Finding even the slightest defects in mirrors is a process that begins long before the mirror is a finished product. From the time the raw materials arrive at the plant, operators and quality control specialists need to have their eyes peeled for potential pitfalls. There are five primary steps to ensuring each product is perfect.
1.) Initial Inspection: Manufacturers should be carefully looking at the raw materials, including the packaging, as soon as it arrives from the supplier. At this stage it’s important to keep an eye out for anything from bad film (which could imprint the mirrors) to sawdust to wood chips. You need to start with clean materials and good masking.
2.) Forming: When operators work to form each mirror to the accurate curvature and with the correct shape, the company’s innovations and ingenuity really have a chance to shine. It is during this step that the manufacturer can produce their own gauges or develop their own methods of identifying anything that could affect shape accuracy. Something as simple as shining a straight tube fluorescent light over a reflective part can help an operator spot image distortions.
3.) Surface Quality: In order to make a mirror reflective, metal has to be evaporated onto the plastic. This layer of metal is extremely thin — just a few hundred nanometers. Any blemish in the surface will be faithfully reproduced, making the defect visible and obvious. Therefore, it’s crucial to protect the integrity of that surface prior to metallization and then to inspect the mirror’s back surface before any paint or protective back coating is applied.
4.) Application of Protective Coating: Once the mirror is determined to be free of surface defects, manufacturers apply a protective back coating. The coating must be applied evenly and completely. Robotic devices are capable of applying the most consistent paint lines. The robot, however, must be programmed and checked by a person, effectively making it an extension of its human operator.
5.) Cutting: The final process step is to cut the mirror to final dimensions. This is another area where technology makes all the difference. A method called computer-numerically controlled (CNC) routing provides an unrivaled level of accuracy. This is especially important for mirrors that will be encased in some sort of housing (bus mirrors, for example), where a perfect seal must be achieved to guarantee that there won’t be any rattling or vibrating when the vehicle is in use.
Good manufacturing starts with the arrival of raw materials and doesn’t end until the product is shipped. True, it is a step-by-step process, but each step provides a necessary link in chain of events, no one step being more important than the other.