Fix a Door Spring With 3D Printing

This all started when I noticed one of my door handles was weak, and after opening it up, I found out that a spring was broken. I replaced the spring with a new 3d printed one. In this article, I'll show you how to do the same! You'll be able to make accurate copies of this simple real object! Keep in mind that the plastic spring is not going to be as strong as a metal one, but it'll definitely be better than nothing and it will be fun to make!

• a 3d printer
• screwdrivers and other tools (whatever you need for the door)
• Inkscape: https://inkscape.org/
• Blender: https://blender.org
• Ultimaker Cura: https://ultimaker.com/software/ultimaker-cura (or another slicer)

First, you'll need to take apart the door handle and get the spring out of the mechanism. Depending on manufacturer and model, this might be as simple as undoing a few screws, or it could require more tools and effort. Observe the thing, think about how it was put together, and how it can be taken apart. You're crafty, I know you can do it! Also take some pictures, so you'll know how to put it back together later!

You need a good, accurate picture of your broken spring in order to make a replica. You should use a paper scanner if you have one. A photo taken with a camera will always distort the object with perspective, but a scanner doesn't do that.
I placed the spring on my scanner, along with a piece of millimeter paper for size reference. I also added a cute little fox, which prevents the lid of the scanner from touching the spring.

Load up your image in Inkscape or a similar program and draw a line following the object in the picture. Programs like Paint are not okay, because that is a raster image and you won't be able to make a nice 3d model out of it. You could do this in Gimp or Photoshop as well, just make sure that you are drawing actual lines, not pixels.

Once you're done tracing, delete the picture in the background because we don't need it any more.

Export your work in the .svg format.

Now it's time to load up your 3D program! I used Blender, it does these things pretty well. First, you'll want to import the .svg file you just created.

There it is! It's very small though.

If you select the model and press N you'll get a menu where you can see the dimensions. Keep in mind that although the size says "m", this will actually become millimeters when you go to 3d print it! Make sure your units are correct. Change the scale until it fits the real size of your object.

Now convert this curve into a mesh, as shown in the screenshot.

To make a 3d object out of it, click on the wrench tab and add the Skin modifier.

It looks very messy right now, but that's because my object has a big scale.
To change the size of the skin, you need to pres Tab to enter edit mode, then press A to select everything, then press N if you haven't already, and here you'll be able to change "Mean Radius X" and "Mean Radius Y". "Mean Radius X" should be some multiple of the size of your printer nozzle, divided by the scale you used on the curve after you imported it.

Now it looks like the real thing!
Export it in the .stl format so we can print it!

Load up Cura or your 3d slicer of choice, and open this stl. Default settings are fine for a simple object like this. I added a brim to make sure it sticks to the glass.

Send it to your 3d printer, or put it on an SD card and load it up on the printer. I'm sure you got this step down if you own a 3d printer ;-)

For the filament, I used PLA, it's the only one I'm experienced with. Feel free to try other, possibly stronger, materials!

The resulting print is very similar to the original object!
Later I made it thicker to make it stronger. I just changed "horizontal expansion" to 0.4 in Cura. I could have done the same thing by changing "Mean Radius X" in Blender.

This is still not as strong as the original metal spring, but it's much better than nothing! You might be able to make it stronger by making the thickness different in some parts compared to others, or changing the design completely. Be careful, as the thicker you make it, the more likely it is that it will break when it bends. I'm happy with this one, though!

For completeness, here is the model I made: https://www.thingiverse.com/thing:4251188

I wish you all happy fixing! ^.^