HP Deskjet 600c

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Bucknell Mechanical Design Home

Contents

Printer Dissection

Figure 1: HP Deskjet 600c Before Disassembly
Figure 2: HP Deskjet 600c Without The Case

Function

This inkjet printer is manufactured by Hewlett Packard, and is used to transpose displayed digital data onto a physical medium.

How It Prints

The computer sends a data stream to the printer through a serial, or usb cable. The control unit inside the printer deciphers the data and instructs the mechanical components to act accordingly. The following is an illustrated outline of the mechanical aspect.


1) Paper is advanced into position by the rubber rollers, which are powered by a stepper motor.

Figure 3: Rubber Rollers That Advance The Paper
Figure 4: The Stepper Motor That Powers the Rollers

















2) Another stepper motor, undocks the printer carriage. The dock is used to secure the carriage, and to keep the printer head clean.

Figure 5: Docking Station For The Carriage
Figure 6: Stepper Motor That Drives The Dock Using A Worm Gear

















3) The printer carriage is operated by a drive belt, which is powered by a third stepper motor.

Figure 7: Belt Drive System
Figure 8: Stepper Motor That Drives The Belt Using A Toothed Pulley

















4) The printer cartridge applies ink onto the paper according to the instructions supplied by the CPU through the copper contacts.

Figure 9: Cartridge To CPU Interface






















Parts

The table belows lists the components for the HP Deskjet 600c printer:

Table 1: HP Deskjet 600c Component List
Part # Part Name Category Function Material Picture
1 Paper Tray Structural Component Holds Paper that is to be loaded in place Plastic
DVTray.jpg
2 Printer Housing Structural Component Protects internal components from the environment Plastic
DVHousing.JPG
3 Large Stepper Motor Input Provides motion to the paper feeder mechanism Metal casing, copper wire, magnet, gear
DVLargeStep.JPG
4 Docking Station Motor Input Controls the motion of the docking station Metal casing, copper wire, magnet, gear
DVDockMotor.JPG
5 Printer Cartridge Holder and Rail Output Slides the Printer head along the railing from left to right Plastic housing and metal rail
DVRail.JPG
6 Paper Feed Gears Transmission Takes the input from the feed motor and controls the feeding of the paper One plastic gear and one metal gear
DVGears.JPG
7 CPU and Power Source Input Controls the entire printer and modulates the power input Silicon, lead, copper, resistors, capacitors
DVCPU.JPG
8 Paper Ejector and Advancer Mechanism Motion Conversion Lowers the black bar so paper ejects cleanly, and raises bottom tray Plastic
DVEject.JPG
9 Print Head Motor Input Provides motion to print head Metal case, copper wire, magnet, gear
DVHeadMotor.JPG
10 Docking Station Motion Conversion / Structural Cleans and houses printer head when not printing Plastic
DVDock.JPG

Cool Animated Videos

<embed src="http://www.youtube.com/v/8_iTSznToHU" type="application/x-shockwave-flash" width="425" height="350"></embed>

Animated Printer Carriage


Right-click here and select "Save Link As" to download the video (.avi)

<embed src="http://www.youtube.com/v/iayt04lR08E" type="application/x-shockwave-flash" width="425" height="350"></embed>

Animated Paper Feed Mechanism

Right-click here and select "Save Link As" to download the video (.avi)


Analysis

Analysis Of The Belt System

Scope of Analysis The two engineering specifications that are quantified for the printer belt tensioning system, are the force on the belt required to accelerate the printer head to its maximum speed, and the force to stop the printer carriage and change direction. Both of these specifications pertain to the Dots Per Inch design parameter. The best design is to obtain the maximum DPI rating in the quickest printing time. To achieve this goal, the belt must be able to cope with the forces to accelerate the printer carriage.


Key Properties

  • Printer Prints 4 pages a minute at 300 DPI
  • Mass of Carriage With Ink Cartridge = 0.14 kg
  • Moment of Inertia of Pulley = 0.5 (.002kg)(0.005^2m) = 2.5 x 10^8
  • The belt is a trapezoidal design, meaning each tooth has the shape of the trapezoid
  • The belt is made out of polyurethane which has good wear resistance and low friction


Assumptions Friction force exerted by the slider on the carriage is always constant when moving, and should have been reduced to a minimum by the manufacturer. Lower friction would reduce the force the stepper motor has to supply to move the carriage. Since it is difficult to measure the exact amount of friction force, and it is relatively small compared to the acceleration forces, friction can be neglected.


Finding The Speed Since, the actual printer head speed I could not be found, a few assumptions had to be made with the available information. The printer has a 300 DPI rating, which means that it can print 90,000 dots per square inch. It can print 4 pages of text per minute. Assuming that it prints 8.5” x 11” pages with a 1” top and bottom margin, and 1.25” side margins, it leaves a total of 54 square inches of text. This equates to 4.86 x 10^6 dots per page. Multiply the dots per page by the pages per minute, and that results in 2.43 x 10^7 dots per minute. 2.43 x 10^7 dots per minute is the average printing rate for the printer. However, if we assume the format is 12 point, Times New Roman font, the total area per line of text is 1.95 in^2 (6.5” x .3”) 0.54 square inches per page multiplied by 4 pages per minute, divided by 1.95 square inches per pass, and taking the reciprocal, yields .009 minutes per line, which is 0.54 seconds per line. Every line is 6.5 inches long, which means that the printer head moves at 12 inches per second. Since information on the acceleration of the printer carriage could not be obtained, it was instead estimated. After careful observation of other inkjet printers, the carriages reach their top speed almost instantaneously, so it was estimated that it takes 0.2 seconds to reach maximum velocity, and 0.25 seconds to stop and change direction.


Calculations

  • Acceleration of Carriage From Rest

Acceleration of Carriage = max velocity/ time = (0.3048 m/s) / 0.2 s = 0.15 m/s2

Mass of Carriage With Ink Cartridge = 0.14 kg

F = ma = (0.14)(0.15) = 0.021 N


Therefore, it takes .021 N to accelerate the carriage from rest to the max velocity

  • Stopping and Changing Direction

Change in velocity = (0.3048+.03048) = 0.6096 m/s

Change in Time = 0.25 s

F = (Mass*Change in Velocity)/ Change in time = 0.34 N


Therefore, the maximum force exerted on the belt due to the change in direction is 0.34 N.

As seen in Figure 10 below, the maximum force to pull the carriage is related to the torque supplied by the motor pulley. Furthermore, the carriage is fixed to one side of the belt, so it translates directly with the belt. During the analysis, the entire carriage is treated as a point mass and represented as a block. Figure 11 shows the free body diagram of the motor pulley. It is evident that the torque from the pulley is directly related to the force on the belt during acceleration.

Figure 10: Free Body Diagram Of System
Figure 11: Free Body Diagram Of Motor Pulley