Short answer: "TPU" is not one material — it's a ladder of hardness grades, and picking the right rung matters more than any print setting. If you want flexible filament that feeds through a standard AMS, the only option is Bambu Lab TPU for AMS (Shore 68D), a semi-rigid grade. For genuinely rubbery parts, step down to TPU 95A HF (the best all-rounder), TPU 90A or TPU 85A — fed externally, ideally with the TPU Feed Assist Module or the dedicated TPU path on the AMS HT. Here's how the Shore scale actually works, what each grade feels like in your hand, and how to print all of them reliably on a Bambu Lab machine in Australia.
What Shore hardness actually means (A vs D, and why 68D is harder than 95A)
Flexible materials are graded on Shore durometer scales. Two of them matter for 3D printing: Shore A for soft, rubbery materials and Shore D for harder, semi-rigid ones. On both scales, a higher number means a harder material — but the scales overlap, which is where most confusion starts. The top of the A scale runs into the bottom of the D scale: Shore 95A is roughly 45D. So Bambu's "TPU for AMS" at 68D isn't a softer TPU than 95A — it's considerably harder, sitting well above the entire A-scale range that most people picture when they hear "flexible filament".
Numbers on a datasheet don't mean much until you've held the material, so here's the ladder in everyday objects:
- Shore 60A — about as soft as a rubber eraser. This is roughly the softest TPU that's practical to mass-produce and extrude on FDM printers.
- Shore 85A — a soft shoe sole or a skateboard wheel. Squashes visibly under thumb pressure.
- Shore 95A — car tyre tread. Firm rubber; flexes and rebounds but doesn't squish.
- Shore 68D — a semi-rigid hard shell, like luggage shell plastic with a hint of give. It bends before it snaps, but nobody would call it rubbery.
The Bambu Lab TPU ladder, from hardest to softest
Bambu Lab's range covers the useful span of the ladder with four grades. From hardest to softest:
| Filament | Shore hardness | Feels like | Feeding | Best for |
|---|---|---|---|---|
| TPU for AMS | 68D | Semi-rigid hard shell | Standard AMS, AMS Lite or AMS 2 Pro | Impact-resistant brackets, RC parts, hinges, phone-case-stiff parts |
| TPU 95A HF | 95A (≈45D) | Tyre tread | External spool; AMS HT TPU path; Feed Assist recommended | Wheels, gaskets, bumpers, tool grips — the all-rounder |
| TPU 90A | 90A | Firm shoe sole | External spool; Feed Assist recommended | Seals, straps, flexible enclosures |
| TPU 85A | 85A | Soft sole / skateboard wheel | External spool; Feed Assist strongly recommended | Grips, vibration dampers, wearables, squishy parts |
The pattern is simple: the softer the grade, the nicer the part feels — and the harder it is to feed. That trade-off, not temperature or speed, is what actually decides whether your TPU print succeeds.
Which grade for which job
Choose 68D (TPU for AMS) when you want toughness rather than squish: drone and RC crash parts, protective bumpers on brackets, living hinges, anything that PLA would snap on. Because it behaves almost like a rigid filament in the extruder, it's also the only TPU you can load into a multi-colour AMS setup and treat like any other spool — see our AMS setup guide for slot rules.
Choose 95A HF for the classic "I need a rubber part" jobs: gaskets, feet, wheels, seals, phone cases with real grip. The HF (high flow) formulation is tuned to print faster than legacy 95A while keeping the same hardness. If you only ever buy one flexible filament, buy this one.
Choose 90A or 85A when the part's whole purpose is compliance — vibration damping, comfortable straps, soft-touch grips. Expect slower prints and take feeding seriously (more below). If you're wondering about anything softer: around 60A is the practical floor for mass-produced FDM filament, and grades that soft are specialist territory — for most "softer than 85A" ideas, a redesign (thinner walls, lower infill, TPU-friendly geometry) on 85A or 90A gets you the same hand-feel with far fewer failed prints.
Three things people get wrong about TPU
1. Hardness is not bounce
Shore hardness measures resistance to indentation, not how energetically a material springs back. A 95A part can feel dead while a softer part bounces like a ball — rebound (resilience) is a separate property baked into the polymer. If what you're actually after is bounce — toys, balls, spring-loaded prints — a dedicated high-rebound material like BIQU PLA-HR will outperform a random TPU grade, and it prints far more easily too.
2. FDM TPU is not the same as resin "flexible"
Flexible photopolymer resins look similar in photos but behave very differently in service: FDM TPU has far better tear strength and fatigue resistance, which is why a printed TPU watch strap survives daily flexing while a flexible resin one develops cracks. For functional flexible parts, filament wins.
3. Printed TPU insoles are not "running shoe" foam
Commercial cushioning midsoles use foamed TPU (expanded beads or foaming filaments) — an entirely different category with its own density tricks. Solid printed TPU at 85A is a fine insole or heel cup, but don't expect big-brand-runner energy return from a solid print.
Feeding TPU on Bambu Lab printers: the part that decides success
Soft filament in a long PTFE path behaves like pushing a wet noodle. Bambu's ecosystem has three answers, and matching your grade to the right one is 90% of TPU reliability:
- Standard AMS route (68D only). TPU for AMS is stiff enough to survive the AMS feed path on the AMS, AMS Lite and AMS 2 Pro. No other TPU is — loading 95A into a standard AMS is how feed gears end up chewing filament mid-print.
- AMS HT dedicated TPU path (95A). The AMS HT has a purpose-built TPU outlet that gives 95A a short, controlled route to the extruder — and you get active drying in the same box, which TPU loves.
- TPU Feed Assist Module (85A–95A HF). The Bambu TPU Feed Assist Module adds a powered feeder that takes the tension out of the spool path. It's compatible with the P1 and X1 series plus the newer P2S, X2D and H2-series machines, and it noticeably improves both success rate and surface consistency on the soft grades — extrusion stays even, so walls stop showing that subtle TPU banding.
On an open-frame A1 or A1 Mini, run soft TPU from the external spool holder with the shortest, smoothest path you can arrange.
Print settings that actually work
Bambu Studio's stock TPU profiles are a good starting point; these are the numbers that matter when you tune:
- Nozzle: 220–240°C. Hotter improves layer bonding; cooler reduces stringing.
- Speed: slow down. Soft grades want gentle, constant flow — this is one place where the HF in 95A HF earns its name, tolerating higher speeds than legacy TPU.
- Retraction: 0.8–1.2 mm on Bambu's direct-drive extruders. Long retractions buckle soft filament inside the extruder.
- Stringing: TPU strings more than any rigid filament. Our stringing fix guide applies double here — and dry filament (next section) is half the battle.
- First layer: TPU grips build plates hard. A textured PEI plate and the fundamentals in our first layer adhesion guide prevent both lift-off and the opposite problem — parts welded to the plate.
Bambu's official wiki has per-material profiles if you want to cross-check.
The Australian problem: TPU drinks humidity
TPU is among the most hygroscopic filaments you can buy, and most of Australia's population lives on a coast running 60–80% relative humidity. Wet TPU shows up as aggressive stringing, popping sounds, bubbly surfaces and weak layer bonding — symptoms people waste days blaming on settings. Dry every TPU spool before serious prints and store it sealed with desiccant between jobs; the AMS HT's heated drying doubles as a solution for 95A users. Our full filament storage guide for Australia covers dryers, dry boxes and target humidity numbers.
FAQ
Can I put Bambu Lab TPU 95A in my AMS?
No — 95A is too soft for the standard AMS, AMS Lite or AMS 2 Pro feed path and will jam or strip. The only TPU rated for those units is TPU for AMS (68D). For 95A, use the AMS HT's dedicated TPU outlet or an external spool with the TPU Feed Assist Module.
What is the softest TPU a Bambu Lab printer can print?
Bambu's softest grade is 85A, which prints reliably with slow speeds and assisted feeding. Mass-produced FDM filament bottoms out around 60A industry-wide; anything softer is usually achieved through part geometry (thin walls, low infill) rather than a softer filament.
Is TPU 68D actually flexible?
Only just — think semi-rigid hard shell rather than rubber. Its value is impact toughness and AMS compatibility, not squish. If you can easily flex the part by hand in your head, you want 95A or softer.
Why does my TPU print bounce less than I expected?
Because hardness and rebound are different properties — a grade can be soft yet absorb energy like a dead blow hammer. For bouncy prints, use a high-rebound material such as BIQU PLA-HR instead of chasing softer TPU.
Do I need to dry new TPU spools in Australia?
Almost always yes. Even factory-sealed spools benefit from a few hours in a dryer, and after a week open in Sydney-level humidity TPU has absorbed enough moisture to string badly. Dry, print, and reseal with desiccant.
Buy TPU that's actually in stock in Australia
3D BRO is an authorised Bambu Lab reseller and Australia's authorised Bambu Lab service centre, with every TPU grade above stocked locally in Regents Park, Sydney and shipped fast Australia-wide — no three-week overseas wait while your project sits half-finished. We print every day on the same machines and materials we sell, so if you're not sure which rung of the hardness ladder your part needs, ask us before you buy. Browse the full flexible range in our filament collection, pair it with the right feeder from the Bambu Lab collection, and if you're still choosing your first material, start with our filament selection guide for Australia.
