5-Axis Milled from 6061-T6, 124 mm Long

About This Part

This fixture is a thin, long bar, 124 mm end to end on an 18 by 10 mm section, and that proportion is what makes it interesting to machine. A part this slender will bow the moment a cutter leans on it, so the route is built around keeping the bar relaxed: multi-pass clamping, light finishing cuts, and the part given every chance to settle before the last pass on each face.

The working geometry sits in the middle of the bar. Milling leaves a 74 mm stepped section between R3 transition radii at the ends, and into that section go the precision V grooves. Each groove is 0.39 mm deep with a 90 degree included angle, held to 0/-0.03 mm on depth, alongside 4.10 mm and 5.00 mm slot widths. These grooves are what seat the scale or optical element, so their depth and angle decide whether the mating part sits on the groove flank or rocks on its edge.

Micro grooves this shallow are cut with small finishing tools at light depth of cut, and the burr question is taken as seriously as the size. The technical requirement states no burrs inside the grooves, so every groove is deburred under magnification before the part moves on. Both ends carry transverse ridges for grip and location, machined in the same setup as the grooves so the pattern stays aligned along the bar.

Surface finish is specified two ways: Ra 3.2 as the general finish and Ra 1.6 on the critical working faces, which is where the mating element actually touches. After deburring the bar goes through black anodize with a sealing treatment. Film thickness matters here, because anodize grows on every face and the 0.39 mm groove depth and the 4.10 mm slot width have to stay in tolerance after coating, so the film is controlled rather than left to chance.

The photographs on this page show the fixture as machined, before anodizing, so the milled V grooves, the transition radii, the grip ridges and the tool finish can be read directly instead of being hidden under the coating. Customers who want to judge the machining state before surface treatment get it straight from these images.

Inspection runs on a 2D vision measuring machine with microscope optics, reading the 0.39 mm groove depth, the 90 degree angle, and the 4.10 mm slot width directly. Groove interiors are examined under magnification to confirm they are burr free, and overall length and the 10 mm thickness are checked with calipers and a height gauge.