CoreXY Enclosed Printer Filament Guide

CoreXY enclosed printers are a strong match for more than PLA because the motion system, rigid frame, enclosed build space, heated bed, and usually direct-drive toolhead give the printer better control over warp-prone engineering filaments. The enclosure does not make every filament better, though. PLA, TPU, and some PETG prints may need an open door or removed top panel, while ABS, ASA, PC blends, nylon, and many carbon-fiber composites usually benefit from warmer, steadier chamber air.

This table compares common 3D printing filaments by how they usually behave in an enclosed CoreXY printer.

Filament	Enclosure Fit	Typical Nozzle / Bed Range	CoreXY Advantage	Watch Point
PLA	Usually print with the door or lid open if the chamber gets warm.	185–235 °C / 50–60 °C	Fast, clean prints for prototypes, models, fixtures, and visual parts.	Too much chamber heat can soften filament near the toolhead and raise heat-creep risk.
PETG	Works with a cool or lightly warmed enclosure; avoid trapping too much heat on long prints.	215–270 °C / 70–90 °C	Good layer bonding, useful toughness, better heat tolerance than standard PLA.	Can string, blob, and stick too strongly to some smooth PEI plates.
ABS	Enclosure recommended for stable layers and lower corner lift.	230–255 °C / 95–110 °C	Better success on boxy parts, brackets, and housings that shrink while cooling.	Use sensible ventilation or filtration; ABS can produce more ultrafine particles than PLA.
ASA	Enclosure recommended.	220–275 °C / 90–110 °C	Good for outdoor parts, covers, clips, and UV-exposed functional pieces.	Needs stable chamber air, good bed adhesion, and controlled cooling.
PC / PC Blend	Warm enclosure recommended, especially for larger parts.	Often around 270–300 °C / 100–115 °C, depending on brand.	Useful when heat resistance and stiffness matter more than easy printing.	Requires a capable hotend, dry filament, and strong bed adhesion.
PA / Nylon	Enclosure recommended; drybox printing is strongly preferred.	240–285 °C / 70–115 °C	Works well for tough, slightly flexible mechanical parts and wear-resistant pieces.	Moisture causes popping, rough surfaces, weak layers, and dimensional drift.
PA-CF / PET-CF / Other CF Blends	Enclosure usually helps, depending on base polymer.	Usually medium to high nozzle heat; check the spool profile.	High-speed CoreXY machines can print stiff, accurate parts with reduced flex.	Use a hardened nozzle. A 0.6 mm nozzle is often easier than 0.4 mm for fiber-filled blends.
TPU	Usually print cool; an enclosure is not required for most TPU.	220–260 °C / 40–85 °C	Direct-drive CoreXY printers handle flexible filament better than long Bowden systems.	Lower speed matters more than chamber heat. Keep the filament path smooth.

⚙️ Why CoreXY Enclosed Printers Change Filament Choice

A CoreXY printer is not only “a faster box.” Its real value is the combination of a light XY toolhead path, a rigid frame, a bed that usually moves only in Z, and an enclosure that can keep the printed part from cooling too quickly. That matters because many engineering filaments fail from uneven cooling, not from a lack of nozzle temperature.

On an open bed-slinger, a tall ABS or ASA part may cool on one side, shrink at the corners, and pull itself away from the plate. In an enclosed CoreXY printer, the air around the part is warmer and more stable. The layers stay closer in temperature for longer. That gives the polymer more time to bond before the next thermal shock arrives.

This is why the same printer can be excellent for ASA and still need the door open for PLA. The chamber is a tool, not a permanent setting.

What The Enclosure Actually Controls

• Thermal gradient: the temperature difference between fresh plastic, previous layers, and surrounding air.
• Warping force: shrinkage stress that pulls corners upward as the part cools.
• Layer bonding window: the short period when the new bead and previous layer can fuse well.
• Airflow exposure: drafts from the room, air conditioning, or strong auxiliary fans.
• Filament path temperature: chamber heat around the extruder, heatsink, and spool path.

That last point is easy to miss. A warm chamber helps ABS, ASA, PC, and nylon. The same warm chamber can make PLA soften too early in the toolhead path. That is where heat creep begins.

🌡️ Chamber Logic by Filament Group

Chamber temperature should follow the filament, not the printer price. A printer with a sealed enclosure, heated chamber, or actively filtered chamber is useful only when the material needs it. For many everyday prints, cooler air is cleaner and more reliable.

This table groups filaments by the chamber behavior that usually gives the most stable results.

Chamber Style	Best Fit Filaments	Why It Works	Practical Setup
Cool / Ventilated	PLA, PLA+, matte PLA, silk PLA, most TPU	These materials usually do not need trapped heat and may print worse when the toolhead area gets too warm.	Open the door, remove the top panel if needed, and keep part cooling active.
Mild Passive Warmth	PETG, PCTG, some tough PLA blends	A little warmth can reduce drafts without overheating the filament path.	Door partly open or closed depending on chamber temperature and stringing behavior.
Stable Warm Chamber	ABS, ASA, HIPS	These filaments shrink enough during cooling that steady air helps keep corners down.	Preheat the bed, reduce drafts, use a brim for broad parts, and avoid aggressive fan settings.
Warm and Dry	PC blends, PA, PA-CF, PET-CF, PPA-CF	These filaments need thermal stability and moisture control at the same time.	Print from a drybox, use a capable hotend, and keep chamber air steady through the whole job.
Industrial High-Temperature	PEI, PEEK, PEKK, PPSU	These polymers need far higher processing conditions than most desktop CoreXY machines provide.	Use only printers designed for high-temperature polymers, not a basic enclosed hobby machine.

Many desktop enclosed CoreXY printers can handle ABS, ASA, PC blends, and nylon composites. That does not automatically make them suitable for PEI, PEEK, or PEKK. Those materials demand a different class of hotend, bed, chamber, plate system, and drying workflow.

🧵 Filament-by-Filament Guide for Enclosed CoreXY Printers

PLA: Fast, Sharp, and Better With Cooler Air

PLA is still the easiest material for a CoreXY printer. It flows well, holds detail, prints quickly, and does not need a sealed chamber. On a high-speed CoreXY machine, PLA often becomes the material for prototypes, organizers, decorative parts, jigs, draft engineering models, and dimension checks.

The enclosure can become a problem when the chamber climbs too high. PLA softens at a relatively low temperature compared with PETG, ABS, ASA, PC, and nylon. In a long print, trapped heat around the extruder may soften filament before it reaches the melt zone. Then extrusion becomes inconsistent. Sometimes it looks like a clog. Sometimes it is heat creep.

• Use the door open when the chamber feels warm.
• Keep the top panel off if the printer design allows it and the room is not drafty.
• Use normal part cooling for bridges, overhangs, and fine text.
• Do not use ABS-style chamber preheating for regular PLA.
• For very fast profiles, raise nozzle temperature only as much as the filament needs for clean flow.

PETG: Functional Without Heavy Chamber Heat

PETG sits between PLA and ABS for many desktop users. It is tougher than standard PLA, more heat tolerant than PLA, and easier to print than ABS or ASA. In an enclosed CoreXY printer, PETG usually likes a calm environment, but not a hot one.

A closed chamber may help if the room is cold or drafty. Too much chamber warmth can increase stringing, soften small details, and make the print look wet even when the spool is reasonably dry. PETG also sticks strongly to some smooth PEI plates, so a release layer can protect the surface.

• Use PETG for brackets, clips, tool mounts, containers, light-duty mechanical parts, and printer accessories.
• Keep cooling moderate, not maxed out like PLA.
• Dry the spool if you see bubbles, rough walls, or stringing that settings cannot fix.
• Use glue stick or another approved release layer if your build plate manufacturer recommends it.

For CoreXY speed, PETG rewards restraint. It can print fast, but not every PETG wants race-mode acceleration.

ABS: Better With Stable Warm Air

ABS is one of the classic reasons to own an enclosed printer. It shrinks more than PLA as it cools, so corners and long straight walls can lift if the surrounding air is too cold. A CoreXY enclosure reduces that cooling shock and gives ABS a calmer build space.

Use ABS when you need machinability, heat tolerance above PLA and PETG, decent impact behavior, and a material that can be sanded or post-processed in workshop settings. It is common for covers, housings, tool fixtures, and mechanical prototypes.

Print settings vary by brand, but many ABS profiles use a hot bed, low fan, and brim for broad parts. Prusa’s material table lists ABS with an enclosure recommendation and a typical range around 230–255 °C nozzle and 95–110 °C bed.[a]

ASA: The Outdoor-Friendly ABS Alternative

ASA prints in a similar temperature zone to ABS, but it is often chosen for outdoor parts because it has better UV and weather resistance than regular ABS. That makes it useful for garden fixtures, exterior clips, light brackets, sensor cases, and printer parts exposed to sunlight.

An enclosed CoreXY printer helps ASA for the same reason it helps ABS: shrinkage becomes easier to manage when the part is not cooled by random room air. ASA still needs bed adhesion. Large flat parts may need a brim, rounded corners, or a design that avoids long stress lines.

• Use a stable warm chamber.
• Keep part cooling low unless the geometry needs it.
• Prefer rounded inside corners in the model design.
• Let the print cool gradually before removing it from the chamber.

ASA is not “ABS with one magic upgrade.” It is its own printing material. Dial it in as its own profile.

PC and PC Blends: Heat Resistance With More Demands

Polycarbonate and PC blends are attractive for parts that need stiffness and heat tolerance. They also ask more from the printer. A CoreXY enclosed machine helps because the chamber reduces thermal stress, but PC still needs a hotend that can hold the required extrusion temperature, a bed surface that can grip without damage, and filament that has been kept dry.

Prusa’s material table lists PC Blend with enclosure recommended and a typical bed range around 100–115 °C for its profile.[a] Other PC blends may need different values, so the spool profile matters.

• Use PC for heat-exposed brackets, stiff functional parts, covers, and load-bearing designs where PLA or PETG would soften too easily.
• Use dry filament. Moist PC can print cloudy, bubbly, and weak.
• Use a release layer if recommended for your plate.
• Prefer a warm, steady chamber over aggressive cooling.

PC is not the right material for every tough part. Sometimes ASA or nylon is easier and more predictable. Choose by the load, temperature, layer direction, and environment.

Nylon / PA: Tough, Useful, and Moisture-Sensitive

Nylon is a strong match for enclosed CoreXY printers when the goal is toughness, wear resistance, snap-fit behavior, and functional movement. It is also one of the fastest ways to learn why filament storage matters.

Polyamide absorbs moisture from the air. Wet nylon can hiss, pop, foam, create rough walls, and lose layer quality. In some cases, the part may look acceptable but feel weaker than expected. Drying before printing and printing from a drybox are normal workflow steps, not optional upgrades.

• Use nylon for gears, hinges, friction parts, clamps, tool holders, and parts that need toughness with slight flex.
• Use a warm enclosure to reduce warp.
• Use a drybox for long prints.
• Use low to moderate fan unless the filament profile says otherwise.
• Expect PA6, PA12, PA-CF, PA-GF, and PAHT blends to behave differently.

Plain nylon can be more flexible. Carbon-fiber nylon is usually stiffer and dimensionally calmer, but the fibers make it abrasive. Use a hardened nozzle.

Carbon-Fiber Filled Filaments: Stiffer Parts, Abrasive Flow

Carbon-fiber filled filament is not one material. It is a family: PLA-CF, PETG-CF, PA-CF, PC-CF, PET-CF, PPA-CF, and more. The base polymer decides the heat, chamber, and moisture behavior. The fiber changes stiffness, surface finish, shrinkage, and nozzle wear.

• Use a hardened steel, ruby, tungsten carbide, or other abrasive-ready nozzle.
• Consider 0.6 mm nozzle size for easier flow and fewer fiber-related feed issues.
• Dry nylon-based and PC-based composites before printing.
• Use slower outer walls if the surface looks furry or under-filled.
• Do not assume all CF filaments are stronger in every direction; printed parts remain layer-dependent.

CoreXY printers with input shaping and high-flow hotends can print CF blends very cleanly, but fiber-filled materials can hide weak layer bonding behind a beautiful matte surface. Test the part orientation before using it in a demanding role.

TPU: Flexible Filament in an Enclosed CoreXY Printer

TPU usually does not need the enclosure. The printer’s direct-drive path matters more than chamber temperature. A short, guided filament path helps flexible filament reach the hotend without buckling.

Print TPU slower than hard plastics. Keep retraction conservative. Avoid unnecessary pressure-advance extremes. If the chamber is warm from previous ABS or ASA printing, let the printer cool before starting TPU.

• Use TPU for vibration pads, seals, feet, bumpers, soft grips, and flexible mounts.
• Keep the door open unless the filament maker says otherwise.
• Use a dry spool if surface quality becomes rough or bubbly.
• Reduce speed before changing too many slicer settings.

TPU rewards patience. Very fast CoreXY motion does not turn flexible filament into rigid filament.

🧩 Settings That Matter More on Fast Enclosed CoreXY Machines

Volumetric Flow Comes Before Speed

A CoreXY printer can move quickly, but filament can only melt so fast. If the slicer asks for more plastic than the hotend can melt, the result is under-extrusion, weak infill, clicking, or thin top surfaces. Raising speed without checking volumetric flow is a common mistake.

For each filament, think in this order:

1. Can the hotend melt the requested volume cleanly?
2. Can the filament handle the chamber temperature?
3. Can the part geometry cool without warping or sagging?
4. Can the extruder grip the filament without grinding?
5. Can the bed surface release the material safely after cooling?

PLA often tolerates high flow better than TPU. PETG may need a little more heat but less fan. ABS and ASA prefer thermal stability over harsh cooling. Nylon and PC want dry filament, steady chamber air, and controlled speed.

Layer Bonding Is a Thermal Process

FFF parts are made from hot roads of polymer pressed against previous roads. Stronger layer bonding depends on temperature, time, polymer movement, pressure, cooling rate, and material chemistry. Research on fused filament fabrication describes layer strength as linked to polymer interdiffusion and entanglement across the layer interface.[f]

That explains why enclosed CoreXY printers can produce better ABS, ASA, PC, and nylon parts than open printers using similar nozzle temperatures. The chamber changes the cooling curve. The part does not freeze as quickly.

Cooling Fan Strategy

Part cooling is not a universal good. It is useful for PLA overhangs and bridges. It can be harmful for ABS and ASA because it sharpens thermal gradients. PETG, PC, and nylon often sit in the middle: enough cooling to preserve shape, not so much that layers become weak or corners lift.

This table shows common cooling tendencies for enclosed CoreXY printing, before brand-specific tuning.

Filament	Cooling Direction	Why
PLA	Medium to high cooling	Helps overhangs, bridges, text, and small details stay sharp.
PETG	Low to medium cooling	Too much fan can weaken layers; too little can soften details.
ABS	Low cooling	Less fan helps reduce warping and layer stress.
ASA	Low cooling	Stable chamber air is usually more useful than strong fan airflow.
PC	Low to controlled cooling	Heat retention improves bonding, but small geometry may need some airflow.
Nylon	Low to moderate cooling	Too much cooling can hurt bonding; too little can soften fine details.
TPU	Low to medium cooling	Depends heavily on shore hardness, speed, and bridge geometry.

💧 Drying and Storage for CoreXY Filament Success

Moisture control matters more once you move beyond basic PLA. Prusa notes that many FFF materials are hygroscopic and that polyamide, PVA, and TPU are more often in need of drying than common filaments like PLA.[c] In a CoreXY printer, moisture problems can look like slicer problems: stringing, weak layers, inconsistent extrusion, rough walls, bubbles, and poor surface finish.

This table lists Prusa drying recommendations for selected materials that are common in enclosed-printer workflows.

Material	Drying Temperature	Drying Time	Use Case Note
PLA / rPLA	45 °C	6 hours	Dry if the spool is old, brittle, stringy, or has been stored in humid air.
PETG	55 °C	6 hours	Dry when stringing, cloudy extrusion, or small bubbles appear.
TPU	60 °C	4–6 hours	Moist TPU can become rough and inconsistent even when feeding is correct.
ASA	80 °C	4 hours	Dry when surface quality or layer consistency changes after storage.
PC Blend	85 °C	5 hours	Drying is often needed for strong, clean PC prints.
PC Blend Carbon Fiber	90 °C	4 hours	Use a dryer and spool that can safely handle the temperature.
PA11 Carbon Fiber	90 °C	6 hours	Print from a drybox when possible.

Do not guess drying temperatures. Spools, cardboard cores, NFC tags, glued sides, and refill systems may have their own heat limits. A filament dryer with stable control is safer than a household oven that swings above the set temperature.

Storage Priority

1. Always protect: PA, PA-CF, PC, PC-CF, PVA, BVOH, TPU, PET-CF, PPA-CF.
2. Usually protect: PETG, ASA, ABS, PCTG, filled PLA, wood-filled filament.
3. Basic storage is often enough: fresh PLA used in a dry room, but sealed storage still helps long-term quality.

For nylon and PC, the best workflow is simple: dry, print from a drybox, then reseal the spool with desiccant. No drama. Just consistency.

🛠️ Nozzles, Build Plates, and Enclosure Hardware

Nozzle Material

Brass nozzles are fine for standard PLA, PETG, ABS, ASA, TPU, PC blends, and plain nylon if the filament has no abrasive filler. The moment the filament includes carbon fiber, glass fiber, glow pigment, ceramic filler, metal filler, or similar abrasive additives, use a hardened nozzle.

• Brass: best heat transfer, good for standard non-abrasive filaments.
• Hardened steel: common choice for CF, GF, glow, and filled materials.
• Ruby / tungsten carbide: higher-cost options for abrasive-heavy workflows.
• 0.6 mm nozzle: often easier for fiber-filled filaments than 0.4 mm.

A hardened nozzle may need a small temperature adjustment because it can transfer heat differently from brass. Do not change everything at once. Raise temperature only if flow, layer bonding, or surface quality asks for it.

Build Plate Behavior

Enclosed CoreXY printers often ship with textured PEI, smooth PEI, engineering plates, high-temperature plates, or flexible magnetic plates. The plate is not just a convenience part; it decides how the first layer grips and how safely the part releases.

This table matches common build-surface behavior with enclosed-printer filament groups.

Filament	Plate Behavior	Release Layer Use
PLA	Usually easy on PEI when the plate is clean.	Usually not needed.
PETG	Can bond too strongly to smooth PEI.	Often useful as a release layer on smooth surfaces.
ABS / ASA	Needs reliable grip during hot printing, then gradual release after cooling.	Often useful depending on plate type.
PC	Can be very demanding and may damage unsuitable surfaces.	Use the manufacturer’s plate and release-layer recommendation.
Nylon	Can be difficult on generic surfaces.	Use a nylon-compatible surface or adhesive system.
TPU	Can grip too strongly to some surfaces.	Release layer may protect the plate.

Exhaust, Filters, and Chamber Fans

An enclosure keeps heat in. It can also keep emissions in until the door opens. NIOSH recommends ventilation, local exhaust, enclosed ventilated racks, outdoor exhaust where suitable, and HEPA filtration as ways to reduce uncontrolled 3D printer emissions in workplace-style setups.[d]

For a home or workshop printer, this points to a practical idea: do not treat the enclosure as a sealed mystery box. For PLA and PETG, room ventilation may be enough in many normal hobby setups. For ABS, ASA, nylon, and PC, use the printer’s filter system if it has one, place the printer in a sensible location, and avoid printing in tiny unventilated rooms.

🧪 Material Safety and Emissions in Enclosed Printing

FFF printing melts thermoplastic. That process can release particles and volatile compounds. EPA summarizes that 3D printing can release gases and particulates, including ultrafine particles, and notes that ABS has been associated with greater particle numbers than PLA in reviewed emissions research.[e]

This does not mean every desktop print is dangerous. It means filament choice, ventilation, printer location, print temperature, and enclosure exhaust are part of the setup. A clean-looking printer can still be doing thermal chemistry inside the chamber.

📌 Choosing The Right Filament for a CoreXY Enclosed Printer

Use the enclosure when the part needs it. Ignore the enclosure when the material does not. That single idea prevents many bad prints.

This table maps common part goals to practical filament choices for enclosed CoreXY printers.

Part Goal	Better First Choice	Upgrade Choice	Why
Fast prototype	PLA	High-speed PLA or PLA+	Low warp, clean detail, easy tuning.
General functional part	PETG	ASA or nylon	PETG is easy; ASA and nylon add heat or toughness when needed.
Outdoor bracket or cover	ASA	ASA-CF	Good weather behavior with enclosure-friendly printing.
Heat-exposed mount	ASA	PC Blend or PC-CF	Higher temperature tolerance than PLA and PETG.
Wear-resistant moving part	Nylon	PA-CF or PA-GF	Good toughness and friction behavior, with drying required.
Rigid technical part	PETG-CF	PA-CF or PC-CF	Fiber raises stiffness and reduces flex, but needs abrasive-ready hardware.
Flexible pad or bumper	TPU	Higher-shore TPU	Direct-drive CoreXY printers can handle TPU well at controlled speeds.
Soluble supports	PVA / BVOH with compatible material	Special support filament matched to the build material	Moisture control and multi-material tuning matter more than chamber heat alone.

Simple Selection Rules

• Choose PLA when you need speed, detail, and easy printing.
• Choose PETG when you need a tougher everyday material without full engineering-filament difficulty.
• Choose ASA when the part will see sunlight or outdoor exposure.
• Choose ABS when you already have the ventilation and chamber workflow for it.
• Choose PC when heat resistance matters and the printer can truly run the profile.
• Choose nylon when toughness, wear behavior, or living-hinge style flex matters.
• Choose CF blends when stiffness and dimensional stability matter, not just because the surface looks good.
• Choose TPU when the part needs flex, grip, damping, or impact absorption.

🔍 Problems That Look Like Filament Failure

Corners Lift on ABS, ASA, PC, or Nylon

• Preheat the chamber longer.
• Use a brim or mouse ears on sharp corners.
• Clean the plate.
• Lower auxiliary fan use.
• Reduce long, straight stress lines in the model.
• Let the part cool slowly before removal.

PLA Jams During Long Enclosed Prints

• Open the door or remove the top panel.
• Lower chamber temperature by venting heat.
• Check heatbreak cooling and toolhead fan operation.
• Reduce nozzle temperature if it is higher than needed.
• Check retraction settings and filament path drag.

PETG Strings Across The Print

• Dry the spool.
• Lower nozzle temperature slightly if layer bonding remains good.
• Reduce chamber heat.
• Tune retraction and pressure advance.
• Keep the nozzle clean; PETG blobs can attach and drag.

CF Filament Looks Matte but Breaks Easily

• Dry the filament, especially if the base is nylon or PC.
• Raise nozzle temperature only within the filament maker’s range.
• Slow down for better layer fusion.
• Check whether the part is loaded across layer lines.
• Use more walls instead of relying only on high infill.

FAQ

Is An Enclosed CoreXY Printer Better for Every Filament?

No. It is better for filaments that dislike drafts and uneven cooling, such as ABS, ASA, PC blends, and nylon. PLA, TPU, and some PETG prints may perform better with the door open or the top removed because trapped heat can cause heat creep, stringing, or soft details.

Can I Print PLA With The Door Closed?

You can, but it depends on chamber temperature, print length, toolhead cooling, and filament type. Small PLA prints may finish fine with the door closed. Long PLA prints in a warm chamber are more likely to show heat-creep symptoms or softened detail.

What Filament Should I Try First After PLA on An Enclosed CoreXY Printer?

PETG is usually the easiest next step. It gives more toughness and heat tolerance than standard PLA without the full chamber, ventilation, and shrinkage management needed for ABS, ASA, PC, or nylon.

Is ASA Better Than ABS for Enclosed Printers?

ASA is often preferred for outdoor parts because of its UV and weather behavior. ABS is still useful for many workshop and functional prints. Both usually benefit from an enclosure, low drafts, a hot bed, and careful cooling.

Do Carbon-Fiber Filaments Need An Enclosure?

The base polymer decides that. PLA-CF usually does not need a hot chamber. PA-CF, PC-CF, and many PET-CF or PPA-CF blends often benefit from a warm chamber and drybox printing. All abrasive CF filaments need an abrasion-resistant nozzle.

Why Does Nylon Print Badly Even in a Good Enclosed Printer?

Moisture is the usual reason. Nylon can absorb water from the air, then bubble, pop, string, and lose layer quality during printing. Dry the spool, print from a drybox, and store it sealed with desiccant between uses.

Can a Desktop Enclosed CoreXY Printer Print PEEK or PEI?

Most desktop enclosed CoreXY printers are not designed for PEEK, PEI, PEKK, or similar high-temperature polymers. Those materials need much higher nozzle, bed, and chamber capability than common ABS/ASA-ready machines.

Should I Vent The Chamber While Printing ABS or ASA?

Do not create a strong cold draft across the print. Use the printer’s intended filtration or exhaust setup, and keep the room reasonably ventilated. After the print finishes, let the part cool gradually before fully opening the chamber.