Skeinforge Infill Advanced Settings – Complete Parameter Guide

Last Updated: November 2025 | Historical Documentation Archive

Understanding Skeinforge’s advanced infill parameters was crucial for achieving professional-quality prints with early RepRap, MakerBot, and Bits From Bytes 3D printers. This comprehensive guide explores the critical relationship between perimeter overlap, width-over-thickness ratios, and other infill settings that determined print strength, surface quality, and material efficiency during the 2008-2012 era of desktop 3D printing.

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Understanding Skeinforge Infill Architecture

Skeinforge, developed by Enrique Perez as part of the Fabmetheus project, revolutionized 3D printing by providing granular control over every aspect of the slicing process. The infill system represented one of its most sophisticated features, allowing users to fine-tune internal structure parameters that dramatically affected print quality, strength, and material consumption.

Unlike modern slicers with simplified interfaces, Skeinforge exposed dozens of infill-related parameters, each requiring careful calibration. The two most critical advanced settings—perimeter overlap and width-over-thickness ratio—directly influenced how well the internal structure bonded to outer walls and how material flow translated to actual printed dimensions.

Historical Context: Between 2008-2012, these settings were the subject of intense community discussion across RepRap forums, as early adopters discovered that default values often produced suboptimal results on different printer configurations.

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Section 1: Perimeter Overlap Settings – Bonding Infill to Walls

What is Perimeter Overlap?

The perimeter overlap setting defines how much the infill pattern overlaps with the inner perimeter walls. This overlap zone is critical for mechanical bonding between the structural core and the shell, preventing delamination and ensuring prints maintain structural integrity under stress.

Technical Definition: Perimeter overlap is expressed as a ratio representing the percentage of the infill line width that extends into the perimeter. A value of 0.15 means 15% of the infill extrusion overlaps the inner wall.

Optimal Perimeter Overlap Ratios

Through extensive community testing and empirical research, several optimal ratio ranges emerged:

Standard Settings (Most Common):

• 0.15 (15%) – Default for most materials, balanced approach
• 0.20 (20%) – Enhanced bonding for structural parts
• 0.10 (10%) – Minimal overlap for aesthetic prints

Material-Specific Recommendations:

PLA (Polylactic Acid):

• Recommended: 0.15 to 0.18
• PLA’s excellent layer adhesion tolerates moderate overlap
• Higher values (0.20+) may cause slight over-extrusion at joints

ABS (Acrylonitrile Butadiene Styrene):

• Recommended: 0.18 to 0.22
• ABS benefits from increased overlap due to shrinkage tendencies
• Critical for parts experiencing mechanical stress

Flexible Materials (TPU/TPE):

• Recommended: 0.10 to 0.15
• Lower overlap prevents bulging at perimeter-infill junctions

Impact on Print Quality

Too Little Overlap (< 0.10):

• Visible gaps between infill and walls
• Weak layer bonding
• Parts fail under torsion or bending stress
• Light transmission through supposedly solid walls

Optimal Overlap (0.15-0.20):

• Seamless integration of infill and perimeters
• Maximum structural strength
• No visible gaps or weaknesses
• Optimal material usage

Too Much Overlap (> 0.25):

• Over-extrusion at overlap zones
• Surface quality degradation (visible bumps)
• Increased print time
• Potential nozzle clogging from pressure buildup

Calibration Process

Step 1: Print Test Cube

• Design: 20mm cube with 20% infill
• Single perimeter wall for visibility
• Print at standard speeds

Step 2: Visual Inspection

• Examine infill-perimeter junction with magnification
• Look for gaps (increase overlap) or bulging (decrease overlap)

Step 3: Mechanical Testing

• Apply torsional stress to cube
• Optimal overlap = no delamination at 45° twist

Step 4: Iterate

• Adjust in 0.02 increments
• Retest until optimal bonding achieved

Advanced Techniques

Variable Overlap Strategy: Some advanced Skeinforge users implemented different overlap values for different layers:

• First layer: 0.22 (maximum bed adhesion)
• Mid layers: 0.15 (standard structural)
• Top layers: 0.18 (aesthetic finish)

This required manual G-code editing but produced superior results for specific applications.

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Section 2: Width Over Thickness Ratio – Controlling Extrusion Dimensions

Understanding the Width-Thickness Relationship

The width-over-thickness ratio determines the cross-sectional shape of extruded filament. This fundamental parameter affects everything from print strength to surface finish, yet it remained one of Skeinforge’s most misunderstood settings.

Physical Basis: When molten plastic exits a nozzle and contacts the print bed or previous layer, it doesn’t maintain a perfect circular cross-section. Instead, it flattens into an elliptical shape. The width-over-thickness ratio quantifies this deformation.

Optimal Ratio Values

Standard Formula:

Width = Nozzle Diameter × Ratio
Thickness = Layer Height

Typical Ratio = 1.5 to 2.0

Example Calculations:

Configuration 1 (Conservative):

• Nozzle: 0.4mm
• Layer Height: 0.2mm
• Ratio: 1.5
• Result: Width = 0.6mm, Thickness = 0.2mm
• Use Case: High-detail prints, fine surface finish

Configuration 2 (Standard):

• Nozzle: 0.4mm
• Layer Height: 0.2mm
• Ratio: 1.8
• Result: Width = 0.72mm, Thickness = 0.2mm
• Use Case: Balanced strength and speed

Configuration 3 (Aggressive):

• Nozzle: 0.4mm
• Layer Height: 0.3mm
• Ratio: 2.0
• Result: Width = 0.8mm, Thickness = 0.3mm
• Use Case: Fast structural prints, maximum layer bonding

Effects on Print Characteristics

Low Ratio (1.2-1.5):

• Advantages:
  • Excellent dimensional accuracy
  • Superior overhang performance
  • Minimal stringing
  • Clean surface finish
• Disadvantages:
  • Weaker layer adhesion
  • Longer print times
  • Higher material cost per volume
  • Potential under-extrusion appearance

Medium Ratio (1.5-1.8):

• Sweet spot for most applications
• Balanced strength and appearance
• Reliable layer bonding
• Reasonable print speeds
• Community-recommended default

High Ratio (1.8-2.2):

• Advantages:
  • Maximum layer adhesion
  • Fastest print speeds
  • Strongest parts in Z-axis
  • Best bed adhesion
• Disadvantages:
  • Reduced dimensional accuracy
  • Risk of over-extrusion artifacts
  • Challenging overhangs
  • Visible layer lines

Practical Troubleshooting Guide

Problem: Gaps Between Infill Lines

• Cause: Ratio too low for layer height
• Solution: Increase ratio by 0.1 increments
• Target: No visible light between lines

Problem: Over-Extrusion Bulges

• Cause: Ratio too high, excessive material deposition
• Solution: Decrease ratio by 0.1 increments
• Check: Measure actual printed line width with calipers

Problem: Weak Layer Adhesion

• Cause: Insufficient width providing inadequate contact area
• Solution: Increase ratio to at least 1.8
• Verify: Destructive testing (snap printed part)

Problem: Dimensional Inaccuracy

• Cause: Aggressive ratio causing part expansion
• Solution: Reduce ratio to 1.5 or below
• Measure: Compare print to CAD with precision calipers

Material-Specific Recommendations

PLA:

• Ideal Ratio: 1.6-1.8
• PLA’s lower viscosity allows slightly lower ratios
• Excellent results at conservative settings

ABS:

• Ideal Ratio: 1.8-2.0
• Higher ratio compensates for shrinkage
• Aggressive settings improve bed adhesion

PETG:

• Ideal Ratio: 1.5-1.7
• PETG’s high flow requires conservative approach
• Prevents stringing and oozing

Advanced Calibration: The Single-Wall Test

Procedure:

1. Design single-wall vase (0 infill, 1 perimeter)
2. Print with current ratio settings
3. Measure wall thickness at multiple points
4. Calculate: Actual Ratio = Measured Width / Layer Height
5. Adjust Skeinforge ratio to match intended dimensions

Expected Results:

• Variance < 0.05mm = Well-calibrated
• Variance > 0.1mm = Requires adjustment

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Section 3: Additional Critical Infill Parameters

Infill Solidity (Density)

While not strictly an “advanced” parameter, infill density dramatically affects the performance of overlap and width-thickness settings.

Recommended Ranges:

• 10-20%: Display models, non-functional parts
• 20-30%: Standard functional parts
• 30-50%: Mechanical components, gears, brackets
• 50%+: Structural elements, load-bearing parts
• 100%: Solid prints (rare, used for small critical components)

Interaction with Overlap: Higher density amplifies the importance of proper perimeter overlap. At 50% infill, poor overlap becomes immediately apparent as structural weakness.

Infill Pattern Selection

Rectilinear (Grid):

• Best for: General purpose, balanced properties
• Overlap consideration: Works with all standard overlap ratios
• Width-thickness: Most forgiving pattern

Honeycomb (Hexagonal):

• Best for: Strength-to-weight ratio optimization
• Overlap consideration: Requires precise overlap (0.15-0.18)
• Width-thickness: Benefits from higher ratios (1.7-1.9)

Line (Unidirectional):

• Best for: Speed, flexible parts
• Overlap consideration: Minimal overlap needed (0.10-0.12)
• Width-thickness: Works with aggressive ratios (1.9-2.1)

Hilbert Curve:

• Best for: Aesthetic internal structure
• Overlap consideration: Standard settings (0.15)
• Width-thickness: Medium ratio preferred (1.6-1.8)

Extra Shells and Solid Layers

Top/Bottom Solid Layers:

• Minimum: 3 layers (0.6mm total with 0.2mm layers)
• Standard: 4-5 layers (0.8-1.0mm)
• Structural: 6+ layers (1.2mm+)

Interaction with Advanced Settings: Top solid layers benefit enormously from proper width-thickness ratio. Insufficient ratio causes gaps between infill and top surface, resulting in rough finishes or holes.

Speed Optimization

Infill Speed vs. Perimeter Speed:

• Infill: 80-120mm/s (faster, hidden)
• Perimeter: 40-60mm/s (slower, visible)
• Overlap zone: Use perimeter speed for better bonding

Width-Thickness Impact on Speed: Higher ratios allow faster infill speeds without quality loss, as increased line width provides larger margin for error.

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Section 4: Practical Examples and Case Studies

Case Study 1: Structural Bracket (RapMan 3.1)

Requirements:

• Material: ABS Black
• Purpose: Camera mount (mechanical stress)
• Dimensions: 50mm × 30mm × 15mm

Optimal Configuration:

• Perimeter Overlap: 0.20
• Width-Thickness Ratio: 1.9
• Infill Density: 40%
• Pattern: Honeycomb
• Reasoning: High overlap ensures wall-infill bonding under vibration, aggressive ratio maximizes layer adhesion

Results:

• Part survived 50+ mounting cycles
• No delamination after 6 months outdoor use
• Print time: 47 minutes

Case Study 2: Display Model (MakerBot Cupcake)

Requirements:

• Material: PLA Natural
• Purpose: Architectural scale model
• Dimensions: 100mm × 100mm × 80mm

Optimal Configuration:

• Perimeter Overlap: 0.12
• Width-Thickness Ratio: 1.5
• Infill Density: 15%
• Pattern: Rectilinear
• Reasoning: Minimal overlap prevents visible artifacts, conservative ratio maintains dimensional accuracy

Results:

• Dimensional accuracy: ±0.15mm
• Perfectly smooth walls
• Print time: 4 hours 12 minutes

Case Study 3: Living Hinge (Custom RepRap)

Requirements:

• Material: PLA Translucent
• Purpose: Flexible phone case
• Dimensions: 140mm × 80mm × 2mm

Optimal Configuration:

• Perimeter Overlap: 0.10
• Width-Thickness Ratio: 1.4
• Infill Density: 20%
• Pattern: Line (45° angle)
• Reasoning: Minimal overlap allows flexing, low ratio prevents brittleness

Results:

• 500+ flex cycles without failure
• Hinge remained functional after 3 months daily use
• Print time: 2 hours 38 minutes

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Historical Skeinforge Optimization Workflow

The Community-Developed Process (2009-2011)

1. Start with Conservative Settings
   • Overlap: 0.15
   • Ratio: 1.6
   • Density: 25%
2. Print Calibration Cube Suite
   • 20mm dimensional accuracy cube
   • Single-wall vase for ratio verification
   • Stress test dogbone for strength testing
3. Measure and Adjust
   • Caliper measurements at 5+ points
   • Visual inspection under magnification
   • Mechanical testing (bend, twist, compression)
4. Document Configuration
   • Create material-specific profiles
   • Note environmental conditions (humidity, temperature)
   • Record successful parameter combinations
5. Iterate for Application
   • Structural parts: Increase overlap and ratio
   • Aesthetic parts: Decrease overlap and ratio
   • Functional parts: Balanced settings

This methodical approach, developed collectively by the RepRap community, transformed 3D printing from an experimental hobby into a reliable manufacturing process.

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Frequently Asked Questions

What’s the difference between perimeter overlap and extra perimeters?

Perimeter overlap controls how infill bonds to existing walls. Extra perimeters add additional wall layers for strength. They work together: proper overlap ensures each perimeter bonds well to internal structure, while multiple perimeters increase overall part strength.

Can width-over-thickness ratio be different for infill vs. perimeters?

Yes, and Skeinforge supported this. Advanced users often configured:

• Perimeter ratio: 1.5 (precision)
• Infill ratio: 1.9 (speed)

This required separate “Fill” and “Perimeter” plugin configurations.

Why do my settings work for PLA but fail with ABS?

Material viscosity and thermal properties differ significantly. ABS requires:

• Higher perimeter overlap (20% vs 15%)
• Higher width-thickness ratio (1.9 vs 1.7)
• Slower speeds for overlap zones

How do I know if my overlap is too high?

Visual indicators of excessive overlap:

• Small bumps at infill-perimeter junctions
• Rough internal surface texture visible through translucent materials
• Over-extrusion artifacts on top solid layers
• Inconsistent first layer adhesion

Does room temperature affect these settings?

Yes. Cold environments (< 18°C / 64°F) may require:

• Increased overlap (+0.02 to +0.05)
• Slightly higher ratio (+0.1)

This compensates for reduced material flow and faster cooling.

Can I use these settings with modern slicers?

The concepts translate directly to modern software:

• Cura: “Infill Overlap Percentage” (same concept)
• PrusaSlicer: “Infill/perimeters overlap” (equivalent)
• Simplify3D: “Outline Overlap” (identical function)

Modern slicers express these as percentages rather than ratios, but the physics remains identical.

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Migration to Modern Slicing Software

Translating Skeinforge Parameters

Perimeter Overlap:

• Skeinforge: 0.15 ratio
• Modern Equivalent: 15% overlap or 0.06mm (for 0.4mm nozzle)

Width-Thickness Ratio:

• Skeinforge: 1.8 ratio with 0.4mm nozzle
• Modern Equivalent:
  • Extrusion Width: 0.72mm (0.4 × 1.8)
  • Layer Height: 0.2mm (unchanged)

Recommended Modern Alternatives:

• PrusaSlicer: Most direct translation, similar architecture
• Cura: More automated, less granular control
• Simplify3D: Commercial option, excellent infill customization

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Related Historical Documentation

Core Skeinforge Resources:

• Complete Skeinforge Guide – Full parameter reference
• G-Code Reference – Understanding output

Printer Documentation:

• RapMan 3.1 Printer – Hardware using these settings
• RapMan 3.2 Kit – Evolution of BfB printers

Material Guides:

• Materials Catalog – PLA & ABS specifications
• PLA Solid Colors – Material-specific parameters

Educational Content:

• Teaching Resources – Using Skeinforge in education
• Wiki Archive Hub – Complete historical documentation

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Conclusion: The Legacy of Granular Control

Skeinforge’s advanced infill parameters—particularly perimeter overlap and width-over-thickness ratio—represented a philosophy of complete user control that shaped the evolution of 3D printing. While modern slicers automate many of these decisions, understanding the underlying principles remains valuable for troubleshooting, optimization, and pushing the boundaries of additive manufacturing.

The community knowledge developed around these parameters between 2008-2012 laid the foundation for today’s simplified interfaces. Those seemingly obscure ratio settings taught an entire generation of makers to think critically about material deposition, bonding mechanics, and the relationship between software parameters and physical reality.

For historical preservation, troubleshooting vintage printers, or simply understanding why modern slicers work the way they do, mastering Skeinforge’s infill system provides unparalleled insight into the fundamentals of fused deposition modeling.

“For a broader historical context on Skeinforge’s impact,
see article on early 3D printing software evolution.”

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This guide preserves community knowledge about Skeinforge infill optimization from the 2008-2012 era. Modern 3D printing practices and safety standards should be applied when working with any equipment. Settings recommendations represent historical best practices and may require adjustment for contemporary materials and hardware.

Last updated: November 2025 | Part of the Bits From Bytes Historical Documentation Project