How to PrePare aeC Files For 3D Printing

How to PrePare aeC Files For 3D Printing And Start Producing Physical 3D Models in Hours Instead of Weeks

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taBle oF Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

How do AEC professionals use 3D printed models? . . . . . 4

Preparation for 3D printing . . . . . . . . . . . . . . . . . . . 6

Decide what would you like to print . . . . . . . . . . . 6

Choose your scale . . . . . . . . . . . . . . . . . . . . . 6

give your model form . . . . . . . . . . . . . . . . . . . 7

Choose a file format . . . . . . . . . . . . . . . . . . . . 8

Print it . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

How to PrePare aeC Files For 3D Printing 2

introDuCtion

as every designer knows, there’s magic in transforming a great idea into a tangible and useful object you can hold in your hand. architects, engineers and construction (aeC) professionals are fast discovering the myriad benefits of 3D printing, including:

• unleashing creativity

• shortening project timelines

• lowering costs

• improving communication

• securing quick approvals

Firms are discovering a new ability to print physical 3D models in hours instead of the weeks needed for handcrafting, while reducing costs and improving model accuracy. the new capability is enabling more productive design reviews; accelerating design phases; and reducing the time and money necessary to create models for review, presentation and marketing. Plus, more accurate models clarify designs for clients and officials, facilitating the approval process and ultimately resulting in more beautiful, higher-quality building designs.

Just as with building information modeling (BiM) software, 3D printing is becoming a strategic necessity for aeC firms. The question is no longer “should we do it?”, it is “how do we implement 3D printing into our practice today?”.

This paper will answer that question by reviewing the wide variety of 3D printing applications in the AEC industry, and then demystifying the process of preparing a digital model for 3D printing.


For a primer on 3D printing, read our white paper:

How 3D Printing WorksThe Vision, Innovation and Technologies Behind Inkjet 3D Printing

How Do AEC profEssionAls usE 3D prinTED moDEls?

You can use a 3D printed model in the same way that you use handcrafted 3D models and renderings. applications include client presentation, massing, detailed models, building performance analysis, clash detection, and building construction phases.

The following examples illustrate how firms of every size use 3D printing to improve design quality, client satisfaction, marketing effectiveness and regulatory relations.


Massing Model

Classic white massing models convey exterior form and proportion. Contemporary design shapes are well suited to 3D printing.

Regulatory Approvals

3D printed models can be combined with other elements to quickly, easily and affordably create multicolor presentations to clients and team stakeholders, helping to close deals and win faster approvals.

Urban Planning

3D printing this Midtown Manhattan cityscape from CaD and gPs data is quicker, more affordable and more accurate than handcrafting the model.

Midtown Manhattan model, printed on a ZPrinter® 650, data courtesy of Parsons Brinckerhoff

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Bentley Microstation plant model printed on a ZPrinter® 650, courtesy of shinryo international and team-s.

Clash Detection

a good plant design packs a lot of mechanical, electrical and plumbing systems into a tight space. 3D print the model, detect any clashes, and collaborate with the construction team.

Building Energy Analysis

You can perform a solar radiation analysis in your BiM software and 3D print the results. this model highlights hot and cold spots over a 24-hour period.

autodesk ecotect analysis model courtesy of autodesk, inc.

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Detailed Model

show complex exterior/interior details with color and texture.

the China House model courtesy of autodesk, inc.

note the use of color to depict design details, complex analysis results, clash detection and construction phases.

PreParation For 3D Printing

Models like these don’t pop out of the 3D printer like your morning toast, but you really wouldn’t want that to be the case. Most designers want control over 3D printing variables in order to produce a specific model type. these variables can include which details to preserve or hide, what scale works best for what you’re trying to communicate, and even what software to use in the first place.

since some 3D software was never designed to produce data for 3D printing however, you’ll have to take a few easy steps to prepare the files. the rest of the 3D printing process, the complicated work, is handled by the software and a ZPrinter®.1 the good news is that if you know the basics of BiM or 3D CaD, you’re 90 percent of the way to printing aeC models successfully.

Step 1. Decide what you would like to print

First, consider what you’re trying to accomplish with your model, and select the features to print.

will it be a conceptual design study showing mass, forms and proportion? if so, then don’t worry about internal details. You’ll want to hollow out your design to save material in the printing.

will it be a very specific and unique architectural detail? in that case, just take that section of the digital model and scale it to fit your 3D printer’s build chamber (fig. 1).

Step 2. Choose your scale

if you designed products instead of buildings, you would often print full-scale models of design concepts for review. Most 3D printers are large enough to print a shoe, cell phone, toothbrush, toy, computer fan, brake pad, or anything else smaller than a breadbox. in aeC, however, you have to think about model scale (fig. 2). Most aeC models are 1/50th to 1/1000th their true size, and that has implications for 3D printing. a load-bearing feature in a 3D printed model, for example, has a recommended thickness of 0.200 inches (about 5 mm). Detail features can be printed as small as 0.025 inches (about 0.6 mm). so if you’re trying to print, say, a 10 cm-diameter post at 1/1000th scale, it will effectively disappear from your model unless you thicken it in your original model.


Figure 1. Detail Study. Detailed design studies can benefit from realistic material colors and textures

Figure 2. Scaling guidelines

1 ZPrinter® is the collective name for this 3D printers range offered by 3D systems.

sauna house design by Juha savisalo

Non-loadbearing features– scaled to printabout 0.50″

Detail features – scaled to print about 0.025″

Load bearing features – scaled thick enough to keep structure together (about 0.200″)


these scaling concerns explain why it’s critical to define what you’re try-ing to communicate to your stakeholders. Exterior shape and form? if so, then delete all internal features and hollow out the model to minimize material consumption. Are you trying to show a specific design concept? if so, section your model and scale it down only as much as needed.2

if you’re having a hard time selecting what to print, consider making several 3D prints, the same way you’d make two or three renderings for a client presentation.

the math in scaling is easier than you might suspect. this free thickness calculator is designed specifically for aeC 3D printing http://www.cadspan.com/calculator (fig. 3).

Step 3. Give your model form

once you’ve defined the model you wish to build and scaled the digital design, you need to review geometry.

a 3D printer can print only what’s in the digital design. a design with gaps or holes will not print properly, so your digital model must have “watertight” geometry. And since lines and planes are abstract concepts, they must be thickened into solids to be 3D printable.

Fortunately, most current aeC design software products automatically produce watertight designs with printable forms. Many have dedicated tools for checking and editing geometric meshes and cleaning up models prior 3D printing. and in many instances, designers have the choice of using 3D tools (cubes, spheres, cylinders, etc.) or 2D tools (planes and lines). opting for the 3D tools will make printing significantly easier.

unlike software that produces watertight designs automatically, design visualization software models sometimes need more preparation. the simple steps described in this section are common for design visualization software like google sketchup or autodesk 3ds Max.

For example, a planar panel is sometimes used in software to represent a column. while this works for on-screen or on-paper visualization, that plane has no real-world shape. it’s nothing more than a geometrical concept. a 3D printer can’t print it until it’s extruded to create a 3D column (fig. 4)

Figure 3. Online thickness calculator

Figure 4. Google SketchUp images

2 the ZPrinter® 850 has the industry’s largest build bed at 20 x 15 x 9 inches (508 x 381 x 229 mm), for larger scale models.

Problem:Flat panels too thin to print

Solution:extrude to at least 3 mm to make them printable


The designer must close all open planes in this model to make the design watertight. You can simply draw rectangular “face” entities to close these open faces (fig. 5):

Step 4. Choose a file format

once your design is watertight and geometrically printable, the next step is to export the BiM/CaD data in a file format that a 3D printer recognizes. Here, too, you have choices and control.

all the popular BiM/CaD software products provide the capability to export basic geometry information as an stl file — the industry standard for monochromatic 3D printing3. the latest version of autoCaD® includes a “send to 3D print service” option that will initiate printing on your own 3D printer, or enable you to send the file to an outside print service.

one limitation of stl is that it describes only the surface geometry of a three-dimensional object without any representation of color, texture, engineering labels or other common CaD model attributes. Fortunately you can add those attributes. even though an stl file contains no color information, ZPrinters include software that enables you to add color — including labels and texture maps — directly into the model file4.

in the example on the right, the user has added color and a company logo to the model base, even though there was no color information provided in the original stl file (fig. 6).

revit users can add color this way, or export the revit file to 3ds Max Design to add color and texture information. if you choose the latter method, you can export either a 3Ds or VrMl file to ZPrint.

Figure 6. Add color and texture maps in ZEdit Pro

Figure 5. Closing up the planes

3 stl is an abbreviation derived from stereolithography.

4 Multicolor ZPrinters print in full, 24-bit color (just like a standard document printer) with millions of color possibilities.

A few products, such as rhino and form•Z, export directly to a 3D printable color file format called ZPr (short for ZPrint) (fig. 7). the ZPr file format has been created to include all the information needed for printing 3D models with colors and simulated textures.

the last important file type is PlY, the format for capturing data from 3D scanners. PlY supports a simple description of a single object as a list of nominally flat polygons. it includes data on color and transparency, surface normals, texture coordinates and data confidence values. although fronts and backs of polygons can have different properties, PlY enables easy 3D printing of scanned objects.

this table summarizes the file formats that selected aeC design software products export. ZPrinters support all of these formats:

microstation, ArchiCAD, 3ds max Design, rhino, form•Z and sketchup pro software are all capable of exporting color and texture information for 3D printing. users of ZPrinters can add color to autoCaD and revit files just before printing.


Figure 7. Exporting a digital model as a ZPR file for multicolor printing

STL VRML 3DS PLY ZPR

autoCaD n

revit6 n

3ds Max Design n n

Microstation n n

archiCaD n n

rhino n n n n n

form•Z n n n n n

sketchup Pro n n n

6 to download the free revit stl exporter, visit http://labs.autodesk.com/utilities/revit_stl/.


Step 5. Print it

at this point, you’ve decided what to print, chosen your scale, made your digital model 3D and water-tight, and chosen your file format. now it’s time to print.

For monochrome 3D prints, the simplest workflow from any CaD or BiM product is the stl export. ZPrint software, included with the ZPrinter®, automatically accepts the file and slices the 3D geometry into hundreds of digital cross-sections for printing. You can opt to print more than one model simultaneously, or manipulate the virtual model on the computer screen to change position (making room for multiple models).

ZPrint software includes tools for scaling, checking, repairing (e.g., inverting surface normals), copying/pasting (to print more than one part per build) (fig. 8), adding drain holes, and estimating print times and material usage. ZPrinters also include other software that makes it easy to split large models into smaller sections that can be assembled after printing.

suMMarY

That’s all there is to 3D printing AEC models. You can now quickly create high-quality models that reflect new creativity, shorten timelines, lower costs, improve communication, and facilitate design approval. simply take your digital model, scale it down, tighten it up, give it form and print it out. then let the magic of the printed model tell your story.

Figure 8. ZPrint software includes a print time estimator for build time and material usage information

333 three D systems Circlerock Hill, sC 29730 usat: +1 (803) [email protected]

aeC-wP-2009

© 2012 by 3D systems, inc. all rights reserved. specifications subject to change without notice. the 3D systems logo and stylized text, and ZPrinter are registered trademarks of 3D systems, inc. all other company and product names are pending trademarks or registered trademarks of their respective holders.

About 3D Systems Corporation

3D systems is a leading provider of 3D content-to-print solutions including 3D printers, print materials and on-demand custom parts services for professionals and consumers alike. the company also provides CaD, reverse engineering and inspection software tools and consumer 3D printers, apps and services. its expertly integrated solutions replace and complement traditional methods and reduce the time and cost of designing new products by printing real parts directly from digital input. these solutions are used to rapidly design, create, communicate, prototype or produce real parts, empowering customers to create and make with confidence.

How to PrePare aeC Files For 3D Printing

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