Surface characteristics can determine a range of scenarios. For instance, the finish on the body of a Formula One car can influence the racer’s finish time, and an engineered part’s surface will help influence its performance. Here The Sempre Group and one of its principals, Sensofar, set out how manufacturers can benefit from optical profiling in R&D applications.

To ensure parts meet their intended purpose, manufacturers will often measure surface finish during development, allowing them to adapt manufacturing techniques accordingly before mass production. As probes that touch the object could compromise the surface,optical profiling is the most common choice.

The Sensofar 3D optical surface profiler uses interferometry techniques for areal surface characterisation, as well as an optical design that makes it possible to double the field of view without compromising the resolution. By using a combination of phase-shifting interferometry (PSI), extended phase-shifting interferometry (ePSI) and coherence scanning interferometry (CSI) techniques, manufacturers can use the profiler to measure a range of surface characteristics.

PSI is best for ultra-smooth and very flat continuous surfaces, such as those on optical components. CSI is the most versatile mode, measuring smooth and rough surfaces with 1 nm resolution, and can also measure transparent layers with thicknesses from 1.5 to 100 µm. Meanwhile, ePSI, a kind of combination of PSI and CSI, is for measuring smooth surfaces with structures, making it suitable for measuring features on semiconductor wafers.

Interferometry has a high level of repeatability and accuracy and is faster than some confocal technologies, like laser confocals. By using this technique, engineers can produce topographies with a high number of measured data points, clearly showing the surface of intricate components.
For further information www.thesempregroup.com

Manchester Metrology was recently in contact with someone who is in the process of restoring an old Kawasaki HX 125 to mint condition. This is a rare motorcycle to find in good condition, and some parts are no longer available, including the front brake disc/caliper cover. There was damage to the existing brake cover, which required full reverse engineering to make pristine again.

Due to the damage, it was not possible to scan the part and directly clean up the mesh for reproduction. As a result, the componentrequired recreating using parametric CAD. The team at Manchester Metrology deployed surfacing techniques to create each surface and blend them into the next.

Scanning of the part took place using a Creaform Handyscan Black Elite. This scanner has an accuracy of 0.025mm for small components, which is important for ensuring a good fit to the mounting points. The use of Geomagic DesignX for surface modelling allowed for a combination of more typical surface techniques along with mesh fitted surfaces where required. Once the surface was created, a thickness was added to make the part solid.
The component was then converted to an STL polygonal model and printed using a Snapmaker A350 with white PLA.

With the bike primarily for show, brake temperatures did not require consideration when selecting material. If temperature was a concern, carbon composite materials with HSHT fibre-glass reinforcement may be more suitable. A brim was used to aid build-plate adhesion, with the print taking over 80 hours to complete.

The print fitted well to the bike first time and did not require any tweaks or adjustments. Subsequently, the client was very happy with the outcome and recommended Manchester Metrology to fellow enthusiasts interested in their own copies.
For further information www.manchester-metrology.co.uk