8 Tips for 3D Printing with Sketchup

Guest Author 3D Printing, Fabrication, News, Tips & Tricks 26 Comments

I am new to the world of 3D printing. So in this guest article, you’ll hear from expert 3D printer/designer Marcus Ritland from Denali 3D Design. He shares some tips to help you create amazing 3D printed models by designing them in Sketchup.

[Update June 2014] Marcus has written a book about 3D printing your SketchUp models! Listen to my interview with Marcus, or grab the book here: 3D printing with SketchUp.

3D Printing

3D printing is awesome – we can all agree on that. You send a 3D computer model to a machine and out comes a finished part, ready to use as an end product or as a prototype before mass manufacturing. With the rise of personal 3D printers like the Makerbot Replicator 2, and 3D print services like Shapeways and Ponoko, nearly everyone has access to this technology.

But how does one get started making awesome models for 3D printing? Its one thing to make a model look good on the screen, but quite another to make a model that looks good and actually works in real life. The process of modeling for 3D printing is much the same as 3D modeling anything else, but with a few specific requirements. Here are some common problems that I see beginners struggling with and how to address them.

1. Make your model “Solid” in Sketchup to be 3D Printable

Models must be “Solid” to be 3D printable. This is by far the most common problem beginners have when modeling for 3D printing. Here are some examples of Solid Sketchup models.

Solid, sometimes called “watertight” or “manifold” simply means the model is a complete enclosure. If you were to fill it with water, none would drain out, and the model must not have any extra lines or faces. If you make your object into a group or component, Sketchup will indicate when its solid in the Entity Info dialog box (Window > Entity Info).

Another way to define solid: Every edge in your model must be bordered by exactly two faces. If an edge has less than two faces bordering it, there is an adjacent hole, and if there are more than two faces touching an edge, there is an extra face that needs to be deleted.

The most common errors (and the corresponding solutions) are:

  • Stray edges (just delete them)
  • Holes (trace an edge to fill them)
  • Internal faces (delete them)

2. Give your walls thickness

Wall thickness is a key element in 3D printing – walls need to be thick so they’re strong enough to work in real life, but also need to be minimized to reduce material costs. I’ll discuss how to determine what wall thickness to design at in just a bit.

Single faces in Sketchup have no thickness, so we need to simulate wall thickness by simply placing two faces a short distance apart.

Here’s an example where Matt demonstrates modeling a vase with a 1/4” wall thickness using the offset tool. The amount of the offset determines the wall thickness, and the thickness you need will vary depending on the material you are printing in. For example, some plastics may require a wall thickness of less than 1 mm, while 3D printed ceramics require a minimum of 3 mm.

3. Scale up by 100 (or 1000) to make small parts

If you design things with features smaller than 1/16”, you may run into trouble where Sketchup doesn’t create faces. You often won’t get an error message or any indication there’s a problem, but Sketchup simply doesn’t generate the geometry.

There’s some interesting history behind this problem. Sketchup was originally developed for architects. Since architects don’t typically need precision greater than 1/16”, the developers designed Sketchup to work best with geometry of about 1/16” and larger. Apparently now it’s nearly impossible to fix the problem without redesigning Sketchup from the ground up.

The workaround for this problem is to scale up your model to perform the work, then scale back down for printing. I typically use a scale factor of 1000 to keep the math simple.

4. Increase circle/arc segments to get smooth curves

Sketchup is a “polygonal surface modeling” program, which means that models are made from flat polygon faces – flat surfaces and curves alike. Curves are approximated using many flat faces – for example the default circle in Sketchup has 24 sides. You can see this clearly by turning on Hidden Geometry (View > Hidden Geometry) while looking at a curved surface. Sketchup uses a visual smoothing technique to make the flat segments look like a smooth curve on the computer screen, but when you 3D print a curved surface, the individual faces (or facets) may be visible.

The good news is that the more faces a curve is made of, the smoother it becomes. When using the arc or circle tools, you can set the number of segments to whatever you need. You should increase the number of segments so each individual segment is about 1/32” (1mm) long. Depending on your printer and the material you’re using, the number of segments needed will vary, but for smooth parts this is a good rule of thumb.

5. Model parts as separate components; use Outer Shell to combine

This is one of those tips that can save you literally hours of work. Often you’ll be modeling away on your project, perhaps nearly complete, when you realize a feature you modeled earlier needs to be changed.

For example, you’re working on a scale house model, and the client decides to change the roof style. If you’ve separated the walls and roof into components, its easier to update the roof if its not attached to the walls than if they’re one connected mass. Using components also lets you hide(or turn off via Layers) different parts of the model to make modeling complex models easier.

Another advantage of separating the model is that errors are easier to find and fix. Make sure each component is solid as you go along, and you’ll have less headaches at the end.

When you’re happy with the model, save a copy so you can still make changes later, then use the Outer Shell (Tools > Outer Shell) command to combine all Solid components of the model into one solid ready for export to a 3D printer.

6. Use plugins to work faster

Plugins can help you work faster or do things that Sketchup simply can’t do. Use Solid Inspector (you’ll need to sign up for a free account at Sketchucation to download the plugin) to help you find errors that prevent your geometry from forming solids. Once you have made a group (or component) that’s not “Solid”, select the problem group and run Solid Inspector from the Tools menu. All the errors in the group are circled in red or yellow. You can use the Tab and arrow keys to cycle through the errors, and Enter to zoom in to them. The tool will not fix the error, but you can sort them out quickly on your own. One thing to look out for – Solid Inspector will not return an error when you have nested groups or components.

(Hey, Matt here… Check out my article Best 3D printing Plugins for SketchUp, where I go over my favorite plugins!)

3D printers don’t take Sketchup files directly, so you’ll have to export to another format – usually STL. To export to STL, use this new plugin from Sketchup: (Direct download Link) Sketchup STL Exporter. When exporting, choose the units of measurement, then choose STL and add the .STL file extension to your export filename in the save dialog box.

7. Know the print material specifications and limitations

As amazing as 3D printers are, they still follow the laws of physics. You’ll get the best experience by understanding how the printers work, and ensuring your part meets the specifications. If you’re an artist designing around the print material, you’ll want to understand the process deeply, while if you’re an inventor using the technology to make prototypes, you just need to determine what material best suits the needs of your particular model.

Design information is often available online for the system you are using. For example, Makerbot has detailed design guidelines available here. Shapeways makes design guidelines available on each materials’ page – here’s what the guidelines for the most popular material looks like: Strong and Flexible Plastic Guidelines.

These guidelines are where you’ll look to find minimum wall thickness, minimum detail, maximum build size, and many more technical details. Print services and 3D printer manufacturers often have a forum for users to ask questions. These forums can be a gold mine of information and a go-to resource to ask specific questions that aren’t answered anywhere else on-site.

8. The more material in your model, the more it costs

The concept of 3D printing – or additive manufacturing – is fundamentally different from subtractive manufacturing, where you start with a block of material and cut away what you don’t need. Using this method if you paid $20 for a sheet of plywood and only use half of it, your material still costs $20. In 3D printing, you pay for only the material you use, so it is best minimize the volume of your model.

Minimizing your wall thickness is the easiest way to reduce volume, but there are other things you can do. Creating a pattern of holes in the part is another way to reduce material significantly, and allows you to add artistic flair. Depending on the part, you may even be able to design a mere skeleton of the part you need, much like Jeff Bare’s iPad wraps.

In fact, some of the best examples of 3D printed art are skeletons of an object. These 3D printed dice designed in Sketchup by Chuck Stover gained a firestorm of attention when they were introduced. What Chuck did, besides designing a beautiful set of dice, was to minimize the amount of material needed to make each part by leaving the centers hollow. While these dice would have been impossible to create in with any other manufacturing method, they are easy to 3D print and indeed helped decrease the costs of manufacturing!

There are many more things to think about when modeling for 3D printing, but the ideas in this post will get you started well on the path to making your first model. If you have specific questions, ask them in the comments below and I’ll do my best to answer them!

Marcus Ritland is the founder of Denali 3D Design, where he offers 3D printing/design services, training, and consulting. To learn more about Marcus, visit his website at www.denali3ddesign.com

Comments 26

  1. Marcus,

    I’d like to point out an error, one that is commonly made. Tip 8 is not at all correct. 3D printed ceramics, for example, is priced by surface area, not volume.

    1. Hi Forrest,

      There are indeed a few situations where volume is not the only factor influencing cost – ceramics is one of them, so thanks for adding that. Out of the dozens of available 3D printable materials, ceramics is a very new addition and currently the only one that doesn’t base cost on volume.

      Depending on the printing service and the material, there are many other factors that may come into play as well – part orientation, % of bounding box that is solid, resolution, and so on. These may be important in some cases but are beyond the scope of this article.

      I respectfully disagree when you say “Tip 8 is not at all correct.” It is mostly correct. In the vast majority of cases, volume is the best indicator of price.

    1. Sketchup is not a “solids” modeler. It’s a “shell” modeler. But for the purpose of 3D printing, Sketchup works great, you just have to make sure your model is water tight, like Marcus explains above.

      1. sir ,
        1st ly thankes for shearing knoledge about sketch up….. .

        I am trying to sketch up out put is model as well as finished working drawing. with accuracy. hatch pattern (brick ,concret,wood ,dimension etc.).
        it can possible..?

  2. Thank u for sharing this tips ! It will be useful for me .. especially when I want to printTFT computer monitor and I see that it is not so easy as I have thought.. I think that I will ask some help my friends to get ready my models that I have choose to the 3D printing. This innovation is really amazing !

  3. Thanks for the tips. I am new to 3D modelling and new to Sketchup can anyone please explain how to set the number of segments on an arch so each segment is 1mm apart as it says in tip #4?

    1. Just do a bit of math. Find the circumference of the circle you want. D X Pi
      i,e Ø50mm X Pi (3.14) = 157 which is the number of segments you want for a circle. Half that for a semicircular arch.

    1. Here’s a trick for doing that. Use the section cut tool, place a section at the midpoint of the model. right click and select “Create Group from slice”. Then explode everything so the geometry sticks together. Then using the eraser tool, click and drag over the stuff you don’t need. If the model isn’t symmetrical, you’ll have to do this to both sides in separate files. Save a copy of the original before you do it. In either case, you probably would be better off modeling each half in separate groups or components to keep them separate.

  4. How do I check if my model respects the minimal recommended distance between parts? (so they would not be printed fused together) I would hope there’s a plugin or function to automatically check this, but I can’t seem to find it.

  5. Great info! Two questions…
    1) on Tip #3 for scaling small models you say “The workaround for this problem is to scale up your model to perform the work, then scale back down for printing. I typically use a scale factor of 1000 to keep the math simple.” Could you please briefly explain the method and workflow you use here – are you using the actual scale tool? I am modeling things that could run into this problem and was using inches but could just as easily use mm.
    2) on Tip #4 segments: If I already have some curves that don’t have as many segments as I would like for printing is there an easy way to beef up the number segments without having to recreate everything?

    1. Hi Mark, yes, use the actual scale tool. Just select the object (typically it’s your entire model contained within a group), grab the scale tool and scale from one of the corners. Once you’ve grabbed one of the corners, type in 100 then press ENTER. Once you’re done modeling, repeat the process, but type in .01 to bring it back to it’s original size.

      Regarding arcs, as long as it’s still an arc entity, you can change the number of segments by clicking on it and opening up the entity info window from the window menu. With the arc selected you’ll see a spot where you can change the number of segments. This works for circles and polygons too.

  6. Hey Matt: Great article! And kudos to Marcus for the tips – the scaling trick is a great one!

    As you know, we create SketchUp tutorials and one more tip we teach that we might not be obvious from this post is that you may need to account for creating an “escape hole” for hollow parts in your SketchUp model to make sure it’s 3D printable.

  7. Hi,

    I have tried to 3D print some Sketcup SANDBOX terrain models with buildings. I guess I ran into some difficulties based on the 0.xx1 scaling I did, ending up with too small surface thickness of the terrain. Anyhow it was almost OK.

    Can anyone give some tips or best practices on this? Can I set terrain surface thickness?

    1. If I understand you correctly, what I have done is draw a rectangle under the terrain, and connect it at each of the four corners. That way you have a solid base to build from.

  8. Hi, great tips thanks so much. Modeling in SketchUp 2014 and printing with a MakerBot Replicator 2, 5th Gen. The problem I get is inconsistent surfaces. The walls seem to print fine, but the flat surfaces come out very rough and stringy. I notice the store downloads from Thingaverse generate really high quality prints and I want to achieve the same quality in my prints.

    will the scale trick achieve this or is there another way to get the same professional quality out of SketchUp? any idea what software the 3D designers at MakerBot use? Thanks so much!

  9. Hi there, great article! My comment relates to trick 3, scaling your model. I just found out after 2 years of messing about with the scaling button, that is actually better to use the tape measure tool to scale the model. Apparently the scaling button is not meant to be used for a whole model consisting of multiple parts -and indeed I ran into many strange things when making my model smaller this way. By using the tape measure tool (and typing in the desired measure), the whole model will be scaled without problems and errors

  10. Dear All,
    I would like to ask all how I can export 3d model in sketchup to only faces. I mean, I have imported one 3d model from autocad into sketchup and I want to create one layer face in the project to simulate.Would you please guide me .
    Yours sincerely,

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