4 Theory of operation
This chapter presents an overview of the major components of the HP Color LaserJet 3000/3600/3800/
CP3505 Series printers, and includes a detailed discussion of the image-formation system.
●
Engine control system
●
Laser/scanner system
●
Pickup-and-feed-system
●
Image-formation system
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Engine control system
The engine control system coordinates all printer functions and drives the other three systems.
The engine control system contains these components:
●
DC controller
●
High-voltage power-supply PCB
● Low-voltage power unit
Figure 4-1
Engine control system components
Table 4-1 Sequence of operation
Period
WAIT
STBY (Standby period)
INTR (Initial rotation)
PRINT
LSTR (Last rotation)
Duration Purpose Remarks
From the time the power is turned on or the door is closed until the drum-phase adjustment is complete
From end of the WAIT or
LSTR period until either the print command is received from the formatter or the power is turned off
Clears the potential from the drum surface, adjusts the drum phase, and cleans the
ETB
Maintains the printer in readiness for a print command
Detects the toner level, cartridge presence, and environment; completes any required calibration (color registration control and image stability)
The printer enters sleep mode when the formatter sends a sleep command, and performs color registration and the image stability control when the formatter sends those commands
From the time the print command is received until the media is picked up
Prepares the photosensitive drum for printing
From the end of INTR period until the fuser paper delivery sensor detects the trailing edge of paper
Forms the images on the photosensitive drum and transfers the toner image to the print media
Performs image stabilization at a specified print interval or at specified times
From the end of the PRINT period until the delivery motor stops rotating
Moves the printed sheet out of the printer
The printer enters the INTR period as soon as the
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Table 4-1 Sequence of operation (continued)
Period Duration Purpose
Power-on sequence
Figure 4-2
Power-on sequence
Remarks
formatter sends another print command
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Motors, fans, and solenoids
Figure 4-3
Motors, fans, and solenoids
1.
Main fan (FM1)
2.
Fuser drive motor (M1)
3.
Print-cartridge drive motors (M6, M7, M8, M9))
4.
Pickup-and-feed motor (M4)
5.
Developing separation solenoids (SL5014, SL5015)
6.
ETB drive motor (M5)
7.
Developing separation solenoid (SL5011)
8.
Cassette pickup solenoid (SL5012)
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9.
Multipurpose tray pickup solenoid (SL5013)
NOTE:
The following parts are included only on duplexing printer models.
10.
Duplex reverse-drive motor (M11)
11.
Duplex flapper solenoid (SL10)
12.
Duplex-feed-drive motor (M10)
13.
Door fan (duplex models only) (FM2)
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Laser/scanner system
The formatter sends video signals to the DC controller, which controls the laser/scanner. When the laser/ scanner system receives those signals it converts them to latent images on the photosensitive drum.
Figure 4-4
Laser/scanner system
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Pickup-and-feed-system
The pickup and feed system consists of several types of feed rollers and sensors.
The DC controller drives the system by controlling the feed motor (M4), ETB motor (M5), and four drum motors (M6, M7, M8, M9) and the solenoids for the trays. In models that include an automatic duplex accessory, the duplexing feed motor (M10) and reversing motor (M11) are also part of the system.
NOTE:
Tray 2 must be installed in order to print from tray 1 or tray 3.
Figure 4-5
Pickup-and-feed system
DC controller PCA
PCA
Fuser
Fuser
Fuser
PCA
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Sensors in the pickup-and-feed system trays (cassettes)
Paper sensors detect media in the trays. Other sensors react to the media as it moves through the paper path. If the media does not reach or pass each sensor within a specified time period, the DC controller determines that a jam has occurred and alerts the formatter. In models that include an automatic duplex accessory, the paper path contains additional sensors that detect movement through the duplex path.
Figure 4-6
Pickup-and-feed system sensors
SR705
SR706
SR707
SR708
SR709
Fuser pressure-release sensor
Output-bin-full sensor
Multipurpose-tray paper sensor
Multipurpose-tray paper-position sensor (HP Color LaserJet 3000, 3800, and CP3505 Series printers only)
Cassette paper-presence sensor
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SR710
SR714
SR6001
SR6005
SW2
Top-of-page sensor
One-sided paper sensor
Paper-loop sensor
Fuser paper delivery sensor
Cassette-presence switch
Cassette pickup mechanism
When the cassette is correctly installed, SW2 detects its presence. The cassette paper sensor (SR709) detects whether media is present in the cassette, and the cassette media sensor detects the type of media. When the cassette is correctly installed and the correct media type is present, the cassette pickup operation begins.
1.
The DC controller receives a print command from the formatter, and then begins rotating the pickupand-feed motor (M4) at the correct speed for the media type.
2.
After the motor reaches the correct speed and the fuser is at the correct temperature, the cassette pickup solenoid (SL5012) turns on and the cassette pickup roller begins rotating.
3.
The cassette lifting plate lifts the paper stack, and the cassette pickup roller picks up one sheet of media. The separation pad prevents multi-feeds.
Figure 4-7
Cassette pickup mechanism
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Multipurpose-tray pickup mechanism
The cassette must be installed in order for the multipurpose (MP) tray to operate. The MP tray paper sensor (SR707) detects whether media is present in the MP tray. When the cassette is correctly installed and media is present, the MP tray pickup operation begins.
1.
The DC controller receives a print command from the formatter, and then begins rotating the pickupand-feed motor (M4) at the correct speed for the media type.
2.
After the motor reaches the correct speed and the fuser is at the correct temperature, the MP pickup solenoid (SL5013) turns on and the MP pickup roller begins rotating.
3.
The MP pickup roller picks up one sheet of media. The separation pad prevents multi-feeds.
4.
When the media reaches SR708, motor M4 stops, the MP tray media sensor detects the media, and then motor M4 restarts and resumes feeding media into the printer.
Figure 4-8
Multipurpose-tray pickup mechanism
Feed-speed control
To optimize print quality, the pickup-and-feed motor rotates at different speeds depending on the type of media.
NOTE:
In the following table, normal speed is 22 ppm for the HP CLJ 3800 and CP3505 models, and normal speed is 18 ppm for the HP CLJ 3600 models. Normal speed is 30 ppm for the HP CLJ 3000 model (black mode only).
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Media type
Plain
Rough
Thin
Thick
Thicker
Postcard
Thicker postcard
Glossy
Heavy Glossy
Extra Heavy glossy
Envelope
Label
Gloss film
Transparency
HP CLJ 3800 and
CP3505
22 ppm
17.6 to 18 ppm
22 ppm
17.6 to 18 ppm
17.6 to 18 ppm
17.6 to 18 ppm
11 ppm
17.6 to 18 ppm
11 ppm
8.8 to 9 ppm
17.6 to 18 ppm
17.6 to 18 ppm
3.6 ppm
3.6 ppm
HP CLJ 3600
17.6 to 18 ppm
17.6 to 18 ppm
17.6 to 18 ppm
17.6 to 18 ppm
17.6 to 18 ppm
17.6 to 18 ppm
11 ppm
17.6 to 18 ppm
11 ppm
8.8 to 9 ppm
17.6 to 18 ppm
17.6 to 18 ppm
3.6 ppm
3.6 ppm
HP CLJ 3000 (fullcolor mode)
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
HP CLJ 3000
(monochrome mode)
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
30 ppm
15 ppm
30 ppm
15 ppm
15 ppm
15 ppm
15 ppm
15 ppm
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Sensor jam detection
1
4
2
3
1.
Cartridge sensor assembly
2.
Paper and registration sensor covers
3.
Cassette media sensor (HP Color LaserJet 3600, 3800, CP3505 only)
4.
Temperature sensor
5.
Media-sensor assembly (500-sheet feeder)
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The following jams can occur during operation:
● Pick-up delay jam. The printer makes three attempts to pick up media from a tray. When the topof-page sensor (SR710) does not detect the leading edge of a page within a specific time after the third attempt, the printing operation stops. The time varies depending on the printer model and the media source, as follows.
HP CLJ 3000: 1.3 seconds from the cassette; 2.2 seconds from the multipurpose tray (tray 1); 2.3
seconds from the paper feeder
HP CLJ 3600: for black printing, 1.0, 1.5, or 1.6 seconds; for color printing, 1.7, 2.7, or 2.9 seconds
HP CLJ 3800 and CP3505: 1.3 seconds from the cassette; 2.2 seconds from the multipurpose tray
(tray 1); 2.3 seconds from the paper feeder
● Pick-up stationary jam. The printing operation stops when the top-of-page sensor (SR710) does not detect the trailing edge of a page within a specific time after it has detected the leading edge.
HP CLJ 3000: approximately 3.2 seconds
HP CLJ 3600: for black printing in Normal mode, 2.3 seconds; for color printing in Normal mode,
4.6 seconds
HP CLJ 3800 and CP3505: approximately 4.0 seconds
● Delivery delay jam. The printing operation stops when the fuser paper delivery sensor (SR6005) does not detect the leading edge of a page within a specific time after it has detected the leading edge.
HP CLJ 3000: approximately 3.0 seconds (in Normal print mode)
HP CLJ 3600: for black printing in Normal mode, 2.2 seconds; for color printing in Normal mode,
3.8 seconds
HP CLJ 3800 and CP3505: approximately 3.8 seconds (in Normal print mode)
●
Wrapping jam. The printing operation stops when the fuser paper delivery sensor (SR6005) does not detect any media within a specific time. The time varies depending on the length of the media that the top-of-page sensor (SR710) detected.
HP CLJ 3000: approximately 1.9 seconds (in Normal print mode with letter-size media)
HP CLJ 3600: for black printing in Normal mode with letter-size media, 1.3 seconds; for color printing in Normal mode with letter-size media, 2.4 seconds
HP CLJ 3800 and CP3505: approximately 2.4 seconds (in Normal print mode with letter-size media)
●
Delivery stationary jam. The printing operation stops when the fuser paper delivery sensor
(SR6005) continues to detect paper for a specific time after the top-of-page sensor (SR710) detected its presence.
HP CLJ 3000: approximately 3.1 seconds (in Normal print mode)
HP CLJ 3600: for black printing in Normal mode, 2.2 seconds; for color printing, 3.9 seconds
HP CLJ 3800 and CP3505: approximately 3.9 seconds (in Normal print mode)
●
Duplexing pickup delay jam (for models that include an automatic duplex accessory). The printing operation stops when the top-of-page sensor (SR710) does not detect the leading edge of the second side of the paper within a specific time after the duplexing feed motor (M10) started rotating.
Pickup-and-feed-system 59
HP CLJ 3000: approximately 2.0 seconds (in Normal print mode)
HP CLJ 3600: for black printing in Normal mode, 1.4 seconds; for color printing, 2.5 seconds
HP CLJ 3800 and CP3505: approximately 2.5 seconds (in Normal print mode)
●
Residual-paper jam. The printing operation stops when any of the following sensors detects media during the initial sequence period:
Top-of-page sensor (SR710)
Paper-loop sensor (SR6001)
Fuser paper delivery sensor (SR6005)
Duplexing reverse sensor (SR823)
Multipurpose tray (MPT) paper-position sensor (SR708)
● Door-open jam. The printing operation stops when the DC controller detects that a printer door is open.
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Image-formation system
The image-formation system, which forms a toner image on media, consists of several interdependent systems:
●
Electrostatic latent-image-formation
●
Developing
●
Transfer
●
Fuser
●
Drum cleaning
The printer includes four print cartridges that contain the toner used to create the image on the media.
Toner is applied in the following order, using only the colors necessary for a specific image: magenta
(M), cyan (C), yellow (Y), and black (Bk).
Figure 4-9
Image formation system
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Image-formation process
Laser printing requires the interaction of several different technologies including electronics, optics, and electrographics to provide a printed page. Each process functions independently and must be coordinated with the other processes. Image formation consists of the following five processes:
1.
Latent-image formation
2.
Developing
3.
Image transfer
4.
Fusing
5.
Transfer-belt cleaning
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These processes are divided into ten steps, which are shown in
Figure 4-10 Image-formation steps on page 63
and described in the following sections.
Figure 4-10
Image-formation steps
Latent-image formation stage
During the three steps that comprise this stage, a latent image is formed by applying a negative charge to the photosensitive drum. You cannot see this image on the drum.
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Step 1: pre-exposure
The pre-exposure LED hits the photosensitive drum surface and eliminates any residual charge on the surface.
Figure 4-11
Pre-exposure
Step 2: primary charging
A high-voltage dc bias is applied to the primary charging roller, which is made of conductive rubber and is in contact with the drum surface. As the roller moves across the drum, it applies the negative charge to that surface.
Step 3: laser-beam exposure
The laser beam scans the photosensitive drum to neutralize the negative charge on portions of the drum surface. An electrostatic latent image is formed where the negative charge was neutralized.
Figure 4-12
Laser-beam exposure
Developing stage
The developing cylinder comes in contact with the photosensitive drum and deposits toner on the electrostatic latent image.
Step 4: developing
Toner acquires a negative charge as a result of the friction from the developing cylinder rotating against the developing blade. When the negatively charged toner comes in contact with the drum, it adheres to the electrostatic latent image. When the toner is on the drum the image becomes visible.
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Transfer stage
Step 5: media feed
The printer generates electrostatic force to pull a sheet of print media to the ETB. The sheet adheres to the belt and travels between the ETB engaged motor and the attraction roller.
The attraction roller transfer positive dc bias to the media so that the negatively charged toner can be easily transferred from the drum to the sheet.
Figure 4-13
Media feed
Step 6: image transfer
The ETB carries the positively charged media over the photosensitive drum. As it passes between the transfer roller and the drum, the transfer roller applies a positive dc bias to the belt. Negatively charged media attracts negatively charged toner from the drum surface. This process is repeated for each toner color.
Figure 4-14
Image transfer
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Step 7: separation from the drum
The beam strength or stiffness of media combined with the ETB holding force causes the media to separate from the drum. The sheet remains on the ETB and continues to travel through the printer.
Figure 4-15
Separation from the drum
Step 8: separation from the ETB
The elasticity of the print media causes it to separate from the ETB. The static-charge eliminator is not involved during this step.
Fusing stage
Until the fusing stage is complete, the image is not permanently affixed to the print media. The toner can be easily smudged until the heat and pressure of the fusing process fix the image to the sheet.
Step 9: fusing
The printer uses a ceramic heater to accomplish the color-on-demand fusing process. The heater has a low heat capacity, which results in a short warm-up period and yields energy savings.
Figure 4-16
Fusing
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Cleaning stage
Not all of the toner is removed from the photosensitive drum during the transfer stage. During the cleaning stage, the residual, or waste, toner is cleared from the drum surface to prepare the surface for the next latent-image formation.
Step 10: drum cleaning
The cleaning blade scrapes the residual toner off the surface of the photosensitive drum and deposits it in the waste-toner container. The drum is now clear, and is ready for the next image-formation process.
Print cartridge
This printer has four print cartridges: magenta (M), cyan (C), yellow (Y), and black (Bk). Each cartridge holds non-magnetic, single-component toner that is composed of resins in the four colors.
In addition to the toner, each cartridge contains a developing cylinder, toner-feed roller, and stirrer. The developer motor rotates these parts so that each print cartridge can deposit toner to form a visible image on the photosensitive drum.
Figure 4-17
Print cartridge
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The cartridges in this printer include the photosensitive drum, the primary charging roller, and the developing roller. Each cartridge performs these functions:
●
Memory tag control
● Cartridge presence detection
●
Developer roller engagement and disengagement control
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Print-cartridge activation
A memory tag is a nonvolatile memory that is built into the print cartridge. The DC controller reads and writes data that is stored in the memory tag. The DC controller reads data at the following times:
●
When the power is turned on
●
When someone closes the front cover
●
When it receives a command from the formatter
The DC controller writes information at the following times:
●
At a specified interval during printing
●
When it receives a command from the formatter
When the read/write operation fails or the wrong data is read or written, the DC controller determines that an error has occurred and notifies the formatter of a cartridge-memory abnormality. Printing then stops.
Figure 4-18
Print-cartridge activation
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