All rights for the original design belong to LEGO A/S. This is not an official Lego-product or Lego-model. I designed it to be compatible with the original ones. Keep small parts away from children, choking hazard. 

Additional information:

This frame is compatible with the original Lego Technic parts and it should fit with the standard Lego Technic pins.

For optimal results, make sure to:

• Use low layer heights (~0.12-0.15mm)
• Use high cooling settings (depending on filament, up to 100%)
• Select slower printing speeds for maximum details

Supports aren't necessary if printed lying. With a smaller nozzle diameter you can achieve even more accurate results (max. diameter should be 0.4mm). If the holes are too small and the axles have too much friction, try to rotate them inside the holes to enlarge them a little. If the results are just too inaccurate, check your print settings or use a smaller nozzle diameter.

Feel free to upload a better remix version or leave a suggestion for improvement

Have fun :)

3D-Render of the frame in gray

3D-Render of the extended frame in gray