The paper cassette is the foundation of every print job in a Konica Minolta bizhub device. It is far more than a simple box for holding paper—it is a precision electromechanical subsystem that performs three critical functions:
- Lifting — Raising the paper stack to the correct feeding position
- Size detection — Automatically identifying the dimensions of the loaded paper
- Presentation — Positioning the top sheet precisely against the pickup roller
When any of these functions fails, the machine cannot feed paper reliably. Paper jams, misfeeds, size mismatches, and elevator errors all trace back to the cassette mechanics. This article provides a comprehensive guide to understanding, diagnosing, and maintaining the cassette system in Konica Minolta bizhub devices.
1. Cassette Mechanical Overview
1.1 Basic Construction
Every paper cassette consists of several key mechanical elements:
- Cassette body — The plastic housing that slides into the machine
- Paper lifting plate — A movable platform that supports the paper stack
- Paper lifting springs or a motor-driven lift mechanism — Raises the lifting plate
- Paper width guide — Adjustable guide that centers the paper in the crosswise (CD) direction
- Paper length guide — Adjustable stop that positions the paper in the feed (FD) direction
- Pickup roller — The roller that pulls the top sheet from the stack
1.2 Two Primary Lift Mechanisms
Konica Minolta employs two main types of paper lift mechanisms across its product line:
| Mechanism Type | Description | Typical Models |
|---|---|---|
| Spring-loaded | Paper lifting plate is pushed upward by springs at all times; a locking mechanism holds the plate down when the tray is removed | bizhub 162, 200, 250, 350; entry-level models |
| Motor-driven | A lift motor raises the plate via gears, belts, or worm drives; sensors control the lift height | bizhub 367, 423, 500, 600, C360 Series, C4000i; mid-range and high-end models |
2. The Spring-Loaded Lift Mechanism
2.1 Basic Operation
In spring-loaded cassettes, the Paper Lifting Plate is pushed upward by Paper Lifting Springs at all times. When the user pulls the cassette out to load paper, they press the plate down until it locks into position. The plate remains locked while the cassette is outside the machine.
When the cassette is slid back into the machine, a mechanical interlock releases the plate. The springs then push the plate upward, pressing the paper stack against the pickup roller.
2.2 Advantages and Limitations
This mechanism is simple, reliable, and requires no electrical components. However, it provides no active control over the paper stack height. As paper is consumed, the springs continue to push the remaining paper upward, maintaining contact with the pickup roller until the cassette is empty.
3. The Motor-Driven Lift Mechanism
3.1 Drive Configuration
Motor-driven lift mechanisms are found on most mid-range and high-end bizhub models. The specific drive configuration varies by model, but the principles are consistent.
Worm Gear and Belt Drive (bizhub 423)
The driving force of the worm gear mounted on the shaft of the elevate motor drives the lift belt. The tray moves up or down depending on the direction in which the lift belt is driven.
Lift Arm and Lever (bizhub C360/C280/C220 Series)
When the drawer is slid into the main body and the device detection sensor is activated, the lift-up motor starts rotating to raise the paper lifting plate. The lift-up motor rotates a lift arm, which pushes the lifting plate upward.
Lift Wires and Pulley (bizhub 600)
The paper lift motors cause the lift wires to be taken up by the pulley to raise the lift plate. This wire-and-pulley system provides smooth, quiet operation.
Coupling-Based Drive (bizhub C4000i, 367)
The drive shaft of the tray lift-up motor is connected to the paper lift-up lever via a coupling. When the drive shaft rotates, the lever rotates to raise the plate.
3.2 Lift Motor Types
| Motor Designation | Function | Typical Models |
|---|---|---|
| M7 / M8 | Tray 1/2 lift motor | bizhub 200, 250, 350 |
| M6 | Tray 1 lift-up motor | bizhub C4000i |
| M124 / M125 | Tray 3/4 lift motor | bizhub 500 |
| M16 / M17 | Paper lift motors /1 and /2 | bizhub 600 |
3.3 The Lift Control Sequence
The lift control sequence follows a precise logic:
- Tray insertion — When the tray is slid into the machine, the tray set sensor detects that the drawer is in position.
- Upper limit sensor check — The machine determines that the upper limit sensor is unblocked (the paper stack is not at the correct height).
- Lift motor activation — The lift-up motor rotates to raise the paper lifting plate.
- Upper limit reached — When the paper stack is raised to the predetermined height, the upper limit sensor is blocked.
- Motor stops — The lift motor stops, holding the paper stack at the correct feeding position.
- During printing — As paper is consumed during the print cycle and the pickup roller is lowered, the lift motor is energized again until the upper limit sensor is blocked.
3.4 Down Operation
When the tray is pulled out of the machine, the coupling of the lift-up motor and the lift-up plate drive shaft are disconnected from each other. When the driving force is released, the paper lift-up plate starts lowering by its own weight.
In some designs, a damper or shock absorber prevents the plate from dropping rapidly, allowing it to descend slowly and safely.
4. Paper Size Detection
Paper size detection is one of the most sophisticated functions of the cassette system. The machine must know exactly what size paper is loaded to ensure proper image placement and to prevent paper jams.
4.1 The Two-Axis Detection Principle
Paper size is determined by measuring both dimensions of the paper:
- CD (Cross Direction) — Paper width (perpendicular to the feed direction)
- FD (Feed Direction) — Paper length (in the feed direction)
The machine’s CPU determines the paper size based on the combination of the CD and FD readings.
4.2 CD (Width) Detection
The CD size detection mechanism is linked to the paper width guide:
- The user adjusts the paper width guide according to the loaded paper.
- The position of the CD size detection lever changes with the paper width guide.
- When the tray is slid into the machine, the CD size detection lever pushes the CD paper size switches.
- The status of the CD paper size switch is changed through the CD size detection lever that is linked with the paper width guide.
The CD detection uses two transmission-type photosensors on the CD paper size board. The sensors are unblocked or blocked depending on the position of the paper width detection plate that is connected to the paper width guide.
Alternative mechanism (circular plate): Moving the Edge Guide activates or deactivates the two CD Paper Size Sensors through the cutout in the lever.
4.3 FD (Length) Detection
The FD size detection mechanism is linked to the paper length guide:
- The user adjusts the paper length guide according to the loaded paper.
- The position of the FD size detection lever changes with the paper length guide.
- When the tray is slid into the machine, the FD size detection lever pushes the FD paper size switches.
The FD detection uses three or four transmission-type photosensors on the FD paper size board. The sensors are unblocked or blocked depending on the position of the paper length detection plate.
Alternative mechanism (circular plate): When the Trailing Edge Stop of the drawer is moved, the circular plate located on the bottom of the drawer turns, allowing the switches to detect the paper length.
4.4 Slit-Based Detection
A slit is equipped on each size detection lever. If the position of the slits and the paper size switches overlap, the switches are turned OFF without pressing the paper size switch. This allows precise detection of multiple paper sizes using a limited number of switches.
4.5 Size Determination
Paper size is determined with the combination of the CD and FD readings:
| CD Sensors | FD Sensors | Detected Size |
|---|---|---|
| ON/OFF combination 1 | ON/OFF combination 1 | A3 |
| ON/OFF combination 2 | ON/OFF combination 2 | B4 |
| ON/OFF combination 3 | ON/OFF combination 3 | A4S |
| … | … | … |
The exact combinations are model-specific and documented in the service manual.
4.6 Bypass Tray Size Detection
The bypass tray uses a different detection method. The bypass CD paper size sensor detects the standard size paper in the paper width direction. Through the movement of the paper guide, the size detection gear rotates and the bypass CD paper size sensor rotates together.
5. Tray Detection and Sensors
5.1 Tray Set Sensor
The tray set sensor detects that the drawer is slid into position. This sensor must be activated before any paper feed operation can begin.
5.2 Upper Limit Sensor
The upper limit sensor (also called the tray upper position sensor) detects when the paper stack has reached the correct height for feeding. It is typically a transmission-type photosensor:
- Blocked — The paper stack is at the correct height
- Unblocked — The paper stack needs to be raised
The upper limit sensor keeps the specified distance between the upper surface of the paper and the pickup roller.
5.3 Near-Empty Sensor
Some models include a near-empty sensor that detects when the paper supply is running low. This sensor triggers a warning on the control panel before the tray is completely empty.
5.4 Sensor Summary
| Sensor | Function | Typical Designation |
|---|---|---|
| Tray set sensor | Detects tray insertion | PS112, PS121 |
| Upper limit sensor | Detects correct paper stack height | PS6, PS7, PS114, PS123 |
| Near-empty sensor | Detects low paper supply | PS3 |
| CD paper size sensors | Detect paper width | PS118, PS119, PS127, PS128 |
| FD paper size sensors | Detect paper length | PSDB3, PSDB4 |
6. Paper Presentation to the Pickup Roller
6.1 The Pickup Position
The ultimate goal of the lift mechanism is to present the top sheet of paper to the pickup roller at the correct position and pressure. The paper stack pushes up the pickup roller, and the lifting motion stops as soon as the sensor detects the upper limit position.
6.2 Maintaining the Correct Height
As paper is consumed during printing, the sensor becomes unblocked, and the lift motor re-energizes to raise the plate until the sensor is blocked again. This servo-like control ensures that the top sheet is always at the same position relative to the pickup roller, regardless of how much paper remains in the tray.
6.3 Pickup Roller Pressure
The pickup roller is pressed against the paper stack by its own weight or by a spring mechanism. When the tray is inserted and the lift plate raises the paper, the top sheet pushes against the pickup roller, creating the friction needed to pull the sheet from the stack.
7. The Coupling System
7.1 Purpose of the Coupling
The coupling system allows the lift motor to remain in the machine while the cassette is removable. When the cassette is inserted, the coupling engages, connecting the motor’s drive to the lift mechanism. When the cassette is removed, the coupling disengages.
7.2 Coupling Operation
- Tray insertion — The coupling engages, and the motor can drive the lift mechanism.
- Tray removal — The coupling disengages, releasing the lift mechanism so the plate can descend.
7.3 Coupling Failure
If the coupling fails to engage or disengage properly, the following symptoms may occur:
- The lift motor runs but the plate does not rise
- The plate rises but does not stop at the correct height
- The plate does not descend when the tray is removed
- Jam codes C0202, C0204, C0206 (tray elevator failure)
8. Troubleshooting Cassette Issues
8.1 Common Symptoms and Causes
| Symptom | Possible Causes | Diagnostic Steps |
|---|---|---|
| Tray does not lift | Faulty lift motor, broken coupling, failed sensor | Check motor operation in Service Mode; inspect coupling engagement; verify sensor function |
| Tray lifts continuously | Failed upper limit sensor | Check PS6/PS7/PS114/PS123 in Sensor Check |
| Paper size not detected | Misadjusted guides, faulty size sensors | Verify guide adjustment; check CD/FD sensors in Service Mode |
| C0202/C0204/C0206 error | Elevator failure | Check motor, coupling, and sensor connectors |
| Paper does not reach pickup roller | Lift mechanism not raising paper fully | Verify upper limit sensor operation; check mechanical obstructions |
| Tray does not descend when removed | Coupling not disengaging | Inspect coupling for damage or contamination |
8.2 Sensor Check Procedure
To verify sensor operation:
- Enter Service Mode
- Navigate to the Sensor Check screen
- Operate the sensor manually (e.g., block/unblock the upper limit sensor)
- Check the display for correct state changes
8.3 Lift Motor Test
In Service Mode, the lift motor can be tested independently:
- Enter Service Mode
- Navigate to the I/O Check or Load Check screen
- Activate the lift motor manually
- Observe whether the lift plate moves correctly
8.4 Mechanical Inspection
When troubleshooting, always perform a mechanical inspection:
- Remove the cassette and inspect for foreign objects or obstructions
- Check that the lifting plate moves freely
- Inspect the coupling for wear or damage
- Verify that the paper guides move smoothly and lock in position
- Check the lift belt, worm gear, or lift wires for wear or breakage
9. Model-Specific Variations
While the principles described in this article apply broadly across the bizhub product line, specific components and designations vary by model:
| Model Series | Lift Mechanism | Lift Motor | Upper Limit Sensor | Size Detection |
|---|---|---|---|---|
| bizhub 162 | Spring-loaded | N/A | N/A | Lever + sensor |
| bizhub 200/250/350 | Motor-driven | M7/M8 | — | 4 FD + 2 CD sensors |
| bizhub 367/287/227 | Motor-driven (coupling) | — | PS7 | 3 FD + 2 CD switches |
| bizhub 423 | Motor-driven (worm gear + belt) | M15 | PS24 | CD + FD sensors |
| bizhub 500 | Motor-driven | M124/M125 | PS19 | 4 FD switches + 2 CD sensors |
| bizhub 600 | Motor-driven (wires + pulley) | M16/M17 | PS2/PS8 | — |
| bizhub C360/C280/C220 | Motor-driven (lift arm) | — | PS114/PS123 | — |
| bizhub C4000i | Motor-driven (coupling + lever) | M6 | PS7 | — |
Always consult the appropriate service manual for model-specific details.
Conclusion
The paper cassette is a precision subsystem that performs three essential functions: lifting the paper stack, detecting the paper size, and presenting the paper to the pickup roller. Understanding how these functions work is fundamental to diagnosing and resolving paper feed issues.
Key takeaways:
- Two lift mechanisms exist — Spring-loaded (simple, passive) and motor-driven (active, sensor-controlled).
- Motor-driven lift follows a precise sequence — Tray insertion → sensor check → motor activation → upper limit reached → motor stops → re-energized as paper is consumed.
- Size detection uses two axes — CD (width) sensors and FD (length) sensors work together to determine the paper size.
- The coupling system allows the lift motor to remain in the machine while the cassette is removable, engaging when inserted and disengaging when removed.
- Sensor failures are the most common cause of lift problems — The upper limit sensor, tray set sensor, and size detection sensors must all function correctly.
- Regular inspection of the lift mechanism, coupling, and sensors prevents failures and minimizes downtime.
By mastering the cassette mechanics, the field technician can quickly diagnose and resolve the most common paper feed issues, ensuring reliable operation and customer satisfaction.