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Modelling an NFC Ring with DesignSpark Mechanical

Print-your-own wearables made easy with the powerful CAD package from RS

The NFC Ring started out as one man’s desire to make a ring do something useful – he was soon to be married, and had a dislike for objects of no function. After some experimentation, a Kickstarter project was launched and successfully funded.

Fast forward to now, you can get NFC Rings from their online store, or you can buy just the NFC tags and make your own!

In this post I will use DesignSpark Mechanical (hereafter referred to as DSM), a free and powerful CAD package from RS, to design an NFC ring, before printing it on an Ultimaker 2 3D printer.

The plan

The NFC Ring team has a great open mindset, sharing much of their data including ring models on their GitHub account. Whilst I could download one of these designs to print, I want to make my own, within DSM.

Things taken into consideration before modelling the ring:

  • Want to create a flat surface for the NFC tag, different to the official NFC Ring, which must be big enough for the NFC tag
  • Decide which finger I want to wear the ring on, and model with the corresponding ring size
  • Add a ‘comfort fit’ radius to inner face of ring

I will sketch a profile in 2D before rotating it through 360 degrees to make up the main body of the ring, then add a ring face section in which the NFC tag will be positioned. This is a common technique when modelling round objects. It is assumed that you have DSM installed and have completed some of the basic tutorials.

Sketching the ring profile

To begin, I chose the Sketch Mode, then Plan View, to get a flat grid view in the main drawing window. Next, to create the profile of the ring, I first used the Line tool to draw two parallel horizontal lines, of 1mm length, before using the Three-Point-Arc tool to add an arc on each side, as shown above.

Next, I used the Create Rounded Corner tool to soften the four corners, using a radius of 0.2mm. This may well be too small to show up in a DIY 3D printed model, but it is worth adding in case a higher resolution printer is used in the future, for example if the file is sent to a professional 3D printing house.

With the ring profile completed, I used the Construction Line tool to draw a line, to form an axis about which I will rotate the ring profile. This construction line should be a distance from the sketched ring profile that equals the desired ring inner radius. I know that a size 10 US ring fits me well, and referring to one of the many online ring charts, this should mean an inside diameter of 19.8mm and an inside radius of 9.9mm.

Selecting the Construction Line tool, I drew a vertical line to one side of the existing profile, in roughly the right location. There are different techniques that can be used to accurately position this line, two of which are detailed below.

Using the Move tool, I clicked the construction line, then the arrow of the axis of movement. A pop-up menu appeared and I chose the Ruler option, then dragged a measurement across to the ring profile. I could then type in the distance required between the two objects and the construction line moved accordingly.

Another way of doing this is to draw a 9.9mm wide rectangle starting from the ring profile, then again using the Move tool, but this time using the Up to option in the pop-up menu and selecting the far end of the rectangle as the point to move to. Once the construction line is in the correct position, the rectangle can be deleted.

In rotation

The Pull tool can be used to revolve and extrude the ring profile around the construction line. With the Pull tool selected, I first clicked the ring profile as the sketch to be affected. Next, choosing the Revolve option and selecting the construction line as the point of rotation. A pop-up menu appears with several options. The Full Pull option gives a full rotation, and therefore a complete ring.

We now have a model that looks like a ring! But I wanted to add a flat part to the front, to hold an NFC Ring tag.

I sketched a 22mm x 4mm rectangle, positioning it in the centre if the ring. Using the Pull tool, ensuring that the No Merge option was selected, I pulled the rectangle to outside the outer diameter of the ring. This option prevents the part being pulled from automatically merging with other 3D parts.

I used the Combine tool to cut away the solid cuboid, removing the inner part, and the overlapping part, leaving just the outer part that wraps around the ring part.

Now we have a flat ring face, but it is not tall enough for the NFC Ring inlay, at only 4mm. This was checked using the Measure tool, as shown in the screenshot below.

I then used a different mode of the Pull tool, by selecting it, then one of the edges of the ring face, then the Pivot Edge option. Dragging the edge upwards then modifies the model as shown below. Each edge was pulled out by 2mm, resulting in a flat ring face of 22mm x 8mm.

Lastly, I drew a 20mm x 6mm rectangle on the face, and pulled it down to create a recess for the inlay, then added a rounded chamfer to the ring face to neaten everything up.

[screen – finished ring]

With the model completed, I exported it to a STL file using the simple export menu, and could then use our Ultimaker 2 to print out the ring! Details of the printing process can be found in another post.

Summary

The Pull tool is a versatile, powerful feature of DSM that can be used in many different ways when modelling parts. It can extrude sketched profiles to create round parts, add chamfers, carve and modify existing parts and much more.

With DesignSpark Mechanical and the Ultimaker 2, I was able to design a part, in this case an NFC ring, and print out a usable physical model within the space of a few hours, making prototyping quick, simple and effective.

maker, hacker, doer

13 Jan 2015, 10:57