A lot of 3D printer fan upgrades start with the wrong diagnosis. You see sagging bridges, a noisy toolhead, or a mid-print extrusion stop, then you order the fan size that showed up in a forum thread. The problem is that a printer does not have one cooling fan doing one job.
Depending on the design, your printer may have only a few fans or as many as six different cooling jobs: hotend cooling, part cooling, electronics cooling, PSU cooling, chamber circulation, and filtration or exhaust. Each job protects a different part of the machine. If you replace a part cooling fan to fix heat creep, or add more airflow to a print duct when the hotend fan is weak, the failure can remain.
This guide focuses on hardware: where each 3D printer cooling fan sits, how axial fans and blowers behave in real ducts, which specs matter, and how to replace a fan without creating a new electrical or thermal problem. It is written for two readers: the owner replacing or upgrading a fan on one machine, and the OEM engineer specifying fans for a printer design.
Quick Diagnosis: Which Fan Is Actually the Problem?
| Problem | Check first |
|---|---|
| Heat creep or mid-print clog | Hotend fan and heatsink airflow |
| Poor bridges or overhangs | Part cooling fan and duct |
| Driver shutdown | Mainboard airflow |
| Weak filter flow | Filter resistance and blower pressure |
| Loud fan | Bearing, blade contact, vibration, or blockage |
One Printer, Several Different Cooling Jobs
A 3D printer cooling fan is any fan that removes heat from the hotend, printed part, electronics, power supply, chamber air, or filtration path. The exact layout depends on the printer, and open-frame machines may not have chamber or filter fans at all. First identify the fan position, then choose the replacement.
| Fan position | Main job | If it fails | Typical examples |
|---|---|---|---|
| Hotend fan | Keeps the heatsink cool above the heat break | Heat creep, clogs, extrusion stops | 25 to 40 mm axial, often 3010, 4010, or 4020 |
| Part cooling fan | Cools freshly extruded plastic and supports bridges | Sagging bridges, curled details, weak overhangs | 4010 axial or 5015 blower |
| Mainboard fan | Moves heat away from stepper drivers and PCB parts | Driver overheating, random shutdowns | 60 to 80 mm axial |
| PSU fan | Removes heat from the power supply | PSU thermal faults or fan warnings | 60 to 80 mm axial |
| Chamber circulation fan | Mixes warm chamber air | Uneven part temperature in enclosed printers | 92 to 120 mm axial |
| Filter or exhaust fan | Pulls air through a filter or out of the chamber | Weak filtration or airflow alarms | 92 to 120 mm axial or blower, by design |
Prusa treats the PSU fan and chamber filtration fan as separate fault objects in its CORE One documentation for that enclosed platform, which is a useful reminder that some printers separate cooling tasks beyond the toolhead. If you are sizing an electronics-bay fan, the heat load and airflow path are closer to a PCB cooling problem than a print-quality problem, so our PCB cooling fan selection guide is the better deep dive for that position.
Users sometimes replace the part cooling fan when the actual problem is insufficient hotend-heatsink cooling. A clogged nozzle points you toward the hotend heatsink, while weak bridges point you toward the duct and part cooling fan. That simple split saves you from chasing slicer settings for an electrical or airflow fault.
Bearing type varies by printer model and supplier. Check the original fan specification rather than assuming that every replacement fan has the same service life. For the broader equipment-cooling context, see our industrial cooling fan applications hub.
The Hotend Fan: The One That Should Not Stop During Heat
The hotend fan protects the cold side of the hotend. If the heatsink warms up too far, heat travels up the filament path, the filament softens too early, and extrusion can stop mid-print. Prusa describes this failure mode as heat creep and links it to cooling around the hotend heatsink.
On several Prusa models, the hotend fan starts when the reported hotend temperature reaches 50°C and then runs through the print. Other printers may use an always-on fan, a different firmware threshold, a toolhead board, or a direct constant-power connection, so check the printer documentation before replacing or rewiring it. For E3D-style hotends, follow the hotend manufacturer’s wiring instructions. The heatsink fan must not be controlled as if it were an ordinary slicer-adjustable part cooling fan.
Quiet swaps need special care here. A lower-noise fan can sound like a win on the bench, but it still has to move enough air through the heatsink during longer prints. If you change this fan, verify hotend temperature behavior and look for heat creep symptoms before you call the upgrade done.
Axial fans are the usual choice for hotend heatsinks because they fit tight toolhead brackets and push air straight through the fins. In ultra-compact printheads or dense heatsink stacks, the hotend fan still works against real resistance, so static pressure matters there too. Do not choose by free-air CFM alone.
Proventofan catalog examples include DC3010 options, DC4010 axial versions, and DC4020 fans. A Proventofan DC4010H24B(S) 24V catalog example is rated at 7,000 RPM, 0.06 A, 1.44 W, 6.66 CFM max, 4.55 mmH₂O max, and 28 dB-A, while a Proventofan DC4020H12B(S) 12V catalog example reaches 7,500 RPM, 8.60 CFM max, and 5.58 mmH₂O max.
Higher-output fans are available, but increased speed, current, noise, vibration, and toolhead mass may make them unsuitable for printer use. Match the thermal risk, space, and noise target instead of copying a fan size from another toolhead.
Part Cooling: Axial vs Blower, and Why Static Pressure Decides
The part cooling fan protects the print, not the hotend. It cools the plastic after extrusion so bridges, overhangs, small features, and fast layers hold shape. Prusa notes that print fans are not used on the first layer and start later according to the material profile, which matches what you see in slicer behavior.
The common debate is 4010 axial versus 5015 blower. The useful answer is not that one category always wins. A blower holds more useful flow through a restrictive duct, while an axial fan can win in free air. The fan curve and your duct decide, not the label.
These are maximum catalog endpoints, not simultaneous airflow and pressure values. Use the complete fan curve to estimate airflow through a specific duct. That distinction is why 5015 blower upgrades became common in the 3D printing community: you give up maximum free-air CFM, but you gain pressure capability that can survive a narrow duct and nozzle. The same comparison also explains why a bare axial fan blowing across an open area may still feel stronger in your hand than a blower.
The duct is where many upgrades succeed or fail. Keep the fan inlet clear, avoid abrupt internal steps, use smooth transitions, and try to keep dual outlets symmetrical if the duct splits around the nozzle. A dual-blower setup can add capacity, but it also adds mass, wiring, vibration risk, and overcooling risk.
The community has a bit of 5015 folklore now, and CPAP remote-air mods are the louder cousin of that same pressure conversation. Fun to read, but not a reason to overbuild every toolhead. If your printed duct was designed around one 5015 blower, start there before adding more hardware.
Material choice sets the cooling direction, but not a universal percentage. PLA usually wants strong part cooling because it benefits from fast solidification. PETG often needs moderate cooling so layers bond without stringing and droop. ABS and ASA often need little part cooling because drafts and fast cooling can increase warping.
These are starting directions rather than fixed percentages. Required cooling also changes with print speed, layer time, nozzle size, geometry, chamber temperature, and material formulation.
The reader takeaway is this: start from your slicer material profile, then tune one variable at a time. Also remember that 50% on a 5015 blower is not 50% on a 4010 axial fan. The duty number is only the controller command, not a universal airflow unit. For the physics behind this tradeoff, see our static pressure vs airflow guide.
Reading Fan Specs: Sizes, Voltage, and What the Numbers Mean
Printer fan names often use four digits. A 4010 axial fan is about 40 mm by 40 mm by 10 mm, and a 4020 is about 40 mm by 40 mm by 20 mm. For blowers, the number describes the blower housing envelope, not a square frame, so the outlet, mounting ears, and scroll shape still need a drawing.
This is where the phrase “5015” causes trouble. In printer forums, 5015 usually means a small centrifugal blower for part cooling. In a fan catalog, you may also see a 5015 axial fan, and it is a different product with a different curve. In our shop language, the drawing wins over the nickname every time.
Voltage is the second filter. Many modern printers use 24V fans, older or smaller machines may use 12V, and some board or accessory fans use 5V. A 12V fan on a 24V output can burn out, while a 24V fan on a 12V output may spin weakly or fail to start.
| Printer position | Fan style | Example sizes | Example catalog values | Voltage options |
|---|---|---|---|---|
| Hotend | Axial | 3010, 4010, 4020 | DC4010H24B(S): 24V/7,000RPM/0.06A/1.44W/6.66CFM max/4.55mmH₂O max/28dB-A. DC4020H12B(S): 12V/7,500RPM/8.60CFM max/5.58mmH₂O max/33.60dB-A | 4010: 5/12/24V; 4020: 5/12V |
| Part cooling | Blower | 5015 blower | DC5015H24B(S) blower: 24V/5,500RPM/0.12A/2.88W/3.07CFM max/14.05mmH₂O max/32.6dB-A. DC5015M24B(S): 4,500RPM/2.57CFM max/10.68mmH₂O max. DC5015L24B(S): 3,500RPM/1.92CFM max/5.76mmH₂O max | 5/12/24V; 24V range 14.0 to 27.8V |
| Mainboard or PSU bay | Axial | 6015, 8025, 8038 | DC6015H12B(S): 12V/4,000RPM/19.83CFM max/2.35mmH₂O max/34.63dB-A/33g. DC8025H24B(S): 24V/3,500RPM/52.91CFM max/8.27mmH₂O max/49.10dB-A/73g. DC8038H24B(S): 24V/5,000RPM/68.81CFM max/15.35mmH₂O max/49dB-A/118g | 6015: 5/12V; 8025: 12/24V; 8038: 12/24/48V |
| Chamber circulation | Axial | 9225, 12025 (120 × 120 × 25 mm) | DC9225H24B(S): 24V/4,500RPM/72.79CFM max/9.30mmH₂O max/45.30dB-A/85g. DC12025H24B(S): 24V/2,600RPM/85.61CFM max/4.65mmH₂O max/41.30dB-A/148g | Both show 12/24V options |
Fan dimensions vary by printer design, so measure the mounting envelope. CFM tells you free-air volume. Static pressure tells you how well the fan holds flow against heatsink fins, mesh, ducts, or filters.
Catalog airflow and static-pressure values represent different points on the fan curve, not one combined operating point. Compare noise ratings only when the measurement method, distance, voltage, and operating condition are equivalent. If you want the measurement basics, use our fan noise dB-A explainer rather than turning this printer guide into an acoustics article.
One buying pattern repeats often enough that we plan for it: in December 2024, a buyer asked us for the lowest-airflow version of a 120 mm frame size, and the real requirement turned out to be a noise ceiling in disguise. That is what the H, M, and L speed grades in these tables are for. Running an L grade at full duty is often quieter and simpler than holding an H grade fan at a low command it may not start at.
Bearing type belongs in the spec review too. Ball and sleeve options both exist in small DC fans, but the right choice depends on temperature, duty, orientation, noise target, and supplier specification. We cover the life and application tradeoffs in our sleeve bearing vs ball bearing fan guide.
Designing a printer or toolhead? Send the duct drawing, voltage, target airflow, connector, cable length, PWM method, tach requirement, and annual volume for fan-curve matching.
Replacing or Upgrading: Match Before You Mount
Specs tell you what to buy. This section is how not to regret it after the fan is mounted.
Work with the printer powered off whenever you touch toolhead or board wiring, and confirm polarity before you power the machine again. Do not open a mains-powered PSU enclosure unless you are qualified to service it. Disconnecting the printer does not automatically make internal PSU components safe to touch.
- 1
Measure the frame, thickness, and mounting holes. Do not order by the forum name alone. Match the screw pattern, outlet position, and cable exit.
- 2
Match voltage first. Read the old fan label and the board output. If you are not sure whether the output is 5V, 12V, or 24V, measure it or check the printer wiring documentation.In March 2025, the fastest sample exchange we handled ran four emails in fifteen minutes, and the customer’s only technical question was the sample fan’s voltage. Experienced validation engineers ask that first, because a wrong-voltage fan does not produce bad test data. It produces no test data.
- 3
Check the connector and wire count. Many printer fans are 2-wire DC fans controlled by board-side PWM switching. A third wire is often tach feedback, not a speed-control wire. A PC-style 4-pin fan is not automatically plug-in compatible with a printer board.
- 4
Confirm airflow direction. The label side is commonly the exhaust side on many axial fans, but verify the arrow or datasheet. The hotend fan should cool the heatsink, not pull hot air away from the wrong side.
- 5
Choose the bearing for the duty. A fan that gets louder is often giving you a bearing warning, not showing personality. Near a hotend or inside a warm chamber, we usually lean toward a ball-bearing option when noise, budget, and supply allow it.
For connector details, see our 2-pin, 3-pin, and 4-pin cooling fan connector guide. For control basics outside printer firmware, see PWM fan control vs voltage control. If you are specifying a fan from scratch rather than replacing an existing printer part, the broader DC cooling fan selection guide is the better starting point.
Firmware is the part many mechanical fan swaps miss. In a typical Marlin configuration, M106 with an S value from 0 to 255 and M107 are used for controllable print-cooling outputs. A hotend-heatsink fan may instead be configured as an automatic temperature-controlled fan or wired to run continuously. Klipper exposes practical parameters such as kick_start_time for startup torque, off_below for the lowest reliable command, and tachometer_pin for fan feedback.
Those settings exist because a small fan may need more torque to start than to keep spinning. After replacement, determine the lowest command at which the fan starts reliably, then configure the startup boost and minimum usable command accordingly.
If PWM control makes a 2-wire DC fan whine, check whether your firmware and board support changing the PWM behavior. In Klipper, settings such as hardware_pwm or cycle_time can change the control signal and may reduce audible whine, but the safe value depends on the fan, board, and MOSFET circuit. Use the Marlin and Klipper documentation for exact syntax, because pins and fan objects vary by printer.
Troubleshooting: Match the Symptom to the Right Fan
Fan troubleshooting is mostly a misdiagnosis filter. Before you print another duct or buy another blower, match the symptom to the fan system that can actually cause it.
| Symptom | Check this fan or circuit | First action |
|---|---|---|
| Clog or extrusion stops mid-print | Hotend fan, heatsink path | Verify spin above hotend temperature threshold |
| Sagging bridges or collapsed overhangs | Part cooling fan and duct | Check direction, duct blockage, and profile command |
| Low speed only buzzes | PWM startup threshold | Raise minimum command or set kick start |
| Fan only runs full speed | Constant-power port, firmware setup, wiring error, incompatible control method, or failed output stage | Confirm board output, port, and control mode |
| Fan error while fan spins | Tach wire, pulses-per-revolution setting, pullup, low-RPM threshold, or PWM interference | Check tach signal and firmware setting |
| Fan gets louder over time | Bearing wear | Plan replacement before failure |
This loops back to the opening problem: do not let one noisy or popular fan size become the answer to every print issue. If the hotend fan is weak, part cooling will not fix heat creep. If the duct is restrictive, a larger free-air CFM number may not fix bridges.
For Printer OEMs: Sourcing Fans at Volume
If you build printers rather than repair one machine at a desk, the question changes. You are not just asking which fan fits a bracket. You are trying to control noise, thermals, wiring, firmware behavior, and supply risk across every fan position in the printer.
A useful RFQ should include the application position, frame size and mounting hole drawing, voltage and current target, airflow and static pressure target or duct drawing, wire count, PWM method, tach feedback need, connector type, cable length, noise target, working temperature, and annual volume. If your toolhead is custom, send the duct drawing early, because the duct decides the fan more than the fan nickname does.
Equipment builders who qualify a fan supplier tend to follow the same arc, in our experience. One qualification we supported for a Taiwanese equipment builder went from a multi-model quotation across AC and DC versions in April 2025, to a sample order of 40 to 100 pieces per model in May, to a production order in June, after which the emails stopped being about price and started being about cartons, weights, and labels. Plan for that sequence and the project moves faster on both sides.
Proventofan covers DC brushless axial fans from 20 to 200 mm, 45 recorded series, 5V, 12V, 24V, and some 48V options, plus the 5015 blower category used for part cooling. Connector, lead length, and speed grade can be adjusted for OEM projects after engineering review.
Need a fan matched to a custom printer duct? Send the mounting drawing, voltage, airflow path, connector, PWM or tach requirements, and estimated annual volume.
FAQ
What does a cooling fan do in a 3D printer?
A cooling fan removes heat from a specific part of the printer. The hotend fan protects the heatsink, the part cooling fan shapes fresh plastic, and electronics, PSU, chamber, and filter fans control heat or airflow in the rest of the machine.
Does PLA need a cooling fan?
Yes, PLA usually benefits from strong part cooling because it needs fast solidification for bridges, overhangs, and small details. Start with the slicer material profile, then adjust based on your duct and fan.
Should I put a fan on my 3D printer?
Your printer almost certainly has several already: a hotend fan, a part cooling fan, and usually electronics cooling. The better question is whether each one is working. Pointing an extra desk fan at the printer is rarely helpful and can cause warping with draft-sensitive materials such as ABS.
Should the hotend fan always be running?
It should run whenever the hotend is hot enough to need heatsink cooling. Several Prusa models start the hotend fan at a reported 50°C, while other printers may use always-on wiring or a different automatic threshold.
4010 vs 5015: which is better for part cooling?
A 5015 blower is often better for restrictive ducts because it can provide higher static pressure. A 4010 axial fan may provide more free-air flow in open spaces, so the duct and fan curve decide.
Can I put a 12V fan on a 24V 3D printer?
Not directly. Use a proper voltage conversion method if the printer output is 24V and the fan is 12V, and confirm current, polarity, and control method before powering the printer.
Why is my 3D printer fan getting loud?
Rising fan noise often points to bearing wear, blade contact, dust, or vibration. Treat it as an early warning, especially on the hotend fan.
Is a 3-wire fan a PWM fan?
Not by default. On many small DC fans, the third wire is tach feedback, while speed control may still happen through the printer board.
Do I need dual 5015 blowers for high-speed printing?
Not always. Dual blowers can add cooling capacity, but they also add weight, wiring, vibration risk, and overcooling risk, so use them only when the duct and print results justify the change.
Can I use a quiet PC fan on my printer’s hotend?
Only if it fits electrically, mechanically, and thermally. Low noise is not enough for a hotend fan, because you still need to verify heatsink cooling and heat creep behavior.
References
- Prusa Knowledge Base: Extrusion stopped mid-print: Heat creep
- Prusa Knowledge Base: Hotend fan glossary
- Prusa Knowledge Base: Print fan is not spinning
- Prusa Knowledge Base: Cooling
- Prusa Knowledge Base: PSU fan is not spinning (CORE One)
- Prusa Knowledge Base: Chamber filtration fan is not spinning (CORE One)
- E3D: Anatomy of a HotEnd
- Klipper: Configuration reference
- Marlin Firmware: M106 Set Fan Speed
Disclaimer
Catalog airflow and static-pressure values represent different points on the fan curve. Maximum airflow is measured near zero system resistance, while maximum static pressure occurs near zero airflow. The installed operating point depends on the intersection of the fan curve and the printer heatsink, duct, grille, or filter resistance. Printer modification involves electrical work, so disconnect power before wiring changes, do not open PSU enclosures unless qualified, and confirm the final fan selection against drawings, voltage, polarity, and engineering requirements.
