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Do Resin 3D Prints Shrink? The Facts Explained

With all the chemical reactions involved in a 3D printing process, it's reasonable to presume there's shrinking involved. Yet is this really the case?

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One prominent concern people have about resin 3D prints is whether they shrink during the printing process. With all the chemical reactions involved in a 3D printing process, it’s reasonable to presume there’s shrinking involved. Yet is this really the case?

Photosensitive resin 3D prints do shrink as you print and cure your models. Typically, a linear shrinkage of approximately 3% can be expected. Shrinkage occurs due to a chemical loss of volume due to the polymerization reaction, accompanied by thermal contraction during cure cool down.

Sizing is crucial when making a 3D print that fits something precisely, which justifies many people’s worry when handling the process.This article will discuss why resin 3D prints shrink and how this can affect your models. Finally, we’ll share tips on how you can reduce resin shrinkage in your 3D prints.

Why Resin 3D Prints Shrink

There are two significant reasons why resin 3D prints shrink. It’s either a thermal expansion and contraction effect or a change on the molecule level.

Thermal Expansion and Contraction

Resin printing involves the photo-polymerization of liquid resin to make rigid plastic models. A high-intensity ultraviolet light is used to instantly cure the resin by triggering a photochemical reaction that results in a cross-linked polymer network. This process generates a lot of heat.

The cured resin layer is immediately blasted with ambient air to help it rapidly cool to properly adhere to the previous layer.

If not taken into consideration, the rapid rise in temperature followed by rapid cooling after polymerization can cause the print to shrink and be severely deformed.

Change on the Molecule Level

The resin’s molecular structure changes dramatically during curing as it changes from short, tiny molecules to long-chain macromolecular polymers.

The liquid resin has small molecules with Van der Waals forces acting on them, whereas the solid-state polymers (solidified resin) have covalent bond lengths between their structural units. Because covalent link lengths are substantially lower than Van der Waals forces, as the liquid resin hardens, the volume of the portion will surely drop, causing the model to shrink.

Effects of Resin Shrinkage on Your 3D Prints

If your 3D print was poorly designed or formed during printing, the shrinkage could cause your 3D model to warp or deform.

Warping occurs when print layers cool too quickly and contract too much. Understanding how to reduce resin shrinkage will help to avoid warping in your 3D prints.

3d resin print object of a sculpture

How To Reduce Resin Shrinkage

Reducing resin shrinkage is an essential step of a successful printing process. To successfully minimize resin shrinkage, here’s what you need to do: 

Choose a High-Quality Resin With Low Shrinkage

High-quality resins with lower shrinkage are available for you, like epoxy adhesives, due to a lack of flexibility or toughness in your resin prints. Warping is more likely to occur when you use less expensive resins with weak properties.

Choosing higher grade resins or resins with robust or flexible properties is the best option to prevent warping in your 3D prints. You can try adding durability to your models by combining strong or flexible resins with regular resin, which has proven successful with no deformation in most prints.

Regulate Room Temperature Accordingly

Whether it’s winter or summer, you can still make your resin 3D prints with low shrinkage as long as you control your room temperature accordingly. Constant room temperature is essential for stable 3D prints that won’t warp from shrinkage.

The temperature impacts how well your resin hardens when exposed to UV light and how well it cures. A high-quality resin 3D printer will control the temperature inside the printer and the curing chambers.

When you control the temperature fluctuations, you can 3D print in cold rooms and hot rooms.

The resin won’t harden entirely during the curing process if the temperatures fall too low in cold rooms. If you want your resin to function effectively, always keep it at room temperature. Maintaining a consistent temperature in your workspace ensures the humidity level doesn’t exceed 50%.

In this case, it all comes down to your power supply and your heated print bed’s ability to create enough power to overcome the cooler surroundings.

Hotter temperatures are usually fine for 3D printing. However, if temperatures reach over 50°C (122°F), it’s best to install effective cooling fans to provide a suitable working environment for the printer. Lowering the print bed temperature is also helpful. In general, try to maintain a temperature of roughly 20°C (68°F).

Reduce Post Curing Temperature and Time

The proper light, heat, and time during post-curing will improve your prints’ physical properties. The length of time it takes for your 3D print to cure is determined by the equipment used, the type of resin used, and the geometry of your 3D print.

Post curing is recommended in all resins because it improves stability, durability, and strength and reduces residual stress in your prints. However, post-curing can also cause thermo-oxidation of the resin, which can degrade your print’s natural fibers.  

If you leave your prints out in the sun for too long in extremely high temperatures, you degrade their rigidity, and they’ll shrink and deform.

Final Thoughts

Shrinkage of resin 3D prints is unavoidable due to changes in temperature and molecular structure of the resin as it solidifies. Excessive resin shrinkage causes your prints to deform, also referred to as warping.

However, the situation can be controlled to avoid warping.

The right print bed temperature is key to a good print. Temperature also plays a big role in resin shrinkage, so you want to regulate your room temperature when it’s cold or hot out. Also, it’s best to use resins with low shrinkage properties and reduce the temperature during the post-curing process and its duration.

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About Ben

I started 3D printing since 2013 and have learned a lot since then. Because of this I want to share my knowledge of what I have learned in the past years with the community. Currently I own 2 Bambulab X1 Carbon, Prusa SL1S and a Prusa MK3S+. Hope you learn something from my blog after my years of experience in 3D printing.