From RobotLab

Contents 1 About 1.1 Contact 2 Usage 2.1 Creating your model 2.2 Exporting your model 2.3 Loading the model into Objet Studio 2.3.1 Fixing broken models 2.4 Building 2.5 Removing the model and cleaning 2.5.1 Even more cleaning

About

The Objet Eden 250 is our new prototyper. It prints at a very high resolution, particularly along the vertical axis (16 micron thick layers).

Contact

Contact Matt Bell for further information (e.g., you want to print something, you're curious about what the printer can do, etc.).

Usage

Note that these are not fully detailed instructions, although they should be a sufficient reference once you have been trained. If you've never used the prototyper before, find someone who knows how to help you.

The Objet printer is controlled from coppa (the computer with the very large screen near the prototypers). This computer is not set up on the SUDIKOFF domain, so you will need to ask Matt Bell to set up an account for you if you plan on using the printer frequently.

Creating your model

Use your favorite 3D modeling program to create your model. (Or you can write custom code to generate an STL file directly if you're so inclined.) coppa has 3ds max available, and the iMacs in 005 have Maya.

Exporting your model

Objet has nice instructions for exporting from a wide variety of CAD programs. In general, you need to export an STL file, although Objet Studio can read SLC files as well.

Loading the model into Objet Studio

Unclosed contours error

Missing geometry leading to unclosed contours

Once you have the model, you need to make sure it actually works. Objet Studio is very finicky about models needing to be closed. Any backwards normals or unconnected edges may cause you to get the "Unclosed contours detected" error (indicated by a purple-colored model). In the example shown above, this is caused by missing geometry, specifically a missing tube between the openings indicated by red circles in the figure to the right. In this case, the missing geometry is the result of a boolean operation not working as expected.

1. To load your model and see if it works, start Objet Studio.
2. Right click on the tray, and select Insert. Find your STL file, and choose your units (millimeters or inches).
3. Once the model is inserted, double-click it to bring up the properties window if it is not already open. Under the Options tab, select either Matte or Glossy. (Matte puts a layer of support material around the entire model, which uses extra material, but produces a uniform matte finish. Glossy leaves the upper surfaces free of support material, resulting in a much clearer glossy surface. However, the bottom surfaces will still be matte finish, and the transitions may be undesirable.)
4. The Transform tab lets you type in any necessary transforms (typically rotation and scaling). You should try to position your models in a way that results in the least usage of support material, as this is both cheaper and faster. Thus, try to orient the model with the largest surfaces close to the bottom.
5. Repeat steps 2-4 for any other models.
6. In the toolbar, select either High Quality (16 micron layers) or High Speed (~30 micron layers). High Speed is obviously faster, at the expense of some resolution, and is thus good for larger models with less fine detail.
7. Click the auto-position button (lightning bolt) to arrange your models on the tray.
8. Click the validate button (exclamation point) to make sure the models are on the tray, not intersecting, and that the STL files are OK. At this point, you may see the unclosed contours error. If so, see the next section on how to fix your model.
9. Click the usage button (dollar sign) to see how much material and time the print job requires (this will show up in the status bar at the lower left of the screen).
10. Save your tray.

Fixing broken models

If the errors are minor, they can frequently be fixed by running admesh. admesh is set up under Cygwin on coppa:

1. Run Cygwin from the desktop or Start Menu
2. cd to the directory containing your STL (for locations not within the Cygwin structure, prefix the path with /cygdrive/c/ (e.g., cd /cygdrive/c/Documents\ and\ Settings\username\Desktop). Tab completion is your friend for long Windows paths with spaces.
3. Run admesh:

   admesh input.stl -b output.stl

   (-b indicates that you want to output a binary STL file. To list other options, run admesh --help).

The output from admesh will include the following:

========= Facet Status ========== Original ============ Final ====
Number of facets                 : 13580               15134
Facets with 1 disconnected edge  :  1700                   0
Facets with 2 disconnected edges :     1                   0
Facets with 3 disconnected edges :     0                   0
Total disconnected facets        :  1701                   0
=== Processing Statistics ===     ===== Other Statistics =====
Number of parts       :     1        Volume   :  3907.759277
Degenerate facets     :     0
Edges fixed           :     0
Facets removed        :     0
Facets added          :  1554
Facets reversed       :  1272
Backwards edges       :     0
Normals fixed         :  1554

If "Number of parts" is incorrect, you should make sure that your model is fully connected. If the number of changes is generally small, you can probably use the fixed output mesh. If it is large, the output mesh is likely to be broken even if Objet Studio accepts it. However, you can use it to locate the regions of your original mesh that have problems. To do this, import the fixed STL back into your 3D software, and look for regions that are incorrect. In the figure at right, the regions with missing geometry were closed up (green circles). In the inset, you can also see that excess triangles were added at the ends of the tube, indicating that the original model may have had a problem here as well. Once you've identified the problematic regions, open up your original model, and take a closer look to see if there are unconnected vertices/facets, or missing geometry.

Building

1. Look at the printer and make sure there is nothing on the build tray. The printer has no way of knowing if the tray is empty, and trying to print with models already on the tray will break the printer.
2. Click the build tray button . You may get a warning confirming that you are overwriting the tray; this is OK.
3. Turn on the small white monitor to the left of the large screen, and press button #1 on the KVM switch to the right of the large screen. The second monitor is attached to the computer in the printer.
4. Click the large red button at the bottom of the Eden 250 application to put the printer in Online mode. The printer will now warm and clean the print heads, and start printing.
5. Press button #2 on the KVM switch to switch back to coppa. The Job Manager will give you an estimated completion time, as well as information about material consumption. It may also notify you of the need to switch material cartridges if the printer is running low on material. If this happens, you need to have another cartridge ready to insert, ideally as soon as possible after the printer pauses to reduce any visible lines in your printed model.

Removing the model and cleaning

1. Once the printer has finished printing, it is generally a good idea to let the model cool for a while. Objet recommends several hours, with a minimum cooling time of 30 minutes.
2. Go to the large gray cabinet on the west wall of the lab. Inside, you will find a wide spatula and a smaller spatula with a slider to extend a razor blade.
3. Use the wide spatula to pry the model off the tray. Particularly for small models, do this carefully to avoid having your model fly off into the depths of the machine. If for some reason you do lose your part inside the printer, contact Matt Bell for help with extricating it from the printer.
4. While prying the model off the tray, please try to minimize the amount of support debris that falls into the inside of the printer. You may find it helpful to keep the shop vac nearby to vacuum up debris as you create it.
5. Once you have the model removed from the tray, there will typically still be some support residue left behind. Use the razor bladed spatula to scrape this off the tray, again taking care to keep the inside of the printer clean.
6. If you have large blocks of support material on your part, you can speed the process up a bit by scraping these free with a knife or other tool.
7. 

   

   The WaterJet cleaning station
   (If the inside of the WaterJet is dry and full of support debris, please use the shop vac to clean it out.)
8. Place your model inside of the WaterJet machine and close the door. Turn on the WaterJet with the switch on the top left.
9. Select a spray nozzle (thin jet or wide spray) using the valve inside the machine. It points towards the selected nozzle.
10. To operate the WaterJet, step on the foot switch while securely holding the selected spray nozzle. Spray the model thoroughly until all the support has been removed.
11. Once you have finished cleaning your model, turn off the WaterJet, and leave the side door open so it can dry out. Make sure to turn the screw next to the door so that the door doesn't slide closed.

Even more cleaning

If the model is not clean enough for you, or if you have tubes that can't be cleaned easily with the WaterJet, you can use sodium hydroxide (NaOH) to dissolve away any residual support material. You need a 2% (by weight) solution of NaOH. This means that if you have 200 mL of water, you need 4 g of NaOH (technically, 196 mL and 4 g, but 200 mL is close enough). 300 mL is 6 g, and so on.

1. Fill the labeled sodium hydroxide beaker with enough water to cover your model.
2. The gray cabinet contains a bottle of NaOH beads, a paper cup marked NaOH for weighing, and a small scale. You may also want gloves to protect your hands, as dry NaOH will give you a chemical burn.
3. Place the cup on the scale and turn on the scale. It will auto-calibrate and include the weight of the cup when zeroing.
4. Unseal the sodium hydroxide (plastic bag, tape, and cap). Using the spoon inside the plastic bag, measure out the appropriate amount.
5. Pour this into the beaker of water.
6. Reseal the sodium hydroxide (cap, tape, and plastic bag). Doing this quickly prevents moisture from getting into the container.
7. Stir the solution until all of the NaOH powder has dissolved. The solution will heat up somewhat in this process, so be careful if you are using large amounts of NaOH (in our usage, 600 mL/12 g does not produce dangerous amounts of heat).
8. Place the model in the solution once it has cooled. Typically, 1-2 hours are enough to remove any residual support material on surfaces. If you are trying to clean out a tube, it may be necessary to repeatedly soak the model in NaOH and spray it clean in the WaterJet until the tube is fully free of support material.