MICRO METROLOGY | CASE STUDY Geting the right tools for the job
Te equipment brought in was two coordinate measuring machines (CMMs), models Crysta-Apex S9168 and S9208, to inspect precision components such as cylinder heads and blocks; an RA-H5200AH Roundtest, which is a dedicated roundform measuring machine for components such as crankshaſts and camshaſts; and an SJ500 Surſtest, a surface roughness tester acquired mainly to ensure that the ground finish of critical bearing surfaces is maintained at the correct material-ratio-parameter value (Abbot-Firestone analysis).
Te new investment quickly paid off: the CMMs endeared themselves to the operators as being capable, quality machines, easy to use and providing no drama – just fast, accurate measurements, prompting the comment, “…we now have versatility on our CMMs…”. Similar sentiments were expressed for the Surſtest, especially appreciated for its excellent functionality.
A difficult component measurement is tamed
However, the star acquisition was the RA-H5200AH Roundtest, a highly accurate machine, capable not only of precision roundness measurement but also of characterising many roundform characteristics such as concentricity, coaxiality, cylindricity, straightness, perpendicularity to axis and plane, flatness, axial and radial runout, as well as other parameters of interest for this unique class of component. An automatic centering and levelling feature makes the essential pre-measurement procedure of component axis alignment with the turntable axis a straightorward task for any operator.
A particularly successful application of the Roundtest was measuring roundness, straightness, parallelism and coaxiality of the main journals and crankpins of crankshaſts. Te challenge with this component was geting the crankpins in position ready for measurement, as the eccentric throw of the pins and the variety of crank angles make the task difficult to accomplish on a general purpose measuring machine. However, the solution lay in a dedicated fixture that was designed and built by Mitutoyo’s Gauging Technology division to mount on the machine’s turntable. Tis fixture clamps the crankshaſt by one end in a chuck mounted on a linear slide so that the crankshaſt is held vertically, while allowing it to be moved on the slide by the amount of crank throw so as to position any crankpin axis within the adjustment range of the automatic centering and levelling mechanism.
Te roundness tester exceeds expectations
Tis was quite a departure from the measuring method traditionally employed for this problematic component and, initially, did not find universal favour, as Michael Hague-Morgan, Autocraſt’s Commercial & Engineering Director, and co-owner, said: “Aſter some initial scepticism from our customer about using the RA- H5200AH for this component, they have since been blown away by its capabilities.” In fact, the possibilities opened up by this novel and highly cost-effective solution mean that Autocraſt are now looking at new streams of business on the sub-contract side. Michael went on to say: “Tis investment has enthused our entire inspection team now that they have quality equipment to work with. We now have data from the Mitutoyo equipment that enables us to converse with a customer in a way we never previously had, and as a result has improved our customer relationships significantly.”
26 | commercial micro manufacturing international Vol 7 No.6
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