Why Default Profiles Aren't Enough

Default slicer profiles are conservative. They're tuned to work acceptably on most printers with most filaments. Once you understand what each setting actually does, you can tune for your specific hardware and get noticeably better results — smoother surfaces, cleaner overhangs, near-invisible seams, and supports that release without damaging the surface.

I'm using Bambu Studio and a Bambu X1C as the reference, but all of these concepts apply to PrusaSlicer and Cura with equivalent settings.

Pressure Advance (PA) / Linear Advance

When your printer changes direction, the extruder motor keeps pushing filament into the hotend for a brief moment due to inertia and pressure buildup. This causes corner bulging — slightly over-extruded outer corners and under-extruded inner corners.

Pressure Advance (called Linear Advance in Klipper/Marlin) compensates by reducing extrusion slightly before a direction change and increasing it after. The result: sharp, accurate corners at high speeds.

Tuning method:

  1. Print the PA calibration model from Orca Slicer or Bambu Studio's calibration menu
  2. Look for the line where corners are sharpest and the surface is most uniform
  3. Read the PA value from that position (typically 0.01–0.08 for a direct drive; 0.5–2.0 for Bowden)
  4. Enter it as your filament's PA value
; Klipper pressure_advance in printer.cfg
[extruder]
pressure_advance: 0.035        ; tune per filament
pressure_advance_smooth_time: 0.04

Retraction Calibration

Retraction pulls filament back when the nozzle travels across empty space, preventing ooze (stringing). Too little retraction = strings everywhere. Too much = grinding, clogging, or gaps in the print.

Key parameters:

  • Retraction distance: How far to pull back. Direct drive: 0.5–2mm. Bowden: 4–7mm. More is not better — it can pull molten filament into the cold zone.
  • Retraction speed: How fast. 25–45mm/s is typical. Too fast can strip the filament.
  • Wipe before retraction: Move the nozzle along the wall before retracting. Reduces ooze significantly.
  • Combing: Keep nozzle travels inside the model perimeter whenever possible, eliminating exposed travel moves. Dramatically reduces stringing on complex models.

Tuning: Print a retraction tower (available on Printables). Look for the minimum retraction that eliminates visible strings at your printing temperature.

Ironing: Mirror-Smooth Top Surfaces

Ironing makes the slicer do a second slow pass over the top surface with minimal extrusion, essentially remelting and smoothing the top layer. The result looks nearly injection-molded. It adds 10–30% print time for the top layers only.

When to use it: Any print where the top surface will be visible. Signs, tiles, phone stands, decorative objects.

Settings:

  • Ironing flow: 10–15% (just enough to fill micro-gaps)
  • Ironing speed: 15–30mm/s (slow enough for the heat to do its job)
  • Ironing line spacing: 0.1mm (slightly less than nozzle diameter)
  • Monotonic top layer fill pattern: combine with ironing for best results

Support Interface Layers: The Key to Clean Surfaces

Standard supports leave rough, sometimes damaged surfaces where they contact the model. Interface layers — a thin layer of different filament or different settings placed between the support and the model — fix this completely.

Same-Filament Interface

Print the interface layers at 0.1mm height (instead of 0.2mm), with a small Z gap (0.2mm between interface and model), and at a slightly cooler temperature. The thin interface is easier to remove and leaves a cleaner surface.

Multi-Material Breakaway Interface (The Professional Solution)

If you have an AMS/multi-color setup, use a different filament for supports that doesn't bond to your print filament:

  • PLA model + PETG support interface: They don't bond. Support peels off with near-zero surface damage.
  • PLA model + PVA support: PVA dissolves in water. Perfect for complex internal supports.
  • PETG model + PLA interface: Same non-bonding principle, reversed.

In Bambu Studio: Enable "Support interface" → select your support filament slot → set interface layers to 2–3.

Wall Ordering and Seam Placement

Wall ordering: "Inner walls first" vs "Outer wall first."

  • Outer wall first: Better dimensional accuracy. The outer wall is printed when the nozzle is coldest (most filament pressure bled off). Default for Bambu Studio.
  • Inner walls first: Better overhangs. Inner walls provide a ledge for outer walls to rest on at angles just over 45°.

Seam placement: Every closed perimeter loop has a start/end point — the seam. Options:

  • Aligned: All seams in one vertical line. Obvious streak on cylindrical objects, but very clean if hidden behind the model.
  • Random: Distributed around the perimeter. Less visible overall but no single clean surface.
  • Sharpest corner: Hides seams in corners where they're least visible. Best for most objects.
  • Rear: Puts seam at the model's back. Great for figures, busts, display pieces.

Per-Object Modifier Settings

Both PrusaSlicer and Bambu Studio let you apply different settings to specific regions of a model using modifier volumes:

  • Add 100% infill only to stress areas (screw holes, hinges) while using 15% elsewhere
  • Reduce layer height in critical tolerance zones while keeping coarse layers elsewhere
  • Apply different support settings to top overhangs vs. bottom supports

In Bambu Studio: Right-click object → "Add modifier" → select a primitive shape → position it over the critical region → adjust settings for that modifier only.

Arachne vs Classic Perimeter Generator

Arachne (the modern perimeter generator used by Bambu Studio and PrusaSlicer 2.5+) adapts wall width based on the model's geometry instead of using fixed-width extrusions. This produces significantly better thin features, sharp corners, and internal geometry. For almost all prints, Arachne is superior to Classic. The only exception: large flat walls with very few perimeters, where Classic sometimes produces more predictable results.

Temperature Calibration Towers

Different batches of the same filament brand can have slightly different optimal printing temperatures. A temperature tower prints a single object at decreasing temperatures (e.g., 230°C down to 195°C in 5°C steps) so you can see which temperature produces the best layer adhesion, surface quality, and bridging in a single print.

Print one for each new filament spool. Takes 30 minutes and saves hours of failed prints.

Key Takeaways

  • Pressure Advance/Linear Advance is essential at high speeds — tune it per filament type
  • Enable combing to reduce stringing before touching retraction distance
  • Ironing transforms visible top surfaces — worth the extra print time for display pieces
  • Multi-material breakaway support interfaces (PLA + PETG) give near-perfect surface quality under supports
  • Arachne perimeter generator is better than Classic for almost all use cases
  • Calibrate temperature with a temp tower for every new filament batch