Again, the community gives back in support and great ideas far more than I can contribute!
I have attached the stl files used to print the modified Nylon608 bearing as seen in the Video as part of Instructable.
For those interested in building their own ball bearings from BBs, I've uploaded a 2D DXF of the profile I use. In your CAD program, you can modify the depth and revolve the profile to make just about any size ball bearing set you need.
The term "608" refers to the stock part # from any bearing vendor. As this part has been modified, the only remaining specs are the thickness and OD.
These files are modified from the original "Printable 608 Ball Bearing" as released by "TheRooster" thingiverse.com/thing:4676
The design was modified to accommodate a 0.250” center hole rather than the metric hole. It was also modified to accommodate the cooling gradient associated with NYLON.
BBs are an excellent low cost alternative to actual ball bearings. While they're not as spherical or have a consistent diameter as ball bearings, the use of Nylon's flexibility make the difference minimal. If you prefer actual ball bearings, I've found that TrueValue HW stores are a good local source.
One of the great advantages of using Nylon, is the flexibility makes assembly a breeze. The BBs just pop in through the center slot and the Nylon simply snaps back into position!
Having measured the diameter of about 50 BBs, it looks as though the mean diameter is 4.4mm.
As you can design and print larger or multi-raceway bearings you will need to keep the Nylon cooling profile in mind. What this means is that you'll want to model your BBs as slightly larger dia. I model mine in Rhino at 4.5mm.
BBs are meant to be through-away, so they're not clean. As these parts are printed in Nylon, they'll not require any lubrication, but you should always wash the BBs in a dish washing detergent to remove grease and dirt from the production process.
If you look closely at the photo, you’ll note a few dropped threads at the top of the outer shell. These were outside of the bearing raceway, however an investigation of the top arc did indicate that it exceeds the 45-degree rule.
The seam on the inner raceway is a function of Z axis stepping. A slight touch of a soldering iron smoothed this out.
The bearing’s final usage is for a “Pre-Programmed Time-lapse Roving Camera” where bearings are needed for an over-all smooth movement along with a percentage of gear damping that the NYLON provides.
The bearings in the photo are made by perimeter only with no equivalent 45 degree fill. (Just a lot of circles). The end use will require the unit to support 8-10 lbs spread over 4 bearings.
While the final usage RPM is very low, the bearings have been tested at 2,400 RPM for 15+min. With no lubrication, there was a temperature rise of +8 degrees.
Vibration was negligible up to about 2,000 RPM as it became obvious that the inner seam needed more touch-up for higher RPMs.
The parts were not printed on the same run. Inner part first, then Y axis offset and then the outer shell.
The Nozzle is a .42mm
The Slic3r V6 Config file for this part:
bottom_layer_speed_ratio = 1
bridge_flow_ratio = 1
bridge_speed = 28
duplicate_distance = 6
duplicate_x = 1
duplicate_y = 1
end_gcode = G0 X-170 Y0
extrusion_axis = A
extrusion_multiplier = 1
extrusion_width_ratio = 0
filament_diameter = 3.1
fill_angle = 0
fill_density = 0
fill_pattern = rectilinear
first_layer_height_ratio = 1
g0 = 0
gcode_arcs = 0
gcode_comments = 0
infill_every_layers = 1
infill_speed = 28
layer_height = .32
nozzle_diameter = .35
output_filename_format = [input_filename_base].gcode
perimeter_speed = 28
perimeters = 100
print_center = 0,0
retract_before_travel = 0
retract_length = 0
retract_lift = 0
retract_restart_extra = 0
retract_speed = 80
rotate = 0
scale = 1
skirt_distance = 12
skirt_height = 1
skirts = 3
small_perimeter_speed = 28
solid_fill_pattern = rectilinear
solid_infill_speed = 28
solid_layers = 0
temperature = 200
travel_speed = 55
z_offset = 0
One last thought.....Keep in mind, that if you need a very small bearing or very thin bearing, you can just use a pressure fit of just Nylon as it's an extremely slippery material on it's own.