Proceedings of the Multi-Disciplinary Senior Design Conference Page 2

Project Number: P10503

FLAT PLATE XEROGRAPHIC TEST FIXTURE

Adam Regula - ME / Steve Snyder - ME / Amar Mohamed - EE

Dan Prosser – ME Lam Nguyen, Jr. - IE

Guide: William Nowak / Guide: Michael Zona

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.

LabVIEW – 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.

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:

Since the Flat Plate Xerographic Fixture had all of the necessary components already, the designing process had to be omitted. This project was more about messing together the analog and digital aspects of the fixture together. In order for the Flat Plate Xerographic Fixture to work properly, continuity between each of the substations had to be flawless and there had to be a clear understanding of the inputs of each of the five stations. Figure 1 below shows a flow chart of the Xerographic process and all the required inputs and expected outputs of each subsystem.

Figure 1: Xerographic Process of Flat Plate Fixture

For the exposure station, the knowledge of the current and voltage characteristics of a diode was crucial to understand in order for this subsystem to work efficiently. Equation 1 below denotes the behavior of a diode within a circuit:

IDIODE=ISeVDnVT-1 Equation 1

The main variable within the above equation that deals with this project is VD, which is the forward bias of the diode. To enable the diodes to turn on, a 700 mA Buckpuck 1-6 Luxeon III Star current driver was used. This current device supplies a constant 700 mA to the load regardless of what voltage is applied to the input terminal. This device has a feedback loop mechanism that regulates this process. The Exposure LEDs are further discussed within the Exposure Station portion of the paper.

Project Planning:

After consulting the customers of P10503 as well as convening as a team, we determined a number of customer needs for the Xerographic Test Fixture. The charts shown below are the result of those efforts.

Figure 2: Customer Needs Tabulation & Ranking

The primary customer needs as a result expectantly came out to be operator/observer safety, functionality of the fixture, and ease of use of the physical fixture and the LabView interface. As seen in the above figure, pair wise comparison was used in order to eliminate any possible ties with respect to ranking the importance of each customer need.

Figure 3: Customer Needs Pareto Chart Sorted by Importance

Safety concerns we noted immediately included settings for voltages, settings for currents, and settings for velocities of both the P/R carriage and rollers because they create pinch points. Functionality of the fixture was defined by whether or not each of the substations were functional as well as whether or not the demonstration of xerography was achieved at the end of the process. Ease of use for the most part includes factors such as being able to use the user interface without much need of documentation (although documentation will still exist) or thorough understanding of xerography, as well as optimizing maintenance and fixture reboot processes.

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) were required in order to provide the proper voltages and current to the fixture. Two HVPS were dedicated solely to the charging station. 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. The last HVPS, which is situated in the Transfer station, is simply denoted as the Transfer bias. These four HVPS evoked the majority of the safety concerns for this project.

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 so toner particles will be attracted to it and then attract it on paper. 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, actual values that represented input and output values of the fixture were converted into digital data and then sent and stored within the LabVIEW software in order to be analyzed and tabulated into easy to read graphs.

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 four DAQs (data acquisition) components. To account for all of the automation and data acquisition involved with this fixture, a total of four DAQs were used in order to accomplish this. The four 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), the NI PCI 6602 (sole purpose is synonymous with NI PCI 6515), and the NI PCI 6229 (sole purpose was to obtain and monitor the analog inputs and outputs of the voltages and currents of each station and to provide a low voltage to be supplied and amplified by the HVPS. Careful integration of the DAQs into the system by meticulous wiring of the desired ports and documenting them within the LabVIEW software database. With this achieved, the next step was to implement the correct algorithms and translate it into LabVIEW code so that a program can be created which easily monitors every single function of the system. Figure 1 below shows the fundamental connections and integration of everything from every power supply, each DAQ, to every component that gave data with labels and how it ties together to the fixture. As with any intricate electrical system, both an Electromagnetic Interference (EMI) Filter (CORCOM) and circuit breaker (SURSUM) are used. The EMI filter is used to reduce the interference of electromagnetic fields from both the 120 V AC line voltage and between the equipment used. In case anything shorts or overloads in current, a circuit breaker is used to stop all operation. Another main attribution to the overall design is the special grounded plates required for the HVPS to ensure proper safety and functionality of the system. The last main portion of the flow of power is how Crydom Solid State Relays (SSR) are used so that LabVIEW can turn on and off each electromagnetic function of the fixture, such as the Exposure LEDs, Exposure Lifting System, and Transfer Drum just by running the software.

Figure 4: Basic Wiring Diagram of Flat Plate Xerographic Fixture

In 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. The ESVM probes are placed before and after the 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 below demonstrates how this data is seen in the final LabVIEW user interface.

Figure 5: Screenshot of LabVIEW User Interface

DARK ENCLOSURE ENDEAVOR AND DARK DECAY

In order to limit the dark decay, which is slow, but evident discharging of a material even when little or no light comes into contact with the material, 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 and maintaining charge on the photoreceptor during these times was crucial. 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.

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. It was also 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 6: Dark Enclosure covering the Xerographic Fixture

In 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, which was a required customer need. 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 7: Measurement of Dark Decay with and without the Dark Enclosure

Figure 5 above shows the rate of dark decay for various environments in which the Flat Plate Xerographic Fixture operates in. It is seen that there is least dark decay when the dark enclosure is used and the lights are off, which was what was expected.

TEST PLAN

Figure 7: Dark Enclosure covering the Xerographic Fixture

The above figure depicts the test plan our team developed for the last ten weeks of the project life cycle along with the owners for each test. Each subsystem on the fixture had a corresponding operational test to ensure that voltages were properly discharging and to ensure that the photoreceptor was being charged, exposed, etc.