Making Replacement Gears – Can You Print On a 3d Printer?


We live in an electronic world. Computers, smart phones, flat screen streaming TVs, you get the point. But there are still plenty of mechanical systems in our lives, and from time to time, parts wear out and need to be replaced.

Printing 3d gears is a good idea for those uses that don’t require high torque or high strength. For many mechanical uses, from xxx to garage door openers, 3d printed gears can work very well.

My garage door opener failed. Well, it started in a failed state when I bought the house, so really, it’s not my fault. Garage doors are quite heavy, so I thought I’d need a super-tough metal gear in the opener box (bolted to the rails that my door opens on). It turns out, I was completely wrong.

The springs on a garage door are there to offset the weight of the garage door. So, the finer you tune that in (tightening the springs to a point where it makes the door neutral in weight, but not too light where it opens by itself), the better you are. The garage door opener does not need to work that hard to open the door, as it’s near-zero weight!

Disassembling my opener, I found what looked like a white disk and a lot of white dust. What I was seeing was the remnants of a nylon gear that was stripped. The last owner didn’t have the springs tightened well, so the chain across the nylon gear stripped the gear smooth. All the white dust inside was actually the shorn off teeth of the nylon gear. That’s a safety feature, believe it or not! It ensures that the motor doesn’t overwork and catch fire, burning your garage (and maybe your house) down. Instead, it would just spin freely.

So printing a replacement gear for this is a perfect use case for 3d printing. The gear is simple, and doesn’t require it to pull a high load. The old, toothless gear gave me the dimensions and holes for mounting, and the remnants of the teeth around the edge gave me a count of the gears.

Can My Printer Handle 3d Printed Gears?

You’ll want to know if your printer can handle the complex task of printing usable gears. To try this, print a test model for gears. David Pechter (dpechter on Thingiverse.Com) has created a great one for download.

·         https://www.thingiverse.com/thing:3211633

Print it and try it out. It will tell you whether your printer is up to the task of printing the teeth as necessary on a gear. Print it out and see what you get. Are the gear teeth all there? Are they well formed? Sometimes, you’ll find that you can print 12 to 24 teeth on a gear, but higher than that, the gear teeth don’t form individually, and are unusable.

Designing 3d Gears

Gears are incredibly complicated to design. You have to be able to calculate the angular displacement for each gear tooth around a circle, and even potentially change the design of the tooth (maybe it’s triangular, or maybe it’s more squared). All this can be a real pain in something like Inkscape or Illustrator, but it’s rather easy on something like GearGenerator.Com.

The cost is somewhat steep if you’re just wanting one gear. If you want several over time, the price goes up, but the value goes up, too. Here are their rates: $2.00USD for a single day, $10.00USD for a single month or $25.00USD for a year’s time for downloads. If you did two gears a month, the yearly plan is just slightly over $1.00USD per gear, and that’s not bad. Remember, though, that you can produce as many designs as you like in that time period. So if you do 200 designs in a single day, that’s only $0.01 per gear, and you’re done!

There’s one little catch. The download is in the SVG file format. You want STL files for use in your 3d printer. Here’s how you convert:

  1. Save the SVG file to your hard drive (by downloading from some place like Gear Generator).
  2. Go to https://www.tinkercad.com/ (Tinkercad) and login (or create a free account).
  3. Import the SVG file into Tinkercad. The import button is in the upper right.
  4. Choose Art in Settings, and adjust the size to fit your 3d printer’s bed.
  5. Click in the center of your gear to bring up the direct input for your dimensions. Type these in and save.
  6. In the top right, again, you’ll find Export. Export the file, but this time in STL format. Save it to your desktop and you’re ready to go!

So yes, there’s an interim step between getting your gear designed in SVG format, and printing it in STL format. Remember to set the dimensions as you want them, download the exported STL file and load it into your slicer. The rest is just like printing any other part on your 3d printer.

You can find some 3d models of gears at some websites, but it’s likely they won’t offer STL files for download. For example, at https://www.mcmaster.com/, you can find Solidworks files for many parts, including gears. You’ll have to find a way to convert this file format into STL files. I don’t use Solidworks, but if you did, you could load the file and export it, similarly to the Tinkercad example above. Unfortunately, Tinkercard.com will only allow you to import STL, OBJ and SVG files. You’ll need something that reads Solidworks files to convert them.

For a great discussion on the math behind gear design, have a look at this article from Instructables.Com:

Nylon, PLA, ABS? What Is the Best Material For Gears?

Nylon is probably the best material for gears, as it has good wear and strength properties, and handles friction well. Unfortunately, it’s notoriously difficult to 3d print well, so it’s worth avoiding unless you absolutely have to use it.

PLA is the best filament for 3d printing gears, for the most part. It has good strength and wear characteristics, and in the example of my garage door opener from above, it worked just fine. Plus it’s usually the cheapest filament to buy, coming in at under $20.00USD per kilogram (2.2 lbs) including the spool! You can print a lot of gears with a kilo of PLA!

Fun Planetary Gear Test For Your 3d Printer

Check out this really cool design on Thingiverse.Com by Benjamin Goetz (Sniff_Biggy) for a planetary gear necklace here:

It gives you a cool little project to print that shows off some well-designed gears that assemble into a neat tchotchke. Sure, you can call it a test project for your gears, or you can just print it for fun!

Related Questions

Can a 3d printer print anything?

No, it can’t. At least not at home. 3d printers can make some pretty complicated plastic parts, but metal objects are beyond the capabilities of home 3d printers … today. Who knows in the future? You’re likely not going to see affordable 3d metal printers for home use for some time, because you’ll need a printer that will keep you safe from heated metal that can be up to 2000 degrees Fahrenheit (where some metals melt, a requirement for 3d printing).

How long does it take to print something in 3d?

3d print time is usually determined first by the height of the product, then by the volume. So, for DLP resin printers, as long as it fits on the print bed area, the height of the part determines the speed. It can print roughly 0.75″ per hour. An FDM filament printer is not that far off, but there are a lot of variables. The smaller the XY area of the model, the faster it can be printed, unlike the DLP resin printer that prints a whole layer at a time, regardless of the size. So figurines can be done at 1″ per hour, but other, wider or longer prints, or multiple items per print job can slow the printer down even further.

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