- 3D scanning is the process of analysing a real object or environment using a device that
collects data on the shape and appearance of the object, with the purpose usually being to
create a 3D model.
This model will consist of a mesh just like we discussed in the simulation and FEA module.
Like most technology, this is developing fast and is constantly becoming more capable and
accessible.
Just a few years ago, the idea that you could accurately 3D scan an object using your smartphone
would have seemed impossible but now that's a reality.
There's a range of types of 3D scanners out there that use different techniques to collect
data from the object and with this variety comes a wide price range.
From 100s of 1000s of dollars down to the price of your phone.
If you unlock your phone using face recognition, then you're already using the 3D scanning.
With this being the most accessible method of 3D scanning, it'll be the focus of this module.
However, the idea is much the same for more expensive scanners, the results are just going
to be better generally speaking.
3D scanning is becoming commonly used in automotive applications for product
development and engineering purposes.
But also for many other areas like video games.
It's become the go to method for scanning real vehicles or other objects or environments in order
to recreate them virtually and that means it can be incredibly useful for CAD users as well.
In some cases, we might want to use some intermediate software to edit and process the
scan to make it easier to work with in CAD.
Simplifying the results from high resolution scanners to decrease the file sizes for example.
Inside our CAD software, we can then use functions to convert the scan to a solid model
and process it to a state that it could be modified or manufactured.
Or we could use this scan as a reference for modelling new designs that will interface with
the scanned object.
In this module, we're going to look at taking a scan with an iPhone and bringing it into Fusion
360 to use.
We'll be using the 3D Trnio app and taking a scan of the same strut tower we used when looking at
canvases in the previous module.
No matter what brand of smartphone, what scanning app you use and what object you're
scanning, the process will mostly be the same and the key things that you need to focus on will
always be the same.
Inside the Trnio app, there are two options for scan modes, object or what's called ARKit.
We'll use ARKit in this case as it's most suited to producing high quality scans that we require
for our CAD work.
It's quite easy to take a 3D scan but just like when taking photos, there are a few tricks that
can make the results significantly better.
We want to first make sure the target is well lit and the lighting is even, without areas of
high brightness or shadow.
Scanners can struggle with reflective and transparent surfaces like glass or polished metals
so sometimes it can be helpful to apply an easily removable product like car wax, plastidip or even
dress up colour hairspray to temporarily remove the gloss finish without affecting the surface
shape.
The scanner works by taking pictures of the object and as it's moved around the object,
it stitches these images together and aligns them based on the texture and features
of the object.
Therefore, objects with repetitive geometry or no texture like a transmission gear or the
door of a vehicle can make it extremely difficult for the scanner software to understand
its position and the shape of the target.
In these cases, we may need to add some texture to the object and this is why you see
the marker dots that are commonly stuck onto surfaces that are being scanned.
Small torn pieces of masking tape are also a great alternative.
Once we start the scanning procedure, as indicated on the app, we keep the camera
pointed at the target so it stays in frame and then slowly and smoothly move around the
target collecting data from all angles.
We don't want to miss any surfaces or details.
With all the data collected and the object covered from every possible direction we can
finish the scan and let the app upload and process the images to create the 3D scan.
Now's a good time to view this scan on the app and make sure that all the key areas look clear
and useful.
You're better to catch that something went wrong and you need to do it again at this point as
opposed to once you start working with it in your CAD software.
Once you're happy with the result, we can choose to export/share icon in the top right corner and
choose to export the scan as an OBJ file.
As we know from our modules on export files, this is a 3D mesh.
Then we can use the normal methods available on our phone and send it to our computer.
Before jumping onto our computer it's important that we take some physical measurements of the
object we just scanned.
As with canvases, we'll use these to check the form of the scan and also scale the geometry.
Ideally we'll have measurements that are large relative to the area that we've scanned and in
multiple directions.
With the files on our computer, we can upload them into the project folder in Fusion 360 so
let's jump in there now.
For this job, we'll be working under the mesh toolbar.
Fusion 360's mesh tools allow you to insert, repair and modify 3D scans and other mesh files.
OK so let's select insert mesh and then locate and select our 3D scan.
We want to choose what units our scan was taken in so one unit in the scan will equal one
of the same unit in the mesh.
With phone apps like Trinio, we don't yet have this functionality so let's just set this as metre
for now which gives us the largest mesh that we can scale down so we don't lose any
resolution just yet.
We should then rotate the scan so it's roughly in the orientation that we scanned it in, just so
it makes things easier to visualise.
Notice we lose the texture of our scan, in some CAD software it is possible
to retain this but there's a bit to this process and it's really not necessary for our purpose.
As the texture isn't shown, the scan resolution doesn't seem as detailed and accurate.
This is really just a tradeoff that comes with using a cheaper scanning method but this
will eventually get better with developing technology and it doesn't mean that the
scan isn't useful.
Let's first combine any separate mesh bodies into one to simplify things.
Using the combine tool, selecting the bodies and setting the operation to merge.
Now it's time to check our dimensions and scale the mesh.
We can use the measure tool here to measure a dimension that we took off they physical object.
For example, we know the strut top studs are all spaced at 95 mm.
If the result isn't quite right, we can use the scale mesh tool to correct this until we get
to a point where we can get correct measurements in at least two different directions.
So we know the scan is true to the original size and form.
A scale of about 0.085 works well for this example.
It's also helpful to use the plain cut tool to remove any areas of the mesh that aren't
needed.
Reducing the size of the mesh will always help with the processing speed, as working with
larger meshes with 100s of 1000s of faces can be quite demanding on the computer.
In our case, let's just remove everything other than the strut tower.
Since we're just going to use this mesh for a reference to model new designs from, we don't
need to use any more of the mesh tools.
So let's just use the convert mesh function from under the modify tab to convert what
we have into a solid or surface body.
We can leave the operation and method settings for this tool as the defaults of parametric and
faceted.
Now we're ready to click OK, this may take some time to process.
Thanks to the magic of editing, you don't have to sit and wait like I did and we can now see our
completed solid and surface bodies in our browser.
Since our mesh was just the surface of an environment, rather than a solid object,
and we didn't use any of the modification tools to edit the mesh and form a complete
enclosed 3D solid body, the main resulting body that we're interested in is this surface.
The other resulting solid bodies are really just
from the occasional part of the original mesh that just happened to form an enclosed 3D
surface.
Moving forward, the most simple method of modelling the space of the strut tower brace
would be to construct a plane using the plane through three points tool and selecting three
points spaced out on the top surface of the strut tower.
Then just like we looked at with the canvas tool, we can sketch on this plane, positioning the
mounting holes to line up with the studs, a clearance hole to access the top of the
strut and an outline that suits the form of the strut tower.
Now all we need to do is extrude the sketch and work to design the rest of the part.
If our scan included both strut towers, the valve cover or any other high points in the
engine bay, we could also add another scan with the underside of the bonnet.
It's easy to see how we would design a concept for the complete strut tower brace and see
how it would fit without interfering with the engine, bonnet or other components.
This module has covered a simple example of creating and utilising a 3D scan with the cheapest
and most accessible device available.
There's a wide range of other options out there that cover a broad spectrum of cost, quality and
performance.
But I'd definitely recommend checking our what your smart phone is capable of before dropping
cash on a dedicated scanner.
While each device usually works with its own proprietary software, there's also a range of
apps for smartphones to choose from and generally the process is the same.
The scanning device is used to capture the shape and appearance data from an object or
environment.
Taking the time to set up the scan and perform it correctly ensures accurate and useful results.
Once the scan is complete and checked, it can then be exported, usually as an OBJ 3D mesh file and
then brought into our CAD software.
In Fusion 360, the mesh toolbar has a collection of tools for working with the mesh that can be
used to modify it as its own design to be manufactured or as a reference for designing
a new part like our strut tower for example.
That was one of nearly 60 modules taken from the HPA Automotive CAD and 3D Modelling course.
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