Inkjet printer

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Contents

Executive Summary

We are dedicating our effort on improving the functionality of a typical Inkjet Printer in this project, As of Febuary 12th, 2007, we have completed the product analysis (shown below) at a depth that we consider as sufficient to properly enter the actual designing stage. Because of the complexity of the product, the analysis below only involves the components we consider most relevant to our design ideas/goals. For additional/complete information, please check howstuffworks.com or other web sources.

Based on our analysis, we have also come to the conclusion that the components of a typical printer have been optimized not only in their functions but their manufacturing/assembly methods. Although the FMEA yields oppotunities for improvement on several components of the printer, those problems could have been addressed efficiently through proper usage and care of the unit. Therefore, we are suggesting to focus the design effort on improving the overall functionality of the printer instead of specific components.

The list of parts under Modification will be directly affected by the additional functionality we are currently planning to design. Other than Part 4, all the parts have to be either re-positioned or modified to generate the required space for additional components resulting from the next stage of design. For example, we might have to cut a hole/slot in Part 5 and attach an additional tray to it for CD/other hard materials' input. Vertical space is the most obvious issue as of now, and we will address these areas as we progress this project to the next stage. Finally, we will also look into ink cartridge situation to see if significant improvement can be achieved.

Inkjet_Printer_Design_Report2_Spring_2007

Inkjet_Printer_temp

Inkjet_Printer_Notes_Spring_2007

Product Study

We have identified five categories for the product study. This product study is served as initiation of our thought process and representation of our point of view in approaching the design. The primary goal of the study is to identify oppotunities in generating unconventional and advanced usage of a typical printer through design improvements.


Function
1. To print images in color or black&white or gray-scale on certain sizes of paper
2. To print images on a variety types of paper that have a certain softness level

Inputs/Outputs
Input
1. Paper
2. CPU data
3. Ink
4. Energy


Output
1. Printed paper

Functional Operation
1. Place Printer on a flat surface
2. Plug in Parallel (or USB) port to CPU
3. Plug in Power Cord to outlet
4. Install Printer Drivers
5. Insert Ink
6. Insert material to be printed
7. Upload Image desired from CPU to Printer
8. Remove Printer Image (End Product)

Different Users
1. Someone inexperienced with computers.
2. People who want to print images on special materials that are not bendable.
3. Physically Disabled/Elderly.

Other Stakeholders
1. Printer/Paper/Ink/Others Manufacturer
2. Providers of Raw Materials
3. Retail Stores
4. Transportation workers

Component List 1: Primary List

In the following list, we have identified all the components existed in a regular injet printer through two formats- "specific compnent" and "assembly". The next two sections will identify crucial sub-assemblies and provide a brief analysis for each.

Part # Part Name QTY Function Materials Dimensions(*inch) Manufacturing Process Picture
1 Lid 1 Prevents dust; allows ink replacement & paper adjustment Plastic 8x3x1 Injection Molding
2 Paper Tray 1 1 Holds pre-printed paper in straight position Plastic n/a Injection Molding/Assembly
3 Paper Tray 2 1 Holds printed paper Plastic n/a Injection Molding/Assembly
4 Input Buttons 1 set Lets users input basic operation commands Plastic/Others n/a Injection Molding/Assembly
5 Rear Cover Assembly 1 The 6 rollers located on the cover assist the paper movement in side of the printer Plastic/Others 8x2x1.5 Injection Molding/Assembly
6 Upper Paper Supporter 1 Holds the printing paper in vertical direction Plastic 7x2x1 Injection Molding/Assembly
7 Middle Paper Supporter 1 Provides constant upward forces to the printing paper Plastic 7x2x1 Injection Molding/Assembly
8 Front Paper Roller Set 1 Rolls the paper out of the roller/supporter assembly Plastic/Others n/a Molding/Assembly
9 Springs set 1 set Acts as an simple shock absorber for the interior supporter Metal n/a *Spinning
10 Rear Upper Plate 1 Serves as the provider of opposite force on the Springs against the interior paper supporter; allows wirings to be attached Metal 7x2x.5 Stamping
11 Paper Feed Sensor 1 senses the paper right before being printed Plastic/Others n/a Molding/Assembly
12 Rear Paper Roller Assembly 1 Rolls the paper into the first stage of printing process Plastic/Metal n/a Molding/Extruding/Assembly
13 Lid Sensor 1 Senses the opening/closing of the lid to trigger the movement of other interior components such as the ink cartridge Plastic/Others n/a Molding/Assembly
14 Main Bracket 1 Holds major components in place, including the brackets holding the motor and rear supporters Metal/Alum n/a Stamping
15 Primary Chip Board 1 set Responsible for the input/output/power signals Plastic/Others n/a Others
16 Power Supply 1 set Converts the voltage supplied by the power supply input from AC to DC Plastics/Others n/a Assembly/Others
17 Inkjet Cleaner Unit 1 Keeps the head of the inkjet cartridge clean in between the operations to prevent the hardening of ink and jamming of the cartridge Plastic/Others 4x2x2 Molding/Assembly
18 Inkjet Catridge Craddle 2 Holds the Inkjet Cartridge and transports it during the printing process Plastic/Assembly 2x1x2 Molding/Assembly
19 Paper Roller Encoder Gear 1 set Sends information to an encoder so that the printer knows how far the paper has traveled inside the printer Plastic/Metals/Others n/a Molding/Assembly
20 Paper Roller Motor 1 set Supplier the mechanical energy to the paper rollers so that can move Metals/Others n/a Casting/Others
21 Inkjet Cartridge Craddle Motor 1 set Supplies mechanical energy to the Inkjet Cartridge Craddle so that it can move Metals/Others n/a Casting/Others

Component List 2: Sub-Assembly Analysis of the Main Gears *Part 19, 20, etc.

This sub-assembly is the set of gears that turns both the main and paper-pickup rollers. It also engages or disengages both the paper ejector mechanism and the paper loading mechanism. It is quite a complicated system, but is also quite ingenious. The picture below gives a breakdown of the different sets of gears and how they are connected. Much of this sub-assembly is left intact because of both the complexity of the overall project, but also because some of the parts would be destroyed in the process of taking them apart.

Description of power transmission:

  1. The axle (axle1) labeled main rollers/encoder motor is the source of power for this sub-assembly. It is also the same axle that the main rollers are on. The power is derived from the encoder-motor sub-assembly. The encoder-motor assembly turns a gear on this axle (not shown in diagram) which also has an incremental encoder on it which gives feedback on how far/fast the rollers have turned.
  2. The gear (gear1) shown in the diagram which is attached to axle1 is what directs power to both the paper-pickup rollers and the paper-feed-lever/paper-ejector-mechanism.
    1. The medium sized gear (gear2) just to the left of gear1 is what directs power to the paper-pickup roller assembly as well as to the small gear (gear3) to the left of gear2.
      1. Gear3 is used when the current print job is done and the printed paper needs to be ejected and a new piece needs to be picked up. When the print-cartridge carriage moves directly above the gearbox (as labeled in the diagram) a lever pushes the gearbox so that gear3 engages the gear (gear4) with a cam on it. This gear then turns allowing the paper-feed-lever to rise and load paper into the paper-pickup rollers. At the same time a lever (labeled [4] in the diagram) attached to the paper ejector mechanism is pushed, ejecting the printed paper. When a new piece of paper is loaded, the printer-cartridge carriage moves away from the gearbox, disengaging gear3.
    2. The other medium sized gear (gear5), below gear1, now transfers power to the smaller gear (gear6) below it.
      1. Gear6, by default, is now engaging gear4. Now gear4 turns again returning the ejector mechanism to its resting position and dropping the paper-feed-lever back down. When everything is back in place gear6 reaches the bare spot on gear4 and stops turning it. Since gear6 can now freewheel, the printer is free to move the rollers in order to get the printheads into place.

Component List 3: Sub-Assembly Analysis of Paper Roller Encoder System, *Part 19

Updated as of March 8th 2007:

After further research we determined that the encoder for the rollers is a rotational incremental optical encoder.

The way this type of encoder works is that there is a light-source, an LED in this case, a clear plastic disk and a photodetector.

The LED shines a light through the clear plastic disk which has two tracks drawn on it.

As the light passes through the disk the encoder circuit can determine how much the encoder gear has turned. The tracks are offset by 90 degrees to so that the encoder circuit can determine the direction of rotation based on which track leads the other.

Subassembly analysis of paper roller encoder system: The subassembly consists of three main components that act as a feedback control system:

1- The encoder circuit

2- The driving motor

3- The encoder gear


1- The Encoder Circuit This circuit is responsible for sending information the to the main printer circuit board. The circuit board sends information about many degrees did the paper roller turn. With this information the main circuit board can keep track of where the sheet of paper is inside the printer. The Encoder Circuit determines this information by using an infrared laser that monitors the movement of the encoder gear.

2- Encoder Gear This gear is directly attached to the Paper Rollers. There is a plastic disc with several small black lines along its circumference. The purpose of the black lines is provide a reference for the infrared laser. As the encoder gear moves the black lines are seen by the infrared laser to as a series of ones and zeros or black line and no black lines. By counting the number of black lines that were crossed the encoder can determine the number of degrees that the encoder gear turned. Using this and by knowing the size of the gears the main circuit board can determine the distance that the sheet of paper has traveled in the printer.

3- Driving Motor The driving motor is the final part of the feedback control system. The motor receives signals from the Encoder Circuit that tells it when to start moving and stop moving. The motor is also geared up to provide additional torque for moving the paper.

Component List 4: Function Flow

Below is the process taken place once printing action initiates

The software application you are using sends the data to be printed to the printer driver.

The driver translates the data into a format that the printer can understand and checks to see that the printer is online and available to print.

The data is sent by the driver from the computer to the printer via the connection interface (parallel, USB, etc.).

The printer receives the data from the computer. It stores a certain amount of data in a buffer. The buffer can range from 512 KB random access memory (RAM) to 16 MB RAM, depending on the model. Buffers are useful because they allow the computer to finish with the printing process quickly, instead of having to wait for the actual page to print. A large buffer can hold a complex document or several basic documents.

If the printer has been idle for a period of time, it will normally go through a short clean cycle to make sure that the print head(s) are clean. Once the clean cycle is complete, the printer is ready to begin printing.

The control circuitry activates the paper feed stepper motor. This engages the rollers, which feed a sheet of paper from the paper tray/feeder into the printer. A small trigger mechanism in the tray/feeder is depressed when there is paper in the tray or feeder. If the trigger is not depressed, the printer lights up the "Out of Paper" LED and sends an alert to the computer.

Once the paper is fed into the printer and positioned at the start of the page, the print head stepper motor uses the belt to move the print head assembly across the page. The motor pauses for the merest fraction of a second each time that the print head sprays dots of ink on the page and then moves a tiny bit before stopping again. This stepping happens so fast that it seems like a continuous motion.

Multiple dots are made at each stop. It sprays the CMYK colors in precise amounts to make any other color imaginable.

At the end of each complete pass, the paper feed stepper motor advances the paper a fraction of an inch. Depending on the inkjet model, the print head is reset to the beginning side of the page, or, in most cases, simply reverses direction and begins to move back across the page as it prints.

This process continues until the page is printed. The time it takes to print a page can vary widely from printer to printer. It will also vary based on the complexity of the page and size of any images on the page. For example, a printer may be able to print 16 pages per minute (PPM) of black text but take a couple of minutes to print one, full-color, page-sized image.

Once the printing is complete, the print head is parked. The paper feed stepper motor spins the rollers to finish pushing the completed page into the output tray. Most printers today use inks that are very fast-drying, so that you can immediately pick up the sheet without smudging it.

Design Considerations

We have identified six aspects for design considerations in order to locate any design oppotunities. Throughout the analysis, it is evident that the manufacturing aspet of the product has been optimized while the only clear design oppotunity lies in the environmental aspet of the design. The initial conclusion is to focus the approach on improving either the efficiency of power and ink usage or on looking to add functionality to the product according to the result of the product study.

Design for Assembly

  • Visible and hidden screws are presented in many areas among the brackets/chip-circuit board/etc to secure every major parts onto the base
  • Brackets/major assemblies are positioned in a way that they have to be put on/off together
  • Many of the parts are designed with an interlock which is held in place by one screw. This reduces the number of screws and bolts which makes assembly much simpler and inexpensive.
  • Almost all of the plastic parts, from the lid to the gears, have snaps that allow them to be easily attached to the main body.

Design for Disassembly

  • Primary bracket has to be loosen before any other major components can be disassemble/removed from the base
  • Difficult to assemble the pieces back to the original state once disassembled
  • Great amount of sub-assemblies present throughout the unit
  • Many of the plastic snap pieces are not easy to remove once they are in place. Many of the clips are on the inside or out of sight, making it much tougher to see and release them.

Design for Environment

  • Plastics are not biodegradable
  • Ink and Power usage by the users
  • The overall reliability of the product is good enough for the unit to last long enough time to make up for the main materials' harmful environment effects

Design for Manufacturing

  • Brackets and major componets are placed in a way that they must all be at the correct position before being fastened with screws to ensure a secure overall fit

Design for Reliability

  • With proper care/upgrades, the product has a very long life
  • Nearly impossible to take apart without proper tools and dedicated intention
  • The main wearing component- ink catridge, is very replaceble

Design for Saftety

  • Proper covers/lids prevent unwanted interaction between human hands and running machinaries
  • Sensors prevent excessive/active interaction between hands and mechanical components once they are exposed

Design Usability

  • CPU/other wirings must be present for input purpose
  • Paper tray assemblies' straight shapes helps to position the papers

FMEA chart

We have identified three FMEA items based on the initial conclusion of the product analysis. The conclusion has led us to focus on locating items that directly relate to user operation, since the inner operation of the product is identified to be optimized. The list contains items that can be avoided with proper user care and usage.

  • S: Severity of failure
  • O: Occurance probability
  • D: ease of Detection
Part Failure Mode Failure Effects S Causes of Failure O Design Controls D RPN
Main Chip Board Breaking/Loosening of chips/etc. Unable to transfer the input data properly; unable to exercise proper printing actions 9 Excessive vibrations possibly through dropping 2 Notify the users on proper resting position of the printer 5 90
Catridge Assembly Blockage of Ink Ink not able to come out of the catridge 6 Excessive dust cumulated at the ink openings; subpar ink quality 4 Quality control; limited chance of exposing the catridge assembly 5100
Primary Roller Assembly Mechanical Failure Paper Jammed/Stucked 4 Incorrect position of printing papers 7 Test paper tray assembly's position before entering actual printing process 5 140

Possible Modification, based on "CD Printing Concept"

Our current analysis have generate the following list of components for possible future design development:

  • Part 4- Input Buttons: improving user interface
  • Part 5- Rear Cover Assembly: possible CD insertion slot location
  • Part 6 through 8- Main Roller/Supporter Assembly: modified to generate addition vertical space
  • Part 9 & 10- Springs and their resting plate: relocated to generate space for CD slot
  • Part 12- Rear Paper Roller Assembly: modified to allow CD carrying movement
  • Part 14- Main Bracket: redesigned to generate additional space for new components
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