This is a heavy-duty gantry for hobbyists looking to make their own CNC. I designed it to use dry, dust-proof bearings from Igus and standard 40 mm profile extrusion. A 3D printer capable of a 200x200x110 mm build volume and impact resistant filament is all you need to make all the connecting parts. Follow the recommendations in the printing section to ensure your parts are very strong.
I modeled this gantry in Fusion 360, but not every single part is in the renderings. So also look at the photos to see where everything goes. I'll be updating the model and BOM over time.
The BOM file lists all the parts, sources and costs I incurred making my initial machine. Note that these parts are better quality than is typically found in a CNC kit of the same price. Use the size calculator tab in the BOM file to recalculate the extrusions for your specified size. To keep the flying weight down, choose the ultra light 40x80mm extrusion type profile for the X axis beam.
This is not a step-by-step instruction manual for the novice. An understanding of the following is required to complete this project: extruded profile cutting and tapping, stepper motors, stepper motor controllers, Arduino Uno, GRBL 1.1, electrical wiring and soldering. There are excellent tutorials for these topics on the internet.
The extruded profiles and Igus bearing rails are very strong and will easily support the weight of a 3 HP router, although I use and include a mount for a Dewalt 1.5 HP router. The 3D printed parts join all the metal parts together as well as support the router and dust collection shroud.
The Z-axis assembly was purchased as a finished unit from CNC4Newbie on Ebay.
See the BOM for all parts, but here are some key details: Dewalt 611 router used as spindle, GT2 x 9 mm wide drive belts, 20 tooth x 10 mm pulleys, profile is 40x80 and 40x40 mm.
Update: Added support for 12mm 2GT belts on the Y axis to reduce hysteresis. Parts are identified with 'B12' in the file name.
0.6 mm wide x 0.3 mm thick
For STRONG 3D printed parts, I first optimized my printer speed and temperature to get excellent inter-layer adhesion with the chosen filament. Then I printed the CNC parts using at least 1.8mm thick walls (3 perimeters with 0.6mm nozzle), 50% infill and 0.3 mm thick layers. If printed correctly, you should not be able to break the parts by hand. Also, the STL files are not necessarily in the correct orientation to be simply dropped into your slicer, so think about which side to put facing down. Most parts don't need supports, but some--like the Y motor mounts--will need supports.
The most highly stressed part is the tensioner slider which bears the full tension of the belt. Make sure it is printed so that all sides are perpendicular to the print bed. This will ensure the strongest part.
When assembling the gantry, do not tighten fasteners such that the plastic is crushed. 3-4 Nm torque was satisfactory for the M8 bolts threaded through plastic parts into the extrusion profile. Metal-to-metal connections should be torqued to 12-15 Nm to ensure proper engagement of blind nuts in the extrusion.