3D Genius

By February 25, 2013 0 Comments

How to make a customisable bath plug to fit any plughole


Download mm versionDownload inch versionWhen the plug in the basin in my bathroom broke, I didn’t want to have to go down to the plumbing store to buy a new one. After all, with a 3D printer, I’d be able to make one myself. Then I thought: I can’t be the only person in this predicament. But others would be unlikely to have the same plughole size as me. How could I make a plug that would be easy to customise to fit any plughole?

The answer, when it finally came to me, was obvious. I’d design my plug to fit a plughole exactly 10 mm in diameter. Then when it came to printing it, all I’d have to do would be to measure the size of the hole, and scale my plug accordingly. My plughole measured 37 mm across, so I scaled the plug by 3.8 to allow a little leeway. Of course, it’s easy to make a version in inches if you don’t use metric measurements: just use inches rather than millimetres in this tutorial.

The plug itself is a rather unusual design. Why shouldn’t a plug be attractive as well as functional? The large, chunky ball on top makes it easy to pull out when you’ve got wet hands, and when it’s removed it looks more like an alien chess piece than a utilitarian object.

I used Autodesk’s free and excellent 123D Design to model the plug. Here’s how it was done.

1. Start with a cylinder

Choose the Cylinder from the Primitives menu. This menu also contains the Sphere, which we’ll use later:


2. Size the cylinder

Because this plug is going to be enlarged at the slicing stage, we’re going to start off with it very small. You can drag to draw the cylinder or, for more accuracy, just type in the radius you want. To draw a cylinder with a diameter of 10 mm, we need to give it a radius of 5 mm. Hit the Tab key to go to the next number field, and type in the height - I’ve chosen a height of just 2 mm:



3. Add a second cylinder

Because the first cylinder is so tiny, you’ll need to zoom in to see it more clearly. The zoom and pan controls are directly beneath the object icons, at the top of the window.

Select the Cylinder tool again, and hover over the existing cylinder: you’ll find the new one will snap to the old one, indicating that it’s going to create it mounted on top. I’ve chosen a radius of 7 mm, which will give an overhang of 2 mm each side. To match this precisely, I’ve chosen a height of 2 mm as well:



4. Add the stem

Add a new cylinder to the stack, which will form the stem of the lifting handle. I chose a radius of 1.5 mm, and a height of 5 mm. All these measurements may sound tiny, but remember it’s designed to be enlarged later:



5. Add the ball

Choose the Sphere from the Primitives menu, and position it so it snaps to the middle of the tall cylinder. I chose a radius of 2.5 mm, which would give a chunky ball when printed:



6. Move the ball down

By default, the ball will be placed so its bottom edge is resting on the cylinder. We need to move it down so it’s continuous with the cylinder. Click on the ball to select it, and a gear icon will appear next to it; click on this to choose Move from the range of options. You can use the arrows to drag it up and down, but it’s often easier to type in the value.

The initial value will be for the X distance; hit the Tab key twice to change this to the Z distance, and type in -1 as the distance to move it:



7. Chamfer the edge

The second cylinder can’t be printed as it stands, of course – not with that 90° overhang. But fixing that will also guarantee a better fit, so the next step is to chamfer the edge. First click on it to select it, then choose Chamfer from the menu that pops up when you click on the Gear icon:



08: The chamfer result

The Chamfer tool cuts away the edge at a 45° angle. Because this object was designed with a 2 mm overhang and a 2 mm height, a 2 mm chamfer slopes it away precisely to meet the cylinder beneath. To create the chamfer, simply drag the arrow:



09: Round the bottom edges

Rounding off the bottom of the plug, and the sharp edge we just created, will make it more hand-friendly and easier to print. Select each edge and this time, rather than choosing Chamfer, choose Fillet instead: this gives a soft, rounded edge:



10: Merge the ball and stem

We want to round the join between the ball and the stem it stands on, purely for aesthetic reasons. But before we can do that, we need to merge them together into a single object. Choose the Combine icon, on the right at the top, then select the two objects. Click the icon on the far right of the pop-up group, and choose Join to make them into a single object:



11: Fillet the join

You can now select the join between the two objects, and choose Fillet from the pop-up menu that appears when you press the Gear icon. As you drag on the arrow, you’ll see the join getting more and more smooth. It’s best to do this by eye, rather than numerically – but if you want to match my design, choose a value of 5.75 mm:



12. Finish the fillet

To finish the design, combine the handle and the middle cylinder using the Combine tool, just as we did in step 10. Now, you can use the Fillet tool to blend these two elements together, in just the same way:



 bathplugphoto113. The finished result

To print the plug, all I had to do was to measure the size of my plughole, and multiply by that number when slicing the STL file.

The result is a beautiful object, which looks good out of the water and sparkles beneath the surface. It also functions surprisingly well as a plug. It’s not made of flexible rubber, which means it won’t keep the water in forever, but in my basin it lasted easily long enough for a wash and a shave.

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