Category Archives: 3D Printers

Designing a Simple Part for 3D Printing

In a previous blog I told about my new 3D printer, and showed a few photos of it printing objects that I had found online. What else can you do with a 3D printer? You can design your own items to print, and those can be anything you can imagine. They might be purely decorative, or could be functional. Here’s something simple that is functional.

Julie has a basket that stands on four metal legs. Unfortunately, the little plastic feet that went on the legs have long since disappeared, and now they scratch the floor.

Simple solution: make some protective feet.

Fortunately, this really is a simple solution. I have some filament that I can print called TPU (thermoplastic polyeruthane) which is flexible but also tough. It sounds like the perfect material for this.

I measured the leg, and it was just a little under 19mm across. So I needed to design a foot that would fit over this 19mm square leg, hold up to some use, and stay on the leg. I decided to make it 2mm thick, as that seemed like a good thickness to not be too flimsy, yet not be overkill.

I use Fusion 360 from AutoDesk for most of my 3D designing. It’s free for hobbyists, and very capable. There are many other 3D design programs that would have worked, but that’s the one I’m most proficient with at this time. Maybe I’ll switch in the future. There is a great open source 3D design program I’m interested in playing with, but for this project I used Fusion 360

How would you go about designing a foot for this? It seems like a simple object, and it is. Just a cube with a hole in it. Like this:

I won’t go into any great detail about designing this, but will give some basic steps.

  • The leg is 19mm square, and I want the walls to be 2mm thick. 19mm + 2mm on each side makes 23mm. Draw a 23mm square.
  • Extrude that up 23mm, making a 23mm cube.
  • On the top surface of that cube, draw a centered 19mm square, leaving 2mm of the original cube on each side.
  • Extrude that down 19mm, subtracting this 19mm cube from the 23mm cube. That gives us the basic shape shown above. Note that by doing this we are left with a 4mm bottom. I could have reduced the height of the 23mm cube so that the sides and bottom were uniformly 2mm, but I figured a little extra material on the bottom would just add to the wear resistance.
  • Export this object as a 3D mesh, slice it, print it, and test it. I found that it fit, but was a bit loose, and probably would fall off over time.
  • Go back to Fusion 360 and tweak the internal (subtracted) cube to 18.5mm. If you’re paying attention (you were, weren’t you?), you’ll notice that the walls are now 2.25mm thick. I didn’t see any reason to go back and adjust this, although it would have been easy to do. At this point I believed I probably had a workable foot. In Fusion 360, it looked like this:
  • Kind of square-ish with sharp edges. Fusion 360 to the rescue. I “Filleted” (rounded) all edges, inside and out, with the exception of the bottom edges, which I “Chamfered” (cut at an angle). Why do the bottom different? Because 3D printers like mine have a problem with steep overhangs, and a fillet starts out with almost a 90° overhang, whereas a chamfer has only a 45° overhang and can be printed by most printers. Because this object is so small, it probably wouldn’t have made any real difference, but it’s a good habit to form when designing objects for 3D printing. I now have this, which looks a lot like the photo at the top of the page:

I think it looks good! Export it, Slice it, Print it. Test the fit…

It looks like a winner to me. It fits snugly, won’t fall off, and will protect the floor. The color? Just happens to be the color of TPU filament I have and a color Julie likes. Which is probably why I have this filament. 🙂

Watch for a future blog on designing a more complex object using a totally different 3D design program.

3D Printers

When 3D printers started becoming somewhat affordable several years ago, I thought it would be fun to have one and learn more about the technology and see what uses I could find for it. But the first ones were a bit out of my budget, and I didn’t see what use I would really have for one.

Scroll ahead a few years. This past summer, at Julie’s urging, I bought one for myself for my birthday (it actually arrived the day of my birthday). The photo below (not a good photo…) is my Creality Ender 3 Pro printer. A little over $200. “Some assembly required.”

The Creality Ender 3 is one of the less expensive printers available at this time. It’s print volume is somewhere around 8” x 8” x 10”. It arrived partly assembled, but there was still some assembly required. I think that was a good thing, as it familiarized me with the printer and took some of the fear of working with it away. More on that later.

Creality Ender 3 Printer

My first discovery was how slow it is to print something! We’re often not measuring print time in minutes but hours. When you begin to understand how it prints, this makes more sense. The printer oozes a small amount of melted plastic through a 0.4 millimeter nozzle (that’s about one sixty-fourth of an inch) and deposits it onto the surface of the object you are printing, creating a layer of plastic in the right places. An average layer is 0.2 mm thick, or less than one one-hundredth of an inch. So to make an object one inch high requires the printer to lay down about 100 layers of plastic. Each layer may take several minutes, depending on the size of the object.

Creality Ender 3 printer in action
Creality Ender 3 Printer in action

So what do you do with a 3D printer? As was pointed out to me early on, you first print things to make your printer better! Things like cable guides or filament guides or tool trays… The list of possibilities is endless. But that’s not all. There are many websites where you can download ready-to-print models, many for free.

Well, almost ready to print. Usually you download an “.stl” file, which is a description of the 3D object. You then must use a “slicer” program to convert that model into instructions that your printer can understand. Then you give that file to the printer, and it magically interprets these instructions into the movements necessary to create a lump of plastic that resembles what you wanted.

Really cool threaded cylindrical container with a lid
Really cool threaded cylindrical container with a lid

Once you’ve printed a number of objects that other people have created, you’ll probably start thinking about designing your own 3D creations. Can you do that? Yes, of course. There are a number of 3D design tools costing from free to thousands of dollars. I’ve tried several, and designed a few simple items.

My first design was simply a knob to replace a missing seat release knob in Julie’s car. Certainly not elegant, but quite functional. My second (ongoing) project has been to create some simple stands to display some Native American pottery. My latest completed project (if a project is ever truly complete – there are always enhancements that can be made!) is a variety of specialized hooks for holding items on 1/2” shelf edges in our camping trailer. And what is in the future? For starters, repair for a plastic part on my “Little Giant” ladder that broke. Photographs have been taken, measurements made with calipers, preliminary drawings have been drafted, but no 3D model – yet.

What is in the printer’s future? I’ve already made a few modifications I haven’t yet mentioned (something for a future blog). I have parts for one more “upgrade.” And I have tentative plans for at least one upgrade beyond that. I have a list of things to print, some quite simple and some fairly complex. With Christmas less than two months away, the printer might get put to use making a few items for that.

Stay tuned