3D Printing InfoFilament comparison
Magnetic vs TPU soft
Compare printing settings, strength, heat resistance, dated prices and sources.
2 selected · all documented properties
| Property | Magnetic filamentSPECIALTY | Soft TPU (below 85A)FLEX |
|---|---|---|
| Market snapshot | ||
| Listing priceUSD/kg; dated snapshots | $64.99/kg median; $64.99–$64.99/kg across 1 dated product listings | $114.04/kg median; $109.80–$122.27/kg across 4 dated product listings |
| Identity & Market | ||
| Base polymer / chemistry | PLA loaded with ferromagnetic iron powder, so printed parts respond to magnets[1] | Very soft thermoplastic elastomers below 85 Shore A. Fiberlogy's FiberFlex 30D measures 81 Shore A, the softest grade with a published datasheet found here[2] |
| Densityg/cm³ | About 1.85 (Proto-pasta manufacturer figure) — 1.5× standard PLA[1] | 1.07 (Fiberlogy FiberFlex 30D, ISO 1183)[2] |
| Typical priceUSD/kg | 1 kg spools cluster near 65[3] | 1 kg-equivalent spools cluster near 115[4][5][6] |
| Price range across brandsUSD/kg | 64–70 across formats; 1 kg spool 65, 500 g 70, 2 kg 70[3] | 110–122 at 1 kg-equivalent; Recreus 70A 110 and 60A 116 at 500 g, NinjaTek Edge 83A 112, NinjaTek Chinchilla 75A 122; the Recreus 3 kg spools fall to 70–73[4][6][5] |
| Market availability1–5 | Niche, a handful of specialist brands[3] | Niche, a handful of specialist brands[2][7][4] |
| Spool sizes & diameters | 1.75 and 2.85 mm; 0.1, 0.5, 1 and 2 kg spools[3] | 1.75, 2.85 and 3 mm; 0.5, 0.85, 1, 2 and 3 kg spools[2][4][8][5] |
| Typical applications | Sensor targets, magnetic fixtures, and props that need to stick to a magnet or rust deliberately[1] | Highly compliant seals, soft grips and prosthetic liners[2] |
| Printing Parameters | ||
| Nozzle temperature°C | 192 (Proto-pasta)[1] | Not documented |
| Bed temperature°C | 60 (Proto-pasta)[1] | 50–70 (Fiberlogy FiberFlex 30D)[2] |
| Enclosure / chamber requirement1–5 | Open frame is fine[1] | Open frame is fine[2] |
| Bed surface & adhesion aid | Not documented | PEI sheet or painter's tape; Polymaker warns TPU can over-stick and advises a glue stick as a release agent[9][10] |
| Maximum volumetric flow (mm³/s; see test conditions)mm³/s | 1.6–2.4 at Proto-pasta's 20–30 mm/s on a 0.4 mm nozzle at 0.2 mm layer[1] | Not documented |
| Overall printing difficulty1–5 | Intermediate — dry filament and a tuned profile; slow, and brittle in filament form[1] | Expert / industrial hardware only — below 85 Shore A the filament buckles in almost any feed path that is not a short, constrained direct drive[8][10] |
| Extruder requirement | Proto-pasta advises an extrusion width 0.05 mm larger than the nozzle and warns feeding is inconsistent below 0.4 mm and on Bowden machines[1] | Direct drive only, with a constrained filament path; Bowden is not viable at this hardness[8][7] |
| Hardware Wear & Reliability | ||
| Nozzle hardness required1–4 | Brass acceptable; hardened steel for volume work[1] | Brass fine indefinitely[11] |
| Abrasiveness1–5 | Moderately abrasive — metal fill[1] | Non-abrasive[11] |
| Nozzle clog risk1–5 | Moderate — needs dry filament and a clean nozzle; Prusa lists metal-filled composites as a higher clogging risk and recommends a 0.6 mm nozzle minimum[12] | High — jams from moisture, heat creep or particles; below 85 Shore A the filament buckles and compresses, and Simplify3D warns that raised feed rates most likely end in a jam[9][10][13] |
| Heat-creep / jam sensitivity1–5 | Not documented | Very high — softens in the cold zone readily[10] |
| Hotend requirement | Proto-pasta recommends a wear-resistant or larger nozzle for longer service intervals[1] | No special hot-end required, but a direct-drive extruder is (Simplify3D)[9] |
| Moisture Behaviour | ||
| Moisture absorption (hygroscopicity)1–5 | Not documented | Moderate[13] |
| Symptoms when wet | Not documented | Bubbling and popping at the nozzle, stringing and a rough surface[13] |
| Effect of moisture on strength | Polymaker rates PLA low-sensitivity and publishes no dry-versus-conditioned figures; absorbed water flashes to steam and shows as bubbling and poor layer adhesion[13] | Polymaker groups TPU with the highly hygroscopic materials; no dry-versus-conditioned figures are published[13] |
| Storage requirement | Not documented | Sealed with desiccant; often kept in a dryer during the print[13] |
| Mechanical Properties | ||
| Elongation at break% | Not documented | 870 at break (Fiberlogy FiberFlex 30D, ISO 527) — the highest elongation in the dataset[2] |
| Brittleness1–5 | Brittle — Proto-pasta describes the filament as more brittle than standard PLA and needing extra care in handling[1] | Very ductile — bends far before failing[2] |
| Hardness (scale-specific)Shore A / Shore D / Rockwell | Not documented | 81 Shore A and 30 Shore D (Fiberlogy FiberFlex 30D, ISO 7619)[2] |
| Creep resistance / sustained load1–5 | Not documented | Poor — no creep test at this hardness; a printed 95A TPU bar crept from 74.5 to 82.7 mm over 5 days at 1.25 kg[14] |
| Fatigue / repeated-flex resistance1–5 | Not documented | Excellent — living hinges viable[10] |
| Elasticity / flexibility1–5 | Rigid[1] | Rubbery / highly elastic[2] |
| Wear resistance & friction | Not documented | Tear strength 95 kN/m (Fiberlogy FiberFlex 30D, ISO 34-1)[2] |
| Thermal Properties | ||
| Melting point / Vicat°C | Not documented | 170 melting (Fiberlogy FiberFlex 30D, DSC)[2] |
| Environment & Chemical | ||
| UV resistance1–5 | Not documented | Good — years with some colour shift; Polymaker lists UV exposure among the conditions TPU withstands[10] |
| Outdoor durability | Deliberately rustable — Proto-pasta markets the iron content as oxidising when exposed to moisture[1] | Not documented |
| Chemical resistance | Not documented | Withstands industrial solvents and UV exposure (Polymaker)[10] |
| Food contact | Not documented | Not food safe without specific certification (Polymaker)[10] |
| Biodegradability / compostability | Not documented | Not biodegradable[10] |
| Recyclability | Not documented | Not accepted in household plastic collection[10] |
| Electrical & ESD properties | Ferromagnetic: Proto-pasta states it responds to magnets and behaves similarly to pure iron[1] | Not documented |
| Health & Safety | ||
| Fume toxicity1–5 | Low hazard — minimal VOC and particle emission; none of these materials was in the chamber study[15] | Low hazard — minimal VOC and particle emission; TPU was not among the nine filaments in the chamber study[15] |
| Ventilation / filtration requirement1–5 | Open a window / occasional ventilation[15] | Open a window / occasional ventilation[15] |
| Post-Processing | ||
| Sanding & machining | Polishing and deliberate rusting are the intended finishes[1] | Difficult to sand or smooth; Polymaker limits post-processing to trimming or tumbling[10] |
| Gluing & solvent welding | Not documented | Cyanoacrylate bonds TPU; no common solvent welds it[10] |
| Vapour / chemical smoothing | Not documented | No practical vapour smoothing[10] |
| Support material pairing | Not documented | Polymaker warns TPU supports are often very difficult to remove[10] |
| Solvents & Solubility | ||
| Soluble in | Chloroform dissolves the PLA matrix and leaves the iron powder behind; laboratory reagent, not workshop stock.[16][1] | DMF, DMSO, NMP and THF dissolve TPU; acetone, MEK and cyclohexanone are partial solvents. All laboratory reagents.[17] |
| Softened or crazed by | Acetone and ethyl acetate plasticise the matrix rather than dissolving it; water attacks the exposed iron.[16][1] | Toluene and benzene swell it up to +50 % by weight at 23 °C; esters swell it severely; ethanol and IPA soften it.[17] |
| Solvent welding & smoothing agent | None — PLA has no workshop-safe solvent, and the iron loading blocks the surface flow smoothing needs.[16] | None practical — the true solvents (DMF, THF, NMP) are laboratory reagents and leave the joint swollen and weak.[17] |
Material entries describe families or representative grades, not an interchangeable specification for every spool. Test methods, orientations and conditions may differ. Unknown values are marked “Not documented”. Prices and source dates remain historical snapshots; check the linked guide for product details. Differences highlight text, not a universal winner.
Sources for this comparison
- Magnetic Iron PLA — product page and technical data Proto-pasta · 2026-08 · tds
- FiberFlex 30D Technical Data Sheet Fiberlogy · 2026-08 · tds
- Proto-pasta product catalogue Proto-pasta · 2026-08 · vendor
- Recreus product catalogue Recreus · 2026-08 · vendor
- Chinchilla product page — print guidelines, spool sizes and price NinjaTek · 2026-08 · vendor
- NinjaFlex Edge product page — durometer, print guidelines and price NinjaTek · 2026-08 · vendor
- Filaflex 82A product page (Shore hardness and elongation) Recreus · 2026-08 · vendor
- NinjaFlex 85A Technical Specifications NinjaTek · 2026-08 · tds
- Flexible (TPE/TPU) — Ultimate 3D Printing Materials Guide Simplify3D · 2026-08 · doc
- TPU — material basics Polymaker Wiki · 2026-08 · doc
- Extrudr Product Catalogue (DURAPRO PA12 data block) Extrudr · 2025-03 · tds
- Composite materials with metal or wood particles Prusa Knowledge Base · 2026-08 · doc
- Wet Filament — signs, causes and drying Polymaker Wiki · 2026-08 · doc
- BambuLab TPU 95A HF vs Qidi TPU 95A HF — results spreadsheet My Tech Fun (Igor Gaspar) · 2024-02 · test
- Emissions of Ultrafine Particles and Volatile Organic Compounds from Commercially Available Desktop Three-Dimensional Printers with Multiple Filaments (Azimi et al.) Environmental Science & Technology 50(3) 1260-1268 · 2016-01 · paper
- Solubility Study of Ingeo Biopolymer Grades in Common Organic Solvents (NWPD003) NatureWorks · 2019-10 · tds
- Elastollan — Chemical properties: swelling and chemical resistance BASF · 2026-08 · tds