Hi all - I am looking for CAD software for a mac that I can use to make minor alterations to an existing STL files. I simply need to put a rectangular slot in the back of a part; preferable to do it by design instead of having to use a dremel tool. SW with a free trial option for mac would be great. Thank you in advance! -Mike

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Hi Mike,

You can try “Blender” or “Fusion360” they are free softwares. It might take a bit of time to get used to their interfaces but can be really useful.

Nahla - 3D Hubs

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Yes, blender is good but hard to learn…

Thanks higonnet! I’ll have to take a look at that this weekend. Since I need only to make the one modification I mentioned, maybe it will be easier. I could possibly find someone local on Craig’s List to act as a consultant to show me how to get there. Thanks again for the recommendation.

Thanks Nahla! That is the second reference to Blender I have seen so I will definitely check it out. I’ll also look at Fusion360 this weekend. This forum is really great, I appreciate the fast help!

FreeCAD will convert stl to step then any 3D cad software can edit it. OpenScad slso will work

You can use Fusion360 or Blender

Thank you Yaniv! I did load Fusion360 and watched a few Lynda.com courses and Youtube videos. The YouTube videos were very targeted and helpful. In just a day I was able to pull STL files into Fusion360, modify them, and save them back out to a printable file. The application is powerful so as usual a little complicated to learn, but there are a lot of great resources available to help. I appreciate this forum and everyone who replied, thanks again.

In my particular application, I needed to cut a notch in an object. In Fusion360 you create the notch shape as an object and then join it to the target object as a “cut” join. The shape of the notch shape becomes a negative space which is subtracted from the target object. If anyone has a similar need I would be glad to share the process.

Others have suggested some great tools but they all generally require installation, setup, and some non-trivial learning curve. By all means dive in and try those apps, but if all you want to do is punch a rectangular hole in the STL those options might not be the simplest way to get the job done.

For simple tasks like this (and for some lightweight design work) I use a free online tool called TinkerCAD. It’s a web-based CAD environment, so you just open the site in your browser and start working. You can import STL files easily, modify them, then export as a new STL file. I do this a lot for customers who upload partially broken designs that might not meet their requirements. It’s also a handy way to chop up an STL file that would best be printed as two halves.

Give it a shot, I think you’ll like it: https://www.tinkercad.com/

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