Hot Plate Assembly Is Plain Screwy

I recently worked on four hot plate stirrers that are used in a lab environment. A beaker of liquid is placed on the hot plate stirrer, where it can be heated. An encapsulated bar magnet is placed in the beaker and rotated by another magnet under the hot plate, thus stirring the liquid.

The safety relays for the heating element were bad in all four units I was working on. This is not unusual. The units have three chassis parts: the top plate, the upper housing, and the lower housing. The top plate uses four one-inch spacers to space the hot plate above the upper housing. Disassembling the parts involves turning the unit over and removing four screws. This is not a problem until the screws are removed. They are three-inch screws that go through the lower housing, the upper housing, the spacers, and then screw into the hot plate. It is the reassembly that is tricky. Because of how it is designed, everything needs to be stacked and lined up before the screws can be inserted.

In addition, the PC board is mounted to the upper housing by four screws. Each screw is different. Two screws are metric and the same pitch but different lengths. Another screw is metric but a larger diameter. The fourth screw is standard thread. Ah, monkeys.

Tell us your experiences with Monkey-designed products. Send stories to Lauren Muskett for Made by Monkeys.

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