For most FDM phone cases, TPU around 95A is the best starting point: it is flexible enough to stretch over a phone yet firm enough to hold camera lips, corners, and button openings. TPU around 90A suits cases that need more cushioning and grip, while 82A–85A grades produce a softer, more rubber-like feel at the cost of harder filament feeding. TPU around 98A or harder is useful for thin, firm bumpers and semi-flexible parts. Very soft 60A–70A TPU belongs mainly in compressible pads, seals, and other parts that need much more deformation than a typical phone case.
| Part | Recommended Starting Point | Why It Fits |
|---|---|---|
| Everyday phone case | TPU 95A | Balanced flex, shape retention, and feed stability |
| Soft-touch phone case | TPU 90A or 82A–85A | More compression, grip, and cushioning |
| Thin or firm bumper case | TPU 95A–98A | Better support for narrow walls and raised edges |
| Flexible buttons and protective caps | TPU 85A–95A | Repeated bending with useful elastic recovery |
| Anti-slip feet and grips | TPU 85A–95A | Grip plus abrasion and vibration resistance |
| Soft gasket or sealing pad | TPU/TPE 60A–90A | Greater conformity under compression |
| Vibration pad or cushioning insert | TPU/TPE 60A–85A | More deformation and damping |
| Flexible guard or strain-relief part | TPU 90A–98A or suitable TPE | Controlled flex with better shape recovery than a very soft grade |
Shore hardness is a starting point, not a complete prediction of the finished part. Two prints made from the same TPU can feel very different when wall thickness, infill, geometry, or print orientation changes.
A Phone Case Needs Flex Without Losing Its Shape
A useful phone-case material has several jobs at once. It must open enough to install around the device, recover after stretching, support the raised rim around the screen and camera, let button areas move, and tolerate repeated handling without behaving like a loose rubber sleeve. Those demands point toward an elastomer, but not necessarily the softest elastomer available.
The geometry also loads different areas in different ways. A corner bumper is mainly asked to deform under impact. A camera lip needs enough stiffness to stand proud of the lens area. A thin button bridge must bend with low finger force. The back panel may need very little flex at all. A single Shore number cannot optimize each feature by itself.
This is why softer does not automatically mean better protection. A very soft material can absorb deformation well, but a case that folds at the camera rim or pulls away from the phone edges has lost useful structure. For most one-piece FDM cases, a medium-flex TPU is the more practical baseline.
TPU 95A Is the Most Practical General-Purpose Baseline
TPU around 95A occupies a useful middle ground between rubber-like compliance and filament-feed stability. Prusa describes its current Prusament TPU 95A as one of the easier flexible materials to print and specifies 220–240 °C at the nozzle and 55–75 °C at the bed for that product.[a] Those temperatures are product-specific rather than universal TPU settings, but they show why 95A grades are commonly supported by normal desktop-printer profiles.
For a phone case, the main advantage is not simply that 95A bends. It is that it can bend while still supporting relatively thin sidewalls, port openings, raised edges, and snap-on geometry. This makes it a good starting point for everyday cases, protective sleeves, cable strain reliefs, feet, bumpers, and other parts that need elastic movement without deep compression.
Published values also show why the label should not be treated as a complete performance specification. UltiMaker’s current TPU 95A data sheet reports 96 Shore A for its material and gives 3D-printed tensile results that change strongly with orientation: elongation at break is reported above 560% in flat XY specimens but 82.3 ± 18.4% in upright Z specimens under the listed ASTM D3039 test conditions.[b] The exact numbers apply to that material and test setup, not to every 95A filament. The practical lesson is that layer orientation can matter more than a small difference in the Shore label.
TPU 90A and 82A–85A Trade Shape Retention for a Softer Feel
Moving down the Shore A scale generally makes a TPU part easier to squeeze and bend when the geometry stays comparable. That can be useful for a phone case designed around cushioning, a soft grip, a wearable contact surface, a vibration pad, or a protective cap that must stretch farther during installation.
Around 90A, a case can retain useful structure while feeling softer than a typical 95A print. Bambu Lab currently positions its 85A and 90A TPU grades for cushioning and impact-absorbing applications, including protective cases, with 85A as the softer option and 90A as the firmer of the pair.[c] That manufacturer positioning is useful as an application example, but it does not mean all 85A or 90A formulations behave identically.
At about 82A–85A, the material can feel distinctly more rubber-like. NinjaTek, for example, rates NinjaFlex at 85 Shore A and reports 660% elongation at break under ASTM D638 for that specific formulation.[d] High elongation is useful for parts that must stretch substantially, but it should not be read as proof that an 85A filament is automatically tougher, more impact-resistant, or longer-lived than every 95A filament.
Use softer TPU when the part actually needs more deformation. A softer spool can improve grip or cushioning, but it can also make camera lips, thin corners, and narrow bridges easier to fold. If a 95A case only feels slightly too firm, changing wall thickness may be a better first adjustment than changing filament.
TPU 98A and Harder Grades Suit Firm Bumpers and Thin Features
A harder TPU can be preferable when the part should flex without feeling soft. Typical examples include thin bumper frames, narrow camera surrounds, semi-flexible brackets, guards, and protective corners that must stay upright under normal handling.
For the same basic geometry, moving from 95A toward 98A usually reduces compliance and makes small features feel firmer. It can also make feeding easier because the filament resists buckling more strongly. The tradeoff is tactile: a harder TPU moves farther away from the soft, grippy feel many people expect from a rubber-like phone case.
Hardness must not be used as shorthand for strength. Tensile strength, tear resistance, abrasion resistance, fatigue behavior, and layer adhesion depend on the formulation and print conditions. A 98A material may hold a thin lip better while another 95A formulation performs better in abrasion or repeated flexing.
TPU 60A–70A Belongs to Very Soft Parts, Not Most Phone Cases
Ultra-soft TPU is useful when the part is supposed to collapse, compress, stretch deeply, or conform to another surface. Recreus currently separates its Filaflex range into 60A, 70A, 82A, and 95A grades, describing 60A as its softest option and 95A as the firmer grade intended for easier printing and more precise parts.[e]
That lower-hardness range is better matched to cushioning pads, highly deformable seals, soft wearable sections, elastic membranes, and vibration-isolation elements. It can be used for a deliberately squishy phone sleeve, but it is usually unnecessary for a conventional case because the raised rim, corner geometry, and sidewalls still need controlled shape retention.
TPE and SEBS Are Alternatives When the Soft Part Needs Different Environmental Behavior
TPU is not the only printable elastomer family. TPE is a broader category, and SEBS-based printable materials can be useful where a soft part also needs a different moisture, chemical, or outdoor-resistance profile. Recreus, for example, sells a 90A SEBS-based TPE and describes it as hydrophobic with chemical and UV resistance.[f] Those claims apply to that formulation rather than to all TPE or SEBS filaments.
For an ordinary phone case, TPU remains the simpler default because it is widely profiled and available across many hardness grades. SEBS or another TPE becomes more interesting for specialized seals, outdoor soft parts, insulation, or parts exposed to fluids where the product’s technical data supports the required environment.
Wall Thickness and Infill Can Change the Feel Without Changing Filament
Shore hardness describes the material under a defined indentation test. A printed object is a structure, so its apparent softness also depends on how much material is placed around and inside it. A thin 95A wall can bend more easily than a thick 85A wall even though the 85A polymer has the lower hardness number.
A recent Recreus demonstration illustrates the distinction. Using one Filaflex 95A filament, the company printed zones with 7% to 25% infill and measured approximate structural durometer readings from about 25 to 40 Shore across those zones. Recreus explicitly notes that the material itself remained 95A; the lower readings reflected the compliance of the printed structure rather than a new material hardness.[g]
The same principle is useful in phone-case design. Fewer or thinner walls make a region easier to bend. More perimeters, thicker ribs, denser internal structure, and shorter unsupported spans make it resist deformation. This allows one material to produce a firm camera rim, flexible button bridge, and softer back region when the model is designed for those different loads.
| Design Change | Typical Effect | Useful For |
|---|---|---|
| Thinner wall | More bending and easier local flex | Buttons, hinges, compliant side sections |
| Thicker wall or rib | More resistance to bending | Camera lips, corners, raised edges |
| Lower infill | More internal collapse under compression | Pads, cushioning zones, soft grips |
| Higher infill | Firmer compression response | Support zones and load-bearing soft parts |
| Longer flexible span | Easier bending | Button bridges and strain reliefs |
| Shorter supported span | Less deflection | Thin rims and dimensional features |
Corners, Camera Lips, and Buttons Need Different Local Behavior
Corner Bumpers
Phone corners are natural impact points, so a bumper needs room to deform without permanently folding away from the device. A medium TPU can work well because the material gives under load while the surrounding geometry helps it recover. Thickening the corner locally often changes its response more predictably than switching the whole case to a harder filament.
Camera and Screen Lips
Raised lips are narrow structural features. If they are too thin for the chosen hardness, they can roll outward or flatten when the case is handled. A firmer TPU, a wider lip base, or local ribs can improve support. Ultra-soft grades are least attractive here unless the geometry is deliberately thick.
Button Bridges
Buttons require the opposite behavior: low-force local flex. A 95A case can still produce an easy-to-press button if the bridge is thin and the free span is long enough. Changing the entire case to 85A just to soften a button can make the sidewalls and camera surround softer than intended.
Port Openings and Strain-Relief Features
Thin material around charging ports is exposed to repeated bending and tearing loads. Rounded transitions and enough material around the opening help reduce stress concentration. For these features, tear behavior and layer orientation deserve as much attention as Shore hardness.
Read More Than Shore Hardness on a Data Sheet
Shore A is useful for estimating surface indentation and general feel, but it does not rank every property a phone case or soft functional part needs. A useful technical data sheet may also report:
- Tensile modulus: useful context for how strongly the material resists stretching in the reported test.
- Elongation at break: the extension reached before rupture under the stated tensile method.
- Tensile strength: a load-related property that should not be inferred from Shore hardness alone.
- Tear resistance: especially relevant to thin openings, straps, membranes, and notched flexible features when the manufacturer reports it.
- Abrasion resistance: useful for feet, wheels, grips, bumpers, and parts that rub against other surfaces.
- Compression behavior or compression set: more relevant than simple tensile elongation for seals and pads held under compression.
- Temperature and chemical data: needed when the soft part will see a hot vehicle interior, cleaners, oils, or outdoor exposure.
Values should be compared only when the test method and specimen conditions are compatible. A molded specimen, a printed XY tensile bar, and an upright Z specimen are not interchangeable data points. Product formulation also matters: two spools labeled 95A can differ in modulus, surface tack, abrasion behavior, processing window, and rebound.
Print Orientation Still Matters With Flexible Filaments
Flexible materials do not eliminate FFF anisotropy. Layers still create directional interfaces, and a feature pulled across those interfaces can fail differently from the same feature loaded within the layer plane.
The UltiMaker TPU 95A data cited earlier makes that visible: its current printed specimens show much lower tensile stress at break and elongation at break in the upright Z orientation than in the flat or side orientations under the documented test conditions.[b] For phone cases and soft parts, this matters most around narrow bridges, straps, port openings, and other sections that repeatedly stretch.
Orientation should therefore follow the expected load path rather than being selected only for surface appearance. A part that must repeatedly open around a device should not place its most highly stretched section across a weakly bonded layer interface when another orientation can avoid it.
Printer Hardware Sets a Practical Lower Limit on Softness
Softer filament is easier to compress inside the feed path, so a short and well-constrained path becomes more valuable as hardness falls. Direct-drive extruders usually make 85A and softer materials easier to control because there is less distance between the drive gears and hotend. Bowden systems can still print flexible materials, but firmer grades are generally the easier starting point.
Manufacturer guidance shows how product-specific this can be. Recreus lists its 95A Filaflex as compatible with Bowden-type printers, while its softer grades are positioned as progressively more elastic materials.[e] That does not make every 95A filament automatically Bowden-friendly; tube length, friction, extruder gaps, and pressure in the hotend still affect feeding.
Automatic filament systems need their own compatibility check. Bambu Lab’s AMS HT documentation lists its dedicated “TPU for AMS” as supported, while generic TPU and TPU 95A are listed as unsupported for automatic feeding in that system.[h] A printer being able to print TPU does not mean every feeder, changer, or multi-material path can transport soft TPU reliably.
Moisture Can Make a Good TPU Look Like a Bad Filament
Flexible TPU can show bubbles, rough extrusion, stringing, or unstable flow after poor storage. Those symptoms can be mistaken for a weak formulation or bad slicer profile. Before judging a spool by surface quality, check the manufacturer’s drying instructions and storage recommendations.
For Prusament TPU 95A, Prusa states that drying is usually unnecessary when storage is good, but recommends at least four hours at 60 °C if moisture-related problems appear; the same guide links moisture with bubbles and stringing.[a] That schedule applies to the cited product. Other TPU and TPE formulations can specify different temperatures and times.
Rigid Filaments Are Different Case Designs, Not Direct TPU Substitutes
PLA, PETG, ABS, ASA, and other rigid or semi-rigid materials can be used for hard-shell phone accessories, but they do not behave like a stretch-on elastomeric case. PETG can flex in thin geometry, and polypropylene can tolerate repeated bending in suitable designs, yet neither should be assumed to reproduce the compression, grip, and elastic recovery of a TPU case simply because a thin test strip bends.
The distinction is practical: flexible, soft, elastic, and tough are different properties. A material may bend without feeling soft, stretch without resisting abrasion well, or resist impact without being suitable for a thin phone-case lip. The part’s required deformation mode should decide the material family.
Choose the Filament by the Failure You Need to Fix
| Problem in the Printed Part | First Change to Consider | Why |
|---|---|---|
| Case feels too floppy | Use thicker walls or a higher Shore grade | Both increase resistance to deformation |
| Case is difficult to stretch over the phone | Reduce local thickness or move to a softer grade | Installation needs more compliance |
| Camera lip folds outward | Reinforce the lip or use firmer TPU | The narrow feature needs more local support |
| Buttons are too hard to press | Thin or lengthen the button bridge | Local geometry can add flex without softening the whole case |
| Soft part tears near an opening | Round the transition and review print orientation | Reduces stress concentration and unfavorable layer loading |
| Filament buckles before the hotend | Use a firmer grade or shorten/constrain the feed path | Softer filament is easier to compress sideways |
| Part strings or shows bubbles | Check moisture before changing material | Wet TPU can disturb extrusion and surface quality |
| Pad does not compress enough | Use softer TPU/TPE or reduce structural density | Compression depends on both material and geometry |
Frequently Asked Questions
Is TPU 95A too hard for a phone case?
Usually not. TPU around 95A is a common practical starting point because it combines elastic movement with enough structure for thin walls and raised edges. If the case feels too firm, wall thickness and local geometry can be adjusted before moving to a softer spool.
Is 85A TPU better for drop protection than 95A?
Not automatically. An 85A TPU can provide more cushioning in comparable geometry, but drop performance also depends on the formulation, wall shape, corner thickness, infill, layer bonding, and how the case fits the device. Shore hardness alone is not a drop-test result.
Can a Bowden printer make a TPU phone case?
Yes, some Bowden setups can print TPU, especially firmer flexible grades such as many 95A formulations. A short, low-friction tube and a tightly constrained path around the drive gears help. Softer grades place greater demands on the feed path and may be impractical on some machines.
Does lower infill change TPU from 95A to a softer Shore grade?
No. The polymer remains the same hardness grade. Lower infill can make the printed structure easier to compress, so the part feels softer even though the material itself has not changed from 95A to 85A or another grade.
Is TPE better than TPU for soft parts?
It depends on the formulation and the job. TPU is widely available across useful hardness grades and is a practical default for cases, bumpers, grips, and strain reliefs. A specific TPE or SEBS formulation may be preferable when its chemical, moisture, UV, compression, or tactile properties better match the application.
Can normal TPU 95A be loaded through an automatic material system?
Only when the system manufacturer explicitly supports it. Soft TPU can buckle or drag in long automatic feed paths. Some systems support specially formulated harder TPU while excluding generic 95A TPU, so printer compatibility and feeder compatibility must be checked separately.
Sources
- Prusa Research — Prusament TPU 95A Material Guide — Supports product-specific print temperatures, flexible-material printability guidance, and moisture troubleshooting. (Official printer and filament manufacturer documentation.)
- UltiMaker — TPU 95A Technical Data Sheet — Supports 3D-printed hardness, tensile, elongation, and orientation-dependent data. (Official technical data sheet.)
- Bambu Lab — TPU 85A / TPU 90A — Supports the current positioning of 85A and 90A TPU for cushioning, impact absorption, and protective cases. (Official manufacturer product documentation.)
- NinjaTek — Technical Specifications — Supports product-specific Shore hardness, tensile, elongation, and abrasion data for 85A and 95A flexible filaments. (Official manufacturer technical specifications.)
- Recreus — Filaflex Flexible Filament Range — Supports the current 60A, 70A, 82A, and 95A hardness range and intended flexibility differences. (Official manufacturer material documentation.)
- Recreus — Filaflex SEBS — Supports the cited SEBS/TPE formulation’s moisture, chemical, thermal, and outdoor-oriented properties. (Official manufacturer product documentation.)
- Recreus — Variable Infill in TPU: Four Hardnesses From One Filament — Supports the distinction between fixed material hardness and geometry-dependent structural compliance in a 95A TPU demonstration. (Manufacturer technical demonstration with stated test conditions.)
- Bambu Lab — AMS HT Technical Documentation — Supports the stated automatic-feed compatibility distinction between dedicated TPU for AMS and generic TPU/TPU 95A. (Official hardware documentation.)