Troubleshooting of Mechanical Devices in Microscopes
The main faults of the microscope coarse focusing mechanism are automatic slipping down or inconsistent tightness during lifting and lowering. Automatic slipping down refers to the phenomenon where the tube, arm or stage slowly descends spontaneously under its own weight without any adjustment when it is stationary at a certain position. 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 exceeds the weight of the tube or arm.
For the coarse focusing mechanisms of inclined-tube microscopes and most binocular microscopes, if the arm slips down automatically, grip the anti-slip wheels on the inner side of the coarse focusing knobs with both hands, and tighten them clockwise at the same time to stop slipping. If this method does not work, professional maintenance personnel should be contacted for repair.
Automatic slipping of the microscope tube often leads to a misunderstanding that the meshing between the gear and rack is too loose. Some people will add shims under the rack accordingly. Although this may temporarily stop the tube from slipping, it puts the gear and rack in an abnormal meshing condition. Continuous movement will cause deformation of both the gear and rack. Uneven shimming, in particular, aggravates rack deformation, resulting in uneven meshing: tight in some sections and loose in others. Therefore, this method is not recommended.
In addition, if the coarse focusing mechanism has not been maintained for a long time and the lubricating grease has dried up, uncomfortable resistance or even friction noise between mechanical parts may occur during lifting. In such cases, the mechanical assembly can be disassembled, cleaned, greased and reassembled.
