PLA, ABS, Nylon & PETG Shrinkage & Compensation: Essential Facts

Have you ever considered how to achieve perfect-sized 3D prints while avoiding warping and cracking issues? In the realm of 3D printing, where material shrinkage poses a significant challenge, do you know how to tackle it to ensure print quality? Let's explore the art of cleverly addressing material shrinkage in 3D printing.

Example of 3D Prints Shrinkage

What is 3D Print Shrinkage?

3D print shrinkage refers to the contraction of a 3D printed material as it cools after being extruded and formed. This shrinkage occurs because plastics and other materials expand slightly when heated to high temperatures during printing.

As the material rapidly cools, it starts to shrink back down, reducing the overall dimensions of the print. Shrinkage happens to some degree with almost all 3D printing filaments and resins.

Typical shrinkage rates are 0.3% for materials like PLA to up to 0.7-0.8% for flexible materials like Nylon. The amount of shrinkage depends on factors like:

• Print temperature
• Cooling rate
• Geometry of the print
• Number of perimeters/shells
• Infill pattern and density

Accounting for the specific shrinkage rate of your material is important to get accurately sized prints that match your digital designs. Warping and cracking can also happen if shrinkage is not properly controlled.

Factoring Material Shrinkage into Your 3D Prints

To get quality 3D printed parts, shrinkage needs to be factored into your print settings and modeled geometry. Here’s how to account for shrinkage when 3D printing:

• Adjust model dimensions: Scale up the model by the expected shrinkage rate for your material. For a 2% shrinkage, scale the model up to approximately 102%.
• Modify custom Gcode: Add commands to scale up extrusion like modifying the XY axes steps/mm.
• Use perimeter gaps: Separate perimeters allow room for contraction.
• Increase number of perimeters: More perimeters reduces shrinkage.
• Optimize print orientation: Minimize surface area exposed to cooling to reduce shrinkage.
• Slow the print speed: Slower cooling reduces material contraction.
• Preheat the bed: A heated bed keeps the material warm and flexible during printing.

Taking shrinkage into consideration, especially when printing large or dimensionally sensitive objects, will ensure your 3D prints come out sized correctly without defects.

Why Shrinkage and Warping Occur

PLA Shrinkage and Compensation

PLA (polylactic acid) is one of the most popular and versatile 3D printing materials. Derived from renewable cornstarch, it provides a glossy, low-friction surface finish and prints easily with minimal warping. And you need to pay attention to the PLA settings to create better quality prints.

The shrinkage rate of PLA filament falls between 0.3% on average. This is relatively low compared to other materials, but still must be accounted for, especially when printing large objects.

To compensate for PLA’s shrinkage:

• Scale up models to 100.3% in your slicer software. OrcaSlicer, Cura, Simplify3D, and others have shrinkage compensation settings.
• Print with 3-4 solid perimeters. Multiple shells prevent cracks and hold dimensions.
• Use a raft or brim to improve bed adhesion as PLA shrinks. This prevents warping.
• Reduce print speed for better layer adhesion and slower cooling. 60 mm/s is ideal for PLA.

With its low shrinkage rate, PLA is an excellent material for high precision prints when proper scaling and print settings are used.

3D Printed Retractable Predator Cosplay Spear - High-precision Spear Printed with PLA

ABS Shrinkage and Compensation

ABS (acrylonitrile butadiene styrene) is a durable, versatile plastic commonly used for 3D printing. It’s especially popular for functional parts that need good impact resistance.

The shrinkage rate for ABS is slightly higher than PLA, averaging 0.4-0.9% overall. Besides, ABS warps easily as it cools and contracts. In fact, when it comes to 3D  printing, PLA and ABS  have more differences other than the shrinkage rate. 

To account for ABS shrinkage:

• Scale models up to 100.4-100.9% in your slicer to match final dimensions.
• Increase the number of perimeters to at least 4 solid shells.
• Use a heated print bed to reduce warping as ABS shrinks. 90-110 ̊C is recommended.
• Print more slowly to prevent defects and improve accuracy. 40 mm/s is ideal for ABS.
• Use an enclosure to control cooling if printing large ABS objects.

Adding extra perimeters is one of the most effective ways to reduce ABS shrinkage. This strengthens edges and corners.

Nylon Shrinkage and Compensation

Nylon is a popular flexible filament known for its strength, durability, and ability to bend rather than break under stress. However, nylon’s flexibility comes from its semi-crystalline structure which is highly prone to shrinking.

Nylon shrinks substantially as it cools, typically around 0.5-1.5%. This is 3-4 times greater than the shrinkage seen in PLA or ABS.

To compensate for nylon’s high shrinkage:

• Scale models up significantly, from 100.5-101.5%.
• Use a heated chamber to reduce cooling and crystallization.
• Print very slowly, 15-25 mm/s, for even cooling.
• Increase number of perimeters to 8-10 solid shells for rigidity.
• Use large layer heights like 0.28 mm to speed crystallization.

The heated chamber is one of the best ways to reduce nylon’s shrinkage by controlling the cooling process. Slow prints also allow the material to solidify more uniformly.

Shrinkage of Parts in 3D Printing

PETG Shrinkage and Compensation

PETG (polyethylene terephthalate glycol-modified) is a durable, lightweight filament known for its strength, flexibility, and ease of printing. Unlike many materials, PETG shrinks minimally, generally 0.3-0.8%.

PETG’s chemical composition gives it a very low shrinkage rate compared to other common filaments. Its amorphous structure solidifies with little contraction.

To work with PETG’s minimal shrinkage:

• Scale models up to 100.3-100.8% in your slicer to match final dimensions.
• Use default print profiles like those for PLA.
• Increase infill slightly to 5-15% for a bit more structure.
• Slow down for overhangs to prevent sagging as PETG remains molten longer.

With such low shrinkage, PETG parts print very accurately to their modeled dimensions. This makes PETG a great choice when precision and tolerances are critical.

When designing, consider shrinkage for success. (photo: i.Materialise)

How to Get the Right Shrinkage Compensation

The key to accounting for shrinkage when 3D printing is applying the right compensation. Some software has automatic presets, but often it must be done manually. The compensation depends on the material, temperature, and model geometry. Together these factors indicate how much the print will shrink so you can compensate accordingly.

Getting the compensation right may take some trial and error since shrinkage varies across brands of the same material. A great way to quantify shrinkage is to print a test model and measure how much it shrinks. Then use that data to calculate the compensation.

A useful test model for measuring shrinkage is the Shrinkage Calculation Object from Thingiverse. Users praise it as a great calibration tool. You can also use the horizontal expansion setting to adjust print size in X/Y to account for shrinkage during cooling.

If creating your own models, you can build in shrinkage tolerances through experience. With practice, you'll learn to apply the right tolerances for your designs.

Mastering Shrinkage Compensation for Perfect 3D Prints

Accounting for the shrinkage rates of materials is key to achieving high accuracy with your 3D printed parts. Use the tips outlined for minimizing shrinkage issues when working with PLA, ABS, Nylon, PETG, and other common 3D printing filaments.

With the right shrinkage compensation strategies, you can get perfectly sized prints that match your CAD models exactly, avoid warping and cracking, and dial in your print quality. Be sure to factor in material shrinkage before starting your next 3D printing project!

FAQS:

1. How do you prevent PETG shrinkage?

PETG shrinks minimally,but also needs scale models up to 100.3-100.8%. Default PLA print settings work well. Slightly slowing down overhangs prevents sagging.

2 How do you compensate for PLA shrinkage?

Scale PLA models up to 100.3% in your slicer, use 3-4 solid perimeters, a raft or brim, reduce print speeds to 60mm/s, and preheat the bed to reduce warping.

3. Why does PETG shrink less than ABS?

PETG shrinks less than ABS because of its amorphous structure and glass-like thermal properties. PETG solidifies with minimal crystallization so low contractions.

See Also:

3D Print with ABS: 5 Tips for Perfect Prints

ABS Filament: How to Print Safely?

PLA vs ABS: What's the difference?