Chrome coating on glass scales typically involves a process known as physical vapor deposition (PVD), which deposits a thin layer of chromium onto the glass surface. In this process, a solid material is vaporized by heating it in a vacuum chamber and the vaporized material condenses on the glass to a thin film.

Before coating, glass blanks are cleaned in the washing machine, to remove any dirt, oil, or other impurities that could interfere with the adhesion or quality of the chrome layer.

It is then placed inside a vacuum chamber, which is evacuated to create a high vacuum environment, and then the main work done by the magnetron, which is the main element. Magnetron creates an electromagnetic field. There is a target on the magnetron that vaporises chromium atoms. When argon gas is injected, it ionises (gains charge) and attacks the target. This produces plasma on the surface, which disrupts the target and causes chromium atoms to escape from it. The blanks are suspended on a carriage which works as an anode. The injected argon gas reduces the vacuum by increasing the number of free atoms and ions, changes the evaporation rate, therefore it important to control intake. In our installations, the process is semi-automatic, because operator controls intake speed according to system, vacuum chamber, valve position data.

Once the coating process is complete, the glass scale is inspected to ensure that the chrome coating is uniform and free from defects or blemishes.

Glass scale quality control is a critical process for ensuring the accuracy and reliability of precision measurement equipment. It is a quality assurance operation during which scales are being inspected visually or using the microscope to ensure that they were accurately manufactured, calibrated, and maintained according to customer requirements. During this operation quality control specialist ensures that the scale does not have any optical coating defects, glass mechanical defects or any discrepancy in optical grating parameters. After that, scales are cut into smaller pieces using laser technology or a glass cutting knife and handed over for packing.

To define the desired pattern on the glass scale, a precise mask is aligned over the photoresist-coated surface. The mask contains transparent and opaque regions that allow or block light exposure. Alignment is critical to ensure accurate positioning and fidelity of the pattern. During the ultraviolet (UV) exposure process, the photoresist-coated scale is exposed to ultraviolet (UV) light through the mask. The regions exposed to UV light undergo a chemical change, while the shielded areas remain unchanged due to the mask’s opaque regions. This selective exposure defines the desired pattern with utmost precision.