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June 26, 2014

3D Printing - My first 'tool'

Now I know what the early cavemen felt like when they found fire - Yep, all warm and fuzzy inside. This 3D printing mallarky is all very well and good, but if you don't use it for a real purpose, then what is the point really. Well, today I built my first useful thing.

For my 3D scanning, I borrowed a compatible tablet for the scanner and started playing with that, given the Microsoft Surface 2 weighs nearly a kilo it's a bit of a burden on the fingers. The tablet needs a cradle I thought. My first challenge was trying to get the tablet on the build plate of the printer... I wanted a cradle that held the tablet in each corner, this would be the most secure and allow me to use the device in landscape mode. A rethink was required. More of a slot in harness... this has upsides, you can take the tablet out easily to use it elsewhere. Hmm...

On to the design

I needed something that would allow my hand to rest as naturally as possible so as to reduce fatigue. I also needed something that would work around the center of gravity of the device so that stress was reduced. Given my printer capacity issue, I could only print a harness that held on to one side of the tablet, and the tablet would have to be used in portrait (at least that was my original, unhappy belief).

There were a few challenges. The tablet was a funny shape, so I had to break out the ruler as well as looking at specs on the web. Based on that I started with the back component and hollowed out the space for the tablet to sit in.

The next worrisome bit was the mount for the handle. This had to be strong but not too bulky, and I was hoping it would be easy to dismantle. Actually I was trying to work out the best way to actually print the thing and the ability to pull the handle and cradle apart seemed like the best way. The main concern was around tolerances. Blender allows for you to create nuts and bolts with an add-on. HOWEVER, you can't create an M10 nut and an M10 Bolt and expect it to work. I started with an M10 bolt and added 0.4mm to the nut for clearance. As it turned out this was just enough.

Here is where I stopped thinking.


The first print

After 4 hours of design it was time to start printing out bits and testing. I tested the bit that the tablet would 'dock' with. More luck than judgement I think, but it fitted perfectly. It was tight enough to hold the tablet in, but not too tight it scuffed the device. The PLA/PHA plastic also allows for a little flex so this was nice.


In testing the handle components I didn't want to print the whole model so I only printed a little bit of it.

An interesting thing happened. While the first bits were printing I thought I'd need a bigger thread so I redesigned the bolt and handle on the fly. When the first bits finished they actually worked really well. The second attempt snapped within seconds... Doh, Back to the first design. This reminds me of an age old piece of wisdom my old woodworking teacher used to tell us, measure twice, cut once.


You'll note that there are 4 parts here. The plate, the handle, the bolt and a custom made screwdriver component. I decided to make the screwdriver because the last time I created a bolt and added a standard Phillips screwdriver head, the metal screwdriver shredded the plastic head. This bit was designed to have a lot of surface area to help with the grip and not shred.

So that was 3 hours of printing and tweaking, time to print the whole thing overnight. 7 hours later and the final product was ready.


In Summary

In less time than it would have taken to find one of these on Amazon and have it shipped next day delivery, I had designed, tested and printed a completely working prototype.

The handle designed had 3 really cool features I had not expected:
  • As it worked out the handle as makes for a really nice stand in portrait layout as well.
  • Because the handle was easily disconnected, it was easily shippable in a flat pack style if this product were to be marketed, but in any event it slipped in my rucksack really easily.
  • As it turned out, the straight handle above held the device in a pretty comfortable position. I could also design and print slightly rotated handles for both left and right handed people to hold the device perfectly portrait, or, as my first hope had been, landscape against my body. Because the handles were removable, they could also be interchangeable.

As a prototype I am really happy how this turned out and really proud about what I had accomplished in such a short time. The whole rig is actually really easy and comfortable to use. Are there any tweaks I would do to improve the product? Yes, there are a few.

  • First of all I would contour the handle a little bit to fit the fingers a little better. Not too much, just enough to get a gravity based grip. I'd also add a foot to the handle so it had a bigger footprint and could balance better fully loaded, although this does add a lot of risk it the tablet fell off for whatever reason.
  • For that reason I would look to add a thin clip that somehow attached to the bolt component and clipped over the top of the tablet. Not to add any structural strength, but just to stop the tablet sliding out.
  • I'd spend a bit more time rounding the edges of the plate and the dock.
  • I thought about adding a pen holder, but decided against this given the already bulky design. I would spend some time adding this if there were to be a version 2 of the cradle - probably to the thumb side of the handle.

Finally, proof that the item was actually useful, here is a buddy of mine sporting the device.