Under-Extrusion

This guide covers how to diagnose and fix under-extrusion on the Vision Miner 22 IDEX V4. Under-extrusion means the printer is depositing less material than required � resulting in thin, weak, or missing layers. Use this guide whenever you see gaps in your prints, rough surfaces, or filament that appears to flow inconsistently from the nozzle.

The most effective approach is to trace the filament path from the spool all the way to the nozzle tip, checking each point for obstructions, misalignment, or mechanical issues. After ruling out the mechanical path, check temperature settings and flow rate configuration.

Safety and Warnings

Warning: WARNING: Several diagnostic steps require the printer to be powered on (checking temperatures, running extrusion tests). For any step that involves touching wiring, removing parts, or working near the hotend � turn off the printer and unplug it from the power outlet first. WARNING: Wait at least 60 seconds after powering off for the capacitors to discharge. WARNING: The nozzle and heater block can exceed 400 �C (752 �F). Let the hotend cool to room temperature before touching any components near it. IMPORTANT: Before working through these steps, confirm you are actually seeing under-extrusion and not a different issue. Under-extrusion shows as thin walls, visible gaps between lines, rough top surfaces, or weak layer bonding.

Tools and Materials

• 2 mm Hex screwdriver (hex wrench)
• Acupuncture needle or nozzle cleaning needle (0.3�0.4 mm)
• Flashlight
• Isopropyl alcohol (IPA)
• Gas torch (butane torch) � for nozzle deep-cleaning only
• Small drill bit (1�2 mm) � for nozzle deep-cleaning only
• Tweezers or pliers
• Clean cloth

1. Identifying Under-Extrusion

Under-extrusion produces visible symptoms on the printed part. Before diving into diagnostics, confirm you are dealing with under-extrusion by looking for these signs:

• Thin or incomplete walls � perimeters that have gaps or look translucent.
• Rough or porous top surfaces � the top layers don't fully cover, leaving visible infill pattern underneath.
• Weak layer bonding � layers separate easily or feel brittle.
• Inconsistent extrusion lines � some sections extrude normally while others come out thin or skip entirely.
• Clicking or grinding from the extruder � the motor skips steps or the gears grind into the filament because material can't flow through the hotend.

2. Filament Path Inspection � Spool to Nozzle

Anytime there is under-extrusion, examine the mechanical path of the filament first. Work systematically from the spool up to the nozzle � this way you isolate the problem area without missing anything.

Spool and Spool Holder

1. Check that the spool is seated correctly on the spool holder and spins freely. Give it a light push � it should rotate without catching or wobbling.

2. Look for tangled filament. A tangle will cause the spool to lock up mid-print, starving the extruder. Inspect the first few wraps on the spool � if any loops cross over each other, untangle them before continuing.

3. Check if the spool is deformed. High chamber temperatures can warp plastic spools over time, causing them to bind on the holder. If the spool looks warped or doesn't sit flat, replace it or transfer the filament to a new spool.

PTFE Tubes (Spool to Extruder)

4. Trace the PTFE tube from the spool holder all the way to the extruder. Look for any sharp bends, kinks, or tight curves. The filament must have a smooth, gradual path � sharp angles create friction that the extruder has to fight against.

5. Check the tube fittings at both ends. The tube should be firmly seated in the pneumatic couplers � push it in and make sure it doesn't slide out when you pull on it.

6. To test the full path for resistance: disconnect the PTFE tube from the extruder end and try pushing filament through by hand. It should slide freely with minimal effort. If there is significant resistance, the tube may have an internal kink, debris, or a damaged section that needs replacing.

Info: IMPORTANT: On the Vision Miner 22 IDEX V4, the rear section has several tube bends due to the filament path layout. If you experience high resistance, opening the rear doors significantly reduces tube bending and often resolves the issue. See the Filament Breaks Inside Tube Guide for a detailed explanation and additional solutions.

Filament Sensor Housing

7. Inspect the filament sensor housing where the filament passes through. Make sure there is no debris, broken filament fragments, or anything obstructing the path.

Extruder

8. Check the extruder lever (tension arm) position. The lever controls how tightly the drive gears grip the filament. If the lever is set too loose, the gears won't grip the filament firmly enough, causing it to slip instead of feeding.

9. Inspect the filament itself. Pull out a short section from the extruder and look for flat spots or grinding marks where the drive gear was pressing. Flat spots usually mean the filament was stuck � the gear was turning but the filament wasn't moving. This confirms a downstream obstruction.

PEEK Tubing, Heatbreak, and Nozzle � Partial Toolhead Disassembly

Warning: IMPORTANT: The following steps (10�19) require partial disassembly of the toolhead � removing the fan shroud, disconnecting the hotend, and accessing internal components. Prepare your tools and cover the build plate with a cloth to catch any small parts that may fall. IMPORTANT: This disassembly procedure is also described in the Extruder Replacement Guide. Only the steps needed for diagnostics are included here � a full extruder replacement requires additional steps.

Removing the Fan Shroud and Cable Cover

10. Unscrew the two screws holding the cable cover and fan shroud using a 2 mm hex screwdriver. On Tool 0 (left toolhead), the screws are on the left side; on Tool 1 (right toolhead) � on the right side (when viewed from the front of the printer).

11. Remove the cable cover and the fan shroud.

Info: IMPORTANT: Before disconnecting any wires, photograph or note the wire positions and order on the terminal block. This will make reassembly much easier.

Removing the Hotend Assembly

12. Disconnect all hotend cables from the terminal block. Press the orange release tab with a 2 mm hex screwdriver while supporting the terminal block holder from behind to avoid bending it.

Warning: IMPORTANT: Support the terminal block holder from behind while pressing the release tab. Pressing without counter-support can bend or break the holder.

13. Unscrew the two screws holding the hotend assembly using a 2 mm hex screwdriver.

14. Remove the hotend assembly (heatsink, heatbreak, heater block, nozzle, and PEEK transition piece) from the extruder. Set it aside on a clean surface.

Inspecting the PEEK Tubing (Extruder to Hotend)

15. Now that the hotend is removed, inspect the PEEK tubing that connects the extruder output to the hotend input. This short tube must be straight, properly seated at both ends, and free of any internal obstruction. If the tube is misaligned or partially blocked, filament will jam at the transition.

Inspecting the Heatbreak

16. Inspect the heatbreak � the metal tube connecting the heatsink (cold side) to the heater block (hot side). A clogged heatbreak is one of the most common causes of under-extrusion. Material that has crept up, expanded, or carbonized inside the heatbreak will restrict filament flow.
17. If you suspect a heatbreak clog, heat the hotend to printing temperature and try pushing filament through manually using the Web Interface extrude controls. If material barely comes out or doesn't come out at all, there is likely a blockage in the heatbreak or nozzle.

Hot Block Connection

18. Verify that the heatbreak-to-nozzle connection inside the hot block is tight. A loose connection creates a gap where molten filament pools and leaks, reducing material flow to the nozzle. Signs of a leak: filament oozing from around the heater block, or blobs of hardened material on the outside of the block.

Danger: Attention: Always tighten the nozzle while the hotend is at printing temperature. Metal expands when heated, and a connection tightened cold will loosen when hot, causing leaks.

Nozzle

19. Check the nozzle for clogs or debris. Remove the nozzle from the hotend and hold it up to a light source � you should be able to see light through the orifice. If the nozzle is partially or fully blocked, clean it using one of the methods described in Section 5: Clearing a Clogged Nozzle.

20. Check for carbonized material on the outside of the nozzle tip. Built-up char around the orifice can deflect the extruded material and disrupt the flow pattern, mimicking under-extrusion.

3. Temperature-Related Causes

If the mechanical path checks out � everything is clear, properly aligned, and moving freely � the problem is likely temperature-related.

Low Nozzle Temperature

21. Verify your nozzle temperature is high enough for the material you are printing. A common mistake is using the temperature printed on the filament spool label � on the Vision Miner 22 IDEX V4, we typically print 20 �C above the manufacturer's recommended temperature. The enclosed chamber adds ambient heat, so the hotend needs a higher set point to maintain proper melt flow.

Info: IMPORTANT: For specific temperature values per material, refer to the Material Tuning procedure. Temperature, pressure advance, and flow rate all interact � tuning one without the others can introduce new problems.

Heat Creep

22. Heat creep occurs when heat travels up from the hot zone into the cold side of the hotend (through the heatbreak and into the PTFE path). The filament softens and expands above the melt zone, eventually jamming.

Heat creep has several common causes:

a) Chamber temperature too high. Every material has a maximum safe chamber temperature. Exceeding it causes heat to build up in the cold side of the hotend. For example, ABS at a 100 �C chamber temperature will very likely result in heat creep and a clog. PLA should always be printed with the top lid open and the doors open � PLA requires minimal or no chamber heating.

Info: IMPORTANT: Always check the recommended chamber temperature limits for your specific material before printing in an enclosed environment.

b) Hotend cooling fan not working. The fan on the heatsink (cold side) keeps the heatbreak cool and prevents heat from creeping upward. If this fan is not spinning or is spinning slowly, heat creep will occur even at normal chamber temperatures. Visually confirm the fan is running at full speed during printing.

c) Incorrect filament retraction. When you retract filament (during filament changes or unloading), pulling it out at too high a temperature causes it to stay soft and expand inside the heatbreak. This leaves material stuck in the cold zone.

Correct retraction procedure for the Vision Miner 22 IDEX V4:

• Cool down before retracting. Drop the temperature by at least 50 �C from the printing temperature. If printing at 300 �C, retract at 250 �C or even 200 �C.
• Retract slowly. Pull the filament out slowly so it has time to cool and solidify as it moves up through the heatbreak. Fast retraction pulls a long string of molten material into the cold zone.

4. Flow Rate and Speed Settings

High Volumetric Flow Rate

23. If you are printing too fast, the hotend physically cannot melt and push material through the nozzle quickly enough. This produces under-extrusion even though nothing is mechanically wrong.

The safe volumetric flow rate settings for the Slice Engineering Copperhead hotend installed on the Vision Miner 22 IDEX V4:

Info: IMPORTANT: These are safe, conservative settings � not absolute maximums. You may be able to push higher rates depending on your specific material and geometry, but if you are troubleshooting under-extrusion, start here and increase only after confirming stable extrusion at these values.

24. Check your slicer settings. The volumetric flow rate is determined by: layer height � extrusion width � print speed. If any of these values is set too high, the combined flow rate may exceed what the hotend can handle. Reduce print speed as the first adjustment � it has the most direct effect.

5. Clearing a Clogged Nozzle

If you have traced the problem to a clogged nozzle, there are two cleaning methods depending on severity.

Method 1: Needle Cleaning (Partial Clog)

25. Heat the hotend to the printing temperature for the material that is stuck inside.

26. Insert a nozzle cleaning needle (acupuncture needle) through the nozzle orifice from below. Push gently and repeatedly to break through the blockage.

27. Try extruding filament again through the Web Interface. If material flows normally, the clog is cleared. If not, proceed to Method 2.

Method 2: Torch Cleaning (Severe Clog)

Use this method when the needle cannot break through, or when carbonized material has built up inside the nozzle.

Warning: WARNING: This procedure involves open flame and extremely hot metal. Wear heat-resistant gloves and work on a fireproof surface. Keep flammable materials away. Attention: Torch cleaning degrades the nozzle's heat treatment. The nozzle will lose some hardness after this process. It remains usable but will wear faster. Consider this a recovery method, not routine maintenance.

28. Remove the nozzle from the hotend.

29. Using a gas torch (butane torch), heat the nozzle until it glows red.

30. While the nozzle is still hot, use a small drill bit (1�2 mm) to push out the carbonized material from inside. The burnt residue should crumble and fall out. Shake the nozzle gently to remove loose particles.

31. Follow up with a needle through the orifice to make sure the bore is completely clear.

32. For extra-stubborn contamination: heat the nozzle with the torch, then immediately plunge it into a container of water. The thermal shock helps dislodge any remaining material from the inner walls. Repeat the heat-and-quench cycle 2�3 times if needed.

33. Reinstall the nozzle into the hotend. Remember to tighten it at printing temperature to ensure a proper seal.

FAQ

How do I confirm it's under-extrusion and not a bed adhesion issue?

Under-extrusion shows as thin/weak/gappy walls and top surfaces throughout the entire print � not just the first layer. If only the first layer is affected, the problem is more likely bed adhesion, Z-offset, or first layer calibration. See NPA Application Guide for adhesion-related troubleshooting.

Can high chamber temperature cause under-extrusion?

Yes. Excessive chamber temperature causes heat creep � heat travels up the heatbreak into the cold zone, softening and expanding the filament before it reaches the melt zone. This creates a plug that blocks flow. Always verify you are within the recommended chamber temperature limits for your material.

What volumetric flow rate should I start with?

For the Slice Engineering Copperhead hotend on the Vision Miner 22 IDEX V4: 15 mm�/s for standard plastics, 10 mm�/s for filled materials, and 5�6 mm�/s for high-temperature filled materials. These are safe starting points � if you get clean extrusion at these rates, you can experiment with increasing speed gradually.

Should I replace the nozzle or try to clean it?

Start with needle cleaning � most partial clogs clear this way. If the needle doesn't work, try torch cleaning. Replace the nozzle only if cleaning doesn't restore normal flow, or if the nozzle bore has been physically damaged.

What should I do after resolving the under-extrusion?

Run a short test print using a simple geometry (a calibration cube or single-wall vase) to confirm consistent extrusion before going back to your full print. If you changed any temperature or speed settings during troubleshooting, note the working values so you can apply them to future prints.

Troubleshooting

• Issue: Filament not extruding at all � no material comes out of the nozzle.
• Cause: Complete clog in the nozzle or heatbreak, or extruder motor not turning.
• Solution: First check if the extruder motor is spinning (listen for clicking or watch the gears). If the motor runs but nothing comes out, follow the path inspection from the extruder forward � check PEEK tubing, heatbreak, and nozzle. If the motor is not spinning, see the Extruder Motor section below.

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• Issue: Extruder motor makes clicking sounds or skips steps.
• Cause: The motor is trying to push filament but the path is blocked (clog downstream) or resistance is too high.
• Solution: The clicking means the motor is stalling against back-pressure. Check for nozzle clog, heatbreak clog, or PTFE tube obstruction. Also verify nozzle temperature is correct � too-cold filament creates very high resistance.

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• Issue: Filament has flat spots or grinding marks from the drive gear.
• Cause: The filament was stationary while the gear kept turning � something downstream is preventing it from moving.
• Solution: This confirms a blockage between the extruder and nozzle. Inspect the PEEK tubing, heatbreak, and nozzle. Clean or replace the clogged component.

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• Issue: Under-extrusion starts mid-print after running fine for some time.
• Cause: Heat creep � the hotend's cold zone gradually heats up until filament softens and jams. Or the spool has become tangled.
• Solution: Check spool for tangles first. Then check if the heatsink fan is running. Verify chamber temperature is within limits for your material. Review retraction settings if the issue occurs during filament changes.

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• Issue: Under-extrusion only on one toolhead. The other prints fine.
• Cause: Toolhead-specific issue � clogged nozzle, misaligned PEEK tubing, extruder lever set incorrectly, or a failing extruder motor on that specific toolhead.
• Solution: Run the same filament through the working toolhead to confirm the material is fine. Then inspect the affected toolhead's entire path: extruder lever and gears, PEEK tubing, heatbreak, and nozzle.

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• Issue: Extruder motor does not spin at all (no clicking, no movement).
• Cause: Motor electrical issue � could be the motor itself, the wiring, or the stepper driver on the mainboard.
• Solution: Disengage the extruder gears by moving the tension lever fully to the left. Try commanding the motor to move via the Web Interface. If it still doesn't respond, the issue is electrical. There are three components to isolate: driver, cable, and motor. Try swapping the motor cable to a different driver output, then try replacing the cable, then try a different motor. Test each change individually.

Danger: Attention: Always power off the printer completely before connecting or disconnecting any motor cables. Hot-swapping motor connections will damage the stepper driver � this is not recoverable.

Support

Vision Miner Support

• Email: support@visionminer.com
• Phone: +1 (949) 522-4422