How to 3D Print Your Site Model Using SketchUp
Need to print a site model? Here’s a practical guide that will walk you through the basic steps, from Revit to print, via SketchUp.
Why SketchUp? If you’ve had any experience with 3D printing, you’ll know that your file has to be in a specific format before it can be put into 3D printing software. This is usually an .stl file, which can’t be officially exported from Revit, and the user-distributed tools for doing so often are out of date. Revit can be directly exported to SketchUp, and SketchUp can export to an .stl file! SketchUp will also help us to clean up the model and make it ready for 3D printing.
Having said this, SketchUp isn’t the only way to achieve this result — you can also go through Rhino, or some other piece of CAD software. We’re going to use SketchUp because it’s easy to use and learn. If you’re more experienced with another tool, feel free to follow along and apply similar techniques, although you’ll have to figure out some of the specifics on your own. We’ll walk you through:
- Installing. Follow this to install the extensions necessary to follow the rest of the steps.
- Cleaning. Follow this to clean your model. Cleaning your model throughout the process makes the rest of the steps much easier.
- Slicing. Follow this to slice your model up into manageable chunks for the 3D printer.
- Exporting. Follow this to export your model into a format acceptable to 3D printing software.
- Setting. Follow this to learn how to set the 3D model up for printing in the 3D printing software.
Installing:
1. Install SketchUp 2017: https://www.sketchup.com/download
2. There are four extensions we need to download: TT_Lib2, CleanUp3, Solid Inspector2, & Zorro2. These will help us to fix the model so that it’s ready for 3D printing, and help us cut the object into the right shape when we need to.
Note: Although this guide will go through some of the functionalities of these extensions, if you ever get stuck or want to learn more about the extensions there are some excellent video and article tutorials on the pages linked.
3. Open up SketchUp, select Window > Preferences, then open the Extensions tab.
4. Install the extensions above in the given order.
Cleaning:
1. Import the model into SketchUp. Don’t scale the geometry down to size just yet — this will cause a lot of issues especially in the clean-up process.
Note: If you’re going to do any modelling in SketchUp, leave it all in “Layer0”. Layers don’t work the same in SketchUp as they do in other programs like Rhino, instead use groups for similar functionality.
2. Select Window > Preferences, then change the precision to as high as possible.
Note: You probably shouldn’t do this while actually working on your model making large changes, as this will slow down the software significantly.
3. Group the model into manageable chunks. In order to group some elements, select them and then right click on them, selecting Make Group. If you make a mistake while grouping, you can ungroup by selecting the group and right clicking again, but selecting Explode instead.
Note: Grouping the model helps your computer not to crash when it tries to clean up the entire model.
4. Select one of these groups and go to Tools > Solid Inspector.
5. There will likely be multiple items such as “Reversed Faces” and “Stray Edges” that will have a button next to them that says fix. Click these buttons to deal with the relevant issues, they should fix themselves!
6. There may be some other items that say “Info” rather than fix. These represent issues that Solid Inspector can’t fix because there are multiple possible solutions. Clicking info will highlight the relevant issues — you’ll need to fix these yourself.
Note: A common issue that will say info is when there is an open surface that isn’t planar. To fix this, draw lines that split the surface into planar parts.
7. If you’ve managed to fix everything, you should see a window like this when you open Solid Inspector!
8. After this, go to Window > CleanUp3 with one of the groups selected.
9. Make sure that either the Local or Selection radio button is selected — selecting Model will ignore the group you set up to avoid this and try to clean everything!
10. If you have any hidden geometry that you would like to keep, either unhide it temporarily or uncheck the Erase Hidden Geometry checkbox.
11. If you exported from Revit, it is very likely that you will want to keep the Merge Adjacent Surfaces checkbox ticked, as walls and ceilings do not automatically ‘connect’ into a single object.
12. For the other buttons, leaving them as they were will most likely be fine. If you’d like to understand what any of them do, mousing over them will give you a description of how they should be used.
13. Click on the “CleanUp” button to start the process.
Note: Repeating this method to clean your model regularly throughout this process will reduce the amount of errors you have to deal with later on.
Slicing:
If your model is too big for your printer, you’re going to have to slice it up. The ones we have here at BVN (Ultimaker 2E+s & 3Es) have a maximum print size of 223mm by 223mm (with a max height of 300mm), and we’ve printed models that are in excess of 600mm by 700mm. Here’s a quick tool you can use to find out whether your print will fit:
Note: If it’s only just larger than only one of these dimensions, you may be able to rotate it to fit it in.
2. When splitting the model, the technique used goes through everything in that slice when not inside a group, and only whatever is inside the group when in a group. For example, the following can’t be cut in the order blue > red > green, because blue will cut all the way through the buildings. Rather, it should be cut with red first.
3. The following is trickier, as there are no full length cuts to base the other cuts off of. To deal with this, either red or green should be cut first, the other next, and then blue last off of the red cut. Whichever cut was made through the right piece can be patched together again using the CleanUp tool used earlier (Merge Adjacent Surfaces).
4. Just before cutting, you need to duplicate the item you want to cut. We need to do this as the way we’re “cutting” is actually deleting one side of the model.
5. In order to start cutting, select Tools > Section Plane
6. Now select a surface that has the angle you want to section from.
Note: If you want to create a section on an odd angle that none of your surfaces have, you’ll have to create a surface at that angle to base it off. You can then hold shift after hovering on this angle with the section tool and move it to a better location while retaining the angle.
7. Once the section has been placed in the right location, right click it and select “Cut at Section”. You’ll notice that on the edge of the cut, the model will be open — that’s just the way SketchUp works, unlike a lot of other CAD software. Patch the hole of the surface up that’s left by re-drawing one of the surrounding lines.
8. Repeat steps 5–7 for the duplicate, except flipping the section by right clicking and selecting “Reverse”.
9. It’s possible to make some cuts that only go through a part of the model by grouping it appropriately, such as the red cut pictured below.
10. After all the cuts have been made, it’s a good idea to clean it again (refer to the cleaning method above).
11. If any part of your model has any overhangs, it will need to be sliced. See this article on how to deal with overhangs in 3D printing.
Exporting:
1. To scale the models down, select everything you want to scale and press S. The model should be in a wire-frame yellow box with green cubes around it.
2. Click on one of the corner green cubes. Then, type the scale you have calculated you want to achieve, with 1 being the original size. The scale appears in the bottom right hand corner of the screen. For example, if you wanted to scale your model down by 1:500, you’ll want to type in “0.002". To decide on how to scale your model, see this article. Press enter to set the scale.
3. After everything has been resized, it’s a good idea to clean it once more (refer to the cleaning method above).
4. The model should be ready for exporting. Make sure each separate piece is on the ground (although this can be fixed later in Cura).
5. Copy each piece into its own separate SketchUp file, so they can be saved and printed separately.
6. Select File > Export > 3D Model
7. Then after choosing your file name, set the “Export type:” to obj, and click “Export”.
Setting:
Now that we’re done with SketchUp, it’s time for some actual printing! Please note that these settings are what works for us at BVN with our models and printers, given the amount of variables going on your experience might vary from ours.
1. To start the printing process, open Cura.
2. Select File > Open File, navigate to yo ur file, and open it in Cura.
3. From within Cura you can do the following things to your model after it’s been selected:
4. After fixing your model, ensure that:
- Print material is set to PLA
- Infill is set to Light
- Enable Support is unchecked
Note: If you are unsure about the other settings, setting them to this is recommended:
You should be ready to print! The final part of the process, actually using your printer, will depend on what printer you have and how you’ve connected it up.
In the end, this is a work in progress. We’re always learning here at BVN, and we’re hoping that you could learn a little bit from this too! Let us know if you have any tips & tricks of your own for this process that you’d like to share. A big thank you to Neil Haybittel & Ayelen Moure for their expertise on this topic.
The next article in this 3D printing series will be on scaling your print and all the challenges that come with it, as we encountered earlier.
