How to Troubleshoot the Coarse Focusing Faults of Microscopes
The main faults of the coarse focusing mechanism of the microscope include automatic sliding down or inconsistent tightness during lifting and lowering. Automatic sliding down refers to the phenomenon that when the tube, arm or stage remains stationary at a certain position, it slowly descends spontaneously under its own weight without any adjustment. This fault occurs because the gravitational force of the tube, arm or stage exceeds the static friction force. The solution is to increase the static friction force so that it is greater than the weight of the tube or arm.
For the coarse focusing mechanism of inclined-tube and most binocular microscopes, if the arm slides down automatically, grip the anti-slip wheels inside the coarse focusing handwheels with both hands, and tighten them firmly in the clockwise direction to stop sliding. If this method does not work, professional maintenance personnel should be contacted for repair.
When the microscope tube slides down automatically, it is often mistakenly attributed to an overly loose fit between the gear and rack. Some people will add gaskets under the rack. Although this measure can temporarily stop the tube from sliding down, it places the gear and rack in an abnormal meshing state. During operation, both the gear and rack will deform. Deformation of the rack becomes more serious especially when the gasket is placed unevenly, resulting in uneven meshing - tight in some sections and loose in others. Therefore, this method is not recommended.
If the coarse focusing mechanism lacks maintenance for a long time and its lubricating oil dries up, an uncomfortable feel will occur during lifting and lowering, and mechanical friction noise may even be heard. In this case, the mechanical assembly can be disassembled, cleaned, greased and reassembled.
