Resin Phone Cases:
The Flexible & Tough
Resin Breakdown
Standard resin shatters. The right flexible resin bends 360°, survives drops, and prints precision detail that TPU filament can't match.
The Case for Printing Cases in Resin
Most 3D printed phone cases you see online are FDM TPU prints. They work well enough — rubbery, grippy, cheap to produce. But they have a ceiling: layer lines, limited detail resolution, and that unmistakable "printed" texture that telegraphs DIY from across a room.
Resin changes the equation. An MSLA or DLP printer like the Elegoo Saturn 4 Ultra 16K can render fine surface textures, ultra-thin walls, and crisp camera cutouts at a level TPU filament simply can't approach. The catch? Standard photopolymer resin is brittle — it'll snap before it bends. That's where flexible and tough resins earn their place.
The best flexible resins for phone cases occupy a specific mechanical window: soft enough to flex over the corners of the phone, stiff enough to resist cracking under repeated bending, and impact-resistant enough to actually protect the device in a drop. Below, we break down the top contenders on the market in 2025.
Resin phone cases work best with a wall thickness of 1.5–2.5mm. Under 1.2mm, even flexible resins can tear at snap-on points. Over 3mm, the case loses the flex that makes it installable.
Best Resins for Flexibility & Durability
We evaluated each resin on four axes that matter for phone cases: elongation at break (how far it stretches before tearing), Shore hardness (how rubber-like it feels), impact resistance (drop survivability), and printability (failure rate, support behavior, wash/cure difficulty).
Siraya Tech Tenacious
Tenacious is the community consensus pick for anything that needs to bend without breaking. At 65D Shore hardness in its clear/obsidian formulation — and a softer 70A in the Flex Black variant — it straddles the line between a rigid part and a rubber part, which is exactly what a phone case needs. It can be bent 360° without fracture and springs back to its original shape. The high polymer content delivers real impact resistance: cases survive drops that would shatter any standard resin print.
One underrated feature: Tenacious can be mixed into any 405nm resin at 10–30% to add toughness and reduce brittleness without fully rubbering the output. That makes it a flexible additive as much as a standalone material.
- 360° bend without fracture
- Excellent drop resistance
- Can mix with other resins
- Low odor, widely available
- Elegoo Saturn 4 profiles exist
- Lower detail vs standard resin
- Needs thick supports (1.2mm tip)
- Print temp should be above 25°C
- Not as rubber-soft as F39
RESIONE F39 Flexible Resin
If Tenacious is the tough flex option, RESIONE F39 is the soft flex option. With a Shore A hardness of 60–75A and an elongation at break of 255%, F39 prints feel and behave more like silicone than plastic. The tear strength is rated at 47.2 kN/m — one of the highest in the consumer flexible resin category — which means the thin walls of a phone case won't split when you're pressing it onto the device.
Note the temperature sensitivity: at ambient temperatures above 20°C F39 is very soft; below 5°C it becomes noticeably stiffer and more impact-resistant. This is a material characteristic to factor in if your customer is in a cold climate.
- Most rubber-like feel of any resin
- 255% elongation — won't tear on install
- High tear strength at the walls
- Industrial-grade formulation
- Gets stiffer in cold temperatures
- Higher cost than standard resins
- Harder to support properly
- Less detail resolution than 65D options
Elegoo ABS-Like Ultra Resin
Elegoo's ABS-Like Ultra isn't a rubbery flexible resin — it's a tough resin that bends without shattering. The distinction matters: if you want a case that snaps on firm and feels like a premium rigid case rather than a soft TPU, ABS-Like Ultra is your material. Its advanced low-viscosity formula makes it among the easiest ABS-class resins to print, with a significantly lower failure rate than earlier ABS-Like versions.
The impact resistance is formulated to absorb drops rather than crack — and for thin-walled phone cases, that's the critical property. This is Dreaming3D's recommended resin for customers who want a sleek, detail-heavy case that still survives real-world use.
- Best detail quality of the three
- Very low failure rate
- Premium rigid feel on finished case
- Drillable, workable surface
- Not a true flexible resin
- Less shock-absorbing than F39
- Snapping over phone requires care
Quick Comparison
| Resin | Shore Hardness | Elongation | Feel | Best For | ~Price / kg |
|---|---|---|---|---|---|
| Siraya Tech Tenacious | 65D / 70A (Flex) | 70% | Semi-rigid, very tough | All-around case, mixing additive | $28–34 |
| Siraya Tech Tenacious Flex Black | 70A | ~120% | Soft rubber | Soft-touch cases | $30–36 |
| RESIONE F39 | 60–75A | 255% | Very soft rubber | Maximum flexibility | $38–45 |
| RESIONE TH72 | ~80A | ~150% | Medium-firm rubber | Figures + tough cases | $35–42 |
| Elegoo ABS-Like Ultra | Rigid-ish | Low | Firm, premium | Detail-heavy rigid cases | $22–28 |
| SUNLU High Toughness | ~75A | 5× standard | Flexible | Budget flex option | $18–24 |
Siraya Tenacious doesn't just flex — it absorbs. The difference between a flexible resin and a tough resin is whether the material stores energy elastically or dissipates it as heat. For phone cases, you want both, and Tenacious comes closest to that balance.
How to Actually Print a Good Phone Case in Resin
The STL is only half the job. Resin phone cases are unforgiving of sloppy settings — under-supported sections warp, over-exposed walls lose detail, and flexible resins need specific support geometry to print clean. Here's the workflow we use at Dreaming3D.
Orient the case at 45°
Flat-on-bed orientation creates massive suction forces on MSLA printers and almost guarantees delamination. Orient the case at 40–50° off horizontal with the camera cutout edge elevated. This distributes peel forces across the print over time rather than applying them all at once to a large flat layer.
Set supports with raft — heavier tips for flex resins
For Siraya Tenacious, use a minimum support tip diameter of 1.2mm with a depth of 0.5mm. Flexible resins move during printing and thin support tips can fail mid-job. For Elegoo ABS-Like, standard 0.4–0.6mm tips work fine. Always use a raft — flex resins are particularly prone to early layer adhesion failure on bare FEP without one.
Exposure: start conservative, test with a lattice
Flex resins are sensitive to over-exposure, which stiffens the final part and reduces the flexibility you paid for. Use the resin manufacturer's base profile for your printer as a starting point, then reduce normal exposure time by 10–15% and test with a small lattice section first. Tenacious for the Saturn 4 Ultra runs well at around 1.5–2.5s per layer at 0.05mm.
Wash shorter — post-cure shorter
Over-washing degrades flexible resins and makes them stiffer. Aim for 60–90 seconds in isopropyl alcohol (or use a dedicated wash station). For post-curing, 2–3 minutes at moderate UV intensity is enough for Tenacious and F39 — extended curing locks in additional crosslinks and removes flex. Check color consistency; stop curing when the surface loses tacky feel.
Remove supports at room temperature, not cold
Flexible resins become brittle in cold — both F39 and Tenacious Flex Black are noticeably stiffer below 20°C. Remove supports at room temperature to avoid tearing the case walls at support attachment points. Light sanding with 400-grit followed by 800-grit finishes the surface cleanly.
Never use standard rigid resin (Elegoo Standard, Anycubic Eco, etc.) for a phone case. The Shore hardness is too high and elongation at break is under 10% — the case will snap before it fully installs on the phone. Always use a flexible, tough, or ABS-like formulation specifically.
Best Places to Find iPhone 13 Pro & iPhone 17 Pro Models
The most time-consuming part of printing a phone case isn't the print — it's finding or building a model with accurate dimensions. Phone case STL files need to be tight: even 0.3mm of slop on the camera module cutout or the charging port placement makes a case feel cheap. Here are the most reliable sources we've found for both the iPhone 13 Pro and the newer iPhone 17 Pro.
Cults3D
The deepest library for iPhone case STL files, including free and premium models for both the iPhone 13 Pro and iPhone 17 Pro. Some premium listings are modeled directly to Apple's official dimensions. Includes SLA/resin-optimized versions and MagSafe-compatible variants.
Free + Paid · iPhone 17 Pro AvailableMakerWorld
Bambu Lab's model platform has grown quickly and now has solid iPhone 13 series coverage, including the 13 Pro. Community-rated models with verified print results. File quality skews high because the rating system filters out bad uploads.
Free · iPhone 13 Pro Strong CoveragePrintables (Prusa)
Prusa's community platform has a large catalog of iPhone case files, particularly for older models like the 13 Pro. Good filtering by material type — some models specifically tagged for flexible resin use. Free downloads with active community comments that flag fit issues.
Free · iPhone 13 Pro LibraryThingiverse
The OG model repository. Huge iPhone 13 library but much lighter on 17 Pro content. Useful as a secondary source and for finding open-source base models you can modify. Check "Thing Details" for community-reported fit feedback before printing.
Free · Legacy Library · 13 Pro HeavyWhen evaluating any phone case STL, look for models that cite the source of their dimensions (official Apple spec sheets or measured from physical device). Models described as "measured by hand" or without dimension sourcing are more likely to have fit issues — especially around the camera module, which is the largest variable between iPhone generations.
For the iPhone 17 Pro specifically, the Cults3D listing by Amentsolutions is among the earliest community models built for SLA/resin printing in place. A separate listing offers a 5mm outer frame based on official Apple dimensions, designed as a base for custom case design work — useful if you want to create an original design rather than printing someone else's geometry.
Resin vs. TPU for Phone Cases: Honest Comparison
It's worth being direct: for pure functionality and ease, FDM TPU filament is still the most forgiving choice for phone cases. It's more rubbery, easier to install, more forgiving of dimension errors, and the material cost per case is lower. If someone just wants a workable case, TPU is the default.
Where resin wins:
| Attribute | Flexible Resin | FDM TPU |
|---|---|---|
| Surface detail / texture quality | Far superior | Visible layer lines |
| Dimensional accuracy | Excellent (0.05mm layers) | Good but limited by nozzle |
| Flexibility | Good (flex resin) / Poor (standard) | Excellent (95A Shore) |
| Install ease | Good with flex resin | Best |
| Drop protection | Excellent (tough resin) | Good |
| Post-processing | Required (wash + cure) | None needed |
| Print time | Fast (MSLA) | Depends on printer |
| Perceived value | Premium finish | DIY feel |
For a service business like Dreaming3D, resin cases command higher price points because the surface finish is visibly premium. Customers who've seen a resin case next to a TPU case don't need convincing — the detail difference sells itself.
FAQ
Can you really print a flexible phone case in resin?
What is the best resin brand for printing phone cases?
Where can I find iPhone 13 Pro and iPhone 17 Pro case STL models?
Do I need to mix flexible resin with regular resin for phone cases?
What wall thickness should I use for a resin phone case?
Can Dreaming3D print a custom phone case for me?
Want a Resin Phone Case Printed Right?
Dreaming3D offers professional resin printing services in San Diego. Bring your STL or let us find the right model — we'll dial in the resin, settings, and finish.