As you can see in the image below, our dryer had a broken knob. It was just a small plastic part but without it, starting the machine became a bit of a hassle. To fix this, I could have gone to a site like Sears PartsDirect or similar, looked up the dryer’s model number, find the part, wait a few days and then get the original replacement part. I chose to go another route… I 3D-printed it myself!
Because this was such a simple part, it was very easy to model a replacement knob quickly in SketchUp. All I needed were the dimensions for the overall knob size and the small switch stem.
As you can see, the stem had a flat bottom that grips nicely into a void in the knob. Also, I was not too eager to replicate the original knob design (although that wouldn’t have been too hard). The knob just needed to fit and function as intended. So I went with a simple design that consisted of a disk and a box shape.
I might upload a video of the 3D modeling in another post, but I essentially used exact dimension entry and the tape measure tool for the main geometry and then the PushPull tool to form all the shapes (pull the grip up and then push the void in). The resulting shapes had quite sharp edges, so I also used Fredo’s Round Corner extension to round the top edges a bit. I then turned on the x-ray face style to be able to look into the object, which allowed me to find some stray lines that prevented this object from being 3D printable. After a few minutes, this was what I got and then exported to STL format using the SketchUp STL extension (click image to navigate):
Fortunate for us here at UMass, we have the MakerBot Innovation Center in the WEB DuBois library. A quick email and a trip to the library provided me with two versions of the knob in just a few hours (and for cheaper than ordering a replacement part):
So, did it fit? As you can see in the following image, it did (admittedly after some manual cleanup). Not too bad a solution!
I do have some tips and tricks in case you want to do something similar, too:
- I didn’t use calipers to measure the exact stem dimensions. As a result, I didn’t get the dimensions correct. The fit was quite tight and I needed to ream the knob out a bit. Use calipers if you have them! Sparkfun has some cheap ones for sale.
- This knob relies quite a bit on the strength of the perimeter of the internal void (to turn the switch stem, which has a bit of resistance). Therefore it is a good idea to increase the number of shells (the outside layers) during 3D printing from the default two to something like four.
- I could also have used the SolidInspector or SolidSolver extensions to check and clean the model up for 3D printing. In this case, I didn’t need to do that because of its simplicity.
Interested in 3D printing with SketchUp? Want to learn more techniques and other ways to 3D print or otherwise make things with SketchUp? Check out my book Architectural Design with SketchUp, 2nd Edition.