## 3D Print a Custom Cut-Out Case for Your Mobile Phone

Following from last month's article summing up 3D printing, this month I'm going to get a bit more practical. I'm going to show you an easy way to make your first 3D printed object, a customized case for your phone.
I'm going to use the online CAD tool, Tinkercad, which offers a powerful solid-based modelling engine with a web interface and library of user-contributed parts.
The customization will be to cut a pattern, drawing inspiration from the Moorish tile work of the Alhambra, the palace citadel of Granada, the last of the Muslim Emirates of Iberia. This tile work is particularly beautiful, as a work of art but also mathematically, inspiring the likes of M.C. Escher with their tessellation and symmetry.
Finally I will 3D print it using Shapeways, a web-based 3D printing service.
The first thing we need is an SVG file with a pattern. These instructions will be for Adobe Illustrator, but you can use any vector package that can produce SVG files. I'm not going to focus too much on the details of generating this pattern, because you can simply trace it from an image, or perhaps build it from scratch using the geometric design tutorials here on Tuts+. I use a method somewhere between the two, taking rough dimensions from the image and then using rotation, translation, alignment and mirroring transformations to ensure symmetry.
Create a New Document. Place the Base Image asset on a layer (File > Place), and resize to fit the artboard. Finally Lock this layer.

The tile work motif I'm interested in is the one with a blue 16-pointed star. Unfortunately it's cut off at the top and bottom, which makes it a little trickier, but you can still see the symmetry.
Create a New Layer, and then with the Rectangle Tool (M) trace the outer large square and the long rectangle. To ensure equal distance, use the Offset Path Tool with a negative size to produce an inner square and rectangle on the other side of the white line.
Use a Non-Uniform Scale Transformation to vertically enlarge the long rectangle1000%.

Select all (Control-A) shapes and apply Horizontal Align Center and Vertical Align Center. Use the Rotate Transform to copy the shapes every 22.5°. Use Control-D to repeat this action.

Copy the inner and outer parts of the fourth long rectangle created in the rotation, and Paste them onto a new layer. Set the lines drawn on the previous layer to 0.01 pt Stroke Weight and lock the layer.
Back on the new layer, drag the pasted rectangles to intersect the eight-pointed blue stars around the edge of our pattern intersected by the second long rectangle created. Ensure the center of this shape matches the center of the eight-pointed blue star.
Draw a temporary Line Segment (\) from the center of the eight-pointed blue star to the center of the 16-pointed blue star. Group (Control-G) this line segment with the long rectangles on this layer.
Use the Rotate Transform to copy the shapes every 22.5°, to produce 16 sets.Drag each new shape so the temporary line segment intersects the center of the 16-pointed blue star. Finally Ungroup and delete the line segments.

Set the lines drawn on the previous layer to 0.01 pt Stroke Weight and lock the layer.
Create a new layer and use the Pen Tool (P) to trace one of the brown five-sided stars. Align the corners with the lines created earlier instead of the actual image to ensure symmetry.
Use the Rotate Transform to copy the shapes every 22.5°, 15 times. Drag each new shape to its place.
The colors aren't required for the end product, but help you see which tiles are which (and it looks better). The Outline View may be required to draw some shapes accurately.
Repeat this process for the blue and black hexagons, the brown kites and the blue 16-pointed star.
Unlock the non-tile layers and Copy them. Create New Layer and Paste these shapes. Drag them to intersect at the outer eight-pointed stars. Lock this new layer.
Create another New Layer and copy the blue hexagon. Use Rotate Transform to copy the shapes every 45°, for a total of eight shapes. Drag each to its correct plane around the eight-pointed star. Use the Pen Tool to trace the black kites and Rotate Transform to copy around the eight-pointed star, and then trace the blue eight-pointed star.
Select all these shapes and rotate around the central blue 16-pointed star.

Continue in this fashion to produce a highly symmetrical pattern. Hide all the layers with guiding lines, just leaving the tiles visible. Save as an SVG file.

If you are not familiar with Tinkercad, consider browsing the learn section first.
The Tinkercad gallery of user-contributed parts is key to this tutorial, and a brilliant part of the maker movement in general. Something like a phone case is somewhat tricky, because you need to get the size just so: loose enough to fit, but tight enough not to fall off. You also need to get holes in the right place for buttons and connectors. Often you'd need some careful measuring, precise CAD work and even then a couple of iterations to get it right.
However, with a gallery of usable parts we can just search for, in this case Samsung S5, we can find a case for which someone else has done those initial steps so we can concentrate on the creative side of things.
Sign in to Tinkercad, and navigate to the Samsung S5 Case or search the galleryfor an alternative. Click Copy & Tinker.

In the top left, click Design > Properties. Give your model a name, and verify that the visibility and license are set as desired (license may be determined by the parent model).
In the top left, click Edit > Copy, and then Edit > Paste. Alternatively use Control-C and then Control-VClick-drag the second case to one side.
We're going to fill the speaker hole in the case. Start by placing the workplane on the back surface of the phone case. You can find the workplane in the Helperscollapsible category on the right. Next place a Box over the hole in the case. The box can be found in the Geometric collapsible category on the right.

Rotate the view to look from underneath by dragging the right mouse button. Reduce the Snap Grid (bottom right) to 0.1 mm increments. Scale the box to the same thickness as the case by dragging the small white cube on the underside of the box. If you are using a different case, jot down the height indicated. Group the case and box to make a single object.

Now that we know the width of the case, we're going to briefly look at materials offered by Shapeways.
There is a range of materials on offer, from simple rough and cheap plastic all the way up to sterling silver. We're going to go for the inexpensive end of things, Strong and Flexible plastic. This is nylon powder fused with the SLS process. Check out last month's article on 3D printing for more details, or the video at the bottom of the Strong and Flexible plastic page. This page also has design guidelines for the material in question, telling us how thin walls and features we can design down to.
It's important to keep these design guidelines in mind when designing, to avoid producing a model that cannot be realized. Our case will fit within the 650 × 350 × 550 mm bounds and has walls thicker than 0.7 mm, so we should be okay to continue. If you're using a different material or different case model, check the design guidelines carefully.

Import the SVG file produced earlier. The file import option can be found in the Import collapsible category on the right. Scale and Height are unimportant in this instance.

Hold Shift and drag one of the white cubes at the corners of the pattern to scale all dimensions uniformlyscaling until the pattern is larger than the case. By dragging the black cone in its center, Move the pattern vertically to be just above the phone case. Move the pattern horizontally to align the central star in the pattern and the gap for the camera in the case. Horizontally aligning the pattern and case can help here. This option is found under Adjust at the top.

Vertically scale the pattern to leave 1 or 2 mm of the rim of the case exposed. This will ensure the case is strong. Convert the pattern into a Hole (in the Inspectorsection top left). Then group with the case—this may take some time.

At this point I decided I didn't like the area around the camera opening. I returned to Illustrator and combined the inner tiles of the central pattern, and re-exported as an SVG. Then I ungrouped and deleted the old pattern, and then imported the new pattern, realigned and scaled, converted to hole and regrouped.

The area around the opening for charger, volume and power switches could be weak. These final steps will address that.

Moving to the second case, place Cylinders at each end of the gap and a Box lined up with the widest part of the cylinder. Change them to holes. Repeat the process for the power and volume buttons.

Drag in a Box and scale it to encompass the entire phone case. Group this box with the hole boxes and cylinders made in the last step. Convert this composite entity into a Hole, and Group with the case to leave the regions around the charger, volume and power switches.

Carefully Align these parts with the patterned case, and then Group everything. We should now have a nice robust case. At this point I ungrouped things and tweaked the scaling for the pattern of the holes slightly, and then regrouped everything for the final model shown below.

The final step in Tinkercad is to export to a file for 3D printing. In the Design menu, select Download for 3D printing and you will see the dialog below. Choose the STLfile format, and it should download.

Back to Shapeways now, where we have our final model. If you don't have an account yet, sign up. Once signed in, go to the Design section. Hit the blueUpload button, ensure millimeters is selected for model units, and upload the STL file downloaded from Tinkercad.

After a moment you should see the screen above, showing the model. This would be a good time to check the dimensions shown, because STL files are very simple, and whilst they have dimensions, they do not store what units they are in! This is why we had to select millimeters in the last step. Take care if you get files from elsewhere that they are the size you expect.
Below is a list of all the available materials, and after a few moments these should run automatic calculations and checks, calculating prices in each material and showing issues (if any) and price.
Oh dear! As you can see below, our model is showing issues. If you click on View Issues it will show a bit more detail.
This shows you where the problem lies—in this case wall thickness. Although we started with a case thick enough to work in this material, where we've sliced there are some thin sections (orange). These sections will be a lot weaker and potentially could not even bond correctly whilst manufacturing.

There is a tool to automatically fix these problems, in this case adding material to thicken them (blue), but personally I find this a bit ugly.  The proper response would be to chamfer or fillet these edges. Unfortunately Tinkercad lacks this option! We could import the STL file into another program, such as 3ds Max, but that's beyond the scope of this tutorial.
Thankfully all these thin sections are adjacent to a thick section so shouldn't take much stress. In this instance I decided to, as they say in Hollywood, fix it in post. I'm going to file and sand these edges on the final model if they prove to be problematic. This is an often overlooked option in 3D printing—it's all too easy to try and perfect the model, but remember you can work on it with traditional methods afterwards if it's easier.
Shapeways gives us the option to ignore the problems and attempt printing in its Print it anyway option. Beware, though—this sometimes goes wrong!

Clicking Buy Now takes us to the page below. Ensuring Print in Anyway is selected, you can check out, fill in shipping and payment info, and it's in the process. There is a manual check they do after the automated checks, but with luck within a day or so you should get an email letting you know manufacturing has begun.

A week or so later the postman turned up with a rather well-wrapped package, shipped from Shapeways Eindhoven in the Netherlands. As you can see below, it's a nice fit for a first try—a little loose in places, and a little tricky to open the door for the charger, but that's often the way with a first prototype!

Looking closely, the texture is a rough, powdery white, and you can see where the individual particles of plastic have melted. If you'd prefer a smoother finish, a polished option is available. Or simply get some wet and dry sandpaper to smooth the areas you wish. Personally I like the rough texture—it gives me a good grip to help me avoid dropping my phone.

This tutorial has shown you how to take a pattern and cut it into a 3D object, how to fill holes in that object, and how to make more complex shapes to cut parts from objects. And also a little on making patterns and printing objects.
Using the skills from this tutorial, you should be able to customize your own case or another object. If you wish to tinker with my case, it's available on Tinkercad. Be sure to leave your comments, suggestions, and tinkered objects below.

### TDasany

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