Ep 43. Battery Tins and Optical Lenses

In season 4, episode 43 of How It's Made, we're taken on a journey through the manufacturing process of battery tins and optical lenses.

First up, we explore the intricate process of creating battery tins. We start off by learning about the necessary components of a battery tin such as the steel coil, the lacquer coating, and the printing ink used to label the tin. The steel coil is first loaded onto a decoiler which facilitates the process of creating the tins. Once the coil is properly set, it's sent through a process called blanking which uses a punch press to create blanks that will later become the tins themselves. The blanks are then fed into a cupping press that presses them into a cup shape, and are then trimmed to their specific sizes.

Next, the cups must undergo a process called deep drawing which involves it being stretched and thinned by a punch and die, resulting in the body of the tin. The lids are made in a similar way, with the steel coil being loaded onto the decoiler and the blanking process resulting in the lid blanks. The lid blanks then undergo a process that places a small dimple into the center to facilitate pressure release when the battery is in use. The lid is then crimped onto the body of the tin to create the final product. Finally, the battery tins are cleaned and labeled with the necessary marking.

After the manufacturing of battery tins, the episode goes on to explore the process of producing optical lenses. We start off learning about the glass material that is commonly used to make such lenses. Optical glass is essentially a highly engineered glass that has specific indices of refraction and properties such as ultra-low thermal expansion. Next, we're introduced to the process of creating the lens blanks which are the starting point for the optical lenses.

The glass blanks are cut to their specific sizes with a diamond-tipped saw, and are then placed into a molding machine to create the correct curvature for the lens. The molds are heated and pressed onto the glass with a specifically designed press that exerts the precise amount of pressure to create the curvature. The molds are then cooled and removed to reveal the lens blank with the desired curvature.

The blanks are then sent to a grinding machine where the rough shape of the lens is created. This is done using diamond wheels with grits of varying coarseness. The grinding machine is computer-controlled to ensure precise grinding of the correct depth and angle. Once the rough shape of the lens is achieved, it undergoes the polishing process which is done by hand. The lens is placed onto a polishing machine, where a polishing pad that has been impregnated with a specially designed slurry is pressed against the surface of the lens. This process is repeated with pads of finer and finer grit until the lens has achieved its final smoothness and accuracy.

Finally, the lens is checked for defects and imperfections both visually and using specialized equipment such as interferometers, which produce light waves that reflect off the surface of the lens and give a precise measurement of its shape. If any defects are found, the lens must undergo further grinding or polishing to correct the issues.

Overall, this episode of How It's Made showcases the meticulous and fascinating processes involved in the manufacturing of battery tins and optical lenses. From the blanking and deep drawing of steel for battery tins to the molding and grinding of glass for optical lenses, viewers will gain a newfound appreciation for the care and precision involved in the creation of these everyday objects.