Wall, overhang, bridge and hole in 3D printing: the limit for each process
Pick a process (FDM, resin, SLS or metal) and see the limits for wall, overhang, bridge, hole and clearance, each with an explanation and a citation. Search by word and compare up to four rules.
Opens without an account 3 times a day. A free account removes the limit.
- 32 rulesacross four processes
- Limits and rangesin mm, degrees, percent and J/mm³
- Search and compareup to 4 rules in one table
- Learning sectionfour short parts on DFAM
What design for additive manufacturing is
3D printing design rules is a free online reference from EduFacturing with 32 rules for designing 3D-printed parts (DFAM). The rules cover four processes: FDM/FFF, resin (SLA and DLP), SLS with polyamide powder, and metal (DMLS and LPBF).
Each rule has a limit or a status, a process and an explanation, and most say what goes wrong when it is broken. The Citation line under the description carries the rule key and, for 24 of the 32, the publication.
The rules differ by process, so the process is chosen before the design, not at the end.
What it does: 32 rules by process, each cited
Shows 32 rules across four processes
Eight are for FDM/FFF, six for resin, nine for SLS and nine for metal. Each is a tile with its key value, for example a hole of at least 2 mm for FDM or an overhang up to 30° for resin.
Searches, filters and compares
Search covers the name, the limit, the tags and the fields, so bridge finds every process. Compare mode puts up to four rules in one table; a missing field shows as a dash.
Opens the details of a rule
The panel has the fields (minimum, typical value, reason), a description of the violation where there is one, and a citation.
Links to technologies, defects and materials
Every rule leads to its technology. 20 of the 32 also lead to a typical defect, and 5 to a material. A collapsible learning section explains what DFAM is.
When you need it: wall, overhang, bridge, hole
A rule is read before the model is finalized, not after the print has failed.
Designing a part
The designer picks the process and checks wall, overhang, bridge, hole and clearance before saving the model. A figure like a 10 mm bridge for FDM decides whether the part needs a support.
Choosing between processes
An unsupported bridge is 10 mm for FDM, 5 for resin and 2 for SLS and metal: you see which process tolerates the shape.
A lesson in design for additive manufacturing
The teacher hands out one part and students look for the rules it breaks for FDM and for resin.
A brief for a manufacturer
Before ordering SLS or metal printing, put the numbers in the brief: clearance of at least 0.5 mm for SLS, a powder escape hole of at least 5 mm, supports and heat treatment for metal.
How the rules are organised
The reference does not calculate on your model. It sorts the rules by process and shows a limit or a status, an explanation and a citation. Two rules are formulas: the FDM wall (2 × nozzle) and the energy density for metal.
Process
The rules sit in four groups, each with its own color. The process comes first: the same parameter has a different limit in each.
Limit
A rule carries its main limit (a minimum, a maximum, a range) or a status such as mandatory, and often a typical or recommended value too.
Explanation and violation
The description says why and, for most rules, what happens when it is broken: a wall with gaps, a sagging bridge, fused parts, or supports that are hard to remove.
| Applies to | Formula | Meaning |
|---|---|---|
| FDM wall | wall ≥ 2 · nozzle diameter | 0.8 mm for a standard 0.4 mm nozzle |
| Metal: energy density | VED = P / (v · h · t) | P power (W), v speed (mm/s), h hatch spacing (mm), t layer thickness (mm) |
| Metal: good range | 50 ≤ VED ≤ 200 J/mm³ | below 50 lack-of-fusion porosity, above 200 keyhole porosity from overmelting |
A citation for each rule, disagreements visible
Every rule has a citation
Under each rule sits a Citation line with its key, and 24 of 32 also name the publication: Hinchy 2019, Xometry Pro, Gibson, Rosen and Stucker (2021), Yang et al. 2017.
Disagreements stay visible
The resin wall is 0.5 mm in the rule set and 1.0 mm in Hinchy 2019. The SLS hole is 1.5 mm per Xometry Pro, 1.0 to 2.0 mm in the rule set. When two sources give different numbers, both are shown.
No file upload
Search, filters and a comparison of up to four rules run in the browser.
The reference does not check your model: there is no file upload and no geometric analysis, so you compare the part with the limits by hand. For an uploaded STL file there is a separate STL analyzer. This reference has no rules for milling, laser cutting or other processes.
The limits are guides, not a guarantee for a particular machine: the printer, the material and the settings move them. The learning section advises a calibration model and calipers.
Questions about wall, overhang and bridge in 3D printing
What is the minimum wall thickness for 3D printing?
It depends on the process: 0.8 mm for FDM (two perimeters with a 0.4 mm nozzle), 0.5 mm for resin, 0.7 mm for SLS in PA12 and 0.5 mm for metal. For resin, Hinchy 2019 recommends 1.0 mm.
What is the maximum overhang angle without support?
For FDM it is 45° from the vertical, for resin 30°, for metal 45°. SLS needs no supports because the powder holds the part, but above 45° thermal stress grows; the ideal is up to 30°.
How long can a 3D print bridge be without support?
For FDM up to 10 mm safely, and up to 30 mm with a good fan and a slow print. For resin it is 5 mm, for SLS and metal 2 mm.
How to design for 3D printing?
Pick the process first, because the same parameter has a different limit in each. Then check wall, overhang, bridge, hole and clearance against the rules for it before you save the model.
What is volumetric energy density in metal printing?
VED = P / (v · h · t): laser power divided by scan speed, hatch spacing and layer thickness. The good range is 50 to 200 J/mm³.
Does the tool check my STL file?
No. It is a reference of the rules, with no file upload and no geometric analysis.
Do I need an account to see the rules?
Without an account the rules open 3 times a day. With a free account there is no limit.
The 3D printing design rules is free. Pro opens the rest
Pro costs 15 EUR a month and opens 45 Pro tools.
Related tools
Types of 3D printing technologyTypes of 3D printing technology: 19 processes from FDM and SLA to SLS and DMLS, with principle, supports and uses. Free, 3 times a day without an account.
3D printing defectsFree 3D printing defects and solutions: 277 defects in 29 technologies with symptom, cause and fix, 242 with drawings. Stringing, warping, layer separation.
3D printing materialsPeriodic table of 3D printing materials: 60 materials from PLA and PETG to resins, powders and alloys, with temperatures and properties. Free to use.
See the rules for your process
Opens without an account 3 times a day. A free account removes the limit.