Every couple of months my son returns home with a new Martial Arts belt, and they’re starting to build up, and generally live as a big pile of spaghetti in his wardrobe. My wife came home from one lesson and said “can you print a storage box for this mess of belts?” She’d had a look online already and didn’t really like anything that was available. This is where the beauty of 3D printing lies – if you can’t find something you want, or need it to be a particular size or colour for your use, you have the power to make it happen – either fetching a design someone else has made off one of the online libraries, or crack out some CAD software and DIY – I chose the latter for this.

In less than 24 hours we went from a mess and idea inception, to a neat stack of boxes – around 2 hours of design + prototype prints, (then sleeping), then 9 hours of printing. As this is for personal use I also traced the school’s logo into the lid, and made use of the printer’s multi-material capability to recolour the rings on each box to match the belt inside it – it just happened that I had filaments for all of the colours he’s earned. Previously I would’ve done that by printing separate parts for each colour and gluing them together, but the Bambu P1S’s multi-material printing meant it could Just Do It in one go by swapping the active colour out periodically.

I’ve tried a couple of CAD packages, and quickly found a favourite in OnShape – it’s browser-based and has a great mobile app. There are objects that I’ve designed entirely on my phone while sat on the sofa or in the car. A bonus of OnShape being entirely cloud-based, means that I can simply share this link to the design for you to explore.

Prototyping

Before jumping in to printing these I wanted to check if the principle of the design was correct. I wouldn’t want to waste 3 hours & 120g of filament for a box only to discover the lid didn’t fit! So first I printed a smaller one. This was the first project where I’d properly explored parametric modelling – because I’d exposed variables for the box dimensions I was able to easily produce a prototype that had a much smaller radius and height, but still retained all of the interlocking features.

The prototype worked reasonably well, but showed that I needed to make a tweak to the underside of the base to eliminate the supports that had appeared there. You can 3D print almost anything, but the best objects are designed for 3D printing, taking into account what it’s good at, and what it’s not so good at. A better design can reduce filament use, weight, time and improve appearance. In this case I’d wanted the boxes to be stackable, but wasn’t sure how to do design bottom of the box to allow this. I’d originally designed the underside so that the box base had a lip to fit around the next box. This left a void on the bottom, and the actual base would float a few mm above the build plate – this is one of those things 3D printers can’t do – they can’t print into thin air. The fix is to print a removable support structure that can be discarded after printing, but in this case it was a nightmare to get out, took ages to print and left a horrible sandpapery texture.

Ideally you want a design that doesn’t need supports at all. After more thinking, in the second prototype I made the box walls slightly thicker and extended the cavity downwards to the bottom face leaving just a ring-shaped slot for the next box to fit into. This does leave a bit of “in thin air” printing, but printers can cope with short bridges – in this case 2mm. Prototype 2’s design turned out to work brilliantly, so I went ahead and made up a bunch of full-size boxes in the right colours for each belt.

After being happy with the second prototype (both of which continue their lives on my desk as pots for printer stuff), I bumped the size back up and created the full stack. If you want to make your own, the STL is now available on Printables.

Ingredients

Materials

• CC3D Lemon Yellow PLA [Unavailable]
• Bambu Orange PLA Basic [Link]
• Bambu Black PLA Basic [Link]
• Bambu Cyan PLA Basic [Link]
• Bambu White PLA Basic [Link]
• Sunlu Purple PLA [Link]
• Sunlu Red PLA [Link]

Resources

• Belt Box [OnShape, Printables]

Tools

• BambuLabs P1S with AMS [Link]