Microtomes cut preserved human, animal or plant tissue specimens that have been processed into extremely thin sections for study under a microscope. A rotary-action microtome is equipped with:
- A specimen holder.
- A segment arc that positions the specimen for sectioning.
- A knife carrier that cuts specimens in a thickness range of 0.5 to 100 micrometers (microns).
- A trimming block for cutting specimens in a thickness range of 5 to 500 micrometers (microns).
- A section waste tray for collection of waste after sectioning.
- An operating panel.
- A large field magnifier or backlighting system (can be added).
The operator places the specimen holder in the segment arc and adjusts the knife carrier to the proper angle before making the cut. Microtomes can be manual, semi-automated (with a manual hand wheel and motorized feed), or fully automated. For the operator’s safety, the microtome is equipped with two features that stop the knife to prevent injury: an electro-mechanical handwheel brake and a handwheel handle.
Common microtome problems:
- Microtome cuts too thick or too thin. This could cause a misdiagnosis depending on the slide reader. A cut that’s too thin could also cause the tissue to fall apart and not adhere to the slide.
- Poor sectioning. This could cause a misdiagnosis depending on the slide reader.
- Excessive chatter/noise. This will cause a nuisance, but it could mean that something is loose and result in poor sectioning.
- The hand wheel, manual or semi-automatic microtome is difficult to turn. This could lead to repetitive-stress injury to the operator.
- The brake doesn’t work. This will cause the machine to keep running and the potential of a severe cutting injury to the operator.
- The knife holder doesn’t clamp. This will cause imprecise cuts and lead to poor sectioning, as well as a potential misdiagnosis.
- The knife holder won’t lock. This will cause imprecise cuts and lead to poor sectioning, as well as a potential misdiagnosis.
- The specimen head is loose. This will cause imprecise cuts and lead to poor sectioning, as well as a potential misdiagnosis.
- A motor doesn’t turn. This will prevent the microtome from advancing and retracting or cutting, depending on the motor.
- The advance motor doesn’t advance. This will cause imprecise cuts and lead to poor sectioning, as well as a potential misdiagnosis.
- No power to the microtome. This will cause the instrument not to operate properly or at all.
- Foot pedal (on manual microtomes) doesn’t work. This will cause a malfunction during sectioning or the instrument might not operate.
In the case of error codes on the tissue processor control panel display, please refer to the product user manual. Different manufacturers use different codes and have different troubleshooting steps. In the case of a loss of power, remember to check circuit breakers or fuses.
When a Tech One technician is needed to make repairs, he will diagnose the problem and make appropriate repairs. The typical service call is one to three hours. However, because a microtome requires precision, service calls might take longer than expected to make sure the instrument is aligned properly after a repair.
Microtome maintenance tips:
- Clean all components daily – particularly the knife holder and specimen holder.
- Make sure that anything requiring locking down is locked down properly.
- Call a Tech One technician for assistance.
Microtomes makes & models Tech One repairs:
- Leica Biosystems: RM2025, RM2030, RM2125, RM2135, RM2145, RM2155, RM2165, RM2235, RM2245, RM2255, RM2265
- Microm: HM 200, HM 310, HM 315, HM 325, HM 340 E, HM 355, HM 355 S
- Reichert-Jung: Biocut 2030, Biocut 2035, RM2135, Histocut 820, Histocut 820-II
- Sakura: Accu-Cut SRM 200
- TBS: Olympus Cut 4060RE
- Thermo Scientific / Shandon: AS325, Finesse 325, Finesse ME
- Knife types: Microtome knives can be made of steel, glass or diamond, depending on the desired thickness of the specimen section.
- Retraction: To protect the knife and the specimen, the microtome retracts the knife carrier at the end of each cut. If desired, this function can be turned off.
- Precision tachogenerator: This guarantees an extremely fast adjustment to section variations in a microtome and a constant cutting speed over the entire cutting stroke. It also ensures optimal section quality in each field of application.
- Operating panel: Fully automated microtomes will show the selected section thickness, trimming thickness, section counter, sum of section thicknesses, remaining travel to the front end position, speed of the coarse feed and the speed of the cutting movement on the display.