Annealing 3D Prints: What Filament Makers Actually Say

Who this guide is for

You've bought, or are about to buy, an engineering filament whose data sheet says "annealed at…" under the heat figures, and you want to know whether you need an oven, what to set it to, and what can go wrong. Our carbon fiber filament guide gives a short overview of annealing for CF grades, and our PLA-CF vs PETG-CF guide compares the two most common CF blends. This page goes further. It covers which materials makers say to anneal and which they don't, every maker's temperature and time, what the process changes and what it costs, and how makers say to set it up.

Everything here comes from documents published by Polymaker, Siraya Tech, Prusa, Bambu Lab, SUNLU, and ELEGOO, listed in the sources. We haven't annealed these materials for this page. Each figure describes one maker's product under that maker's conditions, so a setting for one brand's PET-CF doesn't carry over to another's.

What annealing is, in makers' words

Polymaker's wiki defines it plainly: "annealing is the process of heating up the printed parts at a certain temperature for a certain period of time." It adds that the process "is done for different purposes depending on the material." Makers describe two different purposes:

• Crystallizing semi-crystalline plastics. Polymaker says some materials "do not reach full crystallization without annealing," and that Fiberon PPS-CF10 and Fiberon PET-CF17 "are semi-crystalline and therefore do not reach their full heat resistance without being annealed." For its nylons, it says annealing "ensures the part has reached its highest degree of crystallinity, providing the best thermal and mechanical properties."
• Relieving internal stress. Polymaker says its PC annealing "is done for a completely different reason" than for semi-crystalline polymers. Its PolyLite PC data sheet recommends annealing "right after the printing process to release the residual internal stress." SUNLU's dryer page describes annealing in the same terms, as using heat to accelerate "the relaxation of macromolecules in the plastic, thus eliminating or reducing the residual stresses in the products after molding."

Polymaker says amorphous plastics such as "ABS, ASA, and PETG, do not get nearly the same benefit from annealing as semi-crystalline polymers do," and that the benefits there "are mainly dimensional stability and residual stress reduction."

Which filaments benefit from annealing?

Polymaker's wiki also covers semi-crystalline plastics it hasn't tested: "Other semi-crystalline materials can be annealed though we do not have suggested settings, since annealing runs the risk of deforming the part or changing the dimensions."

Each maker's temperature and time

These are the settings each maker publishes for its own product. They differ a lot, even within one base plastic, so use the figure for the spool you actually have.

Where makers disagree on PET-CF

PET-CF shows the widest spread (our Fiberon PET-CF17 vs Siraya Tech PET-CF comparison sets two of these products side by side). Polymaker says of its PET-CF17: "100°C would be the bare minimum to anneal PET-CF at," and "If annealing is performed at 80-100 degrees, the crystallization rate of PET-CF is very slow and the ideal mechanical properties cannot be achieved." Siraya Tech suggests 90–100 °C for its PET-CF, and Bambu Lab's range for its PET-CF starts at 80 °C. These are different products, so none of them is wrong about its own filament. Just don't borrow one maker's cycle for another maker's spool.

Polymaker also gives two different temperatures for its own nylons. Each Fiberon nylon data sheet and product page says 100 °C for 16 hours, while its wiki says "we generally recommend between 80˚-100˚C for 6-16 hours" across its nylon range. For a specific Fiberon spool, the product's own data sheet is the more specific instruction.

What does annealing change in a print?

Heat resistance

This is the benefit every maker names:

• Polymaker PET-CF17: annealing raises HDT (heat deflection temperature) "from around 70°C to over 100°C." The data sheet lists 105 °C at 1.8 MPa and 147.5 °C at 0.45 MPa (ISO 75). Its note that specimens were "annealed at 120°C for 10h" sits under its mechanical table, not its thermal table, so the sheet doesn't say whether the HDT bars were annealed.
• Siraya Tech PET-CF: HDT rises from 76.6 °C to 118 °C at 1.80 MPa (Method A), and from 86.7 °C to 176 °C at 0.45 MPa (Method B). Siraya Tech doesn't say how its annealed test bars were treated. Its user manual gives a third pair, 78.4 °C and 90.2 °C, without saying whether those parts were annealed.
• Prusament PC Blend Carbon Fiber: Prusa says the filament reaches "114 °C right after printing," and that annealing "If executed properly" can raise "the temperature resistance to 130 °C!" Prusa doesn't name a test method or load for the 130 °C figure. Its data sheet lists an HDT of 114 °C at 0.45 MPa and 106 °C at 1.80 MPa (ISO 75).
• Polymaker nylons: all three Fiberon nylon data sheets give one set of HDT figures (PA6-CF20: 173 °C and 215 °C; PA12-CF10: 105 °C and 131 °C; PA612-CF15: 114 °C and 175 °C, at 1.8 and 0.45 MPa). Each sheet's note that specimens were "annealed at 100°C for 16h" sits under its mechanical property tables, not its thermal table, so the sheets don't clearly say whether the HDT bars were annealed. With no separate as-printed and annealed figures, you can't see how much annealing adds.

Stiffness, hardness, and toughness

Here the makers' claims split. Polymaker and Siraya Tech say, or show, that annealing makes PET-CF stiffer but not tougher:

• Polymaker says annealing PET-CF17 "mainly increases the stiffness (modulus) of the material but does not enhance impact resistance or layer adhesion. This means the material does not become tougher after annealing." In a product-page answer labelled Polymaker, it adds that annealing "is only required if you need added heat resistance, not mechanical improvements."
• Siraya Tech publishes unannealed and annealed columns side by side for its PET-CF:

On Siraya Tech's own figures, annealing raised stiffness and heat resistance, left strength about the same, and cut elongation and Charpy impact. Siraya Tech doesn't publish annealed Z-direction (between-layer) figures.

Other makers describe the effect differently:

• SUNLU says on its FilaDryer E2 page that "Annealing significantly enhances the impact resistance and durability of engineering materials," and lists ABS, PC, PA6-CF, PA12-CF, PA612-CF, and others as materials the dryer can anneal. That runs against Polymaker's PET-CF17 statement and Siraya Tech's impact data above. SUNLU's claim is general, and neither the FilaDryer E2 page nor SUNLU's PA6-CF and PA12-CF data sheets give annealed-versus-unannealed figures.
• Polymaker's wiki says, for its nylons, that its Warp-Free technology lets crystals form across layers, which "will also significantly increase the inter layer adhesion," and that annealing then brings the part to "its highest degree of crystallinity." Its general Annealing Tips page says annealing "can improve part strength, heat resistance, and dimensional stability." So Polymaker credits annealing with more for its nylons than for PET-CF17.
• Bambu Lab doesn't say what annealing improves. Its data sheets say "The annealing effect depends on the annealing temperature, time and the model itself: size, structure, infill and other printing settings."

For how to read strength figures across makers' data sheets more generally, see which filament is strongest by maker data.

Moisture in nylon parts

Polymaker says annealing nylon dries the part out: "When you anneal in a convection oven, you will dry the part out." Its wiki explains that a nylon print then absorbs moisture from the air, which makes it "less rigid but will also become more impact resistant." That's why Polymaker's nylon product pages list "Moisture conditioning after Annealing," and why it suggests "to moisture condition after annealing," since annealing a conditioned part would dry it again. Polymaker's wiki lists three ways to condition: 48 hours in a humid space, a soak in water followed by 48 hours in the air, or about two weeks in normal room air.

Do parts shrink or warp when annealed?

Every maker that publishes annealing guidance warns about shape or size:

• Bambu Lab: "some prints may deform and warp after annealing." For PETG, it says prints "with not very simple shape and structure may deform obviously," and it says something similar for TPU.
• Polymaker: its wiki says "Thin-walled prints are much more vulnerable to warping, softening, and deformation." It also says "Annealing nylon materials can also slightly shrink the part dimensions." On PET-CF17, a reply labelled Polymaker says "We do not have exact data on PET-CF17 but there could be minor dimensional changes," and its FAQ says 120 °C annealing can deform parts with very thin sections.
• Siraya Tech: "Be mindful of potential shrinkage during the annealing process."
• Prusa: for PC Blend Carbon Fiber, "thanks to carbon fiber fill, its shrinkage is less than 1%."
• SUNLU: "Allow for shrinkage, and adjust your design accordingly," and "Test with small models first to reduce trial-and-error costs."

Polymaker's measured shrinkage

Polymaker's Fiberon data sheets include a shrinkage test on a model printed at 30% infill, measured as designed, after printing, and after annealing. These are the figures as printed in each data sheet, with each data sheet's own row labels:

On these figures, annealing shrank PET-CF17 more than the nylons. Its X-Y size fell by 0.54 mm between printing and annealing, against no more than 0.04 mm in X-Y for the three nylons. The nylons moved more in Z, by up to 0.31 mm for PA12-CF10. The PET-CF17 data sheet's after-annealing Z value is printed as "4033mm," which we can't read reliably, so we've left that row out. These numbers come from one test model, and Polymaker's wiki says it is "unable to give a 'standard' for dimensional change for each material since it will heavily depend on your models geometry, size, and infill density."

Nylon parts keep changing after annealing. Polymaker's wiki says a nylon print "will 'grow'" as it absorbs moisture, and that in its test "after annealing the parts shrunk slightly," then "most prints grew past their original size, with the exception of Fiberon™ PA12-CF10." If a nylon part has to hit a tight dimension, measure it after conditioning, not straight out of the oven.

How makers say to do it

The oven

• Bambu Lab (every data sheet above): "it`s required to use an oven that has big enough inside volume and can provides even temperature distribution, such as a blast drying oven (forced-air drying oven)." The filament and prints "need to be away from the heater."
• Polymaker: "Use a heating oven with even temperature distribution whenever possible, ideally a forced-air drying oven." It warns that kitchen ovens "can create hot spots," and that many "do not hold the exact temperature you are setting very well - with some varying up to 5-10°C." The PET-CF17 data sheet asks you to "ensure that the temperature in the oven is uniform."
• SUNLU sells its FilaDryer E2 as a drying and annealing box that reaches 110 °C. Its wiki describes the E2's annealing function as "80–90°C annealing for 2–3 hours." Check that whatever you use can hold your maker's temperature for the full time. Bambu Lab's PET-CF range goes to 140 °C, and Prusa's cycle needs an oven preheated to 140 °C.

Polymaker also mentions water-bath annealing, using a sous vide to hold the temperature. It warns that a hygroscopic print must be "fully dried after annealing," that hard water "can leave white mineral marks," and that the part shouldn't touch the container or sit close to the heat source.

Before the oven

• PET-CF17: Polymaker's data sheet says to make sure prints "have been printed for more than 24h, or placed in an 80-degree oven for 2h to eliminate the internal stress after printing."
• PolyLite PC: the opposite. Polymaker says annealing "is required right after your PC print finishes," with the oven "already at its set temperature before the print finishes," and the print going straight in. It notes "You may need to transfer the print with the build plate."
• Nylons: Polymaker says "you are not on a time crunch" and can anneal "at your convenience."
• Prusament PC Blend Carbon Fiber: Prusa says to print with the PCCF PrusaSlicer profile, preheat the oven to 140 °C, then put the model in.

Support and packing

Polymaker gives the most detail on keeping a part's shape:

• Keep the part on the build plate if the plate fits in the oven, with the plate at the bottom and the part facing upward. The PET-CF17 data sheet says it's "best to enter the oven directly together with the base plate."
• Leave supports on. For PET-CF17, bridges longer than 3 cm and parts with large or small overhangs "all need to add supports and anneal in the oven together with the supports."
• Print with a brim "for extra adhesion during annealing."
• For PET-CF17 walls thinner than 4 mm, "add reinforcing ribs or increase the wall thickness."
• Pack the part in sand or salt. Polymaker says this "can help support the part during heating and reduce deformation," especially for thin or delicate parts.
• During the cycle, "do not touch the sample with your hands or apply any additional load to the sample" (PET-CF17 data sheet).

Ramp up: preheat or step?

Polymaker's own pages disagree here. Its Annealing Tips page says: "Preheat the oven to the target material temperature before placing the part inside. Do not use gradual heating for this process, because starting in a cold oven increases the chance of uneven softening and distortion." But the PET-CF17 FAQ, for thin parts that deform at 120 °C, suggests a "Gradual heating method": first hold at 80–100 °C, "and then slowly heat it to 120°C to avoid rapid heating and internal stress concentration." Its other suggestions for those parts are a lower 100 °C cycle for longer (it suggests 14 hours), or supports and packing in salt or sand. Prusa's PC Blend Carbon Fiber method starts in a preheated oven. SUNLU's general steps say to "Control Heating Rate: Ensure the part is evenly heated." For PET-CF17 thin sections, follow the PET-CF17 FAQ. For other Polymaker materials, the wiki's preheat advice is the general rule.

Cool down

• Polymaker: "let the part cool naturally rather than forcing a rapid cooldown. Sudden cooling can reintroduce stress and increase the chance of distortion." For PC, "let the oven slowly cool to room temperature before removing the print."
• Prusa (PC Blend Carbon Fiber): "Pull the model out and let it cool down to room temperature."
• SUNLU: "Allow for gradual cooling or use controlled cooling for the best results."

Checklist before you anneal

• Check the data sheet for your exact spool. If the heat figures say "annealed at…", that's the cycle the numbers assume.
• Decide whether you need it. Polymaker says annealing PET-CF17 is "only required if you need added heat resistance," and Siraya Tech says its PET-CF works "right off the spool."
• Don't anneal PETG or TPU on the strength of a general tip. Bambu Lab advises against it for both, and Polymaker publishes no setting for its PETG-rCF08.
• Use your maker's temperature and time, not another brand's. PET-CF settings run from 80 °C to 140 °C across makers.
• Confirm your oven or dryer can hold that temperature evenly for the full time. Bambu Lab and Polymaker both prefer a forced-air drying oven.
• Leave supports and the build plate on where you can, and consider packing thin parts in sand or salt.
• Anneal PC right after printing. Let PET-CF17 rest for more than 24 hours first, or give it 2 hours at 80 °C.
• Let the part cool slowly, then measure it. Plan for shrinkage, and for nylon parts that grow again as they absorb moisture.
• Test on a scrap part first.

Ready to choose?

If you haven't bought the filament yet, the carbon fiber filament shortlist and the specialty filament shortlist list each maker's annealing cycle alongside nozzle, drying, and enclosure needs. If you need a box that reaches annealing temperatures, see the filament dryer shortlist and our dryer vs dry box guide. For two nylons with opposite approaches to heat and post-processing, read our Fiberon PA6-CF20 vs ELEGOO PAHT-CF comparison. If parts come out of the oven bent or undersized, start with warping and dimensional accuracy.

Quick answers

Should I anneal PETG or TPU? Bambu Lab advises against annealing its PETG and TPU prints. Polymaker says amorphous plastics such as PETG "do not get nearly the same benefit from annealing as semi-crystalline polymers do," and that the benefits there are mainly dimensional stability and residual stress reduction.

What temperature should I anneal at? Use the figure for your exact spool. Across makers, PET-CF settings alone run from 80 °C to 140 °C, and Polymaker gives 120 °C for 10 hours for its Fiberon PET-CF17.

Does annealing make parts tougher? Not on the PET-CF figures here. Siraya Tech's data shows HDT at 1.80 MPa rising from 76.6 °C to 118 °C while Charpy impact falls from 9 to 4.8 kJ/m², and Polymaker says PET-CF17 "does not become tougher after annealing." SUNLU makes a general claim that annealing enhances impact resistance, without figures.

Can I anneal in a kitchen oven? Makers disagree. Bambu Lab says a microwave or kitchen oven "is not compatible," while Polymaker says a kitchen oven is not the best option but is usable if you have no other. Both prefer a forced-air drying oven.

Will an annealed part change size? It can. In Polymaker's test, a 40 mm Fiberon PET-CF17 model measured 39.94 mm in X-Y after printing and 39.40 mm after annealing, and Polymaker says nylon parts "grow" again as they absorb moisture.

How this page was checked

Every claim above comes from the manufacturer documents in the sources section, retrieved on 2026-10-11 and 2026-10-12. Where makers disagree, or one maker's pages disagree with each other, we report each statement and say which document it comes from. We used product-page Q&A replies only where they're visibly labelled as the maker. Shrinkage figures are taken as printed in Polymaker's data sheets, and we left out one value we couldn't read reliably. Settings change between data sheet versions, so check the current one for your spool. Read more in our editorial standards and affiliate disclosure.

Specialty materials: what to check before you buy a spool ↗