Question of the Week: How Do I Get a 3D Model?

This week’s question delves into the mysterious world of 3D scanning and 3D modeling, typically unknown territory for 3D printing newbies.

Fabbaloo reader Dave Summers writes:

“This is probably way below your pay grade, but I thought I would ask anyway. I have a greens divot tool I purchased thirty years ago and they don’t make it anymore. It is about two and a half inches long, one and a quarter inches wide and about a quarter of an inch thick, but it is curved. That is what makes it the best tool I ever owned for repairing greens. My library says they will print it for me for $2 if I can bring them a 3D image for printing. Where could I get this product imaged?”

I don’t know much about divot tools, but we can make some suggestions about getting this 3D printed. This is a very common question, but usually comes from those who are unfamiliar with how 3D printing works. And by saying “imaged”, it seems clear Summers is not familiar with 3D scanning.

This scenario happens constantly: someone has a “thing” that needs to be duplicated. Unfortunately, the media has over the past years driven a huge misconception in the public’s knowledge of 3D printing. Many in the general public still believe it is much like a Star Trek replicator, where you simply ask the machine to make something, anything.

That’s not how it works at all. The 3D printer is merely a tool, and it requires instructions on exactly what it should be printing for you. Imagine a 2D paper printer, and someone asking you to quickly print a novel. Wait, where does the novel come from? Do you have to write it yourself?

Yes, you do. Unless you happen to have a copy that someone else wrote. That’s exactly the case in 3D printing. You either already have the 3D model to be printed in digital form, or you have to obtain one. That seems to be the specific scenario Summers found himself in.

At this point there are really only two options: finding an existing 3D model or making one. It’s highly likely in this case no such 3D model can be found, as it would be the property of whichever company originally designed the piece. Even if the company still existed, it would be unlikely they even have a digital 3D model, simply because there really weren’t a lot of 3D CAD tools available 3D years ago!

This leaves us only one option left, making the 3D model ourselves. There are two ways to do this.

One way is to simply use a 3D CAD tool to draw the design, or one very similar, to create a printable 3D model. If the design is simple, which is likely the case here, it is possible for 3D CAD novices to quickly design the part. One good introductory tool for this is Tinkercad, but you will have to learn it. There’s a catch, though: not everyone knows how to use 3D CAD tools, and sometimes they can be very expensive to buy and learn.

If you cannot design the part themselves, you’ll have to get a trained 3D CAD designer to do so. Very often at this point the enquirers stop the project because they discover that 3D CAD designers are not cheap, and you may pay well over US$100 per hour for their time. Thus the cheap plastic object you thought should cost only a few dollars to reproduce will end up costing hundreds of dollars just for the design!

That’s because in mass manufacturing situations the pricey cost of the design is defrayed among the million items manufactured and sold. But for a one-off design, no such defraying happens and you have to heft the entire design fee yourself.

An alternative approach might be to leverage a less expensive overseas designer using one of many freelancer sites. In these services you post your “job”, which is to convert a collection of images of the object into a proper, printable 3D model. 3D CAD solid modelers bid on the project and you select one based on their reviews and pricing. You might save quite a bit of money on the project – but you may also not get what you really want. In most cases it’s a better idea to simply pay for the proper design, particularly if it’s tricky.

There is another occasionally useful approach to obtaining the 3D model yourself, and that is to 3D scan the object. However, 3D scanning is as misunderstood as 3D printing: you rarely get a printable 3D model from 3D scanning. The surface will be wobbly, any moving parts will be solidified, and the model itself is likely to have holes or other features preventing clean 3D printing.

Sometimes the geometry of the object is so simple that a 3D scan actually works and results in a printable 3D model, but this is not something you should count on for a given project.

In most cases you will be – guess what – back at an experienced 3D CAD modeler to “fix” the 3D scan. Often the modeler will simply use the scan as a shape to “trace over” with CAD tools to reproduce the object.

And how do you get that 3D scan? There are professional 3D scanning services, but their price range is likely way beyond justification for a project of this type.

One way is to use a photogrammetry approach in which you take a series of still images of the object from all angles and have software (or a service) reconstruct a 3D model from the images. But that is sometimes technically challenging for many people. If you’re very lucky, you may have a friend that can do this for you, or perhaps even have a 3D scanner.

In this case there are really only two good options: have someone design the part from scratch in a 3D CAD tool, or attempt design yourself in a tool like Tinkercad.

Good luck, Dave!