How to Print Custom Phone Cases with TPU

Choosing your shore hardness

TPU 95A is where I'd start. It's semi-rigid, prints almost as easily as PETG, and provides enough flex for a phone case without being floppy. You can make it feel softer by printing 2 walls with 10% gyroid infill. That combination gives a case that feels close to 85A without the printing headaches.

85A is softer, grippier, and gives that premium rubbery feel that commercial silicone cases aim for. But it requires a well-tuned direct drive extruder and slow speeds (15–25 mm/s). The filament buckles and jams in Bowden tubes. If you have a Q2 or similar direct drive machine and you're comfortable with TPU, 85A produces a nicer-feeling case. Otherwise, stick with 95A.

Print settings that actually work

Dry your filament before printing. TPU absorbs moisture quickly and wet TPU produces stringing, popping, and poor layer adhesion. 4–8 hours at 50°C in a filament dryer. The filament types guide covers drying temperatures for all common materials.

Stringing is the biggest headache with TPU. TPU is highly fluid when molten, so it oozes during travel moves. Reduce retraction distance (not more than 1.5mm on direct drive), lower temperature by 5°C increments if stringing is bad, and enable combing in your slicer to keep travel moves inside the print perimeter. Disabling Z-hop can help too.

Getting the fit right

Phone case fit is measured in fractions of a millimeter. Too tight and you'll crack the case corners trying to install it. Too loose and it rattles and slides off.

For a snap-fit case: 0.2–0.3mm clearance per side. TPU's flexibility lets you go tighter than you would with rigid materials. The case stretches slightly during installation and grips the phone through elastic memory.

For a friction-fit case: 0.3–0.5mm clearance per side. Easier to install and remove. Relies on the case walls hugging the phone rather than snapping around it.

My approach: print a test ring (just the bottom 5mm of the case) to check fit before committing to a full 2-hour print. If the ring is too tight, add 0.1mm horizontal expansion in the slicer. If too loose, reduce by the same amount. This 15-minute test print has saved me from at least six wasted full prints.

Measure your phone with digital calipers. Published specs on GSMArena are close but not exact because of curved edges and manufacturing variance. Measure the actual phone you'll put in the case. For more on tolerance management in functional prints, the functional print ideas page has projects that use similar precision.

Design details that matter

Screen lip

Minimum 1mm above the screen surface. This prevents screen contact when placed face-down. Account for tempered glass screen protectors, which add 0.3–0.5mm to the phone's front profile. I design a 1.2mm lip to accommodate the screen protector.

Camera bump

The camera module area needs 0.5–1mm of raised lip to prevent lens contact on flat surfaces. Bevel or chamfer the edges of the camera cutout to reduce print artifacts and make it look cleaner.

Button overlays vs. cutouts

Flexible button overlays (0.6–0.8mm thick TPU over the buttons) give tactile feedback while protecting the buttons from direct impact. Open cutouts are simpler to print and easier to get right. I use overlays for the volume buttons (they benefit from protection) and open cutouts for the power button (easier to find by touch).

Charging port

Add 0.5–1mm extra clearance beyond the USB-C port dimensions. Different cable housings have different widths. If the opening is too tight, some cables won't fit. Better to have a slightly oversized port opening than to need a knife every time you plug in.

Wall thickness

1.5–2.5mm for main walls. Reinforced corners at 3–4mm where impacts concentrate. Gyroid or honeycomb infill absorbs energy in multiple directions, which matters for drop protection.

Where to find phone-specific STLs

Designing a phone case from scratch in Fusion 360 takes 2–3 hours if you know what you're doing. Finding an existing STL takes 2 minutes.

• iPhone 16 series by Victronix (Printables) covers all iPhone 16 models with regular updates.
• Universal Parametric Phone Case by PeteLaric (Thingiverse) is an OpenSCAD design where you input your phone's dimensions and it generates a fitted case.
• 3DX's phone case design guide walks through wall thickness, lip height, and drop protection design from scratch.

For less common phone models, search Printables and Thingiverse by your phone's exact model name. If nothing exists, the parametric OpenSCAD case is your best starting point. Measure, customize, print. Browse the common filaments collection for TPU options.

Customization ideas

This is where printing beats buying. You can't get a $10 commercial case with your name on it, a card slot on the back, and a custom texture. Printed, that's all one print job.

• Raised text or logo: 0.4–0.8mm above the surface. Single-color embossing that's visible in raking light.
• Texture patterns: Voronoi, hexagonal, diamond knurling. These improve grip and hide layer lines at the same time.
• Card holder: a slot on the back sized for 1–2 cards. Design the opening tight enough that the card stays in through daily handling but loose enough to extract with one hand.
• Kickstand: a separate snap-in piece or a living hinge integrated into the case body.
• Lanyard hole: a reinforced opening in one corner for a wrist strap.

For TPU printing techniques that extend beyond phone cases, the TPU furniture feet guide covers the same material at different shore hardnesses. And for full wearable TPU projects, the cosplay armor guide pushes TPU to its limits. The GoPro mount guide covers TPU vibration damping if you're interested in using flexible material for functional cycling accessories.