The Prusa i3 MK3S is one of the most popular desktop 3D printers on the market today. With its large print bed and excellent print quality, it’s a great choice for hobbyists, tinkerers, and small businesses alike. One of the most common questions about the MK3S is just how large of a build volume it can reliably print. In this article, we’ll break down the maximum print dimensions you can expect from the Prusa i3 MK3S and provide tips for maximizing the build area.
Official Build Volume Specs
According to Prusa Research, the official build volume for the MK3S is 250 x 210 x 210 mm (9.8 x 8.3 x 8.3 in). This refers to the maximum volume that is guaranteed to fit within the printer’s frame and allows the print head to fully access all areas of the print bed.
The MK3S uses a PEI spring steel print sheet that is magnetically attached to the heatbed. The standard sheet included with the printer is 250 x 210 mm, matching the maximum guaranteed build dimensions. However, many users find that they can safely print slightly outside of the official volume.
Printing Beyond the Build Volume Limits
While Prusa Research only guarantees prints within that maximum 250 x 210 x 210 mm volume, many users stretch those limits with successful results. The print head carriage and gantry are capable of moving 10-20mm beyond the edges of the build plate on the X and Y axes. This allows prints that are up to 270 x 230 mm or more at the base.
The maximum print height can also be extended above 210mm. The lead screws and Z-axis motors are capable of traveling up to 250-260mm in the Z-direction depending on the print setup. Tall prints may start to lose accuracy and quality at the extreme heights, but there is room to push beyond the standard limit.
When printing near or beyond the build volume edges, careful calibration is a must. Any inaccuracies in the leveling or alignment of the gantry can cause issues during prints with a large footprint. Upgrading to silicone spacers can also help improve stability for tall prints.
Using Full Build Volume with Dual Extrusion
The MK3S can be upgraded with a second extruder for dual-color printing. When using dual extrusion mode, the build volume is reduced. This is because the print head assembly is wider and the nozzles need to move inside the edges of the build plate to function properly.
In dual extrusion mode, Prusa states the maximum build volume is 250 x 200 x 200 mm (9.8 x 7.9 x 7.9 in). Again, users have found the limits can be pushed beyond the official specs. Build volumes up to 250 x 210 x 210 mm are possible with dual extrusion, depending on the specific print settings.
Printing near the volume limits in dual extrusion can be tricky. Having the nozzles move too close to the edges of the PEI sheet can cause adhesion issues on larger prints. Closer calibration of the distance between the nozzles is critical. But utilizing as much build volume as possible produces larger dual color prints.
Largest Single Print Dimension?
While the total build volume defines the maximum 3D space that the MK3S can print in, looking at the largest single dimension can be helpful for visualizing print capacities.
On the MK3S, the longest dimension that can be printed reliably is 250mm on the Y-axis from front to back of the printer. The X-axis bar allows up to 230mm, while prints typically top out around 210mm on the vertical Z-axis.
Knowing these maximum single dimensions makes it easier to quickly visualize whether a particular print will fit within the build envelope or not. Of course, prints don’t have to maximize every dimension to take advantage of the full build volume.
What’s the Optimal Orientation for Maximizing Size?
With its nearly square build plate, the MK3S allows prints of similar dimensions in all orientations. But depending on the specific part geometry, orienting it strategically can help maximize the print size.
For many prints, laying the part down on its back (rotated 90° on the Y-axis) allows it to take full advantage of the 250mm Y-dimension. Parts with a rectangular footprint generally benefit from this orientation.
Tall and narrow prints like vases, models, and figures often print best standing upright, making use of the full 210mm+ Z-height. Pieces with complex base geometries and overhangs also do better standing up to avoid the need for supports.
Consider component orientation and layout when designing parts as well. Aligning the longest dimensions with the Y-axis and minimizing support structures will result in reliably large prints.
Print Bed Surface Area
While the MK3S has a build volume of over 20 liters, it’s important to note the actual print bed surface area is only around 510 cm2 (80 in2). This defines the maximum footprint a single print can have before extending beyond the heated bed.
Large prints with a footprint above this 510 cm2 threshold will start to overhang the PEI print sheet. While building past the sheet edges is possible, it risks reduced adhesion and cooling issues on overhanging sections.
To maximize surface area use, orienting prints diagonally can help. Diagonal dimensions up to 298mm are possible, providing efficient coverage of the circular PEI sheet. Just keep the center of mass targeted close to the bed so as not to induce wobbling of tall angled prints.
Heated Bed Size vs. MK52 Heatbed PCB
It’s also worth noting that while the removable PEI spring steel sheet measures 250 x 210 mm, the PCB heatbed underneath is actually 310 x 310 mm. This is the MK52 heatbed, which extends 20-30mm beyond the edges of the PEI sheet on all sides.
The MK52 itself has open aluminum traces covering the entire area, providing some passive heating to the extended regions. But there are no active heating elements beyond the central 250 x 210 mm zone matching the PEI sheet size.
While it’s possible to print onto these extended passive-heated zones, temperature management and adhesion are much more difficult. For reliability, keep all prints restricted to the actively heated 250 x 210 mm PEI sheet area only.
Modding for Larger Build Volumes
For expert users looking to push the build volume even further, various community mods can help. Typical extended dimensions range from 270 x 300 x 300 mm up to 300 x 300 x 300 mm or more. However, this requires making structural changes to the printer’s frame and motion system.
Common mods for larger build volumes include:
- Longer Y-axis 2020 extrusion frame rails
- Extension of the X-axis motor mounts
- 300mm PEI spring steel sheet
- Z-axis limit switch relocation
- Lengthened cables for X & Y steppers
- Upgraded power supply
These modifications require advanced technical skills and often result in reduced print rigidity/precision. Generally, sticking close to Prusa’s specified build volume offers the best reliability. But for one-off oversized prints, mods can push volumes higher still.
Key Facts on MK3S Build Volume
To summarize the key details on maximizing the Prusa i3 MK3S printable build envelope:
- Official volume is 250 x 210 x 210 mm (X, Y, Z)
- Can reliably print 10-20mm beyond edges (up to ~270 x 230 x 250 mm)
- Optimal orientation depends on print geometry
- Maximum single dimension is 250mm on Y-axis
- Total bed surface area is 510 cm2 (80 in2)
- Advanced mods can expand volume further (with tradeoffs)
With smart orientation and positioning, MK3S owners can take advantage of nearly the full official build volume for large, high-quality prints. While dimensions can be expanded further through community mods, sticking close to Prusa’s specs ensures the best results. Understanding exactly what the Prusa i3 MK3S platform can accommodate helps users get the most out of this versatile desktop 3D printer.
