UNSW Making

CNC for Site Models

Site Models

Looking to create a beautifully milled site model for your latest project? We have compiled a full list of tips, tricks and guidelines to help you get the most out of the CNC routers.

Before we start...

Have you got the CNC Monitor Badge?

In order to use the CNC routers, students and staff will need to have the CNC Monitor badge. This badge will allow you to monitor jobs on the CNC routers and requires you to read the 'Safe Work Practice' before attending a practical training session. If you haven't already, please make sure to get the CNC monitor badge before proceeding to avoid disappointment!

CNC Monitor Badge

The Process

CNC Site model process

1 .

Create your file (CAD)

Files can be created using most 3D modelling software including SketchUp, AutoCad, Revit and Rhino.

CNC Site model process 2

2 .

Create your toolpath (CAM)

Once you have created your 3D model you will need to import it into Fusion 360 to create your toolpath. A toolpath is the set of instructions that we send to the CNC router in order for it to cut your job. You will need to book a toolpath consultation with an AML staff member to review your file and create your toolpath with you. Toolpath consultations can be booked on our CNC Fabrication page here. To make a booking you will need to have the CNC monitor badge. When attending your booking you will need to bring your file imported into Fusion 360 and have an idea of what material you will be using.

CNC Site model process 3


Cut your model (CNC)

Following on from your toolpath consultation you will need to make a booking for time on the CNC routers. You will need to have been granted the CNC monitor badge to use the CNC routers.

1 . Create Your File (CAD)

Buildings vs. Building Pads


Your first thought might be to just CNC your whole site model, this is a possibility... but there are a few restrictions on this based on the size of our tools and the tool holders. Tall buildings will cause problems as the tool will not be able to reach all the way down and will crash into parts of your model. One solution to this would be to reduce the heights of your buildings. This is obviously not a great solution if you are trying to make an accurate scale model. This is where building pads come into play! You can mill out recessed footings for your buildings and then create the buildings using a different process e.g. 3D printing.

CNC Site Models building pads-09.png

Building Pads

An alternative to CNC cutting the buildings as well as the surrounding topography is to model flat surfaces for each building and to make them separately. This just requires more consideration in your design. If the building masses are made by 3D printing, laser cutting or any other method to the exact size of the building pads, the buildings will not fit in as there is no space to allow for variations in construction methods. The CNC operator can enlarge your pads slightly without any modifications to your file, or you can tweak the size your building volumes.

More importantly, the CNC’s round tooling will result in internal radii, essentially filleting internal corners to the radius of the tool being used, minimum 2mm fillet in most cases. You will either need to chisel or file the internal corners of the building pads to allow the building masses to fit, or design the pads for building masses in a way that avoids the problem.

Building pads can be modelled in 2 different ways:

Pads Cut into topography mesh

This will be the most efficient and fast way of machining the building pads since they will be cut at the same time as the terrain contours.

Separated building pads from topography mesh

This method will require more time since the building pads will be sculpted after the terrain contours have been made. This method however enables more flexibility in positioning the level of the building pads.

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But how do I make the buildings?

Buildings can be made using many different methods as outlined below. It is important to consider the tolerances when fitting the buildings to your building pads as dimensions may differ ever so slightly when manufactured using different methods. Internal corners will also always have a radius due to the shape of the tools used on the CNC. This will mean that all of the corners of your building pads will be filleted. As a result you will need to either design your building to have the same radius on the corners or chisel out the corners of the site in the post-processing stage.

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3D Printed Buildings

3D printing is a great way to create buildings for site models as it doesn't require too much extra time to create the files. If you have a 3D CAD model of the buildings then you are halfway there! Tolerances will be the main difficulty as you will need to make sure the buildings fit snug into the cut out building pads.


Laser Cut Buildings

Laser cut buildings are quick and easy to cut. The result is a hollow (shell) building that can include details such as doors or windows that are cut from the panels or engraved. There are many suitable materials available for laser cutting these buildings such as acrylic or plywood that come in a range of colours and thicknesses.

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Solid Timber Buildings

Buildings can be made from solid timber, cut on the bandsaw and sanded to fit in the building pads. Due to the constraints of the machines, these solid timber blocks should be simplified with minimal undercuts.


The contours of the terrain can be converted into layers of your desired thickness, for example, contours of 0.5mm or 1mm height. However, the smaller the contour height, the more time it will take for machining.

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Wall thickness

The thickness of walls on your model is an important consideration as walls that are too thin will easily snap due to the vibrations caused by the CNC. The minimum allowable thickness of the walls will depend on the material you are using as well as the height to thickness ratio.


Roads engraved as lines

Engraving lines to represent roads is a fast and simple way of adding this detail to your site model. The lines should be drawn as planar curves which get imported in 2D into Rhino and projected onto the mesh surface. The lines will be engraved using a V shaped tool.

Roads stepped down into topography surface

This method of making roads can offer a better representations but is more subject to the limitations of CNC. Instead of engraving the outline of the road, the whole road surface is engraved 0.5mm or 1mm deep into the site.

Similar to above, 2D curves will be automatically projected onto the mesh surface. However, these curves need to be closed shapes. Most importantly, the road sections need to be a minimum of 4mm wide so the tool can fit onto the surface.

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2. Create Your Toolpath (CAM)

Importing a file into Fusion 360

If you are working with contour meshes or sets of buildings or curves exported from different software, we suggest compiling it all into one Rhino file before importing into Fusion 360 (the file you will need for your toolpath consultation). Rhino provides a great pathway to Fusion 360 and will interpret files from most other software including SketchUp, Revit and AutoCAD.

If you are wanting some more information about preparing files for CNC, feel free to take a look through our file preparation page for an introduction to getting models ready for CNC routing.

File Preparation Guidelines
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Modelling in Rhino

If you are familiar with using Rhino then creating the 3D site model file is relatively straight forward. Once you have finished modelling the topography, roads and/or building pads, you can export the file as a STEP or IGES. As models made in Rhino can be exported as a NURBs file through the aforementioned formats, this allows you to make minor adjustments to the file in Fusion360 as you can select the different surfaces. Alternatively you can use the below methods to import a file generated in another software into Rhino.

SketchUp to Rhino


Sketchup files can be imported into Rhino by saving the Sketchup file as a Sketchup 8 file format. This format will then be easily imported into the Rhino workspace. Another format possible is a .STL file which are also compatible on both pieces of software. The Sketchup data will be imported as a mesh into Rhino. As meshes are not given control points in Rhino, it is best that you scale the model to the desired scale and moving the model to its origin of 0,0,0 before importing.

Revit to Rhino


Revit files require some additional steps before importing into Rhino but the benefit is a more accurate topographic model with an option of both contours or smooth finishing. Firstly, to make the topographic model in Revit, the terrain is made from creating a topo-surface. The rectangular boundaries of the site can be split using the Modify > Split Surface option on Revit and the Reference CAD/PDF. Similarly, roads can be separated from the same topo-surface and moved down to the desired depth if you would like to have it stepped down in the physical model.

NOTE: This is before scaling, so moving the roads down 100mm in Revit for a 1:100 CNC model will result in a 1mm step down in the physical model.

Alternatively, if you would like to have the roads engraved as lines or do not want to move the road in the 3d model, you will need to export a DWG of the lines as reference. However, this can lead to issues of misalignment when combined with the 3d model in Rhino.

Revit can generate the building pads on the topo-surface at the desired depth so that additional modelling or references are not typically required.

This Revit 3D file can then be exported as a DWG file by selecting File > Export > CAD Formats > DWG. That file can then be imported into Rhino and scaling down the model to its production size. The vertical position (Z) axis of the imported DWG file should be at the proper height.

AutoCAD to Rhino


AutoCAD 2D lines can be imported into Rhino in .DXF format. These lines can either be made into planar surfaces, and raised to the appropriate Z height for which they need to be engraved as building pads or similar, or they can be left as Curves all sitting in the same flat plane, these lines can only be projected or engraved relative to 3D meshes you have also imported. All curves should be Joined, Closed curves.

Rhino to Fusion 360

Once you have exported your 3D site model into Rhino, there are still a few steps before the file is ready to be imported into Fusion 360.


1 . Scale the Model

If you have imported your model from AutoCAD or Revit as a DWG you will need to scale it in Rhino.


2. Move the model to the origin

Move the model to the coordinates 0,0,0 (origin) where the model is in positive X & Y axis.

rhino 3

3. Move Z-axis of model

Move the Z-axis of the model so that the top surface is the desired thickness

rhino 3

4. Save the Rhino file as an .STL file.

The .STL file can then be opened in Fusion 360

Creating Toolpaths in Fusion 360

Once you have created your file you will need to book a toolpath consultation with our AML staff. During the consultation staff will review your file and help build the toolpath ready for use on the CNC routers. To book a toolpath consultation please reach out to Richard on Teams or come and chat to our AML staff in the Design Futures Lab.

Please make sure your file is appropriately named using the following format studentname_zID_coursecode

Chat with Richard

Preparing for your Toolpath Consultation

When attending your consultation you will need to have your file imported into Fusion 360 and have your chosen material (stock) set up in the CAM workflow.


1. Load the file in Fusion 360, make sure that the file is to the correct scale and the origin is in the positive quadrant at 0,0,0.


2. Click the 'Design' tab and change it to 'Manufacture'.


3. By clicking the 'Setup' menu you can set up the stock size for the material you are cutting. Accurately measure the width, length and depth or your chosen piece of material.


4. Set the parameters of your stock. For the mode of stock, select 'fixed size', then enter the measurements taken from your material.


5. Ensure that the stock origin is set to the bottom left of the stock. You are then ready to attend your toolpath consultation!

If you would like to have a go at making your own tool-path, we are more than happy to help! Take a look at the video resources below for tips on getting started. You will still need to book in a consultation with our staff before you can cut, but we would love to see your own generated tool-path!

CAM for Fusion 360

3. Cut Your Model

The Process

Make sure you have the CNC Monitor Badge

Before you can use the CNC routers you will need to attain the CNC monitor badge. This badge will allow you to monitor jobs on the CNC routers and requires you to read the 'Safe Work Practice' before attending a practical training session.

Plan your time

CNC routing is a process that takes time! We recommend starting at least 1 -2 weeks before your submission to give yourself enough time.

Ensure you leave adequate time for the cutting of your model. You will need to monitor the job whilst cutting and be watching it the whole time. We recommend setting aside 1 full day to allow for the full cutting process.

Prepare/purchase your stock

Make sure you have your material ready to go. This might include gluing up timber, planing raw edges, cutting timber down to size. The DFL sells plywood sheets in a range of thickness between 6-18mm. Timber can also be purchased at Bunnings or Anagote.

Set up video equipment

We encourage all students to document the whole process on the CNC routers. This not only will be a valuable resource for your assessment and portfolio in the future but we also love to feature great student work on our platforms! The DFL has a range of photography equipment to borrow including LED lights, DSLR cameras and tripods.


Once the CNC machine has finished running your job, you will have a nearly but not quite finished project.  You may need to remove tabs that held your model in place while it was machined or you may need to cut your model down to size if this was not done as part of the milling process.  As described earlier, perfectly square corners are not achievable with a CNC machine so you may need to chisel out areas where this is critical.  Finally it is important, after spending all this effort making your model, not to scrimp on the last step of sanding and applying any finishes to your timber.

Removing Tabs

Tabs are used to ensure that your model doesn’t move during the final cut out pass with the CNC.  Firstly the tabs need to be broken, they can be snapped by bending the wood however it may splinter so it is safer to cut them with a chisel or bandsaw.  The rest of the tab can be removed either on the disc sander or using a trim router. An alternative to using tabs is to not cut your model out of your timber stock using the CNC.  Staff in the DFL workshop can cut your model to size using the table saw, just make sure to have an accurate idea of the finished measurements!

Trim Router
Chisel Tabs

Chiselling out corners

As the CNC uses round tools, it is impossible to get sharp corners in your model.  Most of the time this isn’t an issue, however if it is, corners can be cut out with a chisel.

Chisel Corners
Chisel corners 2


Your model will not be perfectly smooth when it comes off the CNC machine.  Small imperfections will be visible from the tooling path.  These can be sanded out with medium grit sand paper (approximately 150grit).  Sand paper can be purchased from the DFL shop.

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Oiling or varnishing your model will help protect the timber and will enhance the look of the wood grain.  One of the simplest methods is to wipe on a mixture of 50% mineral turpentine and % linseed oil.  The benefits of this method are that it dries quickly, it can be applied using a cloth and it penetrates deep into the timber, providing good protection.

There are other options for finishing your model including wood stains, varnishes, paint and alternative oils.  Talk to staff at the DFL about the desired look you’re after and they will be able to advise on products.



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Carmen Feng, Stephanie Thelin & William Xie, ARCH1302


Justin Pak, Masters of Architecture

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Adib Imam, Masters of Architecture

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Masters of Architecture, Graduation Studio


Masters of Architecture, Graduation Studio


Masters of Architecture, Graduation Studio

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Masters of Architecture, Graduation Studio

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