How Do You Control Shrinkage in 3D Printing?

What Is Material Shrinkage?

Shrinkage is the size reduction of a part as it cools or cures. When you heat plastic to melt it, it expands. When it cools on the print bed, it contracts. The same happens with resin: liquid turns to solid, taking up less space.

What Causes the Shrinkage?

Three main factors drive the change:

1. Thermal Contraction: Hot material takes more space. As it cools, molecules move closer. This causes volume loss.
2. Curing Shrinkage (Resin): UV light links liquid resin molecules into a solid polymer network. This process pulls material inward.
3. Internal Stress: Different parts of your print cool at different speeds. This uneven cooling creates pull forces inside the part, warping edges and changing size.

Key Term: The Coefficient of Thermal Expansion (CTE) measures how much a material grows with heat. A high CTE means more shrinkage as it cools.

Real Case: A team printed a large ABS housing. The room was cold. The bottom layers cooled fast, the top stayed hot longer. This stress made the part warp up at the corners and shrink more than 1% in length. The part did not fit.

How Much Do Common Materials Shrink?

Each material has a typical shrinkage range. Knowing this helps you pick the right one.

What Are the Numbers?

See this table for key data.

Example: A 200 mm long part in ABS could shrink up to 1.6 mm (0.8% of 200 mm). The same part in PLA might only shrink 1.0 mm.

Why Do Resins Shrink More?

Resin shrinkage is mainly chemical, not thermal. Liquid resin molecules are far apart. When UV light cures it, they form tight bonds. This polymerization pulls the structure inward much more than cooling plastic. This is why resin prints need more compensation.

How Can You Predict Shrinkage?

You need to know the exact rate for your material, your printer, and your settings.

Can You Rely on Vendor Data?

Vendor data is a good start, but it’s a range from lab tests. Your real rate depends on your print environment. Always run a calibration test.

How to Run a Shrinkage Test?

Print a simple test cube (e.g., 50 x 50 x 10 mm). Use your normal settings.

1. Let the part cool fully (for 24 hours).
2. Measure each side with calipers.
3. Calculate: Shrinkage % = [(Design Size – Actual Size) / Design Size] x 100.

Do this test for each new spool or resin bottle. Humidity and age change material behavior.

Pro Tip: Print the test part flat on the bed. Do not use a raft. This gives the most true size reading.

What Are the Main Control Methods?

You have four powerful tools to fight shrinkage: Design, Material Choice, Print Settings, and Post-Process.

Can Design Fix Shrinkage?

Yes. Use shrinkage compensation (scaling) in your slicer or CAD model.

• If your test shows 0.6% shrinkage, scale the model up by 1.006x (100.6%).
• For resin, you may need to scale by 1.02x to 1.035x.

Important: Scaling works best for simple, solid shapes. For very complex parts with thin walls, scaling can distort details. Test on a small section first.

How Does Material Choice Help?

Pick a material with low inherent shrinkage for critical dimensions.

• For FDM, PLA is the most stable. Use it when size is key.
• For resin, choose low-shrink or “engineering” resins. They cost more but change less.

Case Study: A watch designer needed a precise casing prototype for fit check. They first used standard resin. Shrinkage was 3%, ruining the tolerance. They switched to a low-shrink dental model resin (1.2% shrinkage). The next print fit perfectly.

What Print Settings Reduce Shrinkage?

Tune your machine to promote even, slow cooling.

For FDM Printers:

• Lower Nozzle Temp: Use the lowest temperature that gives good layer bond. High temp means more expansion, then more contraction.
• Use a Heated Bed & Enclosure: Keep the part warm as it builds. This reduces the temperature gradient. For ABS, use a bed at 100-110°C inside a closed chamber.
• Slower Print Speed: This allows more even cooling between layers.
• Optimize Infill: High infill (80-100%) has more material to shrink, causing more pull. Use the minimum infill your part needs for strength. 20-40% is often enough.

For Resin Printers:

• Post-Cure Slowly: Do not cure a wet part under strong UV right away. Let it dry fully, then cure in warm water (30-40°C). This reduces stress.
• Orient Parts Smartly: Place the part at an angle. This spreads shrinkage forces, preventing big warp on one side.

Does Post-Processing Help?

Yes, you can fix small errors after printing.

• Heat Treatment (Annealing): For FDM parts (PLA, ABS, Nylon). Bake the part in an oven at a set temperature (e.g., 80°C for PLA). This relaxes internal stress and can make size more stable. Warning: Annealing can also cause new shrinkage of 1-2%. You must test and compensate for this too.
• Conditioning: For Nylon, storing the part in a dry box for a few days lets it reach a stable size.

What About Warping and Cracking?

Shrinkage does not just make parts smaller. It causes warping, layer splitting, and cracks.

Why Do Corners Lift?

The bottom layer cools fast and sticks to the bed. The top layers are hot. As they cool, they contract and pull the edges up. This is classic warping.

Solutions:

• Use a brim (5-10mm wide) around the part. It holds edges down.
• Apply adhesive like glue stick or hairspray on the bed for better grip.
• Ensure your first layer is perfectly squished and flat.

What Causes Cracks Between Layers?

If one layer cools and shrinks fast, it pulls away from the hot layer above. This creates a weak bond or crack.

Solutions:

• Increase printing temperature slightly for better layer fusion.
• Use an enclosure to keep the whole part warm during the print.
• Choose a material with lower shrinkage, like PETG over ABS for large parts.

Is Shrinkage Always Bad?

Not always. In some cases, you can use it. Press-fit and snap-fit joints rely on a tiny bit of shrinkage for a tight grip. Design the joint with a 0.2-0.5 mm interference. The shrinkage will make the final fit perfect.

Example: A snap clip was designed with 0.3 mm extra width. After PLA shrinkage, the clip fit snugly onto a 10.0 mm rod without being loose.

How to write a spec that gets priced correctly

A drawing is a contract. If it leaves a number open, the shop fills that number in with its own default. The default is rarely the one you had in mind. Put these five lines on every RFQ and most of the back-and-forth disappears before it starts.

• File format and units, with the model exported in millimetres
• Process and material grade, not a trade name
• Critical features and the tolerance each one needs
• Surface finish and the faces it applies to
• Quantity for the pilot build and for the year

The point is not paperwork. Each line removes a decision the shop would otherwise make for you. A complete RFQ comes back priced. An incomplete one comes back guessed.

What actually drives the price

Buyers usually push on material because it is the line they can see. In practice the material is rarely the biggest number on a quote. These five lines decide most of it:

• build volume and orientation
• layer height and support structure
• material grade and colour
• post-processing and hand finishing
• quantity per build plate

Ask for the quote split by line. A supplier who cannot break it down is guessing, and you will pay for the guess. The line you can usually renegotiate is the tolerance band, not the raw material.

Problems you will meet, and the fix

Every process has a failure mode it prefers. The same four show up again and again on this kind of work, and none of them are mysteries once you know what to look for.

• Warping on long flat faces where the part lifts off the plate
• Layer lines showing through a cosmetic surface
• Support scars on a mating face nobody flagged
• Dimensional drift on thin walls after cooling

Catch the fault on the first part, not the hundredth. A first-article check costs an hour. A bad batch costs the whole order. Write the check into the purchase order so nobody has to remember it.

What to check on the first article

The first article is the cheapest inspection you will ever buy. Use it properly and the rest of the run becomes boring, which is exactly what you want.

• Every dimension on the drawing, with the measured value written beside it.
• The material certificate, matched to the heat or lot number on the parts.
• The finish against the sample you approved, under the same light.
• Fit against the mating part, assembled rather than measured.
• Packaging, because parts that arrive damaged were never in tolerance.

Check in this order: datums, then mating features, then cosmetic faces. If the datums are wrong, every number after them is noise. Keep the report on file. When a problem shows up in month six, that document is the only thing that tells you what changed.

How to compare two quotes fairly

Two numbers are not comparable unless the scope matches. Line them up before you decide, because a low number with three gaps is not a low number.

Same drawing, same material, same finish, same inspection. Anything else is a different job wearing the same part number. Then look at what each quote leaves out. Freight, packaging, certificates and tooling are the usual gaps.

Ask each supplier to state their assumptions in writing. The one who does is usually the one who has run the process before.

Scaling from one part to a batch

The first part teaches you the process. The hundredth teaches you the process cost.

Watch three things as volume grows: setup amortisation, tool wear, and how much hand work the finish still needs. If the unit price barely moves between ten and a hundred, the cost sits in material or in hand work, not in setup. Ask which, because only one of them is negotiable.

Lead time behaves the same way. A one-off is scheduled around other jobs. A repeat order is scheduled around your forecast. Give the shop a forecast and the lead time gets shorter, not longer.

How to read a supplier's quote

A quote is a short document with a long shadow. Four things in it decide whether the job runs smoothly, and only one of them is the price.

• The scope line. It should name the process, the material and the finish, not just the part.
• The tolerance basis. General tolerance or the drawing, and which standard it follows.
• The exclusions. Tooling, freight, certificates and inspection are the usual omissions.
• The validity date. Material prices move, and an open-ended quote is a promise nobody can keep.

Read the exclusions before you read the total. A quote that leaves out tooling is not cheaper. It is a quote for a different job.

What to send with the first order

The first order sets the pattern for every order after it. Send a complete package once and the shop files it, and the second order takes a fraction of the time.

• A STEP or native model plus a PDF drawing carrying the same revision letter.
• The material callout by standard number, not by trade name.
• The finish and the exact faces it applies to.
• Any test the part must pass: fit, seal, drop, salt spray, dielectric.
• A contact who can answer a question inside one working day.

Then write down what was agreed. An email that confirms the material, the finish and the date is worth more than a longer purchase order that leaves them open.

How Do You Create a Reliable Process?

Follow this step-by-step plan for any new project.

1. Define Your Tolerance: How precise does the part need to be? ±0.1 mm? ±1 mm?
2. Pick Your Material: Choose based on your tolerance and part function. Use the shrinkage table.
3. Run Calibration Tests: Print a test cube with your chosen material and settings. Measure and calculate the real shrinkage rate.
4. Compensate in Your Model: Scale your final design in the slicer by your measured rate.
5. Optimize Print Settings: Set the right temperatures, use an enclosure, add a brim.
6. Post-Process if Needed: Anneal the part if required for stability. Measure again after.
7. Document Everything: Keep a log of material, settings, and results. This builds your own knowledge base.

Shrinkage in 3D printing is a predictable force, not a random error. PLA and low-shrink resins offer the most size stability. You can control shrinkage through smart design scaling, careful material choice, and controlled print settings. Always run a real-world calibration test for critical dimensions. Remember that post-processing like annealing can also change size. By understanding and planning for shrinkage, you move from failed prints to precise, reliable parts every time.

Our solution for Control Shrinkage

YiguProto runs 3D printing in house, from a single prototype to a production batch. We quote the process, the material and the finish as separate lines, so you can see where the money goes instead of arguing with one number.

Send a STEP file or a drawing and you get a DFM report in one to two business days. It flags the features that add cost and the features that will not hold tolerance on the process you picked.

Every order ships with an inspection report on the features you call out. If a part misses, we make it again. Ready to price a part? Start with a free quote and DFM review, or read more about our 3D printing. You can also talk to an engineer before you commit to a drawing.

FAQ about Control Shrinkage

The short version

Control Shrinkage rewards the buyer who reads the data sheet and the drawing together. Pick the option for the property that matters, not for the price per kilo.

Tighten only what mates. Test a sample before the run. Then let the process do the rest.