How do you 3d print from an existing part when you have no CAD drawings?

Question

We have a toy with some broken parts, an Executivity Gear Master. I don't think it's made anymore. Some tiny parts were easy to break and we'd like to 3d print some replacement parts. We don't have CAD or any other 3D drawings file, just a few of the unbroken parts. What's the best way to get some of these printed? Do I have to turn this into a 3D file first? (Is there a quick way to do that from the part itself?) Or is there a way to do it where I just need the part, rather like getting a spare key cut from a pre-existing key being used as the template?

Here's a photo of the part I need to print. Placed next to a quarter for size comparison:

I've seen the same parts used in a marble run toy I had as a kid - you might be able to find them with a bit of searching. — Jonas Czech, Apr 07 '19 at 05:57

score 6 · Accepted Answer · edited Aug 10 '18 at 11:06

You can't print without a 3D model first. There are various ways you can go about this (or pay someone to do the same for you, ignoring any IP issues).

It is possible to generate a 3D model from a sequence of 2D photographs (there is even software which will allow you to do this freehand on a phone). Equipment exists which is specifically designed for this process, and you have likely heard of the services which allow you to get a 3D print of your own body.

You can take a 2D photo and import this into a 3D drawing package. Copy the features into a mesh, and extrude it. This might be a good approach for a complex shape, particularly if appearance is more important than precision.

For the shape you show here, the simplest approach for anyone with modeling experience is maybe to just draw it from scratch (with a few key dimensions). Your shape is only made up of a handful of primitive shapes.

Experiment in TinkerCad which is an online 3D editor to see if you can handle this yourself. It's not clear if you have your own printer, but this sort of part should cost less than $1 to print.

Strength might be a problem if they are already breaking...

As a side note: you say that several of the parts have been easy to break. While you are creating a new model from scratch, you also have a possibility to add reinforcement or otherwise improve on the design! — mbmcavoy, Feb 11 '17 at 16:30
Whats the software to make a 3d image from 2d snaps on a phone? — davidgo, Mar 09 '17 at 18:54

score 6 · Answer 2 · answered Feb 10 '17 at 12:40

Unfortunately, There's no easy way to go about this. The easiest solution is to model the part from scratch. A pair of (digital) calipers is an invaluable tool for doing that.

Given that the part is rather small and (presumably) needs to fit with something, you need very precise measurements. 3D scanning or photogrammetry (reconstructing the models from 2D photographs) are not suitable for this, as they generally result in a model that needs clean up and can't be printed directly (which would be more work than modelling from scratch) and moreover the dimensions won't be accurate enough.

How do you 3d print from an existing part when you have no CAD drawings?

2 Answers2