1. Printers

2. Impact Printers
Dot Matrix
Daisy Wheel

3. InkJet Printers Eject Ink through tiny tubes called jets.
Usually there are four ink wells: Cyan, Magenta, Yellow and Black
Resolution: How close the little dots can be
Speed: pages per minute. B&W usually faster than color

4. Dye Sublimation Printers
AKA thermal dye transfer
Used in high-end applications (photos, publishing, medical)
Continuous tone
Rivals photo lab processing from negative film

5. Laser Printers Electro-photographic Printing
Uses photo-conductive materials to “etch” an image using a laser beam.
Very high quality print and graphics.
Usually black and white.

6. Toner Cartridge Contains Toner!!! Also contains many other parts:
Photosensitive Drum
Primary Corona (Charging Roller)
Developing Cylinder

7. Photosensitive Drum Aluminum cylinder
Coated with photosensitive particles
Cylinder is grounded, particles are not.
Particles are charged.
When laser strikes the photosensitive drum, the charged particles “escape” to the grounded cylinder

8. Erase Lamp Exposes all of the photosensitive drum to light.
Leaves drum electrically neutral (i.e. ground)

9. Primary Corona Very Close but not touching the Photosensitive Drum
Handles extremely high voltage.
Transfers a uniform negative voltage (-600 to Volts) to Photosensitive Drum

10. Toner Toner is plastic covered iron
Toner is charged (via developing cylinder) to about -200 Volts
Toner is uniformly distributed on the developing cylinder (held there by magnetism.
Toner is attracted to photosensitive drum where laser has hit.

11. Laser Printing Large Block

12. Transfer Corona
Charges the paper to attract the toner from the photosensitive drum.
This is usually a very thin wire applying a positive charge to the paper.
Prone to getting dirty.
Must be cleaned
Very fragile. DON’T BREAK!!!!!!

13. Fuser Assembly
Consists of two slippery (Teflon) rollers (sometimes hidden) and a heater.
One roller is heated, presses down on the paper, melts the toner into the paper.

14. Other Parts Turning Gears: moves the paper and rollers
Power Supplies: primary power runs motors, electronics and transfer corona. High voltage Supply for primary corona.
System Board: processor, RAM, ROM, BIOS, Control Circuits
Ozone Filter: eliminates O3
Sensors/Switches: monitors status. Stops Fires

15. Printer Languages
ASCII: American Standard Code for Information Interchange (Text and control)ascii.txt
PostScript: created by Adobe. Printer independent language. Strengths were high resolution graphics and scalable fonts. sigcse97.txt
Printer Control Language: created by HP. Originally for text. PCL6 supports scalable fonts and drawing funtions.

16. Graphical Device Interface
Microsoft print handling component
Uses the CPU (not the printer) to process a print job.
Sends a “Raster” image to the printer.

17. Printer Connections
Parallel Port: Uses special cable to connect 25-pin printer port on computer to 36-pin Centronics port on printer.
USB: Plug and Play???
InfraRed

18. IEEE 1284 Standard Specifies Cable and Electronics configuration.
Centronics Mode: One way 8-bits
Nibble mode: uses status wires to send 4-bit data back to computer
Byte Mode/BiDir: enables half-duplex 8-bit communication
Enhanced Parallel Port: Offloads overhead to parallel port away from CPU.
ECP: uses DMA and data compression (run length encoding)

19. Six Steps of Laser Printing
Cleaning
Charge/Condition
Writing
Developing
Transferring
Fusing
Take place inside toner cartridge
Use components that undergo the most wear

20. Side View

21. Step 1: Cleaning

22. Step 1 Mind-Numbing Detail
Sweeper strip cleans the drum
Remove/swept away by Sweeping blade
Cleaning Blade finishes physical cleaning
Erase lamps remove electrical charge

23. Step 2: Conditioning
Primary Charging Roller conditions drum to contain a Uniform high electrical charge (-600 V)

24. Step 3: Writing
Laser beam discharges a lower charge to only those places where toner is to go

25. Writing Mind-numbing Detail
Uniform charge is discharged only where the laser beam hits (due to photosensitivity)
Mirrors reflect the laser beam onto the Drum
Scanning Mirror directs beam across the page
Main mirror(as wide as the page) reflects beam onto drum through a slit
Focusing lens sharpens the image
Beam detect causes DC controller to step the drum and start a new scan

26. Step 4: Developing
Toner is placed onto the drum where the charge has been reduced

27. Developing Mind-numbing Detail
Charged (~-300V) Toner (resin coated iron) is attracted to the developing cylinder magnetically
Control blade creates even distribution
Charged Toner is pulled off developing cylinder onto drum
Toner is charged by DC bias on Dev.Cyl. The amount of bias controls density

28. Step 5: Transferring
Strong electrical charge draws toner off drum onto paper; takes place outside the cartridge

29. Transfering
As paper is feed to roller a transfer charging roller creates a positive charge
As paper passes by drum, the toner is drawn to the positively charged paper
After paper passes roller the static charge eliminator reduces the charge on the paper and the drum

30. Step 6: Fusing
Heat and pressure fuse toner to paper

31. Fusing Mind-numbing detail
Fusing roller apply heat and pressure.
Toner melts into paper
If temperature exceeds 410 degrees F the fusing system shuts down

32. The End