I’ve been doing a few updates at home, and as part of that ordered three pendant lights to replace the existing ones in the kitchen. When they arrived, I was disappointed to find that the part that attaches to the ceiling is not quite wide enough to cover the electrical boxes in the ceiling from which they are hung. In the photos below, you can see the outline of where the original light fixtures used to be, and how much narrower the new ones are:
I love the lights, though, and since they came all the way from Belgium, they would be difficult to return. So I thought I’d try to find a creative solution. I had never designed or 3d printed anything before, and never used 3d modeling software, but when I heard that my boss, Stephen Toback, designed his own iOS app using AI, I thought maybe I shouldn’t let my lack of experience stop me from trying. My first step was to pose the problem to Claude. Unfortunately, by some glitch, my chat history for my main interaction with Claude wasn’t saved, but the core task was to create a circle large enough to cover the electrical box in the ceiling, with a round cutout in the center to accommodate the brass dome of the light fixture, which the specs told me was 7.9cm. Claude suggested a number of software options, including FreeCAD, which I ended up using. Here is an example of how the conversation went:
I would like my cutout circle to be 7.9cm. How can I set that value?
To set your cutout circle to exactly 7.9cm in FreeCAD, here’s how to do it:
1. Select the cutout circle in either the 3D view or the Model tree on the left
2. Open the Properties panel (View → Panels → Property View if it’s not visible)
3. Look for the “Radius” value under the properties – if you’re working with a circle, this will be half of your desired diameter
4. Since you want 7.9cm diameter:
• Divide 7.9 by 2 to get your radius: 3.95cm
• Enter 3.95cm in the Radius field
• You can type “3.95cm” directly – FreeCAD understands units
What I ended up with in FreeCAD looked something like this:
Pretty simple, and then a quick export into a common format for CAD files (I used .dxf, which worked great). From there, I did a little looking around online for a fabrication service. There were options for 3d printing and options for laser cutting. I chose the latter, via a service called SendCutSend, because they had an option for brass to match the fixture hardware, and because it seemed relatively easy, affordable, and was likely to be quick.
Within a few days I had these in hand:
Unfortunately they were half the size I needed! So I started over in FreeCAD, and asked Claude to help me verify my measurements before exporting this time:
Please explain how to verify my measurements
I’ll help you verify the measurements of your plate using FreeCAD’s measurement tool:
- First, exit any active tool or sketch mode if you’re in one
- Press ‘M’ on your keyboard or click the ruler icon to activate the measurement tool
- To check the outer diameter:
- Click on the outer circular edge of your plate
- The measurement should show 120.00 mm (12cm)
- To check the inner cutout diameter:
- Click on the inner circular edge
- The measurement should show 79.00 mm (7.9cm)
- To verify that the circles are truly concentric:
- Click the center point of one circle, then the center point of the other
- The distance should be 0.00 mm
Remember that you can also check these values in the Properties panel:
- Select your sketch in the Model tree
- Look under the “Constraints” section
- You should see two diameter constraints matching these measurements
Would you like me to help you adjust any measurements that aren’t correct?
I’m still not sure exactly what went wrong the first time, but it may have something to do with how in FreeCAD you use radius measurements instead of the whole diameter, and I probably halved the radius measurement I was working with in an attempt to conform to that requirement. Fortunately though, my next shipment from SendCutSend, though a bit pricier because of the larger size, was exactly right:
Since I still need to touch up the paint before I permanently install the brackets, I can’t show you the finished product, but here you can see that they do the job they need to in covering the electrical cutouts, and match the fixture pretty well. They’re even a tight enough fit that they stay put without the mounting screws.
Once I get the paint touched up, I’ll use brass screws to mount them to the beadboard ceiling. One good thing about having the smaller mistake pieces is I was able to test drilling holes for the screws, and luckily encountered no problems there:
Great Job!!