An easy way to create complex shapes.

There’s one aspect of 3D modelling that’s often a challenge for novices, and that’s complex shapes. Tinkercad and other simple-to-use software are great to keep the learning curve low, but it can be a challenge creating more complex shapes.

There are few ways to circumvent the challenges and some of the troubles you may have with complex shapes, at least in some circumstances.

In this simple example, we’ll work through a simple method to create extrusion-style shapes from automotive gaskets. These can be used to create fabrication moulds, cover plates, adaptor plates, and so much more.

It doesn't take a huge amount of time and has great results.

THE BACKGROUND

The idea for modelling this way started with a transmission rebuild project. I needed a method for “blocking” off any openings on the transmission while the exterior was ground, sandblasted, and finally painted. Often we cover up these areas with masking tape / heavy paper etc. to stop things getting where we don’t want them. However, the paper can easily be punctured, the tape can lift off, and all sorts of things can happen along the way.

I decided to make 3D printed block-off plates that use the standard bolt holes, which were robust and could be firmly fastened to the machined surfaces to protect them from any intrusion.

While it may not always be practical to undertake this process for repainting something, you can use the fundamentals of this modelling method for many different purposes.

FLAT TEMPLATES

Often when there are physical objects we’re trying to cater for with our modelling, we can shortcut the process by using the object, or a part for it, as the basis for our template.

Here we’re using the gasket that we’ll eventually use during reassembly. It’s the perfect option as it’s lightweight and precisely the correct shape. You can just as easily use the actual item you want to model for too. It’s only used to get the raw shape. While the surface is flat, it’s a fairly complex shape that could take hours to model using subtractive and additive modelling with something like Tinkercad.

GETTING THE RAW SHAPE

There are two simple methods to get the basic shape needed to be able to digitise it. Those are scanning and photography. Scanners aren’t nearly as popular as they were in recent years, but fortunately, just about everyone has a powerful camera in their phone!

Scanning is the most accurate, but a good photo will still get you what you need, with these handy tips:

• Ensure you’re holding your phone/camera perpendicular to the object to minimise distortion
• Distance yourself away from the object so it doesn’t appear distorted. Having a lower resolution is better than a distorted image
• Get a clear exposure so you can see the edges and features clearly that you’ll need to do

A scanned image will usually be clearer and easier to model from, but with care and practice, the photo should be just as good.

Once you have your image, it should look something like this:

A photo will probably have a background, but that’s OK too since we’ll remove that shortly.

TRACING THE SHAPE

Next, you’ll need to import the image into suitable software which can create vector images.

This is why it doesn’t really matter whether you photographed or scanned the object because the modelling is much the same either way. We use our human eye to transform the image into a vector. A vector is made up of lines and algorithms, not pixels full of data.

We use Adobe Illustrator in our office, and you can download a 30-day trial for free from the Adobe website. This method will work in a similar way with just about any vector-illustrating software available, such as the popular Inkscape or Vectr.

Carefully trace around the gasket image, using shape tools or pen tools if you’re familiar. We won’t cover this in great depth as it will depend on the software you’re using. If you are new to doing this process there are likely to be YouTube videos that can teach you how to trace an image in the software you are using.

Effectively, what you’re doing is creating a vector “path” using the photo or scan of a gasket as an image.

You’ll notice that we’ve refined some edges for ease of trace and printing. It’s up to you how accurate you are, and will have different consequences depending on your application. Once you have traced every aspect of the gasket, you’ll want to save it as an SVG (Scalable Vector Graphics) file. First, delete the background reference image, and save / export as SVG. This can then be imported by Tinkercad easily. Your SVG file will look something like this:

IMPORTING THE MODEL

When you bring your SVG file into Tinkercad, you’ll likely have to size it. The easiest way to do this is to measure the physical object, then set those sizes on the import. Of course, you can do this later if you prefer, but once things are in “real” sizes, it usually becomes easier to understand.

Locate the import button and select it.

Set the size based on the physical size of the item.

Tinkercad will then import it with the default height of 10mm. You now have a 3D shape!

FILLING THE GAPS

Now that you have your default 3D shape, you can get to work filling things out, In our case, blocking off ports that we don’t want to use, as well as the main face (i.e. the giant hole in the middle). We could have taken these out at the tracing stage, but this gives us more flexibility later.

Boom! Now you have an end cap you can use which is a perfect fit, complete with bolt holes!

You can easily see how well the model matches the original. Here's one we did a test-print with to see how close our digitised and printed version was. It's basically an identical 3D-printed clone!

Printing it at this stage isn't a bad idea for some shapes, especially where specific bolt-patterns need to be matched, as it will take a lot less time to print that, than your finished extrusion. Modifications can then be made if necessary, potentially saving you from a poorly shaped 35hr print!

DIFFERENT EXTRUSIONS

You don’t have to create just a blank plate either, take a look at the following models which have a dome-top, and a centre-extrusion. The dome top is fairly self-explanatory, but the centre-extrusion allows us to bolt up the plate where it is expected to go, while the hollow cavity provides room for whatever machinery may protrude that we need to allow for. In this case, we separated the extrusion and top-cap, to make 3D printing easier. The top cap simply friction-fits over the extrusion for a tight seal (which can be bolstered with glue, screws, or tape).

WHERE TO FROM HERE?

Get modelling! This can be used for making basic models of just about any complex shape, though they do really need to be flat on the main face - such as machined parts. However, this provides you with a powerful springboard to skip-ahead to advanced modelling of replacement parts and fittings, without exhaustive modelling training or experience.