21-Liter Full ATX PC Case (Prusa CORE One compatible)

What This Is

A compact (~21L) PC chassis designed to fit a standard full-size ATX motherboard and ATX power supply, split up so can be printed on the Prusa CORE One.

• The motherboard sits on truss frame for airflow.

• The power supply hangs from the top.

• A sliding dovetail rail system suspended under the top holds up to 4x 3.5" HDDs and 3x 2.5" SSDs.

• Motherboard support: Tested with standard ATX. Standard mATX boards will also work without changes because they share the same top-left mounting standoff grid and rear I/O spacing.

Print Orientation & Layer Lines (Load Bearing)

Print each part in the orientation provided in the files.

The biggest engineering challenge in designing this case was aligning the layer lines with the mechanical load axes. Parts are oriented so that the weight of the hanging power supply, suspended drive cage, and frame tension loads act along the XY plane (along the extruded filament paths) rather than pulling layers apart along the Z-axis. Rotating parts flat or sideways just to avoid supports or save bed space will compromise structural strength.

Hardware Needed

M3 hardware assortmentused:

• M3 Knurled Heat-Set Inserts: Use the diagonal / helical knurled style shown in the photo (~4mm long, 5mm outer diameter). Do not use straight-grooved inserts; diagonal knurls prevent spinning under torque and give much better pull-out strength. The recommended inserts feature a smooth round pilot section at the tip that centers into the hole before you apply heat with a soldering iron, making it easy to drive them in straight.

  (Exact inserts used: AliExpress link)

• M3 Motherboard Standoffs: 15mm standoffs are recommended to give you ample airflow space and room for cable routing under the board through the bottom trusses. Shorter ones (12mm or 10mm) will also work if needed.

• M3 Hex Nuts: Standard M3 nuts that drop into pre-molded captive slots.

• M3 Machine Screws: An assortment of lengths (M3x6mm, M3x8mm, M3x12mm, M3x16mm, etc.). Test-fit and choose lengths that bite firmly without bottoming out or punching through the printed plastic.

• Standard PC Screws: A few regular chassis screws for securing the power supply and 3.5" hard drives.

• Front I/O Buttons: Two momentary metal push-buttons with DuPont wiring:

  
  

  • 19mm button for POWER

  • 16mm button for RESET

    
    

    (Search: "16mm 19mm PC Power Push Button PC Restart LED Metal Button with 50cm DuPont Line")

How It Goes Together

Refer to the Onshape screenshots and the live model for assembly orientation:

• Tool-less Joints: Frame dovetail studs slide together and held with screws M3 6mm or 8mm direct into plastic. The two main ceiling pieces (TOP_PLATE_Near and TOP_PLATE_Far) slide and connect directly to each other without inserts or nuts, held with screws straight into plastic.

• Right Side Panels: PANEL_Right_Near and PANEL_Right_Far join together along the seam with just 2 M3 screws into plastic pilot holes.

• Direct into Plastic: The outer cosmetic side, front, and rear panels attach via dovetails and screws directly into plastic pilot holes. These holes are sized between 3.0mm and 3.2mm. There is low load and easily replaced, so heat-sets are not needed.

• Inserts vs. Captive Nuts: Holes between 3.0mm and 3.2mm are for direct plastic threading, wider bores are for heat-set inserts, and hexagonal recesses hold the captive nuts.

• Dovetail Fitting: Dovetails are modeled with tight tolerances for frame rigidity. Depending on your printer's flow rate and nozzle elephant's foot, scrape the edges with a hobby knife or deburring tool to get a smooth, solid slide.

Prototype Photos Notice (Work in Progress)

The photos of the physical case shown here are from a test print done in standard PLA to check mechanical clearances, tolerances, and cable routing before committing to expensive filament.

• The physical test print in the photos does not have the top Power and Reset button holes cut out and other small edits and changes.

• The uploaded CAD and 3MF files DO have the 19mm / 16mm cutouts modeled and ready on the front top plate (TOP_PLATE_Near), along with small iterative refinements.

Live Onshape CAD Model

To inspect internal clearances, measure hole dimensions, or remix parts, explore the complete file in Onshape:

🔗 Onshape 3D Model

Prusa CORE One Print Stats & Part Breakdown

• Total Filament Weight: 1,551.5 g (~1.55 kg) (Requires two 1 kg spools)

• Total Cumulative Print Time: 44 hours, 14 minutes

• Sliced Profile: 0.25mm Structural / Draft

• Material Preset: PLA (225°C nozzle / 60°C bed)

• Nozzle: 0.4 mm

This is for PLA and have these bgcode files attached...

⚠ Hobby Project & Liability Disclaimer

• Hobby / DIY Nature: This design is a personal DIY hobby project shared freely with the maker community for educational, experimental, and evaluation purposes only. It is not a certified commercial consumer product.

• Provided "AS IS": All CAD files (.STEP), slicer projects (.3MF), and print files (.bgcode) are provided on an "AS IS" and "WITH ALL FAULTS" basis, without warranties of any kind—either express or implied—including but not limited to fitness for a particular purpose, safety, structural integrity, or electrical compliance.

• Builder's Sole Responsibility: Assembling, printing, wiring, and operating computer hardware inside a custom enclosure involves inherent risks, including heat buildup, fire hazard, short circuits, and mechanical failure. You—the builder—assume 100% of the risk and responsibility for:

  • Selecting safe, suitable print materials (such as flame-retardant filaments where appropriate).

  • Ensuring proper electrical grounding, mains insulation, and cable routing.

  • Verifying component clearances, cooling/airflow, and operating temperatures.

  • Safe handling of tools (soldering irons, hobby knives, power tools) during post-processing and assembly.

• Limitation of Liability: In no event shall the author or designer be held liable for any direct, indirect, incidental, punitive, or consequential damages whatsoever (including, without limitation, hardware damage, data loss, personal injury, burns, or property damage) arising out of the download, printing, modification, or use of these files or physical builds derived from them.