For creating a 3D model of a robot finger with indentations and curves, especially if you're starting with limited CAD skills, you might want to consider a few different approaches:

1. 3D Scanning: If you have access to a 3D scanner, you can scan the existing finger and create a 3D model from the scan. There are also apps available for smartphones that can perform 3D scanning using the phone's camera, although the quality may not be as high as with a dedicated 3D scanner.

2. Photogrammetry: This technique involves taking a series of photographs of the object from different angles and using software to stitch them together into a 3D model. There are several photogrammetry software options available, some of which are free or have trial versions. This method can be quite effective but may require a bit of learning and experimentation to get good results.

3. CAD Software: For more control over the final model, using CAD software is the best option. While Tinkercad is very beginner-friendly, it might not have the advanced features needed for intricate designs. You might want to try software like Fusion 360, which is more advanced but still accessible to beginners. Autodesk offers free access to Fusion 360 for hobbyists and startups, and there are plenty of tutorials available online.

4. Hiring a Designer: If creating the model yourself seems too daunting, you could consider hiring a freelance 3D designer. Websites like Upwork or Fiverr have freelancers who specialize in 3D modeling and can create a model based on your specifications and measurements.

5. Community Help: You can also reach out to the Synthiam community or other online maker communities and forums. Often, members are willing to help with such projects, and someone might be able to create the model for you or guide you through the process.

As for converting a photo into an STL file, this is generally not straightforward because a single photo doesn't contain enough depth information to create a 3D model. However, if you have multiple photos from different angles, you can use photogrammetry, as mentioned above.

Remember, creating a detailed 3D model can be a complex task, especially for parts with intricate geometries. It might take some time to learn the necessary skills or find the right person to help you with the task.

I think jeremie uses tinkercad - it looks pretty simple to use. I think that's what it is called, maybe he'll chime in.

I use SolidWorks but that's way too much for what you need. Lots of online cad designers that are free

This is a perfect opportunity to rectify a weak area. If you can take all measurements, etc, you can then draw it in a multitude of programs. It's called reverse engineering. Tinkercad is a very easy program to master, just takes time. Like DJ, I use solid works. Anyhow, the point of this post is..... Sure there are easy ways, but you'll be stuck next time, and the time after. Learn the skill, and the "I fail horribly" becomes "how can I make something, or do something better" a reality. Loads of tutorials on YouTube, or others for a small fee.

I played with tinkercad on the weekend as I mentioned but as it is primitive based it is very blocky and I struggle at capturing all curves etc I  guess I need to watch some videos play some more.

example here is original and my bad attempt to replicate.  

OK Watched some videos looks like you have to make your own primitives to carve out shapes. Think I'm getting the hang of it now.  Thanks

Is that tinkercad?

Yep.  Horrible tool :-).

Really? Jeremie swears by it. I think there was an AutoCAD online that was free as well. I am not sure if they pulled the plug on it or not. At the hype of 3d printing, there were a kazillion free editors because they thought DIY would revolutionize local manufacturing and kids would grow up innovative. But instead, TikTok...

I don't really swear by it, TinkerCAD is a useful tool in a few instances, it's great when you are making basic shapes or combining STLs. In those applications, it excels and you can make things quite quickly. When it comes to making professional-looking pieces with Chamfers and fillets, it fails miserably. As Nink suggested, you have to make your own chamfers out of shapes. This is the exact reason I'm migrating to Fusion360. Chamfers and Fillets are a breeze and it supports importing of TinkerCAD files. It will take a lot of time to make the migration but I'm ready to move to the next level on my CAD journey.

Here's the popular CAD software for 3D print modelling these days:

FreeCAD is an open-source parametric modeling tool and Blender is an open-source direct modeling tool. I have tried both. Both are free for the full versions of the software. Fusion360 and Onshape are subscription-based with free access to some tools and are limited without a subscription.

FreeCAD has a terrible UI IMHO. Blender is direct modelling and I want parametric (much better for engineering models) OnShape isn't as popular as Fusion360.

I am choosing to go the Fusion360 route because the UI is really good, there is a ton of support on YouTube, and TinkerCAD files are supported (of which I have made 400+ designs over the past 5 years).

Thanks Jeremie. I just Installed fusion 360.  There is a FREE version Woot!. wow learning curve on this is going to be steep.

Fusion360 is great as well. Bonus is they post their own tutorials and tons of folks do too. Making strides there Nink