Improvements

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Heated Chamber — K2 Plus

The K2 Plus has an actively heated chamber with a dedicated PTC (Positive Temperature Coefficient) heater element. This page explains how the chamber system works in Klipper and how to get the best results from it.

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Hardware Overview

Component	Klipper name	Pin	Type
Chamber heater element	chamber_heater	PC12	heater_generic
Chamber temperature sensor	chamber_temp	PC5	EPCOS 100K thermistor
Chamber cooling fan	chamber_fan (temperature_fan)	PA0	PWM, watermark control
PTC fan (heater companion)	chamber_fan (heater_fan)	!PB14, enable PB2	Auto with heater
PTC power enable	ptc_power	PB2	output_pin, default value 1

The PTC fan (!PB14) runs automatically when chamber_heater is active. The cooling fan (PA0) runs in temperature_fan watermark mode to maintain a target_temp of 35°C when cooling is needed.

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Temperature Ranges

Setting	Value	Notes
Chamber heater max temp	80°C	Hard limit in Klipper config
Chamber sensor max	125°C	Safety limit
Cooling fan target (passive)	35°C	Maintains ambient when not actively heating
verify_heater check_gain_time	345600 s (4 days)	Effectively disabled — chamber heats slowly

80°C is the hard maximum

The chamber_heater max_temp is set to 80°C. Setting a target above this will cause Klipper to shut down. For most materials, 40–60°C is sufficient.

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Recommended Chamber Temperatures by Material

Material	Chamber temp	Notes
PLA	0 (off)	PLA warps in warm chamber; leave off or run cooling
PETG	30–40°C	Mild warmth reduces warping
ABS	45–55°C	Critical for preventing layer delamination
ASA	45–55°C	Same as ABS
PA (Nylon)	50–60°C	Reduces moisture absorption during print
PC	55–70°C	High-temp materials benefit from maximum chamber heat

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Controlling the Chamber

Set chamber temperature

SET_HEATER_TEMPERATURE HEATER=chamber_heater TARGET=45

Wait for chamber to reach temperature

TEMPERATURE_WAIT SENSOR="heater_generic chamber_heater" MINIMUM=43

Turn off chamber heater

SET_HEATER_TEMPERATURE HEATER=chamber_heater TARGET=0

Check current chamber temperature

In Fluidd, the chamber heater appears in the Temperatures panel as chamber_heater with both current and target temperatures displayed.

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Chamber Pre-heat in START_PRINT

For ABS/ASA prints, add chamber pre-heating before bed leveling so the chamber is warm before the first layer:

[gcode_macro START_PRINT]
gcode:
  {% set CHAMBER_TEMP = params.CHAMBER_TEMP|default(0)|float %}
  {% set BED_TEMP = params.BED_TEMP|default(60)|float %}
  {% set EXTRUDER_TEMP = params.EXTRUDER_TEMP|default(200)|float %}

  G28

  {% if CHAMBER_TEMP > 0 %}
    SET_HEATER_TEMPERATURE HEATER=chamber_heater TARGET={CHAMBER_TEMP}
    M140 S{BED_TEMP}
    ; Soak until both bed and chamber are close to target
    M190 S{BED_TEMP}
    TEMPERATURE_WAIT SENSOR="heater_generic chamber_heater" MINIMUM={CHAMBER_TEMP - 3}
  {% else %}
    M190 S{BED_TEMP}
  {% endif %}

  Z_TILT_ADJUST
  BED_MESH_CALIBRATE
  M109 S{EXTRUDER_TEMP}
  LINE_PURGE

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Chamber Cooling After Print

For materials that must cool slowly to avoid warping (ABS, PC), keep the chamber warm during the cool-down phase by leaving the heater on at a reduced temperature for a period after the print ends:

[gcode_macro END_PRINT]
gcode:
  ; ... park toolhead, disable steppers ...
  ; Slow cool: hold chamber at 40°C for 10 minutes then turn off
  SET_HEATER_TEMPERATURE HEATER=chamber_heater TARGET=40
  G4 P600000   ; wait 10 minutes
  SET_HEATER_TEMPERATURE HEATER=chamber_heater TARGET=0
  M140 S0
  M104 S0

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PTC Power Pin

The ptc_power output pin (PB2, default value 1) keeps the PTC circuit enabled. Do not set this to 0 during printing — it would cut power to the chamber heater entirely. The helper script macros do not touch this pin.

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CFS Maintenance — K2 Plus Combo

Regular maintenance of the CFS (Color Filament System) keeps filament changes reliable and prevents clogs, failed cuts, and feed errors.

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Maintenance Schedule

Interval	Task
Every 500g of filament	Clean the purge chute
Every 1kg of filament	Inspect and clean the cutter blade
Every 2kg	Lubricate the CFS feed rollers
As needed	Re-run cutter calibration
After any filament jam	Full inspection before resuming

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Cutter Maintenance

The cutter is the most maintenance-sensitive part of the CFS. A dull or misaligned cutter causes failed filament changes.

Cleaning the Cutter

1. Unload all filament from the active slot.
2. Navigate to the cut position manually using the touchscreen or via Fluidd console:

   G90
   G1 X10 Y200 F12000  ; move to pre-cut position
   

3. Use a soft brush or compressed air to remove filament debris from the cutter blade area.
4. Check the blade for nicks or buildup.

Re-running Cutter Calibration

After cleaning or if cuts are inconsistent, re-calibrate:

• Touchscreen: Settings → CFS → Cutter Calibration

The calibrated cut_pos_x value is saved to the SAVE_CONFIG block in printer.cfg:

#*# [box]
#*# cut_pos_x = -7.40

Check this value is within the valid range: -5.5 to -9.5 (as defined by check_cut_pos_x_max and check_cut_pos_x_min in box.cfg).

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Purge Chute Maintenance

Purged filament collects in the chute area at X=133–160, Y=378. Over time this can build up and cause the wiper to miss.

Cleaning

1. Cool the printer fully.
2. Open the front enclosure panel.
3. Remove any accumulated purge strings and blobs from the chute area.
4. Clean the silicone wiper pad (at X=160–170, Y=374) with IPA if filament residue has built up.

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Feed Roller Maintenance

The CFS units use motorised rollers to push filament. Debris on the rollers causes slipping and under-extrusion during filament changes.

1. Open each CFS unit.
2. Clean the drive rollers with IPA and a cotton swab.
3. Apply a small amount of PTFE-safe lubricant to the roller shafts if they feel stiff.

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RS-485 Cable Check

The CFS communicates with the printer over an RS-485 cable on /dev/ttyS5. If the CFS stops responding:

1. Check both ends of the RS-485 cable are seated firmly.
2. Restart Klipper: /etc/init.d/S55klipper restart
3. Verify the bus is active: ls /dev/ttyS* — /dev/ttyS5 should be present.

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Filament Sensor Calibration

If the filament sensor (filament_switch_sensor filament_sensor on nozzle_mcu:PA11) gives false positives or misses runout:

Check sensor status in Fluidd under Sensors → filament_sensor.

The sensor pin is ^!nozzle_mcu:PA11 — the ^ is a pull-up and ! inverts logic. Do not modify these unless you have replaced the sensor hardware.

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CFS Troubleshooting Quick Reference

Symptom	Likely cause	Fix
Filament not cut cleanly	Dull blade or miscalibrated cut_pos_x	Clean blade, re-run cutter calibration
Filament not feeding to nozzle	Roller debris or RS-485 disconnect	Clean rollers, check cable, restart Klipper
BOX_CHECK_MATERIAL_REFILL triggers constantly	Filament sensor false positive	Check sensor wiring and pin
CFS not responding in Fluidd	RS-485 bus fault	Check cable, restart Klipper
Purge string not wiped off	Silicone wiper dirty or wiper position off	Clean wiper, adjust clean_pos_* in box.cfg
Cut position error after factory reset	SAVE_CONFIG block wiped	Re-run cutter calibration from touchscreen

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Calibrate Extruder — K2 Plus

Extruder calibration (also called e-step calibration) ensures the printer extrudes exactly the amount of filament requested. This improves dimensional accuracy and reduces under/over-extrusion.

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When to Calibrate

Calibrate your extruder when:

• Installing a new extruder or drive gear
• Changing filament diameter significantly
• Noticing consistent under or over-extrusion that is not resolved by slicer flow rate adjustments
• After any extruder hardware modification

The K2 Plus uses a direct drive extruder. The stock rotation_distance in printer.cfg is 6.9 — this is a good starting point but may need fine-tuning for your specific hardware.

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Method 1 — Mark and Measure (Cold)

This is the most accurate method.

1. Remove the bowden tube from the extruder or work with filament loaded.

2. Mark the filament 120mm from the extruder entry point with a marker.

3. From the Fluidd console, command the extruder to move 100mm:

   M83          ; relative extrusion
   G1 E100 F100 ; extrude 100mm slowly
   

4. Measure the distance from the extruder entry to your mark. If the printer extruded exactly 100mm, the distance should now be 20mm.

5. Calculate the actual distance extruded:

   actual_extruded = 120 - remaining_distance
   

6. Calculate the new rotation_distance:

   new_rotation_distance = current_rotation_distance × (100 / actual_extruded)
   

7. Update rotation_distance in the [extruder] section of /mnt/UDISK/printer_data/config/printer.cfg and run FIRMWARE_RESTART.

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Method 2 — Flow Rate Calibration (Hot, Recommended for Fine Tuning)

After setting a baseline rotation_distance, fine-tune flow with a calibration cube:

1. Print a single-wall calibration cube (20×20×20mm, 1 perimeter, 0% infill).
2. Measure wall thickness with calipers.
3. Expected thickness = nozzle diameter (0.4mm).
4. Adjust flow in OrcaSlicer or via M221 S[value] until walls measure correctly.
5. Once happy, bake the flow rate into your filament profile rather than changing rotation_distance further.

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K2 Plus Extruder Notes

The K2 Plus uses a high-torque dual-drive extruder. Key values in stock printer.cfg:

[extruder]
rotation_distance: 6.9
microsteps: 16
max_extrude_only_distance: 1000.0
pressure_advance: 0.038
pressure_advance_smooth_time: 0.038

After calibrating rotation_distance, also consider tuning Pressure Advance for better corner quality. Run:

SET_PRESSURE_ADVANCE ADVANCE=0.04

and adjust while printing until corners are sharp without bulging. Save the final value in printer.cfg.

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