Multi-Disciplinary Senior Design ConferenceKate Gleason College of Engineering

Rochester Institute of TechnologyRochester, New York 14623

Project Number: P10503

FLAT PLATE XEROGRAPHIC TEST FIXTURE

Adam Regula - ME Steve Snyder - ME Amar Mohamed - EE Dan Prosser – ME Lam Nyguen, Jr. - IE

Guide: William Nowak Guide: Michael Zona

Copyright © 2008 Rochester Institute of Technology

ABSTRACT

The objective of this project was to make an existing xerographic fixture operational and usable in a classroom setting as well as research and development. In order to achieve these goals, the project group concentrated on determining nominal operational and safety values for various controls concerning velocities and voltages/currents as well as creating a LabView interface that is both easy to use and functional. A summary of the results of the project will go here when we get there.

NOMENCLATURE

ESVM – Electrostatic Volt Meter: These devices are used to measure the voltage across a certain element. Unlike regular voltmeters used in everyday practice, electrostatic voltmeters do not require the use of an actual physical connect: instead of leads, probes are placed in the vicinity of the component being measured in order to obtain a more accurate reading. Four of these are used in order to monitor the voltage drop at crucial points during experimentation.

PC – Photoreceptor Carriage: This is the device which the photoreceptor is attached to. It moves down the line along each of the substations while the photoreceptor is being manipulated by the substations.

PR – Photoreceptor: A device that becomes an insulator in the dark and a conductor when exposed to light. The photoreceptor is the main component of this experiment since it will hold a latent image and maintain toner on its surface.

DAQ – Data Acquisition: The device that obtains analog data from a system and transfers it into digital signals that can be stored and manipulated by the LabVIEW software.

HSVP – High Voltage Power Supply: These power supplies generate a large amount of power to the devices of the Xerographic Plate Fixture. A total of four are used in this system. EM – Electromagnetic FieldLabVIEW – Laboratory Virtual Instrumentation Engineering Workbench: The software that enables the storage and manipulation of data into a user friendly form. This software also controls every device in the Xerographic Fixture through the user interface.

NI – National Instruments: The company that manufactured LabVIEW.

MC – Motion Controller: A digital device that controls the photoreceptor carriage. LED – Light Emitting Diode: An electrical circuit device that emits light when a positive voltage forward biases the device and a current passes through it.

UI – User Interface: The style and display of a program in which someone who is controlling the computer must use.

INTRODUCTION

Prior to P10503, the xerographic test fixture was worked on but not to completion and not to full operational capacity. The objective of this project was to achieve operational capacity for the fixture as well as create an interface through which professors and students as well as people involved in R&D to manipulate the fixture. Another overarching objective was to determine nominal settings for various controls as well as safety limits to ensure fixture integrity as well as operator well being. The customer of this project was Professor Marcos Estermann of the RIT ISE department and was guided by Xerox adjuncts William Nowak and Michael Zona.

Theory:- Fixture described series of inputs that become

outputs for next station, using this structure we know which controls/inputs influence which outputs for testing purposes (here describe all inputs and outputs)

Project Planning:- Show top customer needsshow CAD

drawings, interface screenshots, concept creening results, link each back to customer needs

Assumptions:- Foam core will be able to block out all

relevant light sources- Encoder has good enough resolution for data

acquisition and carriage control purposes- Debugger interface has enough functionality

for testing purposes

Methods:- Various test plans for each station to ensure

operational capacity and determine nominal values

- Test plans to determine effectiveness of dark enclosure

Experiments:

- Describe each test, each setting in the debugger interface for each test (here link back to specs)

ASSEMBLY OF XEROGRAPHIC FIXTURE

In order to successfully enable the fixture to work, the main project was divided into five subsequent stations, each of which contributes heavily towards the end result. The five substations in order are as follows: Charging, Exposure, Development, Pre-Transfer, and Transfer. Even though the functionality of the next station depends on the state of the prior station, each station was worked on individually and then a series of tests were used in order to link their individual process together.

Even though each individual station was responsible for different tasks regarding the entire project, the equipment and assembly of the fixture had to be taken care of individually. Four high voltage power supplies (HVPS) from the company TREK were required in order to provide the proper voltages and current to the fixture. Two HVPS were dedicated solely to the charging station. One of them, designated to be the Corona, had to supply a current of around 1800 µA in order to induce a strong electromagnetic (EM) for the charge to situate itself on the photoreceptor material.This HVPS supplied a total of -650 V to the

The third HVPS, which was used for the Toner Bias, was situated at the Development station in order to attract the toner particles onto the photoreceptor. This power supply also applied a high voltage to the toner on the order of -525 V. The last HVPS, which is situated in the Transfer station, is the simply denoted as the Transfer bias. These four HVPS evoked the majority of the safety concerns for this project.

Figure 1: Basic Wiring Diagram for the four High Voltage Power Supplies

There were two main challenges to this project: to be able to successfully run and control the xerographic fixture and to be able to obtain the data and convert it into a readable form that can easily be analyzed. The first one involved extensive research of how to charge the photoreceptor and charger the toner particles and then attract it on paper, but the latter involved using LabVIEW, which enabled both the automation of different aspects of the xerographic fixture and the acquisition of the output analog data produced from the xerographic fixture, convert it into digital data, and then send and store it into the computer to be analyzed.

In order to obtain data and operate the xerographic fixture from the computer for convenience, the software of LabVIEW had to work with a total of three DAQs (data acquisition) components. To account for all of the automation and data acquisition involved with this fixture, a total of three DAQs were used in order to accomplish this. The three DAQs used were the NI PCI 7330 MC (sole purpose was to control the movement of the photoreceptor carriage), the NI PCI 6515 (sole purpose was to control the electromechanical automations from pneumatics to turning on the Exposure and Pre-Transfer LEDs), and the NI PCI 6229 (sole purpose was to obtain and monitor the analog inputs of the voltages and currents of each station and to provide a low voltage to be supplied and amplified by the HVPS.

Figure 2: EDTS System Controls State Diagram for the LABView InterfaceIn order to test the functionality of each station, four TREK model 344 ESVMS are utilized. These devices, unlike regular voltmeters, are independent of the source of measurement by the use of probes, thus enabling a more accurate measurement. Three of the

five stations, Charge, Exposure, and Pre-Transfer, each have voltage outputs that need to be monitored extensively. The ESVM probes are placed before and after these stations and the voltage values are then sent back to the computer through the 6229 DAQ. These values are then displayed in the form of a graph on the monitor by the LabVIEW UI, specifically voltage versus time graphs to show and monitor the changes in voltage.

Figure 3: Screenshot of LabVIEW User Interface

DARK ENCLOSURE ENDEAVOR AND DARK DECAY

In order to limit the dark decay due to the sensitivity of the photoreceptor to light, a dark enclosure was designed. The dark enclosure was built over the charging, exposure, and development stations since at these three stations the charge on the photoreceptor was at its peak sensitivity due to the abrupt changes in voltage at such abrupt times. After the PC exits the photoreceptor, the presence of light is negligible since the photoreceptor does not need such a high amount of voltage across the last two stations. Since the main objective of the dark enclosure was to shield the operating fixture from light, the material chosen had to be opaque and the dimensions had to be large enough to encase the entire fixture, but not inhibit any of the actions that occur during operation time.

The material chosen for the dark enclosure was foam core, a thick, three-layered polystyrene material that satisfied all of the needs for the dark enclosure. The foam core used was black and completely opaque, two characteristics which made it the optimal dark decay inhibitor, easy to cut, which made it easy to assemble the photoreceptor, and extremely lightweight, which made it easy to do all of the applicable dark decay testing necessary. Once completed, the dark enclosure, whose shape was rectangular, covered the stations of the fixture like a box on all sides, but had a reversible hinged door at the end of the development station side so that the PC attached with the photoreceptor can move back and forth through the dark enclosure with ease.

Figure 4: Dark Enclosure covering the Xerographic FixtureIn addition to the reversible hinged door, the dark enclosure was assembled with a door at its side so that the first three stations can be seen for the purposes of troubleshooting and being able to demonstrate the process of Xerography to observers. The quality of the lightweight foam core made the dark enclosure even more efficient since it can be taken off easily from the fixture. The bottom of the enclosure attaches the bottom of the fixture table by Velcro and can be taken off easily so that a series of tests can be run in order to measure the dark decay rate of the individual photoreceptors due to the access to the back of the fixture can be accessed easily for troubleshooting.

Figure 5: Measurement of Dark Decay with and without the Dark Enclosure

PHOTORECEPTOR

There were two types of photoreceptors used during this project: Xerox photoreceptor and Kodak photoreceptor; however, mylar, a polyester made from polyethylene terephthalate known for its strong

electrical insulation, often used in the applications of helium balloons, was also used for experimental purposes. The main concept of a photoreceptor that proves its utmost importance in this experiment is its ability to act as an insulator in the absence of light and then emulate the characteristics of a conductor in the light. A multitude of tests were used on each of the photoreceptors, such as varying the charging voltage, exposure station duration, to changing the overall speed of the PC.

CHARGING STATION

The charging station is responsible for applying a large voltage to the photoreceptor, typically in the range of -600 to -700V. This voltage is applied through the HVPS designated as the Grid Voltage. Accompanied by the Grid Voltage in this station was the Coronode Current, which was necessary in establishing the electromagnetic field needed to ionize the air particles so that charge can be delivered to the photoreceptor. The corona HVPS typically supplied 1.8 mA to the charging station.

Figure 6: Graph of Charging Station Potential and Photoreceptor Carriage Velocity

The main problem that inhibited progress from the charging station was the orientation of the photoreceptor when it was to be connected to the PC. A ramification of this obstacle was the difficulty with the polarity of the photoreceptor and the voltage supplied from the Grid Voltage. Initially, this problem inhibited the progress of the xerographic process since it was believed that the photoreceptor had to be opposite polarities; however, this was not the case. The polarities of both the photoreceptor and the Grid Voltage had to be the same. Another concern that had to be taken into account was the actual polarity of the toner particles used. Also, the polarity of the of the coronode current and the grid voltage must be the same, but opposite of the photoreceptor. INSERT

EXPOSURE STATION

The exposure station is responsible for illuminating the photoreceptor as the PC crosses over the exposure mount. When the charged photoreceptor is centralized over the exposure mount, the PC stops and beneath the mount, twelve light emitting diodes turn on, illuminating the photoreceptor. This illumination from the LEDs serves two main purposes. The first one is to embed the image onto the photoreceptor. From the properties explained earlier about the photoreceptor, the uniformly charged photoreceptor is exposed to both the lights and the image. The image that is on the exposure mount blocks the light from reaching the parts of the photoreceptor that will continue to hold charge and which in turn, will develop the image, while the unshielded regions of the photoreceptor will discharge once light reaches it. The light that shines on the photoreceptor also discharges it.

The main problem within the exposure station is the inadequate knowledge of the properties of the photoreceptors used. Because of this, it was difficult to see what color of LED to shine on the photoreceptor. The initial LEDs used in the exposure station were twelve blue batwing Luxeon LEDs. This choice, however, seems incompatible with the Kodak photoreceptors since they are both of a blue color. Because of this implication, the blue LEDs were replaced with white batwing Luxeon LEDs.

DEVELOPMENT STATION

The third process of the xerographic process is known as the development stage. In this stage, the toner particles that will be transferred onto the paper are finally introduced. Toner particles are infinitesimally small polymer particles that have a unique pigmentation and are polarized. The polarization characterization of the toner particles plays a vital role in the xerographic process. This is due to the fact that the chosen toner particle’s polarity has a lot of ramifications on how the other components of the xerographic fixture functions with regards to charging the devices to a positive or negative bias. These toner particles are stored within a container and then transferred onto the charged areas of the photoreceptor remaining from the exposure station by the means of roller.

The roller located within this station is known as the development roller and its purpose is to transfer the toner particles within the development station container onto the photoreceptor by the use of a skiving blade. Before this is done, however, the development roller is charged to -525 V in order to charge the toner. When this is all set, the skiving blade, saturated with toner particle, spreads across the photoreceptor and the toner particles are attracted to

the charged areas of the photoreceptor left by the latent image due to the exposure station. Due to the high potentials involving both the charged photoreceptor and toner particles, a strong electric field between the two enables a clear path for the toner particles to travel onto the photoreceptor.

PRE-TRANSFER STATION

After the photoreceptor carriage leaves the development station with the toner particles charged onto the photoreceptor, it enters the pre-transfer station. Most xerographic fixtures classify this station to be an adjunct to either the development station or the actual transfer station, but within this fixture, the pre-transfer light emitting diodes are considered independent of either of these stations. The pre-transfer light emitting diodes within this xerographic fixture consists of an array bar that emits red light. This erases the charge to a mere -50 V in order to make the transition of the toner particles from the photoreceptor to the transfer roller drums much more smooth.

TRANSFER STATION

The final process of the xerographic process, the transfer station is where the allocation of toner particles from the photoreceptor to the transfer drums and then finally to the paper. Within the transfer station are two roller drums which attract the charge from the photoreceptor. The first drum is charged to a bias of 2000 V in order to attract the -50 V charged toner particles to the drum. Once the toner comes off the photoreceptor and onto the initial spinning drum. The second drum is applied with a bias of equal magnitude and opposite polarity, giving it a -2000 V bias. Once the second drum has been given the required voltage and starts rotating, the toner on the initially charged drum will move to the second latter of the two roller drums. The paper is then pushed in between the two rollers and the toner is transferred onto the paper.

RESULTS AND DISCUSSION

Evaluation of success: effectiveness of dark enclosure, effectiveness of user interface enforcement of safety limits both through interface and on hardware operational capacity of each subsystem, nominal values of settings determined through testing

CONCLUSIONS AND RECOMMENDATIONS

This section should include a critical evaluation of project successes and failures, and what you would do differently if you could repeat the project. It’s also important to provide recommendations for future work.

REFERENCES

[1] Schein, Lawrence B. Electrophotography and Development Physics. New York: Laplacian P, 1996.

[2] The Story of Xerography 1999.

[3] Ientilucci, Emmett Fundamentals of Xerography 1994

ACKNOWLEDGMENTS

Thanks to the help and guidance of faculty guides Michael Zona, William Nowak, and Marcos Esterman, the endeavor of making the Xerographic Flat Plate Fixture was a success. In addition to these people, special thanks goes out to the attendees of the Detailed Design Review, which included but not limited to John Arney, Dale Mashtare. But most importantly, the project would not have been completed in time without the help of the LabVIEW Specialist Jeffrey Robble, the teaching assistant assigned to P10503.