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# Slicers

This document provides some tips for configuring a "slicer" application for use with Klipper. Common slicers used with Klipper are Slic3r, Cura, Simplify3D, etc.

## Set the G-Code flavor to Marlin

Many slicers have an option to configure the "G-Code flavor". The default is frequently "Marlin" and that works well with Klipper. The "Smoothieware" setting also works well with Klipper.

## Klipper gcode_macro

Slicers will often allow one to configure "Start G-Code" and "End G-Code" sequences. It is often convenient to define custom macros in the Klipper config file instead - such as: `[gcode_macro START_PRINT]` and `[gcode_macro END_PRINT]`. Then one can just run START_PRINT and END_PRINT in the slicer's configuration. Defining these actions in the Klipper configuration may make it easier to tweak the printer's start and end steps as changes do not require re-slicing.

See sample-macros.cfg for example START_PRINT and END_PRINT macros.

See the config reference for details on defining a gcode_macro.

## Large retraction settings may require tuning Klipper

The maximum speed and acceleration of retraction moves are controlled in Klipper by the `max_extrude_only_velocity` and `max_extrude_only_accel` config settings. These settings have a default value that should work well on many printers. However, if one has configured a large retraction in the slicer (eg, 5mm or greater) then one may find they limit the desired speed of retractions.

If using a large retraction, consider tuning Klipper's pressure advance instead. Otherwise, if one finds the toolhead seems to "pause" during retraction and priming, then consider explicitly defining `max_extrude_only_velocity` and `max_extrude_only_accel` in the Klipper config file.

## Do not enable "coasting"

The "coasting" feature is likely to result in poor quality prints with Klipper. Consider using Klipper's pressure advance instead.

Specifically, if the slicer dramatically changes the extrusion rate between moves then Klipper will perform deceleration and acceleration between moves. This is likely to make blobbing worse, not better.

In contrast, it is okay (and often helpful) to use a slicer's "retract" setting, "wipe" setting, and/or "wipe on retract" setting.

## Do not use "extra restart distance" on Simplify3d

This setting can cause dramatic changes to extrusion rates which can trigger Klipper's maximum extrusion cross-section check. Consider using Klipper's pressure advance or the regular Simplify3d retract setting instead.

## Disable "PreloadVE" on KISSlicer

If using KISSlicer slicing software then set "PreloadVE" to zero. Consider using Klipper's pressure advance instead.

## Disable any "advanced extruder pressure" settings

Some slicers advertise an "advanced extruder pressure" capability. It is recommended to keep these options disabled when using Klipper as they are likely to result in poor quality prints. Consider using Klipper's pressure advance instead.

Specifically, these slicer settings can instruct the firmware to make wild changes to the extrusion rate in the hope that the firmware will approximate those requests and the printer will roughly obtain a desirable extruder pressure. Klipper, however, utilizes precise kinematic calculations and timing. When Klipper is commanded to make significant changes to the extrusion rate it will plan out the corresponding changes to velocity, acceleration, and extruder movement - which is not the slicer's intent. The slicer may even command excessive extrusion rates to the point that it triggers Klipper's maximum extrusion cross-section check.

In contrast, it is okay (and often helpful) to use a slicer's "retract" setting, "wipe" setting, and/or "wipe on retract" setting.

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