Lesson 4.1: Print Technologies & Imaging Process
Filament: Size
- 1.75 mm = most popular - 3.0 mm was the original size
Examples of impact printers
- Dot matrix - Daisy wheel
Laser Printer: Electrophotographic Imaging Process
- EP imaging process is by which an EP laser printer forms images on paper 1. Processing 2. Charging 3. Exposing 4. Developing 5. Transferring 6. Fusing 7. Cleaning
Laser printer: laser scanning assembly
- EP photosensitive drum can hold charge if not exposed to light - Laser scanning assembly shines on particular areas of photosensitive drum - discharging the drum - as drum rotates, laser scanning assembly scans the laser across the photosensitive drum exposing image to it
Laser printer: high-voltage power supply
- EP process requires high voltage electricity - high voltage power supply (HPVS) - converts AC current from wall outlet (120V / 60v) into higher voltages - voltages used to energise charging corona and transfer corona
What are the two methods in which ink jet printers spay ink?
- Hewlett-Packard (HP) - Epson
What is NLQ?
- Near Letter Quality - when a letter printed by dot matrix was almost the same as daisy wheel
Filament: Type
- PLA (Polylactic acid) + ABS (acrylonitrile butadiene styrene) is most popular - ABS shrinks as it cools
What are the two materials that can be used in a 3D printer?
- PLASTIC FILAMENT = creates objects - LIQUID RESIN + UV LIGHT
What are thermal printers primarily used for?
- POS (point of sale) terminals - print on thermal paper (waxy), heat sensitive that turns black when heat passes over it
What is a 3D resin printer?
- SLA/DLP (stereolithography/digital light processing printers) use a reservoir of liquid resin combined with UV light that hardens resin to create objects - Print bed is at the top and printed object rise out of liquid resin - SLA/DLP printer can print in finer detail than FDM but are slower
Laser printer: Fusing Assembly
- Toner in EP toner cartridge will stick to paper due to negative static charge - Fuser = uses two rollers that apply pressure and heat to fuse the plastic toner particles to paper - Fuser has 3 main parts = halogen heating lamp, Teflon aluminium fusing roller, and rubber pressure roller - Halogen lamp heats fusing roller to 165 - 200 degrees - as paper passes through, pressure roller pushes paper against fusing roller
What happens at the end of the 3D resin printing process?
- a light source at bottom shine UV light to cure resin - after 3D printing finished - uncured resin is removed with a rinse of isopropyl alcohol
What is an impact printer?
- a printer that makes physical contact with the paper to print an image
Inkjet printer: Duplexing assembly
- allows for printing on both sides of paper - when the first side is printer, givien a few seconds to dry, the duplexing assembly pulls paper back in, flip it to print second side
What is the speed of a daisy wheel printer rated on?
- character per second (cps) they can print
Inkjet printer: interface circuitry
- commonly called a port - makes physical connection to whatever signal is coming from the computer (USB, serial, network, infrared) - connects physical interface to the control circuitry - interface circuitry converts the signals from the interface into data stream the printer uses
Inkjet printer: power circuits
- conductive pathways convert 110v (US) or 220v (Europe) from wall outlet into voltages printer uses (12v or 5v) - accomplished through TRANSFORMER
EP imaging process: Step 1 - Processing
- consists of two parts (1. Receiving the image, 2. Creating the image) - computer send print job to printer which receives it via interface (USB, wireless) - printer needs to create print job - render image one horizontal strip at a time to create image (scan line/ raster line) - Raster Image Processor (RIP) manages raster creation using PostScript (PS) or Printer Control Language (PCL)
EP imaging process: Step 5 - Transferring
- developed image is rotating into position - controller notifies registration rollers that the paper should being to feed through - controller sends a signal to the charging corona wire or roller and tells it to turn on - corona wire/roller acquires a strong positive charge (+600VDC) and applies charge to paper - the paper pulls the toner from the photosensitive drum at the line of contact between the roller and the paper because paper and toner have opposite charges - once the registration rollers move the paper past the corona wire, the static eliminator strip removes all charge from the line of the paper - toner is now held in place by weak electrostatic charges and gravity
Filament: colour
- doesn't matter
EP imaging process: Step 3 - Exposing
- exposes drum to image - laser is turned on and scans drum from side to side, turning on and off depending on info sent from printer controller - wherever laser beam touches, photosensitive drum's charge is reduced (from -600VDC to -100VDC)
Main concepts of a thermal printer
- feed assembly - heating element - heat sensitive thermal paper - store in cool location
Why do thermal printers have long lives?
- few moving parts
Parts of a 3D filament printer
- frame = holds printer together - printer plate/print bed = where object is created - extruder = heats up/melts filament - cooling fan = keeps extruder cool - PCB circuit board = controls movement of extruder assembly - Filament
Laser printer: Ozone Filter
- high voltages create ozone - ozone is a chemically reactive gas created by high voltage coronas inside printer - ozone reduces life of laser printer components - filter needs to be removed and cleaned with compressed air periodically - new printers don't have filters as they use transfer corona rollers (not wires) which reduce ozone emissions
Laser printer: DC power supply
- high voltages used in EP process can't power other compents - logic circuitry and motors require low voltages (+5VDC - +24VDC) - DCPS (DC power supply) converts current into 3 voltages (+5VDC, -5VDC, +24VDC) for paper transport motors
Laser printer: Toner cartridge
- holds the toner - contains EP print drum - which is coated with photosensitive material that can hold static charge when not exposed to light but cannot hold charge when exposed to light - contains cleaning blade - scrapes used toner off the photosensitive drum
What are the chambers inside an ink cartridge?
- ink cartridges contain serval chambers - at top of each chamber there is a metal plate and tube leading to ink supply - at bottom of each chamber is a small pinhole - pinholes are used to spray ink on page to form characters in a pattern of dots
Laser Printer: Printer controller circuitry
- large circuit board that converts signal from computer into signals for various assemblies in laser printer in a process called rasterising - when computer prints to laser printer, it sends signal through a cable to the printer controller assembly - controller assembly formats the information into a page's worth line by line commands for the laser scanner
Laser printer: Transfer corona wire
- laser writes (exposes) image to photosensitive drum, the toner then sticks to exposed areas - transfer corona assembly is given a high voltage charge which is transferred to the paper which pulls toner from photosensitive drum - Transfer corona wire = Charged by HVPS - Transfer corona roller = peforms same function as transfer corona wire but it's a roller - supports higher speeds
Laser Printer: Duplexing Assembly
- located inside or back of printer - it's responsible for taking paper, turning it over and feeding back into printer
What happens to the print head when it's done printing (inkjet printer)?
- moves back to its maintenance station - the station contains a small suction pump and ink-absorbing pad - to keep ink flowing freely, before each print cycle, the maintenance station pulls ink through ink nozzles using vacuum suction - the pad absorbs the expelled ink
Laser printer: Paper Transport Assembly
- moves paper through printer - has motor and several rubberised rollers that perform different functions 1. Feed Roller/Paper pickup roller = D shaped roller that rotates against paper and pushes into printer - has a seperation pad to prevent more than one sheet being fed into printer 2. Registration Roller = two of them which work together - synchronise paper movement with the image-formation process in the EP carriage 3. Electric Stepper Motor = operates both rollers - moves in small increments - powers all paper transport and fuser rollers
What is a daisy wheel printer?
- oldest printer tech - raised letters and symbols on each petal - when it needs to print a character, it sends signal to mechanism (print head) on the wheel - print head rotates the daisy wheel until required character is in place - an electromagnetic hammer (solenoid) then strikes the back of the petal containing the character - character presses up against an inked ribbon that strikes paper
Inkjet printer: paper feed mechanism
- picks up paper from paper drawer and feeds into printer - pickup rollers are small rubber rollers that rub against paper as they rotate and feed paper into printer - the rollers work against small cork or rubber patches (separation pads) which keeps rest of paper in place (so only one sheet goes into printer - pickup rollers turned on a shaft by the pickup stepper motor
Inkjet printer: printer tray
- plastic tray in front of printer that hold paper until it's fed into the printer
Disadvantages of dot-matrix printers
- poor image quality (compared to daisy wheel) - noisy
Disadvantages of daisy wheel printers
- poor speed - noisy - only one font
Inkjet printer: head carriage
- print head carriage is the component of an inkjet that moves back and fourth during printing - contains physical and electronic connections for the print head
Laser printer: Print head/ink cartridge
- print head contains 100 - 200 nozzles that spray ink in small droplets - print head is part of ink cartridge that contains reservoir for ink and print head
How does a dot matrix printer work?
- print head contains row of pins - pins are triggered in patterns that form letters as print head moves across paper - pins in print head wrapper with coils to create a solenoid that are held in a rest position by a magnet to trigger a pin, printer controller sends signal to print head which energises wires that repels the print pin forcing it against the ink ribbon
Advantages of daisy wheel printers
- print on multipart forms (receipts) - inexpensive - print quality easily readable - letter quality (LQ)
Parts of an inkjet printer
- printer head/cartridge - head carriage, belt, and stepper motor - paper feed mechanism - control, interface, power circuitry
What are the two functions of the maintenance station (inkjet printer)?
- provide a place for print head to rest when printer isn't printing - keep printer head working
EP imaging process: Step 7 - Cleaning
- rubber blade inside EP cartridge scrapes any toner left on the drum into a used toner receptacle inside the EP cartridge - a fluorescent lamp discharges any remaining charge on the photosensitive drum
Inkjet printer: cleaning cycle
- set of steps the inkjet printer goes through to purge print heads of any dried ink - uses suction cup to pull ink through print head
Inkjet printer: Print buffer
- small amount of memory (512kb to 16MB) used to store print jobs as received from printing computer - buffer allows several jobs to be printer at once
Inkjet printer: printer control circuits
- small circuit board that contains circuitry for stepper motors, also responsible for monitoring health of printer
How does an inkjet printer work?
- spray ink on the page to form image - use a reservoir of ink, a pump, and nozzle
Inkjet printer: Stepper motor and belt
- stepper motor and belt make the print head carriage move - stepper motor is an electric motor that can move in very small increments each time it's activated - a belt is placed around two small wheels and attached to print head carriage - carriage belt is driven by carriage motor and moves print head back and forth across page while it prints - carriage rests on stabiliser bar to keep it aligned and stable while it traverses the page
EP imaging process: Step 4 - Developing
- surface of drum holds electrical representation of image being printed - toner is transferred to the areas that were exposed (during the exposing step) - metallic roller (developing roller) inside an EP cartridge acquires -600VDC charge (bias voltage) from HPVS - toner sticks to this roller because there is a magnet located inside the roller and because of the electrostatic charges between the toner and developing roller - while the developing roller rotates around the photosensitive drum, toner acquires the charge of the roller (-600VDC_ - when toner comes between developing roller and photosensitive drum, the toner is attracted to the areas that have been exposed by the laser (-100VDC) - toner is repelled by the unexposed areas (-600VDC) - this toner creates a fog of toner between the EP drum and developing roller - the toner is stuck where the laser has written to it - photosensitive drum continues to rotate until developed image is ready to be transferred to paper
Inkjet printer: paper feed sensors
- tell printer when out of paper/paper jams
EP imaging process: Step 2 - Charging
- the charging corona within EP toner cartridge (above photosensitive drum) get high voltage from HVPS - uses voltage to apply strong negative charge (-600VDC) to surface of photosensitive drum
EP imaging process: Step 6 - Fusing
- the registration rollers push paper towards fuser rollers - fuser grabs the paper, the registration rollers push for a short time longer - the fuser is now in control of moving the paper - as paper passes through the fuser, the 350 degree f fuser roller melts the polyester resin of the toner and the pressure roller presses it permanently to the paper - paper continues through the fuser and eventually exits printer
Why are laser printers and inkjet printers referred to as page printers?
- they receive print job instructions one page at a time - rather than receiving instructions one line at a time
Laser printer: EP imaging basic components
- toner cartridge - laser scanner - high-voltage power supply - DC power supply - paper transport assembly (paper-pickup rollers & paper registration rollers) - transfer corona - fusing assembly - printer controller circuitry - ozone filter
Laser printer: Toner
- toner is black carbon substance mixed with polyester resins to make it flow better - contains iron oxide particles making it sensitive to electrical charge - allow toner to be attracted to photosensitive drum and melt into paper - toner contains medium called developer which carries the toner until used by EP process
What is the Epson method of ink spraying?
- uses a piezoelectric element (small rod) that flexes when energised - the outward flex pushes ink from the nozzle - on return sucks more ink from reservoir
What is a thermal transfer printer/thermal wax printer?
- uses heat sensitive ribbon (instead of paper) - thermal print head melts wax-based ink from ribbon onto paper
What is the Hewlett-Packard (HP) ink spraying method?
- when a chamber needs to spray ink, an electric signal is sent to the heating element (energising it) - elements heat up quickly, causing ink to vaporise - ink vapour expands and is pushed out of pinhole and forms a bubble - as ink expands, bubble breaks off to form a droplet - rest of ink is pulled back into chamber by surface tension of the ink
How do you clean pickup rollers?
- with mild soap and water - not alcohol as it can dry out the rollers
Inkjet printing process
1. Click print button to initiate printing process 2. Software sends the data to be printed to a printer driver 3. Printer driver uses a page-description language to convert data into format the printer understands 4. printer driver sends into to printer via USB, netowrk or serial 5. Printer stores data in its onboard buffer memory 6. If printer not been used in a while, printer control circuits active a cleaning cycle 7. Once printer ready to print - control circuitry activates paper feed motor - sheet of paper fed into printer - activates paper feed sensor that stops feed until print head is in right position 8. Once paper is positioned properly - print head stepper motor uses print head belt and carriage to move the print head across page 9. Motor moved small step and print head sprays ink on paper 10. Stepper motor moves print head another small step - process repeats 11. at end of a pass across page - paper feed motor advances the page a small amount - print head repeats step 8 12. Print head returns to beginning of line and prints in again or moves backward across page so printing occurs in both directions 13. Once page finished - feed stepper motor is actuated and ejects page from the printer into the output tray 14. Print head is parked and process finished
The 3D printing process
1. Design object using CAD (AutoCAD) 2. Export file from CADs software - CAD program to slice the object into layers - preparing for printing - exported file will be an STL file 3. Send job to the printer 4. printer performs collaboration and self test - FDM printers, the extruder heats up and calibrate its position on the x-, y-, z-axes
Summary of the EP Imaging Process
1. Printer receives and processes the image and stores a page in memeory 2. Printer places a uniform -600VDC charge on the photosensitive drum by means of a charging corona 3. laser 'paints' an image onto the photosensitive drum, discharging image areas to much lower voltage (-100VDC) 4. developing roller in the toner cartridge has charged (-600VDC) toner stuck to it - as it rolls the toner toward the photosensitive drum, the toner is attracted to (and sticks to) the areas of the photosensitive drum that the laser has discharged 5. the image is transferred from the drum to the paper at its line of contact by the transfer corona wire (or corona roller) with a +600VDC charge - the static-eliminator strip removes the high positive charge from the paper 6. paper enters fuser where a fuser roller and pressure roller make image permanent - paper exits printer 7. printer uses rubber scaper to clean the photosensitive drum
How to identify parts of the inkjet printer?
1. Unplug printer from power source and computer 2. open top cover = exposing inner print mechanism 3. Locate and identify paper tray 4. Locate and identify paper feed sensor 5. Locate and identify pickup rollers 6. Locate and identify pickup pads 7. Locate and identify print head, carriage assembly, belt 8. Locate and identify ink cartridges
Advantages of dot matrix printers
1. Work fine in dusty and dirty environments. 2. Carbon copies can be produced with carbonated paper. 3. Very cheap to buy and maintain. 4. Good for continuous printing.
What does CMYK mean?
Cyan, Magenta, Yellow, Black
What would happen if the photosensitive drum wasn't cleaned?
Ghost images of previous pages
What is a thermal printer?
generates images by pushing electrically heated pins against the heat-sensitive paper
