Epson Ink Maintenance Box which is also commonly identified by the internal part number SJMB5000.
 
The code C33S021291 refers to an Epson Ink Maintenance Box which is also commonly identified by the internal part number SJMB5000.
This is a mandatory, user-replaceable consumable for specific Epson commercial and industrial label printers.
Here is a detailed breakdown of its function and usage:
⚙️ Function and Importance
Waste Ink Collection: Its primary purpose is to collect and contain the "waste ink" that is flushed out of the printer's system. This ink is generated during:
Printhead Cleaning Cycles: Routine or manual cleaning cycles that the printer performs to prevent nozzle clogs and ensure optimal print quality.
Initial Ink Charging: Ink that is flushed through the system when new ink cartridges are installed.
Internal Protection: By safely storing the excess ink, the maintenance box prevents it from leaking onto and damaging the printer's sensitive internal components (like the paper transport system or electronic boards).
Required Consumable: Like an ink cartridge, this box has a finite capacity. Once the absorbent pads inside become full, the printer's internal chip will detect it and alert the user. The printer will stop working until a new maintenance box is installed.