Transcript
V3.5 – February 9, 2015
3D PRINTING The school’s 3D printers create models in plastic or powder. The printers are fee-based and open to Arch students and faculty, first-comefirst-serve, but with preference given to digital fabrication classes. Only architecture-related work will be printed (no ornaments, gifts for friends, jewelry, etc.). 3D PRINTER TYPES We have three different models to choose from. It’s all about material, length of time to print, cost, resolution, and how much work it takes to post-process the model after it leaves the printer. 1) INVISION SR - PLASTIC The Invision creates translucent, acrylic plastic models. The plastic is heated to a liquid, sprayed like ink in layers on the build platform, and then zapped with ultraviolet light to harden it. Wax is used as a support structure for the plastic, and it melted away after. It takes about 5 hours to print one inch in height, and the max model size in inches is 11.5 L x 7 W x 8 H. The cost is $7.25 per oz for the plastic and $4.00 per oz for the wax support material. Of the three printers, this produces models with the best resolution and durability, but is the most expensive. Models are paintable. 2) ZPRINTER 350 - POWDER The 350 makes models from a white powder, held together with a binding agent. Models can be up to 10 L x 8 W x 8 H in inches. Time to print is approximately 2 hours per inch in height, but when finished, models require a couple of hours to dry. The cost is $4.00 per cubic inch. Models can be fragile and may be strengthened by dipping in cyanoacrylate at extra cost. 3) REPLICATOR 2 - PLASTIC Makerbot’s Replicator 2 prints using a 1.75 mm bioplastic filament called PLA (in many colors!). Think of it as a hot glue gun that lays down plastic in 100 micron layers. Maximum build size in inches is 11.2 L x 6.0 W x 6.1 H. At 6 cents per gram, it’s very inexpensive. Time to print is approximately 1 hour per inch in height, although full size models can take 25 hours or more to print. The models are fairly durable, but removing the support material can be extremely difficult. MAXIMUM BUILD SIZE (INCHES)
X (length) Y (width) Z (height)
Zcorp 10” 8“ 8”
Invision 11.5” 7” 8”
Replicator 11” 6” 6”
COST The cost is based on volume or weight and will be calculated before it is printed. Fees are deducted from your lab printing account prior to printing. If there are insufficient funds in your account, the model will not be printed. The cost to build a model is cheapest on the Replicator 2, followed by the Zprinter, then the Invision. Zprinter $4.00 per cubic inch
Invision $7.25/oz plastic $4.25/oz wax (support material)
Replicator $0.06/gram
If you would like to know the cost prior to printing, be sure to check the appropriate box on the 3D Printer Job Submission Form and we will contact you. TIME TO PRINT Models take from 1-36 hours to print, based on size. We will attempt to print multiple models at once when possible. Students should plan to queue their files several days in advance of deadlines.In general, the Zprinter prints fastest, followed by the Replicator, then the Invision.
V3.5 – February 9, 2015
3D PRINTER COMPARISON
Speed: Cost: Durability: Resolution: Post-processing:
Zprinter Fastest Medium Lowest Lowest Minimal
Invision Slowest Highest Highest Highest Minimal
Replicator Medium Lowest Medium High Medium Moderate to High
HOW TO PREPARE MODEL FOR PRINTING Models are created in 3D programs such as Rhino and must be saved in the STL format. Use the following steps to prepare your model in Rhino.
Make sure your model unit scale is in inches, not feet. Even though the dimension scale may be in inches, you still need to make sure the model units are in inches. Type ‘units’ on the command line to change this. Your finished model size should be 1:1 with the size you want it printed.
When working with surfaces, use BooleanUnion to combine the objects into one polysurface. Click Solid > Union. If the union doesn’t work, you will likely have errors and other problems later. Rework the model so that the union is successful before going on to the next step.
After the Union command has been applied, create a Polygon Mesh. Highlight the object, select Mesh > From NURBS Object. With highly curved surfaces, increase the number of triangles in the mesh. Straight surfaces need less.
Next, click the object to select the Polygon Mesh. With the mesh selected, drag it off the surfaces. Don’t forgot to do this, otherwise you may inadvertently export the surfaces along with the mesh!
Issue the command CheckMesh to see if you have a good mesh. If you have a bad mesh, search Rhino help for ‘check/repair meshes’. This will give you many fix-it commands. A common problem is naked or unjoined edges, which are revealed with the command ShowEdges, and usually fixed with MatchMeshEdge. FillMeshHoles will repair holes, but is more likely to change the shape of the model. ExtractDuplicateMeshFaces will separate identical faces for easier removal, but be aware it could generate naked edges. It may be helpful to make a copy of the mesh before using these tools in order to check the results. Visit http://tinyurl.com/c7zono for more tips on creating a good stl file from Rhino.
When done fixing the model, export the Polygon Mesh as an STL file (export ONLY the mesh—make sure the surfaces aren’t underneath or you may get tons of errors when checking in Magics). Select the mesh, then click File > Export Selected. Change the Save As Type to STL. When the File Type Options appears, choose BINARY. Export each model to a separate STL—don’t combine them in one STL.
USE MAGICS TO FIX ERRORS AND CHECK THE MODEL After creating the STL file, check the model in Magics, which is a software program available on the lab computers.
Magics has a Fix Wizard which repairs common problems. Click Tools, Fix Wizard. Click Diagnose on the left, then click the Update button to see what errors are present. Ideally, you want to end up with zero errors in each category and one shell. If there are errors, you can click ‘Go to Advised Step’ to walk through the fix-it steps. Or you can pick an area listed on the left to work on, such as ‘Normals’, and try letting it automatically fix the errors. Each time you fix some errors, go back to Diagnose and reclick the Update button to check the error counts. Sometimes the automatic fixing can drastically change the model so use with care. There’s also a ‘combined fix’ but with more complex models this usually gives poor results.
Other useful tools under the Tools menu are Triangle Reduction, Extrude, Offset Part, and Smoothing. If you make changes to the model in Magics, use File > Save Part As to keep it in the STL format.
V3.5 – February 9, 2015
HOW TO SUBMIT YOUR FILE - DROP BOX AND JOB FORM 1. Copy your STL file into the 3D Printer Drop Box folder, which is found on the K drive on the lab computers. Make sure the filename includes your NetID (i.e. jrsmith-myfile-01.stl) 2.
If you have several parts to print, put each part in its own STL file. Do not give us an STL file with multiple parts.
3.
Print and fill out the 3D Printer Job Submission Form (download from website). Submit the form in one of the following ways: o o
Slide it under the door of Tim Brower’s office in Room 008b (inside the model shop) or slide it under 008 door if closed, OR Scan the completed form, save it as a PDF, and copy it to the 3D Printer Drop Box folder (make sure the filename includes your NetID).
POST-PRODUCTION AND MODEL PICK UP 1. We will contact you via email when your model is done printing. 2.
We encourage you to stop by and learn how to clean and infiltrate your Zcorp model(s). This involves powder removal and optionally treating the model with salt water or a cyanoacrylate bonding agent to increase the durability. Invision models may require additional cleaning to remove the wax support material. Replicator models may require trimming of the plastic supports.
FINISHING YOUR MODEL - PAINTING, SANDING, GLUING Sanding - Sand the model to remove imperfections or layer lines from the surface. Wet sanding tends to keep the part cool and prevent melted material from “gumming up” the sand paper. It also minimizes dust. If you dry sand the part, wear a NIOSHapproved (or equivalent) dust mask. Do not sand Zprinter powder models that have been dipped in the cyanoacrylate (Colorbond) bath.
Painting - Before painting a part, wipe the surface with isopropyl alcohol and apply a lacquer-based paint primer. After priming, brush on any oil- or water-based paint that is compatible with the primer. Excellent painting results have also been achieved with air brushes and water-based acrylic paint.
Gluing - Use “super glue” (cyanoacrylate) to join parts. Wipe the mating surfaces thoroughly with isopropyl alcohol before gluing for a stronger bond.
Dipping (Zprinter powder models only) - For an extra cost, you can dip your models in a cyanoacrylate-based liquid called Colorbond through our office. This liquid infiltrates the model, making it stronger. Students have also used Zap-A-Gap to coat their models. Another option is to mix up a solution of Epsom salts and water in a 1 to 6 ratio in a spray bottle. Lightly spray the model and wait for it to dry. Repeat over and over and eventually the salt coating will create a more durable finish that strengthens the model. Be very careful not to spray too much or it will disintegrate your model. We can loan you the spray bottle/salt solution.
Dewaxing - The Invision plastic models may have a slight white coating, which is wax residue. A hair dryer on the hot setting can be used to melt the wax—then use paper towels to absorb the melted wax. A heat gun can be used, but it can easily ruin your model if not used carefully.
REFUND PROCESS Refunds will be granted only if the printer malfunctions or the model is accidentally broken by an operator. Errors in the STL file are a student’s responsibility.
