Printers & MFDs Flashcards
Impact Printers (General)
Printers that create an image on paper by physically striking an ink ribbon against the paper’s surface.
Daisy-Wheel Printers
An electric typewriter attached to the computer instead of directly to a keyboard (have largely disappeared)
Dot-Matrix Printers
Printing process in which ink is applied to a surface using a relatively low-resolution dot matrix for layout
Able to print arbitrary patterns (not just specific characters)
Use a grid/matrix of tiny pins (aka: printwires) to strike an inked printer ribbon and produce images on paper.
Printhead: Case that holds the printwires
BIOS in printer interprets the raster image the same way a monitor does
Reasons for Dot-Matrix Use
Dot-matrix printers have a large installed base in business, and can be used for multipart forms because they actually strike paper.
Can print receipts/docs in duplicate, triplicate, or more.
POS machines represent major market for impact printers
Tractor-Feed Paper (Impact)
Dot matrix uses continuous-feed paper with holes on its sides that are engaged by metal sprockets to pull the paper through.
Duplex Assemblies
Enable the printer to automatically print on both sides of the paper.
Inkjet Printers (Ink-Dispersion Printers)
Uses a printhead connected to a carriage that contains the ink.
A belt & motor move the carriage back and forth so the ink can cover the whole page.
Roller grabs paper from a paper tray/feeder and advances it through the printer.
Ink is ejected through tiny tubes (most use heat to move ink, some mechanical)
Inkjet (Heat Method)
Uses tiny resistors or electroconductive plates at the end of each tube that literally boil the ink.
Creates a tiny air bubble that ejects a droplet of ink onto the paper.
Print Resolution
How densely the printer lays down ink on the page.
Measured in DPI (dots per inch)
Higher DPI = Higher quality
Print Speed
Measured in PPM (pages per minute)
Inkjet Maintenance:
Calibrate, Clean Heads, Replace Cartridges, Calibrate, Clear Jams
When first setting up, printer will instruct you to perform a routine (calibration) to align printheads properly. Printer will print a test page.
Cartridges simply slide into place, but printer may have clips to lock them in.
Ink inside printhead nozzles can dry out, blocking the ink. Inkjets have head-cleaning maintenance programs (either on printer itself or in Windows)
Humidity can cause paper to cling together. Sometimes overheated printer can do so as well.
Give the printer a break and fan the sheets of paper before inserting into the tray.
Impact Maintenance:
Replace Ribbon, Replace Print Head, Replace Paper
Keep the platen and the printhead clean with denatured alcohol.
Lubricate the gears & pulleys according to manufacturer specifications.
Replace ribbon every so often.
Finish feeding the rest of the current paper roll. Swap out old roll with new paper roll and feed the new roll according to manufacturer specifications.
Thermal Maintenance:
Replace Paper, Clean Heating Element, Remove Debris
Heating Element: Turn off printer & open it according to manufacturer instructions. Use denatured alcohol and a lint-free cloth to wipe off the heating element.
Clean rollers with cloth/compressed air to remove debris so they can properly grip paper.
Swap paper roll out with new one and feed through the heating element.
Laser Maintenance:
Replace Toner, Apply Maintenance Kit, Calibrate, Clean
Clean printer every time you replace the toner cartridge.
Use compressed air to remove paper dander and excess toner from the printer (preferably outdoors). If indoors, use a toner vac (low static vacuum).
Clean guide rollers with denatured alcohol & fibrous cleaning towel.
Many manufacturers provide maintenance kits that come with replacement parts (fuser, rollers, pads). Reset page counter after installation.
Some ozone filters can be vacuumed, some require replacement. Fuser assembly, transfer corona & paper guides can be cleaned with denatured alcohol.
Check heat rollers for damage, if scratched, replace the fuser unit. (Most will give error code)
Check printer manual for registration & color calibration methods. Some will do this automatically.
Apple: Bonjour Print Service & AirPrint
Bonjour provides a general method to discover services on a LAN. It locates devices such as printers & other computers, and the services those devices offer.
AirPrint is a feature of macOS that allows printing via WLAN either directly to AirPrint compatible computers, or non-compatible shared printers on Windows/Linux.
Thermal Printers (General)
Use a heated printhead to create a high-quality image on special/plain paper.
Direct Thermal
Use a heating element to burn dots into the surface of special heat-sensitive thermal paper.
Many retail stores use this for receipt paper.
Use large rolls of thermal paper housed in a feed assembly that automatically draws paper past the heating element.
Thermal Wax Transfer
Uses film coated with colored wax (ribbon roll)
Thermal printhead passes over the ribbon & melts the wax onto paper
Don’t require special papers like dye-sublimation (more flexible/cheaper)
Laser Printers (General)
Laser printers use electro-photographic imaging to produce high-quality & high-speed output of both text & graphics.
They rely on photoconductive properties of certain organic compounds. Most use lasers as the light source (some lower-end use LED arrays).
Photoconductive (Definition)
Particles of compounds that, when exposed to light, will conduct electricity.
Laser Printers: Imaging Drum
An aluminum cylinder coated with particles of photosensitive compounds.
The drum itself is grounded to the PSU (coating isn’t).
When light hits the particles, whatever electrical charge they have “drains” out through the grounded cylinder.
Laser Printers: Erase Lamp
The erase lamp exposes the entire surface of the imaging drum to light, making the photosensitive coating conductive.
Any electrical charge present in the particles bleeds away into the grounded drum, leaving surface particles electrically neutral.
Laser Printers: Primary Corona/Charge Roller
When charged with an extremely high voltage, an electric field (corona) forms, enabling voltage to pass to the drum & charge the photosensitive particles on its surface.
Primary grid regulates the transfer of voltage, ensuring the surface of the drum receives a uniform negative voltage between 600-1000V.
Laser Printers: Laser
Acts as the writing mechanism of the printer.
Any particle on the drum struck by the laser becomes conductive & its charge is drained away into the grounded core of the drum.
Drum surface has negative charge between 600-1000V following its charging by the primary corona.
When particles are struck by the laser, they are discharged & left with a -100V charge.
Laser Printers: Toner
Fine powder made up of plastic particles bonded to pigment particles.
Toner cylinder charges the toner with negative 200-500V.
Falls between negative charge of photosensitive drum (600-1000V) & charge of particles on drums surface hit by laser (-100V).
Particles of toner are attracted to the areas of the drum hit by the laser.
Laser Printers: Transfer Corona/Transfer Roller
To transfer from drum to paper, paper must be given a charge that will attract particles off of drum & onto paper.
Transfer corona/transfer roller applies a positive charge to the paper, drawing the negatively charged toner particles to the paper.
Static charge eliminator removes the charge from the paper in order to prevent it from wrapping around the drum.
Laser Printers: Fuser Assembly
Toner must be melted to the paper to make the image permanent.
Two rollers used to fuse toner to paper:
Pressure Roller: Presses against bottom of page
Heated Roller: Presses down on top of page, heating it
(Nonstick coating [Teflon] to prevent toner from sticking)
Laser Printers: Power Supply
The corona requires extremely high voltage from the power supply, making a laser printer’s power supply one of the most dangerous devices in computing.
Laser Printers: Pickup Roller
Grabs the paper and passes it over to the separation pad.
Laser Printers: Separation Pad
Uses friction to separate a single sheet from any others that were picked up.
Duplexing Assembly
A duplexing assembly is used for reversing the paper, allowing printing on both sides.
Ozone Filter
Coronas generate ozone (O3).
It isn’t harmful to humans, but to printer components.
The ozone filter: filters out ozone to prevent damage to components.
3D Printers
Use melted material to create prints of 3D objects.
Most use plastic filament on spools.
Build in tiny layers/slices one by one.
Virtual Printers
System goes through all the steps to prepare a document for printing and then sends off to to the virtual printer.
Print to File: produces a file that can later be printed without access to the program that created it (legacy option; not common anymore)
Print to PDF
Print to XPS
Print to Image (BMP, GIF, JPG, PNG, TIFF)
Printer Languages
ASCII: Basic language (alphabet, other symbols)
PostScript (Adobe): Defines the page as a single raster image & makes files very portable.
PCL (HP Printer Command Language:
Commands expanded from ASCII; scalable fonts; line-drawing commands
GDI (Graphical Device Interface):
Handles print functions (OS component); Uses CPU to process print job;
TrueType Text: Printer sees as a picture
XPS (XML Paper Specification):
Several improvements from GDI (enhanced color management & better print layout fidelity)
Scanners
Flatbed Scanners:
Place a photo/object face down on glass, close lid, & use software to initiate scan.
Runs a bright light along the length of the platen 1+ times to capture the image.
Can use image-editing software to choose & acquire from scanner.
Ex: GIMP
OCR
Optical Character Recognition:
A way to scan a document and have the computer turn the picture into text that you can manipulate.
Scanner Variables
Resolution (DPI): Modern Recommendation = 2400 x 2400 DPI or better
Color Depth: Defines the number of bits of info the scanner can use to describe each individual pixel (color/shade/hue/etc)
Each bit doubles the color detail.
Common: 24 & 48-bit
Grayscale Depth: Defines how many shades of gray the scanner can save per pixel.
Common: 8, 12, & 16-bit
Scanning Speed: Higher DPI, higher color depth = longer scan time
ADF
Automatic Document Feeder:
Used to grab pages to copy/scan/fax.
Typically on top of the MFD & you place a stack of pages in the tray.
Depending on the machine, face up or face down.
Laser Imaging Process: 7 Steps
Processing Charging Exposing Developing Transferring Fusing Cleaning
Print Resolution (Laser Printers)
2400 x 2400 DPI
First number: Horizontal; determined by how fine a focus can be achieved by the laser
Second number: determined by smallest increment by which the drum can be turned
RET
Resolution Enhancement Technology:
Enables the printer to insert smaller dots among the characters, smoothing out the jagged curves that are typical of printers that do not use RET.
Enables laser printers to output high-quality jobs.
Requires a portion of printer’s RAM
(Disabling RET can help avoid mem overflow errors)
Print Spooler
Enables one to queue up multiple print jobs that the printer will handle sequentially.
Laser Imaging Process: Processing
CPU processes print request & sends print job to print spooler.
OS sends job to printer (first potential bottleneck)
Printer receives print job
Printer hardware takes over & processes image (second potential bottleneck)
Printer generates raster image of the page (pattern of dots), representing the final product.
Uses laser imaging unit to “paint” a raster image on the photosensitive drum. (Paints entire surface of drum; one page at a time)
RIP
Raster Image Processor:
Translates raster image into commands to the laser.
Takes digital font/graphic info & converts it to a rasterized image made up of dots that can be printed.
Stores data in RAM.
Laser Imaging Process: Charging
To make the drum receptive to new images, it must be charged.
Using the primary corona wire, a uniform negative charge is applied to the entire drum surface.
Charge = (Negative) 600-1000V
Laser Imaging Process: Exposing
A laser is used to create a positive image on the surface of the drum.
Every particle on the drum hit by the laser releases most of its negative charge into the drum.
Laser Imaging Process: Developing
Those particles with lesser negative charge are positively charged relative to the toner particles and attract them, creating a developed image.
Laser Imaging Process: Transferring
The printer must transfer the image from the drum onto the paper.
Transfer corona/roller gives the paper a positive charge.
Negatively charged toner particles leap from the drum to the paper.
Particles are resting on the paper & must be permanently fused to the paper.
Laser Imaging Process: Fusing
Because toner particles are mostly plastic, they can be melted to the page.
Heated roller (w/nonstick coating) & pressure roller melt the toner to the paper & permanently affix it.
Static charge eliminator removes the paper’s positive charge.
Printer ejects the printed copy & starts again with the next page.
Laser Imaging Process: Cleaning
Printing process ends with the physical & electrical cleaning of the photosensitive drum.
Residual toner from previous page must be removed. Surface of drum is scraped with a rubber cleaning blade.
Cleaning mechanism either deposits residue in debris cavity or recycles it.
1+ erase lamps bombard the drum surface with the appropriate light, causing the surface particles to discharge into the grounded drum.
Print Settings: Layout
Duplex: Double-sided printing Orientation: Landscape/portrait Multiple page: multiple docs on one page Scaling: fitting a larger doc on one page Reverse/invert: print mirror image
Print Settings: Paper
Paper size
Paper type (thickness, coating, format)
Paper source: select any available paper trays or manual feed
Print Settings: Quality
Resolution
Mode/quality Preset
Ink reduction
Print Settings: Other
Watermark
Header/footer
Collate: specify the order in which multiple copies of a multi-page document are printed
(Default: prints all copies of each page at a time)
Calibration (Definition)
General term for manual/automatic process that corrects differences between how a device/component currently works & how it should work.
Color Calibration (Printers/Monitors)
Uses hardware to generate an ICC color profile.
(A file that defines color characteristics of a device)
OS uses profile to correct any color shifts in your monitor.
When printer & monitor are correctly calibrated with profiles installed, your prints & monitor display should match.
ICC & WCS
International Color Consortium:
A color management system designed to help match color between applications, operating systems, and display media (printers/monitors)
Windows Color System:
Helps to build color profiles for use across devices.
MFDs: Data Privacy
A lot of MFDs in professional/personal environments have sensitive data being printed, which can be a target.
It’s important to make sure this info isn’t leaking out.
It’s common for modern devices to contain storage media used to cache copies of documents that are printed/scanned/faxed/copied.
Schedule regular deletion of cache or manually clear it.
Risks can be limited by requiring authentication to access cache.
