Stratasys FDM Titan User manual

Brand: Stratasys

Model: FDM Titan

Type: User manual

FDM Titan

™

User Guide

Version 1.9

FDM Titan User Guide

Notice

The information in this document is subject to change without notice. This User Guide

is published for informational purposes only and the information so provided should

not be considered as all-inclusive or covering all contingencies. If further information is

required, Stratasys Inc. should be consulted.

STRATASYS INC. MAKES NO WARRANTY OF ANY KIND WITH REGARD TO THIS

MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Stratasys Inc.

shall not be liable for errors contained herein or for incidental or consequential

damages in connection with the furnishing, performance, or use of this material.

may be photocopied, reproduced, or translated into another language without the prior

written consent of Stratasys Inc. Printed in the USA.

Trademarks

•FDM Titan

™

, WaterWorks

™

, Insight

™

, and Smart Canister

™

are all trademarks of

Stratasys Inc.

•FDM

and Stratasys

are registered trademarks of Stratasys Inc.

•Krytox

, Ultem

, Lexan

, TriGEL

, Windows NT

, and Windows 2000

are

registered trademarks of their respective companies.

Stratasys Incorporated

14950 Martin Drive

Eden Prairie, MN 55344 USA

Tel: 1.800.937.3010 (US toll free)

952.937.3000 (local)

Fax: 952.937.0070

www.stratasys.com

Publication Number: 105135-0010

Publication Date: November, 2006

FDM Titan User Guide

About the FDM Titan

Welcome to the FDM Titan™. This system incorporates the latest in innovative

technologies to provide you with precise prototypes from a CAD design. The

machine’s high-capacity oven, with a build envelope of 16 x 14 x 16 in. (406 x 355 x

406 mm), accommodates the building of large parts or numerous smaller parts.

Stratasys’ Fused Deposition Modeling (FDM) technology provides prototype parts,

including internal features, that can be used to test form, fit, and function.

With rapid prototyping, physical models of parts can be generated directly from CAD

in a matter of hours. The Titan features a servo/belt driven XY gantry with multiple

high temperature modeling material capability.

There are five major components that make up the Titan Modeling System:

• Insight Slicing Software

• A Computer Workstation (not sold by Stratasys)

• The Titan Modeling Machine

• Modeling Material

• Support Material

FDM Titan User Guide

iii

About This Guide

This guide is your introduction to building prototypes using a Stratasys rapid prototype

system. Typically learning about a high-tech machine can be a long, difficult process.

But with this guide, you can make that learning process much easier. This guide was

designed as a learning and reference tool that explains system operation in an easy to

understand, step-by-step, process. This guide is specifically written for controller

software version 2.4.0. Screen descriptions may be different for other versions.

How to Use This Guide

This guide is divided into easy-to-follow chapters. The tabs allow you to quickly and

easily find the information you want. You can read this user guide chapter by chapter

or use the tabs, Table of Contents, and Index when you need to quickly find specific

information. Keeping this user guide close to your system will efficiently allow you to

troubleshoot and maintain the system.

Conventions Used in This Guide

The following conventions are used in this guide.

• When you see text in italic, it indicates that this is a menu item that can be

selected from the Operator Panel Screen. For example, select Build Last Job.

• If you see text in BOLD CAPS it indicates that this is a key located on the

Operator Panel keypad. For example, From the Main Menu select Build Job and

press ENTER.

• If you see boxed blue text, it indicates that this information is being shown on the

Operator Panel Screen. For example:

Build Job..

>Operator Control..

Modeler Status..

Maintenance..

|*Tips: Model T16

|* Support T16

FDM Titan User Guide

Table of Contents

Notice

About the FDM Titan..........................................................................................ii

About This Guide.............................................................................................. iii

How to Use This Guide..................................................................................... iii

Conventions Used in This Guide...................................................................... iii

Service & Support

FDM Titan Service........................................................................................1 - 1

Software Support..........................................................................................1 - 1

Consumable Orders......................................................................................1 - 1

Safety Instructions........................................................................................1 - 2

Hazard Classifications...............................................................................1 - 2

Product Safety Signs.................................................................................1 - 2

Specific Safety Practices...........................................................................1 - 3

Guard Door Interlocks...............................................................................1 - 4

General Safety Practices ..........................................................................1 - 4

Setup & Installation

Preparing Your Facility for Installation ..........................................................2 - 1

Identifying Your Machine ..............................................................................2 - 1

Making the Network Connection...................................................................2 - 1

Making the Power Cable Connection ...........................................................2 - 2

Using the Main Circuit Breaker.....................................................................2 - 2

Using the Uninterruptible Power Supply (UPS)............................................2 - 2

Thermal Cut-Out Fuses................................................................................2 - 3

Initial Network Configuration (IP Address)....................................................2 - 4

Upgrading Software or Downloading a Code ...............................................2 - 5

Moving the Machine......................................................................................2 - 8

Machine Components

Accessing Machine Components .................................................................3 - 1

Opening the Hood.........................................................................................3 - 4

XY Gantry Assembly.................................................................................3 - 4

FDM Titan User Guide

Head Assembly............................................................................................3 - 5

Liquefier Tips and Slice Heights ............................................................... 3 - 5

Head Buttons for Unplugging Tips............................................................ 3 - 7

Z Stage & Oven Components ......................................................................3 - 8

Opening the Oven Door............................................................................ 3 - 8

Oven Lights............................................................................................... 3 - 9

The Platen .............................................................................................. 3 - 10

Moving the Head and Z Stage using “Move Relative” ............................ 3 - 10

Lowering the Z Stage.............................................................................. 3 - 12

Material & Canisters

Materials Used in the Titan...........................................................................4 - 1

Accessing the Canister Bays .......................................................................4 - 1

Canister Bay Components...........................................................................4 - 2

Canister Bays ........................................................................................... 4 - 2

Canister Drive Levers............................................................................... 4 - 3

Interpreting the LED Indicators................................................................. 4 - 3

Waste Basket............................................................................................ 4 - 4

Canister Auto Changeover ....................................................................... 4 - 4

Smart Canister.......................................................................................... 4 - 5

Storing Canisters..........................................................................................4 - 5

Changing Canisters......................................................................................4 - 6

Installing a Canister.................................................................................. 4 - 6

Removing an Empty Canister................................................................. 4 - 10

Removing a Partially Used Canister....................................................... 4 - 10

Loading Material Filament to the Liquefiers............................................... 4 - 11

Unloading Material Filament from the Liquefiers........................................4 - 12

Purging Blue Material from Liquefier ...................................................... 4 - 13

Changing Material Type or Tips .................................................................4 - 14

Recovering From a Head Plug...................................................................4 - 19

Moving the Head to the Head Service Bracket (Service Location)............4 - 21

Operating the Machine

Using the Operator Control Panel................................................................5 - 1

Keypad Button Descriptions ..................................................................... 5 - 2

Screen Symbols ....................................................................................... 5 - 3

Powering Up the Machine............................................................................5 - 3

FDM Titan User Guide

iii

Powering Down the Machine........................................................................5 - 4

Building a Job...............................................................................................5 - 5

Before Building a Job................................................................................5 - 5

Selecting a Job to Build.............................................................................5 - 6

Warnings Before Job is Built.....................................................................5 - 7

Information Available While Building.........................................................5 - 7

Information Available If a Job Fails While Building ...................................5 - 7

Pausing or Aborting a Job.........................................................................5 - 8

After Building a Job...................................................................................5 - 8

Manually Removing Support Material...........................................................5 - 9

Removing Supports from a PPSF Part .....................................................5 - 9

Removing WaterWorks Support Material......................................................5 - 9

Working with the Job Queues.....................................................................5 - 10

Using the Maintenance Menu.....................................................................5 - 11

Changing the Modeler Default Values.....................................................5 - 11

User Placement on Platen ......................................................................5 - 12

Displaying Machine Status..........................................................................5 - 13

Finding the Temperature Status ..............................................................5 - 13

Finding the Odometer Status ..................................................................5 - 13

Finding the Material Status......................................................................5 - 14

Finding Your Machine’s Software Version...............................................5 - 15

Finding the Sensor, System, or UPS Status............................................5 - 15

Checking Air Pressure and Vacuum...........................................................5 - 16

Changing the Build Sheet...........................................................................5 - 16

Setting the Oven Temperature....................................................................5 - 17

Operating Insight

Starting Insight..............................................................................................6 - 1

Opening a .STL File in Insight ......................................................................6 - 1

Selecting Modeler Setup Settings.................................................................6 - 2

Configure Your Modeler ............................................................................6 - 2

Part Build Parameters...............................................................................6 - 4

Orientating the Part in the Build Envelope....................................................6 - 5

Slicing the Part..............................................................................................6 - 5

Building Supports and a Base for the Part....................................................6 - 6

Saving the Job File.......................................................................................6 - 6

Creating Toolpaths........................................................................................6 - 6

Saving the Toolpath (.CMB file)....................................................................6 - 6

FDM Titan User Guide

Flag Button Shortcut ....................................................................................6 - 7

Sending the Part to the Machine..................................................................6 - 7

Insight Status................................................................................................6 - 8

Managing Parts in the Job Queue............................................................ 6 - 8

Monitoring the Part Build .......................................................................... 6 - 9

Viewing Information about Built Parts ........................................................6 - 10

Setting Up Remote Notification.................................................................. 6 - 11

Calibrating Liquefier Tips

Automatic Calibration...................................................................................7 - 1

Manual Calibration.......................................................................................7 - 5

Maintaining the Machine

Maintenance Schedule.................................................................................8 - 1

Daily Maintenance Tasks .............................................................................8 - 2

Cleaning the Platen .................................................................................. 8 - 2

Cleaning the Waste Chutes and Waste Basket........................................ 8 - 2

Weekly Maintenance Tasks..........................................................................8 - 3

Vacuuming the Build Envelope.................................................................8 - 3

Monthly Maintenance Tasks.........................................................................8 - 3

Inspecting & Replacing the Tip Wipe Brushes.......................................... 8 - 3

Replacing the Silicone Wiper.................................................................... 8 - 3

Inspecting the Purge Ledge...................................................................... 8 - 4

Lubricating the XY Guide Rods ................................................................ 8 - 4

Lubricating the Z stage Lead Screws and Guide Rods ............................ 8 - 5

Quarterly Maintenance Tasks.......................................................................8 - 5

Cleaning the Vacuum System In-Line Filter and Jar................................. 8 - 5

Cleaning the Cone Sensor ....................................................................... 8 - 6

As Needed Maintenance Tasks....................................................................8 - 6

Platen Flatness Diagnostic....................................................................... 8 - 6

Replacing the Entire Tip Wipe Assembly.................................................. 8 - 6

Cleaning Exterior Machine Surfaces ........................................................ 8 - 7

Cleaning the Head Tray............................................................................ 8 - 7

Cleaning the Liquefier Tips....................................................................... 8 - 7

Replacing an Interior Lamp ...................................................................... 8 - 7

Troubleshooting

FDM Titan User Guide

Getting Help..................................................................................................9 - 1

Finding a Remedy.........................................................................................9 - 2

Index

Appendix A: PPSF Materials User Guide

Introduction to PPSF....................................................................................A - 1

Terminology .................................................................................................A - 1

Hazard Classifications.................................................................................A - 2

Pre-Processing............................................................................................A - 2

Setting up PPSF in Insight (Version 3.5 or Later) ................................... A - 2

Titan Operation with PPSF ..........................................................................A - 3

Switching to PPSF From Another Material..................................................A - 3

Replacing the Tip .................................................................................... A - 3

General Operation with PPSF .....................................................................A - 3

Removing PPSF_S Supports ......................................................................A - 4

Using the Support Removal Toolkit Items....................................................A - 5

Tool Maintenance .................................................................................... A - 5

Support Removal Tool Kit ........................................................................ A - 6

Reheating a PPSF Part ...............................................................................A - 9

Reheating with the Titan Oven .............................................................. A - 10

Reheating with a Convection or Consumer Oven ................................. A - 10

Reheating with Laboratory Ovens ......................................................... A - 10

Reheating with a Hot Air Gun ................................................................ A - 10

Material Safety Data Sheets (MSDS)........................................................A - 10

Material Abbreviations ........................................................................... A - 10

PPSF Properties........................................................................................ A - 11

Mechanical Properties ............................................................................A - 11

Thermal Properties .................................................................................A - 11

Physical Properties ................................................................................A - 11

Environmental Resistance .....................................................................A - 11

Special Properties......................................................................................A - 12

Sterilization ............................................................................................ A - 12

Flame Test and Emissions Test ............................................................. A - 12

Finishing ....................................................................................................A - 12

Sealing/Adhesive .................................................................................. A - 12

Drilling and Sanding .............................................................................. A - 13

FDM Titan User Guide

Appendix B: UI Menu Structure

FDM Titan User Guide Service & Support

1 - 1

Chapter 1

Service & Support

FDM Titan Service

If you have a problem with your FDM Titan™ that is not covered in this user guide,

please contact Stratasys Customer Support:

• Call (800) 801-6491 (7:00 a.m. to 5:00 p.m. C.T.)

• E-mail us at support@stratasys.com

When calling in for service, always have your machine’s software version (see

“Finding Your Machine’s Software Version” on page 5-15), and hardware serial

number available (see “Identifying Your Machine” on page 2-1). You may also need

access to your Insight workstation to provide a diagnostic file from your hardware.

Software Support

If you have a software problem that is not covered in this user guide, please contact

Stratasys Customer Support:

• Call (800) 801-6491 (7:00 a.m. to 5:00 p.m. C.T.)

• E-mail us at support@stratasys.com

When calling for support, please have your system’s serial number and software

version available.

Consumable Orders

If you need to order consumables for your FDM hardware, contact Stratasys

Consumable Orders by using one of the following methods:

• Call (800) 801-6491 (7:00 a.m. to 5:00 p.m. C.T.)

• Email us at consumab[email protected]

• Fax a copy of your request to Consumable Orders: +1.952.906.2727

When ordering consumables, always have your system’s serial number and software

version number available.

Service & Support FDM Titan User Guide

1 - 2

Safety Instructions

Hazard Classifications

Stratasys recommends that all services be performed by qualified personnel. All

personnel working on or around this machine should be knowledgeable of what the

following hazard classifications mean throughout this guide.

Product Safety Signs

We make every effort to ensure that our machines are safe and reliable at all times.

However, there will be times when you must access areas of the machine where

potentially high voltages, hot temperatures, and/or moving mechanical components

could cause severe injury.

Personal Injury Sign. The personal injury sign indicates that you are

near moving mechanical parts, and severe personal injury is possible.

Always use extra care. Do not wear ties, loose clothing, or dangling

jewelry. Keep long hair tied up and away from any moving parts.

High Voltage Sign. The high voltage sign indicates the presence of

high voltages. Always stay away from any exposed electrical circuitry. It

is recommended that all jewelry be removed.

CAUTION: Indicates a potentially hazardous situation which, if not

avoided, may result in minor or moderate injury.

WARNING: Indicates a potentially hazardous situation which, if not

avoided, could result in death or serious injury.

DANGER: Indicates an imminently hazardous situation which, if not

avoided, will result in death or serious injury.

Note: Always read and adhere to safety statements, and be aware of the

following safety signs when you see them on the machine.

FDM Titan User Guide Service & Support

1 - 3

Hot Surface Sign. The hot surface sign indicates the presence of

devices with high temperatures. Always use extra care when working

around heated components. Always wear the safety gloves and safety

sleeves provided in the Titan Startup Kit.

Gloves & Sleeves–Required Sign. The gloves sign indicates that if

you enter the area specified by the symbol you must wear safety gloves

and sleeves approved for high temperatures (provided in the startup

kit).

Sharp–Object Sign. The sharp object sign indicates the presence of

sharp objects. Do not touch sharp objects as they may cause a loss of

body parts.

Crushed–Hand Sign. The crushed hand sign indicates that a hazard

exists where you could get your hand crushed between two objects.

One or more objects move in the area that you are working.

Specific Safety Practices

The following components and areas of the machine are highlighted as potential

safety hazards that may cause machine failure or reliability problems if proper safety

procedures are not followed.

Note: Head temperatures in this machine can exceed 350° C (662° F).

Oven............... The oven temperature is extremely hot and controlled by a safety

thermal breaker that shuts the machine off when temperatures

reach 260° C (500° F).

Note: When you open the oven door, the heaters turn off.

WARNING: Always wear safety gloves and sleeves when working

inside the oven. Components are very HOT!

XY Gantry......... Beneath the top hood of the machine is the XY Gantry. This area

houses the mechanical drive components of the X and Y axes.

Use extreme caution whenever accessing this area of the

machine. The servo drive system, including the motors, pulleys

and belts are extremely powerful, and care must be taken.

Service & Support FDM Titan User Guide

1 - 4

Guard Door Interlocks

The state of the oven door and hood can be detected by the interlock switches. For

safety reasons, the top hood and oven door must be closed when the X, Y and Z

motors are moving. The only exception to this is during the Z Stage Zero with Shim

Calibration procedure, shown on page 7-5. During this calibration, the oven door must

be open while the tip is shimmed to the build sheet. Only movements of less than 0.10

inches (2.45 mm) are allowed to minimize the safety hazard.

General Safety Practices

Abide by these general safety practices when working with this machine.

Note: These servo motors are disabled when the front door or top hood is

opened.

WARNING: Never wear a tie, loose clothing, or dangling jewelry. You

risk the possibility of severe injury.

The XY pinch hazard between the timing belts and pulleys is

minimized by locking the hood while building and disabling the

motors when the top hood is open.

Z Stage............. The drive belt, pulleys and Z stage servo motor can cause severe

injury. The Z stage crushing hazard is minimized by locking the

door during Z stage moves and disabling the Z motor when the

door is open.

DANGER: High voltage is present in the machine even if the system is

Off and the power cord is unplugged. This is due to the

Uninterruptible Power Supply (UPS).

DANGER: Only use an OSHA or CE approved step stool when

accessing the area under the hood located at the top of the

machine.

WARNING: Always wear safety gloves and sleeves when working in the

oven or with the head or liquefier tips. These components

are very hot.

CAUTION: Always level the machine prior to operation. Improper

leveling could cause the door to swing closed while you are

working in the oven.

FDM Titan User Guide Setup & Installation

2 - 1

Chapter 2

Setup & Installation

Preparing Your Facility for Installation

Follow the T-Class Site Preparation Guide to ensure that your facility is effectively and

safely prepared for the system to be installed.

Identifying Your Machine

Use the following two tags to identify your machine:

• Serial Number Tag. Refer to

this number when requesting

service.

• Model Tag. The model number,

the power requirements, and the

company’s address and phone

number are given on the tag. All

patent numbers associated with

the machine are listed on the

lower left part of the tag.

Both of these tags are located on the

back side of the machine near the

bottom. They are typically placed near the machine’s power connection. Use the

information on these tags when identifying your machine.

Making the Network Connection

Processed job files are transferred to the FDM modeler

through your facility’s Ethernet network. An RJ45 network

connector is located in the lower left corner of the back

panel for the network connection.

Model TagSerial Tag

RJ45

Connector

Setup & Installation FDM Titan User Guide

2 - 2

Making the Power Cable Connection

This machine requires a high voltage connection, which is made behind the machine

near the bottom. High voltage is applied to the machine via a Delta connection.

Stratasys recommends that the power cable connection be made by a licensed

electrician. The main breaker must be off until a Stratasys Service Technician has

verified the connection. This machine is only provided with a Delta connection.

Using the Main Circuit Breaker

If the machine encounters a high current surge, the main circuit breaker trips,

protecting the machine’s electrical and electronic components. The circuit breaker is

located behind the machine in the bottom right corner. To place the machine back into

operation, you must reset the circuit breaker. This is done by pushing the circuit

breaker handle all the way down and then back up.

Using the Uninterruptible Power Supply (UPS)

The UPS unit is a battery standby system that supplies AC voltage to the processor

and cooling fans in the event of an AC voltage power loss. It does not run the entire

machine. You can access it from the back of the machine. In the event of an

overcurrent condition, the UPS is protected by a combination on/off switch and circuit

breaker located directly above the main breaker.

• It shuts itself off if power is not restored to the machine.

• If power is lost to the machine you may need to manually power the unit back up.

However, this should not be necessary unless the UPS has been manually turned

off. To regain power, hold the “On” button on the front of the UPS unit until a beep

is heard and/or LED lights appear.

High Voltage

Power Cable

Connection

High Voltage Power Cable Connection

Main Circuit

Breaker

UPS Switch

FDM Titan User Guide Setup & Installation

2 - 3

• The LED display shows the UPS status.

The UPS also has the purpose of cooling the

system when power is lost or turned off. The

UPS keeps the blowers running to carry the heat

away from the heating elements. If the heating

elements are not sufficiently cooled at power-off,

the thermal protection circuits may open. In

addition to the thermal protection circuits failing,

the machine may be damaged by high

concentrations of thermal energy.

Thermal Cut-Out Fuses

There are two thermal cut-outs installed on the machine. When a cut-out reaches its

set temperature, it opens, and power to the machine is removed. This is to prevent

damage to the machine and facility in case of an overheating condition. Contact

Customer Support if a thermal cut-out opens.

‘

WARNING: High voltage is present in the machine even if the power

cord is unplugged. This is due to the UPS.

Note: See “Powering Up the Machine” on page 5-3 for more information.

Note: Allow the machine to cool down before unplugging the power cable to

prevent the oven cut-out from opening. If the cut-out opens, call

Customer Support.

On Button

Mode Indicator Lights

On/Off

(Hold in for 2 seconds to activate)

Load Level Indicators

Off Button

Reset Button

UPS 5125

UPS

Switch

Setup & Installation FDM Titan User Guide

2 - 4

Initial Network Configuration (IP Address)

Before operating the machine, you must enter the IP, Netmask, and Gateway

addresses.

1. Power up the machine, as shown on page 5-3.

2. From the Ready screen, select Maintenance and press ENTER.

3. Select Administration and press ENTER.

4. Select Network Configuration and press ENTER.

5. Select IP and enter the address using the keypad. Press ENTER. You can use the

DEL key to erase incorrect entries.

6. Select MASK (Netmask) and enter the address. Press ENTER.

7. Select GW (Gateway) and enter the address. Press ENTER.

Build Job..

Operator Control..

Modeler Status..

>Maintenance..

| *Tips: Model T16

| * Support T16

Modeler Default..

>Administration..

Reboot Machine..

>Network Configuration..

Receive Software Upgrade or Code..<E>

Field Service.. password:

>IP : [172.16.70.10]

MASK: (.none found)

GW : [172.16.100.1]

Note: See your system administrator if you do not know the IP, Netmask, or

Gateway address.

FDM Titan User Guide Setup & Installation

2 - 5

Upgrading Software or Downloading a Code

The system’s software and unique code can be downloaded from an Insight

workstation. Only Insight v4.0 and later supports the code download process.

1. Verify that the machine is idle.

2. Place the machine in the Upgrade mode.

• From the Main Menu select Maintenance and press ENTER.

•Select Administration and press ENTER.

•Select Receive Software Upgrade or Code and press ENTER.

The machine is now ready to receive the new software upgrade or code from

the Insight workstation.

3. To install a software upgrade:

• Open the Administration program.

• In the administration application, select the system to upgrade.

Build Job..

Operator Control..

Modeler Status..

>Maintenance..

| *Tips: Model T16

| * Support T16

Modeler Default..

>Administration..

Reboot Machine..

Network Configuration..

>Receive Software Upgrade or Code..<E>

Field Service.. password:

>Waiting for Software Upgrade or Code

Press MENU key to Cancel

Note: You will automatically be notified when a new upgrade file is available for

download. Download the upgrade file and follow this procedure for

installation.

Setup & Installation FDM Titan User Guide

2 - 6

• Click on the “Install new software to the modeler” icon button.

The administration software verifies that the system is in the Upgrade mode

and displays a File>Open dialog box.

• Navigate to the location of the upgrade file. Upgrade files (UPG) are

downloaded into the ‘Stratasys’ folder on your workstation.

• Select the Upgrade file (.UPG file) from the dialog box.

• Confirm that you want the download to begin and click Yes to acknowledge

that the machine will need to reboot. Downloading begins, a progress bar

appears showing you the downloading progress.

• Select “Reboot and Install Software Upgrade <E>” and press ENTER.

• Press ESCAPE on your keyboard to cancel the upgrade.

The system reboots and upgrades the file. The system is now in its normal

power up state. Log files and calibration files are preserved by the upgrade

installation process.

Note: The default location for the ‘Stratasys’ folder is directly below the

‘Program Files’ directory. This location may be different on your

workstation depending upon choices made during previous software

installations.

Page is loading ...

Stratasys FDM Titan User manual

Stratasys FDM Titan User manual

Stratasys FDM Titan User manual

Related papers

Other documents