Customer 3D Printer Nozzle Modification for Composite Filaments
A customer's innovative solution using threaded adapters and 3D printer nozzles. Learn about jetting prevention through ultra-low speed extrusion and why the Nexus Mk2 excels at small-diameter filament production.
Introduction: A Customer's Innovative Solution
One of the most rewarding aspects of manufacturing desktop filament extruders is witnessing the innovative solutions our customers develop for their unique projects. Recently, a client who purchased a Noztek Touch filament extruder shared an ingenious modification that perfectly demonstrates the adaptability and versatility of our desktop extrusion systems — and taught us valuable lessons about nozzle design and extrusion velocity.
This particular customer approached us with a specialized project requiring polymer extrusion with a precise 0.8mm filament diameter. While the Noztek Touch comes standard with a 0.75mm stainless steel nozzle, their application demanded the slightly larger diameter for optimal performance. We initially provided blank brass nozzles for drilling, but our innovative customer had a different approach in mind.
Their solution: Rather than drilling out the blank nozzles, they modified the standard 0.75mm stainless steel nozzle by adding 6mm threading and attaching a standard 0.8mm 3D printer nozzle. This created a modular nozzle system that allows quick changes between different filament diameters by simply swapping 3D printer nozzles.
Customer Feedback
"The machine is working great. Just as an FYI, I made an adjustment on the 3mm nozzle head and had it tapped to accommodate the 8mm 3D print heads so I can change the size of the filament for my own project. Some pictures to explain — it extrudes 0.8mm no problem."
But what made this modification particularly successful wasn't just the mechanical ingenuity — it was understanding the critical relationship between nozzle size, extrusion velocity, and a phenomenon called "jetting" that can ruin filament precision at small diameters.
Understanding Jetting: The Critical Challenge with Small Nozzles
What is Jetting?
Jetting is a phenomenon that occurs when molten polymer exits a small-diameter nozzle at high velocity. Instead of the filament being smoothly drawn and cooled in a controlled manner, it shoots or "jets" from the nozzle opening, resulting in:
- Uncontrolled diameter variation (±0.20mm or greater)
- Irregular surface finish — bumps, waves, thickness variations
- Difficulty maintaining consistent line speed
- Impossible to achieve precision tolerances
Flow Comparison
Normal Flow (slow): Nozzle → ===smooth filament===
Jetting (high speed): Nozzle → ~~~~~~~spray/jet~~~~~~~
Why Jetting Occurs
- High exit velocity: When a small nozzle (0.4–1.0mm) operates at normal production speeds (50–150 RPM), the linear velocity at the nozzle exit can reach 50–200 mm/s — essentially spraying molten polymer rather than extruding it.
- Low melt viscosity at exit: As high-pressure polymer exits into atmospheric pressure, it experiences sudden expansion and acceleration.
- Insufficient draw force: At high velocities, the cooling filament cannot provide enough draw force to control the jetting stream.
- Die swell amplification: Jetting amplifies die swell effects — the polymer not only expands but also accelerates and sprays.
Die Swell — Controlled
- Predictable expansion: 1.1–1.8× die diameter
- Can be managed with temperature and speed
- Occurs at all speeds, varies in magnitude
Jetting — Uncontrolled
- Unpredictable spray pattern
- Cannot be managed above threshold velocity
- Prevents any consistent diameter formation
- Only solution: reduce speed below threshold
Jetting Velocity Thresholds by Nozzle Diameter
| Nozzle Diameter | Jetting Begins | Safe Velocity | Ultra-Precision |
|---|---|---|---|
| 0.4mm | >10 mm/s | <5 mm/s | <2 mm/s |
| 0.6mm | >8 mm/s | <5 mm/s | <2 mm/s |
| 0.8mm | >6 mm/s | <4 mm/s | <1 mm/s |
| 1.0mm | >5 mm/s | <3 mm/s | <1 mm/s |
| 1.2mm | >5 mm/s | <3 mm/s | <1 mm/s |
"For small nozzles (0.4–1.2mm), jetting begins when exit velocity exceeds 5–10 mm/s. Below this threshold, polymer flows smoothly. Above it, jetting disrupts dimensional control. The solution: ultra-low speed extrusion (1–3 RPM) that keeps exit velocity well below the jetting threshold."
Why the Noztek Nexus Is Ideal for Preventing Jetting
While our customer successfully used the Noztek Touch for their 0.8mm filament project and achieved excellent results, the Noztek Nexus Mk2 takes this approach even further with capabilities specifically designed for ultra-low speed precision extrusion.
Most desktop filament extruders — including the Touch — are optimized for production throughput (100–500 g/hr), which requires screw speeds of 30–150 RPM. The Nexus Mk2 is engineered from the ground up to excel at ultra-low speeds (1–5 RPM) that completely eliminate jetting with small nozzles.
Ultra-Low Speed Capability
Speed range: 1–150 RPM continuously variable. The Nexus Mk2 reliably operates at 1–2 RPM for extended periods.
Mass flow: 0.30 g/min = 18 g/hr
Exit velocity: 480 mm/min = 8 mm/s
6–12× slower than typical 3D printing
Why Low Speed Prevents Jetting
- ✓Exit velocity below jetting threshold (<1 mm/s)
- ✓Minimal molecular orientation — polymer chains relax
- ✓Reduced elastic energy storage at exit
- ✓Consistent flow — minimal pressure fluctuations
- ✓Low shear heating — temperature stays stable
- ✓Gravity assists in drawing filament evenly
Motor Torque at Low Speed
The Nexus Mk2's DC motor with gearbox provides consistent torque at 1 RPM to handle all polymer viscosities and filled materials.
Why stepper motors fail: insufficient torque at low RPM, microstepping noise creates pressure pulsations, poor thermal management at low duty cycles.
Temperature Stability
At ultra-low speeds, residence time in barrel is 5–10 minutes, allowing full temperature equilibration. The Nexus three-zone PID control maintains ±2°C stability.
Consistent melt temperature at nozzle exit = consistent die swell = consistent diameter.
No Additional Equipment
High-speed requires:
✗ Tolerance puller (£2k–£3k)
✗ Laser measurement (£0.5k–£1.5k)
✗ Feedback electronics
✗ Extended cooling
Ultra-low needs only:
✓ Nexus Mk2 extruder
✓ 3D printer nozzle (£3–£30)
✓ Simple water bath (£200)
✓ Basic winder (£300)
Speed vs. Production Guide
| Speed | Output | Application |
|---|---|---|
| 1–5 RPM | 10–30 g/hr | Research, precision, small batches |
| 10–30 RPM | 50–150 g/hr | Prototype production, balanced precision |
| 50–100 RPM | 200–400 g/hr | Production, use with tolerance puller |
Nozzle Selection for Target Diameters
Selecting the correct 3D printer nozzle diameter depends on your target filament diameter and expected die swell for the specific material.
Target: 1.75mm Filament
| Material | Expected Die Swell | Nozzle Diameter | Actual Output |
|---|---|---|---|
| PLA | 1.08× | 1.6mm ⭐ | 1.75mm ±0.05mm |
| PETG | 1.10× | 1.6mm ⭐ | 1.76mm ±0.06mm |
| ABS | 1.13× | 1.5mm | 1.75mm ±0.07mm |
| Nylon | 1.15× | 1.5mm | 1.73–1.78mm ±0.08mm |
| TPU | 1.05× | 1.7mm | 1.75mm ±0.04mm |
Practical Recommendations
- Start with 1.6mm nozzle for PLA/PETG — most common and readily available (E3D, Bondtech)
- Use 1.5mm nozzle for ABS/Nylon if available from specialty suppliers
- Fine-tune by adjusting screw speed ±0.5 RPM and temperature ±5°C
- 1.7mm nozzles are rare but ideal for TPU applications
3D printer nozzle installed in Nexus Mk2 nozzle adapter. Standard M6 or E3D-compatible nozzles can be used for precision filament production.
Process Parameters for ±0.10mm Tolerance
Achieving ±0.10mm tolerance (0.2mm total variation) requires control over multiple process variables.
1. Screw Speed (Most Critical)
Target range: 1–3 RPM for maximum precision.
PLA
1.5–2.5 RPM
Low die swell, easy to control
PETG
1.5–2.0 RPM
Moderate die swell
ABS
1.0–2.0 RPM
Higher die swell, slower needed
Nylon
1.0–1.5 RPM
Highest die swell, slowest essential
TPU
2.0–3.0 RPM
Low die swell, can run slightly faster
2. Temperature Profile
Strategy: Process at the upper end of the material temperature range to minimise viscosity and die swell.
| Material | Feed Zone | Compression | Metering | Nozzle |
|---|---|---|---|---|
| PLA | 180°C | 190°C | 195°C | 190°C |
| PETG | 230°C | 240°C | 245°C | 240°C |
| ABS | 220°C | 230°C | 235°C | 230°C |
| Nylon 6 | 240°C | 250°C | 255°C | 250°C |
| TPU | 210°C | 220°C | 225°C | 220°C |
Temperature Effects on Diameter:
+10°C → Reduces diameter by 0.03–0.05mm (lower viscosity, less die swell)
-10°C → Increases diameter by 0.03–0.05mm (higher viscosity, more die swell)
3. Cooling Strategy
Water Bath (Recommended)
- Water temperature: 15–25°C
- Bath length: 0.5–1.0m
- Entry angle: 45–60° downward
- Exit: filament fully solidified, cooled to <40°C
- 30–60 seconds in cooling zone at ultra-low speed
Air Cooling (Alternative)
- Room temperature natural convection
- Cooling length: 1.5–2.5m
- Forced air fan NOT recommended — causes uneven cooling
- Gradual cooling minimises internal stresses
Step-by-Step Process
Equipment Setup
Required Components
- Remove standard extrusion die from Nexus
- Install nozzle adapter (if not already present)
- Thread 3D printer nozzle into adapter — hand-tight, then ¼ turn with wrench
- Ensure nozzle tip extends slightly beyond adapter face
- Install thermocouple in correct position and verify accuracy with independent thermometer
- Allow 30 minutes for thermal stabilisation before starting
Material Drying (Essential for Hygroscopic Materials)
Nylon
80°C / 4–6 hours
Moisture: <0.1%
PETG
65°C / 3–4 hours
Moisture: <0.02%
PLA
50°C / 2 hours
Moisture: if humid
ABS
80°C / 2–3 hours
Moisture: standard
TPU
60°C / 2–3 hours
Moisture: standard
Startup Sequence
- Load dried material into hopper
- Set temperature profile per material (see table above)
- Wait 30 minutes for thermal stabilisation
- Set screw speed to 2 RPM for initial startup
- Begin extrusion — observe melt flow for consistency and bubbles
- Extrude 50–100g purge to clear previous material
- Allow 1 meter of filament to extrude, then measure diameter at 10 evenly spaced points
- Calculate average diameter and standard deviation
Measuring filament diameter with digital caliper. Measurements should be taken at multiple points and orientations to assess roundness and consistency. Achieving ±0.10mm tolerance requires careful monitoring and parameter adjustment.
Diameter Adjustment Logic
Diameter Too Large (>0.10mm over target)
- Reduce screw speed by 0.3–0.5 RPM
- Or reduce temperature by 5–10°C
- Re-measure after 0.5m of extrusion
Diameter Too Small (>0.10mm under target)
- Increase screw speed by 0.3–0.5 RPM
- Or increase temperature by 5–10°C
- Re-measure after 0.5m of extrusion
High Standard Deviation (>0.05mm)
- Temperature instability → improve PID tuning
- Flow instability → check hopper bridging
- Cooling instability → stabilise water bath
- Take-up instability → adjust winder tension
Throughput Examples (1.75mm target)
1 RPM
~18 g/hr
~145 m/hr
~3.5 km/day
2 RPM
~36 g/hr
~290 m/hr
~7 km/day
Practical
50–100m/run
4–6 hour runs
Troubleshooting
| Issue | Likely Cause | Solution |
|---|---|---|
| Diameter varies by >0.15mm | Temperature instability | Check PID tuning, thermocouple position |
| Filament breaks during extrusion | Too much tension from winder | Reduce winder speed, decrease tension |
| Bubbles or voids | Moisture contamination | Re-dry material more thoroughly |
| Inconsistent diameter in sections | Pellet size variation | Screen pellets for uniform size |
| Diameter gradually increases | Material degradation | Increase screw speed slightly, reduce temperature |
| Surface roughness | Temperature too low | Increase temperature 5°C, clean nozzle |
| Excessive die swell | Screw speed too high | Reduce to 1 RPM or lower |
Nozzle Materials and Durability
Advantages and Limitations
Advantages
Minimal Equipment Investment
No tolerance puller (£2,000–£3,000 savings). No laser measurement (£500–£1,500 savings). Total system cost under £4,000.
Standard Components
3D printer nozzles widely available (£3–£80). Quick changeover between diameters. No custom tooling.
Excellent Diameter Control
±0.10mm achievable without active feedback. ±0.05mm possible with careful optimisation.
Material Flexibility
Works with all thermoplastics. Suitable for filled materials with hardened steel nozzle.
Forgiving Process
Slow speeds allow manual intervention. Easy to troubleshoot. Minimal material waste during startup.
Limitations
Low Throughput
10–40 g/hr typical. Not suitable for production volumes over 5 kg/day. Long run times required.
Requires Nexus or Equivalent
Must have extruder capable of stable 1–2 RPM. Most desktop extruders cannot run this slowly reliably.
Manual Diameter Monitoring
No automatic feedback control. Operator must measure samples periodically.
Material-Specific Optimisation
Each material requires parameter development. Must re-optimise when switching polymers.
Nozzle Wear
Brass nozzles wear relatively quickly. Must monitor and replace to maintain tolerance.
Applications and Use Cases
Research & Development
- Material characterisation
- PhD/Master's thesis work
- University laboratories
- Testing novel additives and fillers
Small-Batch Specialty
- Custom colours for artistic applications
- Specialty conductive or magnetic filaments
- Medical-grade filaments for research
- Proprietary formulations
Prototype Production
- Functional prototypes with specific properties
- Short production runs (10–50 parts)
- Testing 3D print settings
- Rapid iteration cycles
Cost-Sensitive Applications
- Start-ups with limited capital
- Individual researchers and inventors
- Small businesses exploring extrusion
- Educational institutions
Conclusion
Using 3D printer nozzles for precision filament production is a practical, cost-effective approach for researchers, small businesses, and anyone producing specialty filaments in small quantities. The key to success is ultra-low speed extrusion (1–3 RPM) to minimise die swell, and the Noztek Nexus Mk2 is uniquely capable of providing stable operation at these extremely low speeds.
By combining readily available 3D printer nozzles (£3–£30) with controlled extrusion parameters and simple cooling systems, it's entirely possible to achieve ±0.10mm diameter tolerance without expensive tolerance pullers or laser measurement systems. The trade-off is throughput: at 10–40 g/hr, this approach suits research samples, material development, small-batch specialty production, and proof-of-concept work — not high-volume manufacturing. But for these applications, it represents an accessible entry point into the world of custom filament extrusion.
Key Takeaways
Ready to Start Precision Filament Production?
The Noztek Nexus Mk2 is the ideal platform for ultra-low speed precision extrusion with standard 3D printer nozzles.