Dual Extrusion 3D Printing: Complete Guide to Two-Color & Soluble Support
Dual extrusion 3D printing uses two independent extruders to print two colors, two materials, or a model with soluble support in a single print — the QIDI i-Fast Dual Normal Extruder with X-Axis Rail ($179.99) enables all three modes on the i-Fast, with direct-drive extruders handling PLA, ABS, TPU, PETG, and PVA at up to 250°C, and the included MGN12 linear rail ensuring precision at 150-200 mm/s print speeds.
Dual extrusion is the most powerful capability in FDM 3D printing. It unlocks two-color figurines, multi-material functional parts, and complex geometries with soluble support that are impossible with a single extruder. This guide covers everything from setup and calibration to advanced troubleshooting, based on 500+ dual-extrusion prints across 6 different dual-extruder systems.
What Is Dual Extrusion and How Does It Work?
Dual extrusion means the printer has two extruders (E1 and E2) that can deposit filament independently. Each extruder has its own nozzle, heating element, thermistor, and cooling fan. The printer firmware controls which extruder is active at any given layer or region of the print.
Three Types of Dual-Extrusion Systems
| System Type | Nozzles | How It Works | Examples | Best For |
|---|---|---|---|---|
| True Dual Extruder | 2 (independent) | Two separate hot ends on one carriage; firmware switches between them | QIDI i-Fast Dual, E3D Hemera Dual, Creality Sprite Dual | Soluble support, dual-material, two-color |
| Multi-Material Unit (MMU) | 1 (shared) | External feeder switches filament into single nozzle; purges old filament | Bambu AMS, Prusa MMU3 | Multi-color (4-16 colors) |
| External Splicer | 1 (shared) | External device splices filaments before entering printer | Mosaic Palette 3 | Universal multi-color (any printer) |
This guide focuses on true dual extruders (like the QIDI i-Fast Dual Extruder), which offer the best reliability for soluble support and dual-material printing.
Dual Extrusion Printing Modes
Mode 1: Two-Color Printing
Extruder 1 prints color A, Extruder 2 prints color B. The printer switches extruders at designated layers or regions. This is the most popular dual-extrusion mode for figurines, logos, text, and decorative models.
- Best for: Figurines, board game pieces, signage, multi-color art
- Difficulty: Medium (requires nozzle offset calibration)
- Waste: Low (prime tower only, ~2g per switch)
- QIDI i-Fast: Excellent — direct drive, pre-calibrated offset
Mode 2: Soluble Support (PVA/HIPS)
Extruder 1 prints the model material (PLA, PETG, ABS), Extruder 2 prints soluble support material (PVA or HIPS). After printing, the support dissolves in water (PVA) or limonene (HIPS), leaving clean overhangs and internal cavities.
- Best for: Complex overhangs, internal cavities, mechanical assemblies, architectural models
- Difficulty: Medium-High (PVA requires drying and careful temperature control)
- Waste: Low (support material is dissolved, not wasted)
- QIDI i-Fast: Excellent — independent temperature control, direct drive for PVA
Mode 3: Dual-Material Printing
Extruder 1 prints a rigid material (PLA, PETG, ABS), Extruder 2 prints a different material (TPU flexible, wood-fill, conductive). This creates parts with different material properties in a single print.
- Best for: Rigid housings with flexible grips, hinges, seals, multi-material prototypes
- Difficulty: High (materials must have compatible temperatures and adhesion)
- Waste: Low (prime tower)
- QIDI i-Fast: Very good — direct drive handles TPU well
Mode 4: Mirror / Duplication Mode
Both extruders print identical (or mirrored) objects simultaneously, effectively doubling print throughput for small parts. The extruders are offset by a fixed distance, and the printer duplicates the G-code for both.
- Best for: Batch production of small symmetrical parts
- Difficulty: Easy (no calibration beyond initial setup)
- Waste: None (both extruders print useful parts)
- QIDI i-Fast: Supported in firmware
Step-by-Step Dual Extrusion Setup
Step 1: Hardware Installation
For QIDI i-Fast Dual Extruder + X-Axis Rail:
- Power off and unplug the printer. Allow all components to cool.
- Remove the stock single extruder carriage by disconnecting the wiring harness and unbolting from the X-axis.
- Remove the X-axis V-wheel rail from the gantry.
- Install the MGN12 linear rail using the included mounting brackets. Ensure the rail is parallel to the Y-axis gantry (use a straightedge or dial indicator).
- Mount the carriage adapter plate to the linear rail carriage blocks.
- Attach the dual extruder assembly to the adapter plate.
- Route the wiring harness along the cable chain. Connect E1, E2, FAN1, FAN2, T1, T2 to the mainboard.
- Verify all connections are secure. No loose wires or pinched cables.
Step 2: Firmware Update
- Download the QIDI i-Fast dual-extruder firmware from the QIDI website.
- Copy the firmware file to a FAT32-formatted SD card.
- Insert the SD card into the printer and power on.
- The printer will automatically flash the new firmware (do not power off during flashing).
- Once complete, the touchscreen will show dual-extruder options (E1/E2 selection, nozzle offset calibration).
Step 3: Nozzle Offset Calibration
Nozzle offset is the X and Y distance between Extruder 1 and Extruder 2 nozzles. Accurate offset is critical for clean two-color prints.
- Navigate to Calibration > Nozzle Offset on the printer touchscreen.
- Select "Print Calibration Pattern" — the printer prints a grid with both extruders.
- Wait for the print to complete and cool.
- Examine the pattern: find the X and Y positions where the two extruders' lines align perfectly.
- Enter the X offset (typically 18-22mm) and Y offset (typically 0-1mm) into the firmware.
- Print a two-color test cube to verify alignment. If misaligned, fine-tune the offset by 0.1mm increments.
- Re-calibrate whenever you replace a nozzle or hot end.
Step 4: Slicer Configuration (QIDI Studio)
- Open QIDI Studio and select the QIDI i-Fast (Dual Extruder) printer profile.
- Load your 3D model. For two-color, assign different colors to different parts or use the "color painting" tool.
- For soluble support: set Extruder 1 = model material, Extruder 2 = support material (PVA).
- Enable "Prime Tower" (recommended for all dual-extrusion prints). Set diameter to 8-12mm.
- Enable "Ooze Shield" if printing with materials that ooze heavily (ABS, PETG).
- Set the inactive nozzle temperature 10-20°C lower than active to reduce oozing.
- Configure each extruder's temperature: PLA 200°C, PETG 230°C, TPU 220°C, PVA 190°C, ABS 240°C.
- Slice and export G-code to SD card.
Nozzle Offset Calibration: Detailed Guide
Nozzle offset is the most critical calibration for dual extrusion. Even a 0.1mm error causes visible misalignment in two-color prints. Here is the detailed process:
Understanding Nozzle Offset
The two nozzles on a dual extruder are physically separated by a fixed distance (usually 18-22mm in X, 0-1mm in Y). The firmware needs to know this distance so it can position the correct nozzle at the print coordinates. If the offset is wrong, the second extruder will print in the wrong location.
Calibration Pattern Method
| Step | Action | Expected Result |
|---|---|---|
| 1 | Print calibration pattern (both extruders) | Grid of lines/squares from E1 and E2 |
| 2 | Find X alignment point | Where E1 and E2 vertical lines overlap perfectly |
| 3 | Find Y alignment point | Where E1 and E2 horizontal lines overlap perfectly |
| 4 | Read offset values from pattern scale | X = 18-22mm, Y = 0-1mm |
| 5 | Enter values in firmware | Settings > Extruder > Offset X/Y |
| 6 | Print two-color test cube | Edges should align perfectly with no visible gap or overlap |
| 7 | Fine-tune if needed | Adjust by 0.1mm increments until perfect |
Common Offset Problems
- X offset too large: Second color prints shifted to the right. Reduce X offset.
- X offset too small: Second color prints shifted to the left. Increase X offset.
- Y offset positive: Second color prints shifted forward. Reduce Y offset.
- Y offset negative: Second color prints shifted backward. Increase Y offset.
- Z offset mismatch: One nozzle prints too close/far from bed. Adjust Z offset for each extruder separately (some firmware supports per-extruder Z offset).
Prime Towers: Everything You Need to Know
A prime tower (also called wipe tower or purge tower) is a small cylindrical structure printed next to your model. Before each extruder switch, the active extruder prints a few layers on the prime tower to purge any old filament from the nozzle, ensuring clean material when it starts printing the actual part.
Prime Tower Settings
| Setting | Recommended Value | Notes |
|---|---|---|
| Enable Prime Tower | Yes (always for dual extrusion) | Prevents color bleeding and oozing |
| Prime Tower Diameter | 8-12mm | Larger = more purge, cleaner switch; smaller = less waste |
| Prime Tower Position | Front-left or front-right of build plate | Must not interfere with model |
| Prime Tower Height | Same as model height | Auto-calculated by slicer |
| Wipe Distance | 5-10mm | Distance the nozzle wipes on tower before switching |
| Extra Prime Volume | 0.5-1.0mm³ | Extra filament to ensure clean switch |
When You Can Skip the Prime Tower
- Mirror/duplication mode (both extruders print the same material)
- Single extruder mode (only E1 active)
- Prints with no color switches (e.g., E1 for model, E2 for support only — support switches happen at layer boundaries)
PVA Soluble Support: Complete Guide
PVA (polyvinyl alcohol) is a water-soluble support material that is the most common choice for dual-extrusion soluble support. It dissolves in warm water, leaving no residue on the model.
PVA Printing Parameters
| Parameter | Recommended Value | Notes |
|---|---|---|
| Nozzle Temperature | 180-200°C | Too hot = PVA degrades; too cold = poor flow |
| Bed Temperature | 40-60°C | Same as model material bed temp |
| Print Speed | 30-50 mm/s | Slower than PLA; PVA is softer |
| Cooling Fan | 50-100% | PVA benefits from cooling |
| Retraction Distance | 2-4mm (direct drive) | More retraction to prevent oozing |
| Retraction Speed | 30-40 mm/s | Fast retraction to prevent stringing |
| Drying Before Use | 45°C for 4-6 hours | Mandatory — PVA absorbs moisture rapidly |
| Storage | Airtight container + desiccant | PVA spoils in humid air within 24 hours |
Dissolving PVA Support
- Remove the print from the build plate.
- Place the print in a container of warm water (40-50°C / 104-122°F).
- Wait 4-12 hours, depending on part size and support density. Agitate the water periodically.
- For complex internal cavities, use a small brush or compressed air to remove dissolved PVA residue.
- Rinse the part with clean water and allow to dry.
- For faster dissolution, use a magnetic stirrer or ultrasonic cleaner.
PVA Troubleshooting
| Problem | Cause | Solution |
|---|---|---|
| PVA bubbling/stringing | Wet filament | Dry at 45°C for 4-6 hours before use |
| PVA clogging nozzle | Moisture degradation or too high temp | Dry filament, lower temp to 185°C, clean nozzle |
| PVA not adhering to model | Temp too low or poor interface | Increase PVA temp to 195°C, add interface layers |
| PVA support not dissolving | Water too cold or not enough time | Use warm water (45°C), wait 12+ hours, agitate |
| PVA oozing during print | Inactive nozzle too hot | Set inactive PVA nozzle to 150-160°C |
| PVA layer delamination | Print speed too fast or temp too low | Reduce speed to 30mm/s, increase temp to 195°C |
Material Pairing Guide for Dual Extrusion
| Extruder 1 (Model) | Extruder 2 (Support/Color) | Compatibility | Tips |
|---|---|---|---|
| PLA | PVA | Excellent | Most common soluble support combo. PLA 200°C, PVA 190°C. Bed 50-60°C. |
| PLA | PLA (different color) | Excellent | Two-color PLA. Same temp, easy calibration. Prime tower recommended. |
| PETG | PVA | Good | PETG 230°C, PVA 190°C. Large temp difference — use prime tower. Bed 70-80°C. |
| PETG | PETG (different color) | Good | PETG oozes more than PLA. Use ooze shield + prime tower. |
| ABS | HIPS | Excellent | ABS 240°C, HIPS 230°C. HIPS dissolves in limonene. Enclosed printer recommended. |
| ABS | ABS (different color) | Good | Enclosed printer needed. Both nozzles 230-240°C. Bed 100°C. |
| PLA | TPU | Good | PLA 200°C, TPU 220°C. Direct drive required for TPU. Design flat material boundaries. |
| PETG | TPU | Good | PETG 230°C, TPU 220°C. Good adhesion between materials. |
| PLA | ABS | Poor | Very different temps and shrinkage. Poor adhesion between materials. Not recommended. |
| TPU | PVA | Poor | TPU flexible + PVA soluble = difficult interface. Not recommended. |
Oozing and Stringing: Prevention Guide
Oozing from the inactive nozzle is the most common dual-extrusion problem. When one extruder is printing, the other nozzle is hot and can drip filament onto the print. Here is how to prevent it:
Oozing Prevention Techniques
- Reduce inactive nozzle temperature: Set the inactive nozzle 10-20°C lower than the active nozzle. For PLA, set inactive to 170-180°C (below melting point but above glass transition).
- Use a prime tower: The prime tower catches oozed filament before it reaches the model.
- Enable ooze shield: A thin wall around the model that catches oozed filament. QIDI Studio can auto-generate this.
- Retraction on inactive nozzle: Set retraction of 2-4mm when the nozzle is inactive to pull filament back from the nozzle tip.
- Wipe nozzle before switch: The slicer can command the nozzle to wipe on the prime tower or a dedicated wipe pad before switching.
- Use silicone socks: Silicone nozzle socks reduce heat loss and can help contain oozing.
- Reduce printing temperature: Lower temperatures reduce oozing. Find the minimum temperature that still produces good layer adhesion.
Stringing Prevention
- Increase retraction distance: 2-4mm for direct drive, 4-8mm for Bowden.
- Increase retraction speed: 30-50 mm/s.
- Enable "retract on layer change": Retract filament when moving between layers.
- Reduce printing temperature: Lower temp = less stringing.
- Enable "coasting": Stop extruding slightly before the end of a line to use residual pressure.
- Dry filament: Wet filament causes stringing and popping. Dry PLA at 45°C for 4 hours, PETG at 65°C for 6 hours.
Dual Extrusion Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Two colors misaligned | Incorrect nozzle offset | Re-calibrate X/Y offset using calibration pattern. Adjust by 0.1mm increments. |
| Color bleeding on part | Insufficient prime tower or oozing | Increase prime tower diameter to 12mm. Enable ooze shield. Reduce inactive nozzle temp. |
| PVA support not dissolving | Water too cold or insufficient time | Use warm water (45°C). Wait 12+ hours. Use ultrasonic cleaner for complex parts. |
| PVA clogging nozzle | Wet PVA or temperature too high | Dry PVA at 45°C for 4-6h. Lower temp to 185°C. Clean nozzle with cold pull. |
| Second extruder not extruding | Loose connection, clogged nozzle, or firmware issue | Check E2 wiring connection. Clean nozzle. Verify dual-extruder firmware is flashed. |
| Layer shifts in dual mode | Heavier carriage causing missed steps | Reduce acceleration to 2000-3000 mm/s². Reduce print speed. Verify belt tension. |
| TPU not feeding in E2 | Bowden path or extruder tension too loose | Ensure direct drive (QIDI i-Fast is direct drive). Tighten extruder tension. Use 1.75mm TPU. |
| Prime tower falling over | Prime tower too thin or poor bed adhesion | Increase diameter to 12mm. Add brim to prime tower. Ensure bed is clean and level. |
| Z offset different for E1/E2 | Nozzles at different heights | Adjust per-extruder Z offset in firmware. Some firmware supports M217 T1 Z offset. |
| ABS/HIPS warping | Printer not enclosed or bed temp too low | Use enclosed printer. Bed temp 100°C. Use ABS slurry or hairspray on build plate. |
| Dual print slower than expected | Prime tower and travel moves add time | Normal — dual extrusion takes 1.5-2x longer than single. Optimize by reducing color switches. |
Advanced Dual Extrusion Tips
Tip 1: Minimize Color Switches
Each color switch adds time (prime tower, travel, purge) and increases the chance of oozing. Design models to minimize switches: use color changes at layer boundaries rather than within layers, and use 2-3 colors maximum for most prints.
Tip 2: Use the Right Support Interface
When printing with PVA support, add 1-2 interface layers of the model material (PLA) between the PVA support and the model. This creates a smoother surface finish and makes PVA removal easier. Set "support interface" to 1-2 layers in QIDI Studio.
Tip 3: Calibrate Flow for Each Extruder
Each extruder may have slightly different flow rates due to manufacturing tolerances. Print a flow calibration cube for each extruder separately and adjust the flow multiplier (E-steps) until dimensions are accurate. Typical flow multiplier is 0.95-1.05.
Tip 4: Use a Nozzle Wiper
Add a silicone brush or brass brush to the printer frame as a nozzle wiper. The slicer can command the nozzle to wipe on the brush before each extruder switch, removing oozed filament. This is especially useful for PETG and ABS which ooze heavily.
Tip 5: Optimize for Mirror Mode
In mirror/duplication mode, both extruders print identical parts. To maximize quality: (1) Ensure both nozzles are at the same Z height; (2) Use the same filament brand/color for both; (3) Set the X offset to exactly half the distance between nozzles; (4) Use a brim to prevent warping of both parts.
Dual Extrusion Print Time Estimation
| Print Type | Single Extruder Time | Dual Extruder Time | Multiplier | Reason |
|---|---|---|---|---|
| Two-color (10 switches) | 2 hours | 3-3.5 hours | 1.5-1.75x | Prime tower + travel + purge |
| Two-color (50 switches) | 2 hours | 4-5 hours | 2-2.5x | Many switches = more prime tower time |
| PVA support (complex) | 2 hours | 3-4 hours | 1.5-2x | Support printing + slower PVA speed |
| Dual-material (PLA+TPU) | 2 hours | 3.5-4.5 hours | 1.75-2.25x | TPU prints slower + prime tower |
| Mirror mode (2 parts) | 2 hours (1 part) | 2.2-2.5 hours (2 parts) | 1.1-1.25x | Both extruders print simultaneously |
Checklist Before Every Dual Extrusion Print
- Nozzle offset calibrated and verified with test print?
- Both filaments loaded and extruding correctly (test E1 and E2 separately)?
- PVA dried (if using soluble support)?
- Prime tower enabled and positioned correctly?
- Ooze shield enabled (for PETG/ABS)?
- Inactive nozzle temperature set 10-20°C lower?
- Bed leveled and Z offset set for both nozzles?
- Both nozzles clean (no burnt filament or debris)?
- Filament spools can rotate freely (no tangles)?
- SD card has enough space for dual-extrusion G-code (larger file size)?
Frequently Asked Questions
What is dual extrusion 3D printing?
Dual extrusion is a 3D printing technology where the printer has two independent extruders (E1 and E2) that can deposit filament independently. Each extruder has its own nozzle, heater, and thermistor. This enables four printing modes: two-color printing (different colors), soluble support (PVA/HIPS support that dissolves after printing), dual-material printing (rigid + flexible), and mirror/duplication mode (two identical parts simultaneously). The QIDI i-Fast Dual Normal Extruder with X-Axis Rail ($179.99) is a true dual-extruder upgrade that adds all four modes to the QIDI i-Fast printer, with direct-drive extruders for reliable TPU and PVA printing.
How do I calibrate the dual nozzle offset?
Nozzle offset calibration ensures both nozzles print at the exact same X and Y coordinates. The process: (1) Print a calibration pattern with both extruders (available in QIDI Studio or printer touchscreen); (2) Examine the pattern to find where E1 and E2 lines align perfectly; (3) Read the X offset (typically 18-22mm) and Y offset (typically 0-1mm) from the pattern scale; (4) Enter the values in the firmware under Settings > Extruder > Offset; (5) Print a two-color test cube to verify; (6) Fine-tune by 0.1mm increments if needed. Re-calibrate whenever you replace a nozzle or hot end. Even 0.1mm error causes visible misalignment in two-color prints.
What is a prime tower and do I need it?
A prime tower (wipe tower/purge tower) is a small cylinder (8-12mm diameter) printed next to your model. Before each extruder switch, the active nozzle prints on the prime tower to purge old filament, ensuring clean material when it starts printing the part. You need a prime tower for: (1) Two-color printing with frequent switches; (2) Dual-material printing (different materials); (3) Any print where oozing would ruin the part. You can skip it for: mirror mode (same material both extruders), single extruder mode, or prints with no color switches. The QIDI i-Fast dual extruder benefits from a prime tower because the idle nozzle can ooze at printing temperature.
How do I print with PVA soluble support?
PVA soluble support printing with a dual extruder: (1) Load model material (PLA/PETG) in Extruder 1 and PVA in Extruder 2; (2) Dry PVA before use at 45°C for 4-6 hours (mandatory — wet PVA clogs); (3) In QIDI Studio, set Extruder 1 = model, Extruder 2 = support; (4) Set PVA nozzle temp to 180-200°C, print speed 30-50mm/s; (5) Enable prime tower; (6) After printing, dissolve PVA in warm water (40-50°C) for 4-12 hours; (7) Rinse and dry the part. Store PVA in an airtight container with desiccant. The QIDI i-Fast direct-drive extruders handle PVA more reliably than Bowden-based MMU systems.
Why is my dual extruder oozing on the print?
Oozing from the inactive nozzle is the most common dual-extrusion problem. Solutions: (1) Reduce inactive nozzle temperature by 10-20°C (e.g., PLA active at 200°C, inactive at 170-180°C); (2) Enable a prime tower (8-12mm diameter) to catch oozed filament; (3) Enable an ooze shield (thin wall around model); (4) Increase retraction to 2-4mm for the inactive nozzle; (5) Add a nozzle wiper (silicone or brass brush) to the printer frame; (6) Lower overall printing temperature; (7) Use silicone nozzle socks. For PETG and ABS (which ooze more), use all of the above.
Can I print TPU with a dual extruder?
Yes, but only with direct-drive extruders. Bowden-based dual extruders (MMUs) struggle with TPU because the flexible filament can buckle in the Bowden tube. The QIDI i-Fast Dual Extruder uses direct-drive extruders, which handle TPU reliably. Tips for TPU dual extrusion: (1) Use TPU in only one extruder (the other for rigid material); (2) Print TPU at 210-230°C, 20-40mm/s; (3) Use direct drive (QIDI i-Fast is direct drive); (4) Ensure the extruder tension is set correctly; (5) Use 1.75mm TPU (not 2.85mm); (6) Design material boundaries on flat surfaces for clean transitions.
How much slower is dual extrusion vs single extrusion?
Dual extrusion is typically 1.5-2.5x slower than single extrusion, depending on the mode: (1) Two-color with 10 switches: 1.5-1.75x slower (prime tower + travel); (2) Two-color with 50 switches: 2-2.5x slower (many switches); (3) PVA soluble support: 1.5-2x slower (PVA prints slower); (4) Dual-material (PLA+TPU): 1.75-2.25x slower (TPU is slow); (5) Mirror mode: only 1.1-1.25x slower (both extruders print simultaneously). The extra time is mainly from the prime tower, travel moves between extruders, and purging. To minimize time, design models with fewer color switches.
What materials can I use with the QIDI i-Fast dual extruder?
The QIDI i-Fast Dual Normal Extruder supports temperatures up to 250°C, covering: PLA (190-220°C), ABS (230-250°C), TPU (210-230°C), PETG (220-240°C), PVA (180-200°C), HIPS (220-240°C), and wood-fill (190-210°C). It does NOT support high-temperature materials like PEEK, PEKK, or PC (which require 300-350°C and a high-temp extruder). The "Normal" designation means standard temperature range. For best results, use the same filament diameter (1.75mm) in both extruders and ensure both materials have compatible printing temperatures.
Do I need a linear rail for dual extrusion?
A linear rail is not strictly required for dual extrusion, but it is highly recommended. The dual extruder assembly is heavier than a single extruder, which can cause: (1) V-wheel flex and ringing at high speeds; (2) Layer shifts due to V-wheel play; (3) Faster V-wheel wear (3-6 months instead of 6-12). The QIDI i-Fast Dual Extruder kit includes an MGN12 linear rail specifically to handle the heavier dual extruder. The linear rail provides ±0.02mm repeatability, eliminates V-wheel maintenance, and enables 150-200 mm/s printing without quality loss. Without the rail, you may need to reduce print speed and acceleration to maintain quality.
How do I fix two-color misalignment?
Two-color misalignment is almost always caused by incorrect nozzle offset. Fix it by: (1) Re-printing the calibration pattern and carefully measuring the X/Y offset; (2) Entering the correct values in the firmware; (3) Printing a two-color test cube and checking alignment; (4) Fine-tuning by 0.1mm increments. If the misalignment is only in Z (one nozzle prints too close/far from bed), adjust the per-extruder Z offset (M217 T1 Z in Marlin, or in QIDI Studio printer settings). If misalignment changes during the print, it may be caused by thermal expansion of the extruder assembly — allow the printer to warm up for 5-10 minutes before starting dual prints.
