A part may look correct after printing but still fail during assembly. For example, a shaft designed with a 10 mm diameter may not fit into its matching hole if the printed dimensions change by a few tenths of a millimeter. Likewise, a snap-fit enclosure may become too loose after post-processing, while a threaded feature may require additional machining before use.
These dimensional changes are common in 3D printing. Every process produces parts differently because materials expand, shrink, cure, and cool in different ways. Build orientation, part size, wall thickness, and support removal also influence the final dimensions.
Instead of applying the same tolerance to every printed part, engineers usually consider the capabilities of the selected printing process during the design stage. This approach reduces assembly issues, minimizes secondary operations, and improves the likelihood that the first printed part meets its intended fit.
This guide compares the typical tolerance ranges of major 3D printing processes and explains the factors that influence dimensional accuracy, helping you select a suitable process for your application.
What Is Tolerance in 3D Printing?
Tolerance in 3D printing is the allowable difference between the dimensions in a CAD model and the dimensions of the finished printed part. It defines how much a feature can vary while still meeting its intended function. For example, if a hole is designed with a diameter of 20.00 mm and the printing tolerance is ±0.20 mm, the finished hole may measure between 19.80 mm and 20.20 mm.
Unlike CNC machining, 3D printing builds parts layer by layer. Material shrinkage, curing, thermal distortion, build orientation, and post-processing can all affect the final dimensions. Therefore, engineers account for these variations during the design stage by specifying practical tolerances and adequate clearances for mating features.
Tolerances in 3D Printing: What to Expect & Standard Tolerance Ranges by Technology
A 3D printer does not reproduce every CAD dimension exactly. For example, a 100 mm enclosure may print within a few tenths of a millimeter, while a 12 mm hole can finish slightly smaller than its nominal size.
The amount of variation depends on the printing process, material behavior, part geometry, and any finishing steps after printing.
Because of this, 3D printing services publish typical tolerance ranges instead of a single accuracy value. These values indicate what a process can normally achieve under standard production conditions.
They provide a practical starting point during design, although critical features may still require machining, reaming, drilling, or other finishing operations after printing.
The table below compares the dimensional tolerances commonly achieved by major industrial 3D printing technologies.
Typical Tolerance Comparison of 3D Printing Processes
| Process | Typical Dimensional Tolerance | Typical Build Accuracy | Suitable For |
| FDM | ±0.30 – 0.50 mm (±0.5%) | Moderate | Functional prototypes, fixtures, and large parts |
| SLA | ±0.15 – 0.25 mm (±0.2%) | High | Visual prototypes, medical models, and small detailed parts |
| SLS | ±0.20 – 0.30 mm (±0.3%) | High | Functional nylon parts, snap-fit assemblies |
| MJF | ±0.20 – 0.30 mm (±0.3%) | High | Production of plastic parts, housings, and brackets |
| PolyJet | ±0.10 – 0.20 mm | Very High | Fine-detail prototypes, transparent parts |
| Carbon DLS | ±0.10 – 0.20 mm | Very High | End-use polymer components |
| DMLS / SLM | ±0.10 – 0.20 mm | High | Aerospace and medical metal parts |
Engineering Note: These values describe the overall part dimensions rather than every individual feature. Small holes, thin walls, internal channels, and mating surfaces often require additional clearance during design because their dimensional variation can differ from the rest of the printed part.
Designing Parts with Proper Clearance
Proper clearance prevents parts from binding after printing. The required gap depends on the printing process because every technology produces different dimensional variations.
- SLS and MJF: 0.2 to 0.4 mm clearance: These powder-bed processes produce consistent dimensions and do not require support structures. This clearance works well for snap-fit features, hinges, sliding parts, and assemblies with moving components.
- FDM: 0.4 to 0.6 mm clearance: FDM parts typically show greater dimensional variation due to layer height, nozzle size, and material shrinkage. Larger parts, long mating surfaces, and enclosed features often benefit from additional clearance.
- SLA: 0.1 to 0.2 mm clearance: SLA produces fine details and smooth surfaces. However, resin curing can slightly change feature dimensions, especially for holes, slots, and internal cavities. Small clearances usually work well for precision components.
- Increase clearance for large assemblies: Long rails, covers, enclosures, and multi-part assemblies can accumulate dimensional variation across several features. Adding extra clearance simplifies assembly and reduces fitting issues.
- Allow extra space after finishing: Sanding, vapor smoothing, bead blasting, coating, and painting; remove or add material. Review the finishing process before finalizing clearances for mating features.
- Print a fit sample before production: For shafts, bearings, threaded inserts, snap fits, and sliding parts, print a small test coupon first. A simple fit check takes less time than modifying an entire assembly after production.
What Is the Impact of Post-Processing on Tolerances
A printed part may meet the required dimensions immediately after printing, but post-processing can change its final size. Material removal, surface coatings, heat treatment, and curing all affect dimensional accuracy to different degrees. Therefore, any operation performed after printing should be considered during the design stage, especially for mating features and precision surfaces.
Sanding and Surface Finishing
Sanding removes material from the part surface. Hand sanding can round sharp edges and reduce the size of external features, while aggressive sanding may change the flatness on larger surfaces. If the part contains locating faces, sealing surfaces, or precision dimensions, protect these areas during finishing or machine them after printing.
Bead Blasting and Surface Texturing
Bead blasting mainly changes the surface texture with minimal material removal. However, repeated blasting can slightly affect thin edges, small ribs, and delicate features. This process is commonly used to improve surface appearance rather than dimensional accuracy.
Support Removal
Support structures often leave small marks after removal. Manual trimming or grinding can slightly change nearby dimensions, particularly around holes, slots, and thin walls. Support locations should be selected to avoid functional surfaces whenever possible.
UV Curing for Resin Parts
SLA, DLP, and other resin-printed parts continue to stabilize during UV curing. Small dimensional changes can occur as the material fully cures, particularly in thin sections and enclosed features. Designers should account for this during tolerance planning for precision components.
Heat Treatment for Metal Parts
Metal additive manufacturing often includes stress-relief heat treatment before machining or inspection. Although dimensional changes are generally small, internal stress redistribution can affect flatness and straightness on larger components. Critical features are commonly finish-machined after heat treatment.
Painting, Coating, and Plating
Surface coatings add material instead of removing it. Paint, powder coating, electroplating, and similar finishes increase feature dimensions, which can reduce the clearance between mating parts. Holes, threads, and precision fits may require masking or machining after coating.
Factors Affecting Tolerances in 3D Printing
Several conditions during printing can change the final dimensions of a part. Reviewing these factors before production makes it easier to achieve the required fit and reduces unexpected design changes.
- Large parts show more dimensional variation: A 30 mm connector is generally easier to control than a 400 mm enclosure. Small dimensional changes become more noticeable as the overall part size increases.
- Thin sections can move during printing: Long walls, narrow ribs, and thin plates may bend, curl, or distort while the material cools or cures. Keeping the wall thickness more uniform usually produces better results.
- The same part can measure differently after changing its build position: Rotating a model changes how layers are deposited and how supports are added. A hole printed vertically may produce different dimensions than the same hole printed horizontally.
- Small features require additional design allowance: Holes, slots, threads, embossed text, and fine details rarely print exactly as designed. Critical features are often oversized, undersized, or finish-machined after printing.
- Every material behaves differently during production: Nylon, resin, stainless steel, and titanium each shrink or cure differently. Material behavior should always be considered before assigning critical dimensions.
- Support removal can change nearby features: Cutting, sanding, or grinding supports may leave small marks on the surface. Avoid placing supports on locating faces, sealing surfaces, and other functional areas whenever possible.
- Surface finishing changes the final dimensions: Sanding removes material, while painting, plating, and powder coating add material. These changes should be included when designing mating parts.
- Printer setup influences dimensional consistency: Machine calibration, laser alignment, nozzle condition, and process settings all contribute to the final dimensions. Even identical printers may produce slightly different results if they are not calibrated equally.
- Part geometry often influences accuracy more than the tolerance value itself: Simple blocks usually print close to their nominal dimensions. Complex shapes with deep pockets, overhangs, internal channels, and large flat surfaces are more likely to require dimensional adjustments.
Summary Table: Factors Affecting 3D Printing Tolerances
Different production variables influence the final dimensions of a printed part. The table below summarizes their typical impact and common engineering practice.
| Factor | Typical Value / Range | Effect on Tolerance | Engineering Recommendation |
| Material Shrinkage | PLA: 0.2 – 0.8%
ABS: 0.7 – 1.8% PA12 (SLS/MJF): 1.5 – 2.5% Photopolymer Resin: 0.3 – 1.2% Metal (DMLS): compensated by software |
Dimensional reduction after cooling, curing, or sintering | Use process-specific shrinkage compensation supplied by the manufacturer. |
| Layer Height | FDM: 0.10 – 0.30 mm
SLA: 0.025 – 0.10 mm MJF: 0.08 mm SLS: 0.10 mm DMLS: 0.02 – 0.06 mm |
Smaller layers improve detail on curved and angled surfaces. | Use finer layers for sealing surfaces, threads, and cosmetic features. |
| Minimum Wall Thickness | FDM: ≥1.0 mm
SLA: ≥0.6 mm SLS: ≥0.8 mm MJF: ≥0.8 mm DMLS: ≥1.0 mm |
Thin walls may warp, crack, or distort during production. | Keep wall thickness uniform throughout the model. |
| Minimum Hole Diameter | FDM: ≥2.0 mm
SLA: ≥0.5 mm SLS/MJF: ≥0.8 mm DMLS: ≥1.0 mm |
Small holes often print undersized. | Drill or ream precision holes after printing if required. |
| Feature Size | Embossed text: ≥0.5 mm
Engraved text: ≥0.4 mm |
Very small features may lose definition. | Increase feature size beyond the minimum process capability. |
| Part Size | Parts above 300 – 400 mm generally show greater dimensional variation. | Thermal movement increases across long distances. | Split oversized components into multiple sections where practical. |
| Support Structures | Process dependent | Support removal may affect nearby surfaces. | Avoid placing supports on locating faces and sealing surfaces. |
| Surface Finishing | Sanding: removes 0.05 – 0.30 mm
Powder coating: adds 60 – 120 μm Painting: adds 30 – 80 μm |
Final dimensions change after finishing. | Include machining or coating allowance during design. |
Get Custom 3D Printed Parts from Premium Parts
A good CAD model does not always produce a part that fits on the first build. Features such as holes, locating pins, threads, and mating surfaces often require process-specific adjustments before printing. Reviewing these details early reduces design changes and unnecessary finishing after production.
Premium Parts works with customers from prototype development through production. Our engineering team reviews your drawings, recommends a suitable 3D printing process, and identifies features that may require clearance adjustments, machining, or surface finishing. This review helps avoid common manufacturing issues before printing begins.
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