Stereolithography Tutorial

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This is a tutorial for the Mechanical Engineering Department's Stereolithography Machine, SLA-190. It provides the student with a method needed to produce a SLA part from Pro/ENGINEER's Part mode, and can be used as a guideline for all part productions. All steps should be followed in the order presented from beginning to end. It has detailed explanations so there will be minimal reference to the SLA-190 reference manuals. However, there may be a need to look further into a specific procedure. In this case, refer to Maestro Workstation User Guide and SLA-190 Buildstation User Guide provided at the workstation.

This tutorial is written in the format as follows: All bullets represent execution key strokes, and all italicized text are comments and explanations that should provide the necessary understanding for the operation.

From the Pro/ENGINEER Part mode:

Pre-processing: A STL file needs to be created. Pro/ENGINEER is capable of creating such a file.
• From the part menu select: Interface, Export, and SLA. This converts the file format.
• Enter the cord height and the angle control. See the Pro/E user guide for more information on this process.
• Select: Output, and click on a coordinate system.
• Enter the file name - Enter>. * A message will prompt that some points have non-positive coordinates. It will ask to "continue?" Enter Y and - Enter> and the file will be created.
• Save onto a floppy to be moved to the SLA machine.

Turn laser on and warm for 20 minutes:
• From main menu, select #6 Tool box - Enter>.
• Select: #1 Utilities - Enter>.
• Select: #1 Power Sequence - Enter>.
• From the Power sequence menu Select: #5 Set Chamber Thermostat -Enter>. * Verify the vat temperature and thermostat temperature are as close to 30 degrees Celsius as possible. This is the calibrated working temperature of the resin. If not within 2 degrees, exit and select #2 Heater Power - Enter>, to heat vat. From the Utility menu, select #6 Vat Utility and then #5 Stir Liquid - Enter>, then select stir speed medium or slow.
• Select: #1 Laser on - Enter>. Remember the door must be closed and locked. The shutter indicator will be lit in white and the "laser-on" indicator will be lit in blue on the right side of control panel. Wait 20 minutes.

Getting started:
• Under the 3DSYS directory, type MAESTRO - Enter>.
• From the spreadsheet select: File, Load, and Component STL. Select the file to be Built (highlighted in yellow). Click on Select button.

Checking positive and negative spacing in relation to the tray (fitting the part to the tray):
• From the spreadsheet select: View, and the file to be built. * A new screen will appear. The part will be displayed on the left side on a coordinate plane. It will be desirable to place it in a view that can locate its position in space. In the Viewing Transformation Menu on the right hand side of the screen, different views can be selected with the right mouse button. Choose the one that locates the part for the best viewing.
• To view the coordinates of the part in space, select: Query, Objects. * Another menu will appear showing a numerical representation of the parts location.
• Move x, y, and z positions by entering the positive value of the negative number in the appropriate x, y, or z place on the Object Transformation Menu, then push the Refresh button. Repeat the process until no more negative space exists.

Arranging the part to minimize build time: * To minimize build time, three items are of concern: Z-axis height, Z-wait (a function of surface area), and laser drawing time. Z-axis height manipulation will be discussed now, the other items will be covered at the end of the tutorial.
• Minimize Z-axis height by orienting the part where the Z value is minimized while still creating an effective part. Press the refresh button.
• Select: File, and Save. * It will be desirable to place the part in positive space where the creation of the support structures will not extend into negative space. To do so, the addition of 0.25 inches is usually sufficient.
• Add 0.25 inches to positive x, y, and z planes using the translation menu.
• Verify that the part does not exceed 7.5 inches in any direction in the Query Object Menu.
• Select: File, and Save.
• Select: File, and Quit, and when prompted to exit, select "yes". A warning prompt to default will appear, select "Okay".

Creating Support Structure:
• From the spreadsheet, click on the part column cell containing the filename in blue.
• From the Components Menu select: Create Supports. Highlight the filename and select Change Vista Style button. *A new menu called Select Support Parameter File will appear.
• Select: Support Parameter Menu.
• Select: /usr/3d/lib/styles/sla190/in/. *A new menu will appear.
• Select: Epoxy_20.srg . * The 20 stands for the minimum angle tangent to a surface of 20 degrees. Epoxy is the polymer the SLA machine uses.
• Select: Load Support File button (it will turn from red to green).
• Select the Create button. * The spreadsheet will appear with a menu that will run and create the layers of the part.
• Select: Finished when the layer creation process is done. * A new column will appear where the part column was located called the support column. The part column will move to the right.
• Select: View, All. * The part will appear and the supports will be displayed in red. You can visually observe the supports to make sure they will be efficient in the build process. If not, you can increase/decrease the angle of the supports.
• Select: File, and Quit when done viewing. * The spreadsheet will appear.

Edit the Support Column: * Editing must be done in the support column. At the bottom of the part column, SLA5170AP will appear. It will also be displayed in the support column. SLA5170AP in the support column must be changed to SLA5170AS.
• Click on the cell SLA5170AP in the support column, then Add. * A new menu will appear.
• Select: /usr/3d/lib/styles/sla190/in/. * A new menu will prompt you.
• Select: SLA5170AS.sty.
• Select: done. * The bottom of the support column will change to SLA5170AS.
• Select: File, then Save. * A prompt will appear to name the part.
• Enter the part name.

Edit the recoat column: * Only part SLA5170AP is entered at the bottom of the recoat column. This needs to be changed to SLA5170AS and SLA5170AP needs to be entered in the cell directly above LA5170AS.
• Click the box SLA5170AP in the recoat column, then click Add from the menu that appears. In the new window that appears, change SLA5170AP to SLA5170AS. * Now you need to add a cell which has SLA5170AP just above the SLA5170AS cell in the recoat column.
• Click the cell in the recoat column that contains SLA5170AS. Now, click "Add" from the menu that appears. In the window that appears, change the End Z: entry to 0.25in.- Enter>.
• Select the done box at the bottom left hand of the window. * You will now return to the spreadsheet. Make sure both entries in the recoat column are correct. If not, click the desired box, then add, then click on user/3d/libstyles/sla190/in/. Then correct the box by selecting the correct configuration, whether it be SLA5170AS or SLA5170AP.
• Save.

Z Wait Time Manipulation: It will be desirable to change the time the STL machine waits after dipping the part in the polymer before the laser begins to draw a new layer. The proper Z wait time depends on the surface area on the xy plane. Changing Z wait time will be beneficial for part accuracy and time savings when the part cross-section begins to decrease as the layers are built up. Look in the User's Guide in Appendix A for proper wait times. * Make sure you look under the correct table for the epoxy resin the STL machine is using. Changing the Z wait time will be done in the recoat column.
• Click the bottom entry in the recoat column. When the new menu appears, select edit. * A new screen will appear. The Z wait time can be changed in this screen. In the recoat column, squares can be added and Z wait times can be entered for different layers in the build process. Make sure you enter the proper ending depth for the Z wait time you choose. The depths can be changed on the same screen that the Z wait time is changed. * Also in the Z wait time screen, the pre-dip delay, post-dip delay, z-dip delay, z-acceleration, and z-dip distance can be modified if problems arise when creating a certain part. The default values are usually sufficient for part building.

Layer Depth Manipulation: Layer depths can be modified for better resolution or thicker layers when creating a part. The default value is 0.006 in./layer. To change the layer thickness, click on the box in the part column where you desire to modify the layer thickness. A new screen will appear. There will be a box where the default layer thickness is displayed. You can edit this value in the box. The maximum depth of a layer should not be greater than 0.02 in.. The thicker the layer, the longer the laser has to strike the surface of the area to cure the polymer. The minimum depth of a layer should not be less than 0.0025 in..

Creating A Build File: Now you need to prepare the STL file into a build file. Four files will need to be created. They are a range file, a parameter file, a vector file, and a layer file. All of these files are necessary to create the desired part on SLA.
• Click prepare at the top of the spreadsheet with the right mouse button until the square around it becomes blue. Release the mouse button and a message box will appear.
• Click Prepare All. * This will create the layers for building the part. It will take a moment to do so.
• Click Finished when the files are done being created.
• Exit the spreadsheet by selecting File at the top of the spreadsheet, then Quit. * A new screen will appear, with a DOS prompt.
• Enter: List - Enter>. A number of files will appear. You need the four files that begin with the name of your part and which in (partname).l, (partname).r, (partname).prm, and (partname).v. Make sure these four parts are listed. If not, something has gone wrong with your spreadsheet. You will have to refer to the User's Manual for troubleshooting. Once you see the four files listed on the menu, you will need to import them to the STL machine using file transfer protocol (ftp). This is done by entering commands from the STL machine's workstation. The commands are get (partname).l, get (partname).r, get (partname).prm, and get (partname).v. Once the files are entered into the STL machine, the part is ready to build.
• Enter: bye-Enter>.
• Enter: dir-Enter>. * Make sure the four files are on the menu.
• Enter: menu-Enter> to move the part building menu.

The pre-building process: (from the SLA-190 workstation)
• From Main Menu, select: #4 Prepare - Enter>.
• From the available files listed, type in filename - Enter>.
• Select: #1 Parameter Range - Enter>. Check number of part to be created and if necessary check xyz shrink. More information on shrink can be found in user manual.
• If needed, Select: # U Update - Enter>.
• From Main Menu, select: #5 Build - Enter>.
• From the Build menu, type in filename/sim - Enter>. This starts a simulated build in order to see if the are any problems. It should be run through all layers. To accelerate, push the "C" key on the key board once, or hold it down.

The Build:
• From the Main Menu, select: #5 Build - Enter>.
• Type in the filename - Enter>. A note should appear on the screen "Checking resin level". After a few minutes another message will appear prompting you to add or remove resin. Add only SLA5170 resin and add it very slowly until multiple beeps are heard, then stop. Press any key to repeat process or if process is done, to begin build. * Resin reacts to Ultra-violet light, keep in dark space. * * The build process can be aborted by pressing control - C>. However, this must only be done when in the Z-wait phase i.e. when the laser is not active and the tray is recoating.

It is very important to wear Nitrle (NT Surgical) rubber gloves throughout post processing. Continuos exposure to the resin can cause skin irritation.

Removing part:
• Open chamber door a few inches for one to two minutes to ventilate the chamber.
• Remove the platform with the part by releasing the 4 clips.
• Tilt the platform upward for five to ten minutes to drain resin from the platform.
• Place the platform on a tray to drain.
• Use paper towels to soak up excess resin.
• Pour TMP (Tripropyleneglycol Methylether) solvent onto the platform and part. Use a stiff bristled brush to work in the TPM in detailed areas.
• Use a knife to break the support structure from the platform.
• Return the part to the tray with solvent to rinse again.
• Scrape off excess resin from the platform with a knife.
• Wash the platform in solvent again.
• Rinse the platform in a sink with water.
• Wipe and dry the platform with paper towels and pressurized air.
• Cut the support structure from the base of the part.
• Again, place the part in a tray with solvent. * Note: Be careful to remove all resin from detailed surface of part. If the resin is not removed, the part will not cure correctly and remain gummy.
• After rinsing the part with TMP, dry it with paper towels.
• Place the part in a beaker and pour denatured alcohol (Lacquer Thinner) to remove the solvent from the part.
• Use paper towels to dry the part.
• The part is now read to be placed in the UV (Ultraviolet) curing oven for 3-6 hours or more, depending on the size of the part.

  Congratulations, you now are a "Stereolithography Geek!"

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  Links to other related Web-sites

  SDSU's College of Engineering Web-page!

  Facility for Applied Manufacturing Enterprise (FAME).

  SDSU's Mechanical Engineering Dept's Homepage.

  U of Delaware's Free Form Fabrication page