Gary Rinsem

RF Shield Tester
For Cell Phones
by Gary Rinsem

It was 1996 and cell phones were still very basic. Many didn't even have a display. The most advanced phones had a game or two that you could play. Chase around the screen as a snake and every time you eat you grow, until there's no more room for you to move. You only win if you get to that point without eating your own tail. Remember the game? I spent MANY hours waiting in airports with nothing else to do, then waiting at the car rental... more snake game... I built machines to test the coating that shielded the cell phone cases. Each machine could test about 60,000 cell phone cases per day, far more if they could keep fresh operators feeding the machines. It took less than one second to test each part. Operators wore out quickly and slowed down. There's more going on than you might notice from such a simple looking contraption. Cases are dropped onto a chute and slide into position where a stop block holds them in the right place. Four probes descend and contact the shielding inside the phone case. The meters below the control cabinet spring to life and immediately pass or fail the shielding. The probes retract and the stop block lifts allowing the phone case to slide onto a small conveyor. Most pass, but those which fail are shoved off the conveyor onto the small raised platform. Cases with good RF shielding pass under the print head and get printed to indicate they were tested and passed. Each type of phone case required a different test plate configured with all the hardware for that specific part. It's the bit of the machine at an angle, with tiny compressed air lines running to it. Operators could quickly change test plates when they changed the product being tested.

Each machine took two operators. It was horrible work done happily by folks who didn't speak English. One operator used both hands to grab phone cases out of an egg crate style box. They could quickly grab four cases in each hand, between the fingers of their hands, and turn to slip the cases into the chute. It only held three cases at a time and took less than a second to test a part. To keep the tester testing, they had to be fast at filling the chute. A second operator stood to the left of the picture and collected the tested phone cases, putting them into another egg crate style box. Depending on how many testers were running, it also took one or two people to supply pallets of untested parts and to haul off the pallets of tested parts.

The white box with wires going into the top and bottom is a PLC (Programmable Logic Controller). That's a common type of industrial computer. They're all business and very reliable. Unfortunately, every brand and every model need different expensive software to program them. Also, every one has oddities in the programming. If it could all be standardized then the industry would be much easier to deal with.

These machines were made with the highest quality components and a very heavy duty design. They ran at least a couple years with no issues. The owner of the company made a lot of money by testing every part.

The pic is a bit blurry, but you can see wing nuts on top to remove the plate which holds the interchangeable part of the machine. Remove wing nuts, unplug air hoses and one cable. Install a different plate and test a different part.