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Please note that this chapter is in outline form and will be fleshed out later. Use it to guide you through your own research.
Photocopiers and Laser Printer use identical technology except for the way the image is formed. A photocopier uses lenses and is essentially a camera. A laser printer uses a laser to draw an image.
Passes paper over narrow slit in a mask
May use a thin moving mirror to expose optical system to a narrow strip of paper
Exposed paper illuminated by bright light
Lens focuses image onto a grounded metal drum that has a photoconductive coating.
Photoconductive: high resistance in dark, low resistance when exposed to light
Drum rotates at speed to match speed of paper as it is passed by the slit
High voltage on "corona wire" charges drum to high negative voltage
Coating becomes conductive where light hits it
The image focused on the drum is that of the original paper to be copied. The white background discharges the drum in those areas. The black writing, etc., leaves the drum charged in those areas.
Some printers use photoconductive belts instead of drums
Drum passed by hopper of toner
Toner is a fine powder that is a mixture of carbon, powdered iron and low-temperature thermoplastic
Toner may be positively-charged to aid in transfer to the negatively-charged image on the drum
A magnetic drum in the hopper picks up toner and lightly touches it to the drum
Toner sticks to parts of drum that remain charged (where the black writing, etc., focused on the drum).
Fresh paper is passed between drum and positively-charged "transfer corona" wire.
Toner is pulled to paper by transfer corona
Paper is passed between heated rollers (the fuser) to melt the thermoplastic onto the paper
Finished copy passes out of the copier
Drum passes by cleaning station that scrapes off left-over toner and exposes the drum to light to discharge it.
Waste toner is collected in a container that must be emptied or discarded periodically
Works like a photocopier except a laser is scanned across the drum to form the image.
Laser beam is moved by rotating mirrors and focused by complex lens
Some printers use a row of LEDs rather than laser
These may or may not be called LED printers. Some may be called "laser-type" printers
A modern digital copier is actually a scanner and laser printer.
Four drums, one exposed to white light and others are exposed through colored filters so each reacts only to one of the three subtractive primary colors.
Cyan, Magenta, Yellow and Black toners used at appropriate drums.
Special laser printers that use white toner in addition to cyan, magenta and yellow are used in the apparel decorating industry to print on black cloth
Use a special toner vacuum for large toner spills
Vacuuming toner produces a substantial static charge. Vacuuming toner with a standard vacuum can be an unpleasant experience.
The fine toner powder will clog standard vacuums
Wash clothes that get toner on them in cold water
Hot water can melt the toner into globs and cause it to bond with the clothing
Most problems are in the toner cartridge
Most of the printing mechanism (except the fuser) is contained in the toner cartridge. A new toner cartridge fixes most problems
Indicates that drum was charged but not discharged by exposure to an image or laser
Exposure lamp may be out on photocopier
Laser or LED mechanism is not working
Major repair. Refer to trained technician
Dark streaks (may be horizontal or vertical, depending on which way the paper passes through the print mechanism)
Can be caused by dirty corona wire. Always try cleaning the corona wire before getting into major things.
Damaged drum
Dirty fuser
Clean corona wire
Clean fuser
Replace toner cartridge
Dirty corona wire.
Dirt prevents charging as drum passes by corona wire, leaving uncharged streaks on the drum.
Toner sticks to uncharged streaks
Clean corona wire
Remove the toner cartridge and find a pull tab or slider that rubs a pad on the corona wire
Pull and reinsert the tab or move the slider back and forth several times
Some printers may have corona wire external to the toner cartridge. Looks for pull tabs near cartridges
Dirty roller
Dirty or damaged drum
Spacing between smudges and help determine which roller
Clean or replace
(paper has ghost image of previous sheet or sheets)
Bad erase lamp
Previous image not erased
Major repair. Refer to trained technician
http://www.explainthatstuff.com/photocopier.html
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