Print Orientation and Strength
Print orientation is which way a part sits on the build plate, and it changes how strong the part is between layers compared with along them.
How much does orientation change FDM part strength?
Published Z-strength ratios for FDM range from about 12 percent to about 89 percent of the in-plane strength, and the biggest driver is machine class and print settings, not the material. No single ratio here is safe to use as a design rule without its own study, material and machine attached.
The low end here comes from a desktop Prusa i3 printing ABS at 20 percent infill. The high end comes from Stratasys's own ABS-M30 datasheet on its F900 industrial machine. Machine class and print settings explain most of that gap, not the plastic itself.
What does Stratasys's own data show?
Stratasys's repeatability white paper, built from 1,400 ASTM D638 coupons across 16 machines, found the upright ZX orientation held 64 percent of the flat XZ strength for ASA on the F370, 80 percent on the Fortus 450mc, and 87 percent on the F900. Its ABS-M30 datasheet separately puts that ratio at 71 percent on the F770 and 89 percent on the F900.
The same white paper puts Nylon 12CF at about 45 percent and ULTEM 9085 at about 60 percent. These are OEM numbers from Stratasys's own industrial machines, not a promise about a part printed on a different printer.
| Material | Machine | ZX as percent of XZ (percent) | Provenance |
|---|---|---|---|
| ASA | F370 | 64 | Stratasys repeatability white paper |
| ASA | Fortus 450mc | 80 | Stratasys repeatability white paper |
| ASA | F900 | 87 | Stratasys repeatability white paper |
| Nylon 12CF | Not machine specific in the source | about 45 | Stratasys repeatability white paper |
| ULTEM 9085 | Not machine specific in the source | about 60 | Stratasys repeatability white paper |
| ABS-M30 | F770 | 71 | Stratasys ABS-M30 datasheet |
| ABS-M30 | F900 | 89 | Stratasys ABS-M30 datasheet |
What do desktop studies show?
Rodriguez-Panes and coauthors, publishing in 2018 and printing on a desktop Prusa i3 at 20 percent infill, measured PLA holding 72 percent of its flat strength when printed upright and ABS holding only 12 percent. That 12 percent sits at the low end of every ratio published here, on a desktop machine rather than an industrial one.
Aldawood et al. 2025 found the opposite pattern in PLA: vertical specimens up to 64.7 percent stronger than horizontal ones. Orientation naming is not standardized across these studies, so a direction called vertical in one paper is not always the same build direction as vertical in another.
| Material | Parallel to layers (MPa) | Perpendicular to layers (MPa) | Perpendicular as percent of parallel (percent) | Provenance |
|---|---|---|---|---|
| PLA | 38.47 | 27.63 | 72 | Rodriguez-Panes et al. 2018, Materials, PMC6119930 |
| ABS | 26.40 | 3.15 | 12 | Rodriguez-Panes et al. 2018, Materials, PMC6119930 |
Does elongation drop more than strength across orientations?
Yes: in Stratasys's own ASA data, elongation at break fell harder across orientations than tensile strength did, from 6.0 percent in the flat XZ orientation on the F900 to 1.7 percent in the upright ZX orientation. A part that needs to stretch before it breaks loses more of that ability between orientations than one that only needs to hold a static load.
What is the Z-strength ratio for PETG?
No credible published figure exists here for a PETG Z-strength ratio, so this page publishes none. Treat any PETG anisotropy number you see elsewhere as unsourced until it names its study, material and machine.
What this page does not tell you
- This page compares published strength ratios from different machines, materials and studies. It does not predict the strength of your specific part, since layer adhesion depends on temperature, cooling and machine settings that are not published anywhere general.
- Every figure below comes from a named study or a named OEM machine. None of it was measured on the printers that will make your part.
- Orientation naming is not standardized across these sources, so the same word can describe a different build direction from one study to the next.
When to print a test coupon instead
Print a test coupon in the orientation you actually plan to use before committing a load bearing part to a single build direction, especially when the part depends on stretching without breaking. Send the file through a review request and tell us which orientation and load worry you. A person reviews your request and follows up by email.
Sources
- Repeatability and Performance of Stratasys Fused Deposition Modeling (FDM) Technology, Stratasys
1,400 ASTM D638 coupons across 16 machines. States ZX (upright) strength as a percent of XZ (flat) strength for ASA: 64 percent on the F370, 80 percent on the Fortus 450mc, 87 percent on the F900. Nylon 12CF about 45 percent, ULTEM 9085 about 60 percent. States ASA elongation at break on the F900 falling from 6.0 percent XZ to 1.7 percent ZX.
- ABS-M30 Material Data Sheet, Stratasys
States ZX orientation strength as 71 percent of XZ strength on the F770 and 89 percent on the F900.
- Materials 2018, 11(8):1333 (PMC6119930), MDPI Materials, PMC open access
Prusa i3 desktop printer, 20 percent infill. Measured PLA tensile strength 38.47 MPa parallel to layers versus 27.63 MPa perpendicular (72 percent), and ABS 26.40 MPa versus 3.15 MPa (12 percent).
- Polymers 2025 (PMC12526709), MDPI Polymers, PMC open access
Found vertical PLA specimens up to 64.7 percent stronger than horizontal ones, the reverse of the usual pattern. Notes that orientation naming differs across studies.
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Published 5 September 2026.