3D Printed Parts

This page details the creation of the various 3D printed parts in LoCO.

Any decent 3D printer should work for this robot, though the printer must be able to handle a print of at least 8 inches in one dimension. A build plate of over 8 inches is recommended so that the larger parts can print horizontally for a stronger print. The original parts were printed with a Lulzbot TAZ 6. The most difficulty will come with preventing warps and higher precision on the smaller holes.

While any filament material may work, it is recommended to use stronger materials that are stiff, such as PETG. Remember that the plastic must withstand immersion in harsh conditions, such as chlorinated or saltwater, depending on the use of the robot. PLA or ABS should work, but the original LoCO used PETG plastic for higher temperature resistance, higher chemical resistance, and higher mechanical strength.

General Tips

Bed Adhesion

Make sure you are getting good bed adhesion when you are printing your parts, as warped plastic makes assemblies much more difficult. Depending on the 3D printer you are using, adjusting the bed temperature, adding tape to the bed, or using a gluestick on the bed may help with adhesion. For the Lulzbot TAZ 6 printer with a glass bed, printing PETG worked best with a thin layer of washable Elmer's glue.

Small Holes

Printing holes can be difficult for any FDM 3D printer, no matter how fancy. The easiest way to get good fits for screws and bolts is to print the holes slightly oversized to get close (holes print smaller than the actual dimensions for FDM printers) and then drill the hole out with the exact size you want. Most holes in LoCO are slightly drilled out in the post-processing of the plastic to get good fits.

Print Orientation

The orientation of the part on the printer's bed is important for the strength of the part. Always try to print with the strands of plastic (grain?) along where the force will be applied, so that the forces attempt to pull apart or crush the stands lengthwise. The plastic will crack apart between layers, so avoid having major tension forces pulling the layers apart, though compression against layers is fine. Print orientation also affects the support needed to print the part, so make sure to use an orientation that uses less support, for less post-processing.

Post-Processing

The post-processing of the plastic is important to get a clean finish and good tolerances. Drilling out holes to get the best tolerances can be very important. Using a metal file can smooth a part to remove sharp edges and get better fits, though it also roughs up the plastic and changes the look of it.

Laser Cut Parts

The original LoCO's wooden base plates are made of 1/4" Medium Density Fiberboard (MDF), which were cut using a laser cutter. While it is possible to make these pieces by hand using drawings (such as the ones provided here), using a laser cutter speeds up the process considerably while also improving precision. Any material that is 1/4" thick could be used as long as it is stiff and non-conductive, but wood is easiest for cutting on a laser cutter and post-processing with common tools.

While any good laser cutter should do, the original parts were cut on a Universal Laser Systems laser cutter. The laser cutter only has to be large enough to cut a piece roughly 2 foot long of 1/4" MDF, which is not bad. The CoralDraw program was used to transfer the .dxf file into a file for the laser cutter, but any program that does the same process should work.

Additional Notes

The only important part of the manufacturing of the base plates other than the laser cutting itself is the addition of the chamfers on the bottom sides of the wood, where the bases contact the acrylic tubes in the final assembly. These chamfers allow for the bases to sit a little lower in the tubing while still being very stiff and adding strength to the internal structure. In the original LoCO, this was done after the laser cutting by using a dremel, though other tools could work as well. The chamfer should be roughly a 45-degree angle that takes half the width of the sides off (see CAD below for better visualization). This only needs to be applied to the bottom edges of the bases that face sideways out of the tubes, not the front or the back. Increasing the size of the chamfer may be necessary to get a good fit into the acrylic tubes.

Unlike 3D printing, laser cutting produces holes that are slightly oversized to what the original drawing specified, which is why the holes in the drawing are a little smaller than necessary (though this correction is smaller for a laser cutter than for a 3D printer). For getting better precision, use the same technique as 3D printing, and drill the holes out manually to the desired size to fit the bolt or screw. Depending on the material used and the head of the bolt/screw, washers should be used as to not damage the material when tightening the screws. The original LoCO used washers for the smallest screws that attach 3D printed parts to the wood base.

In one specific case, two small counterbores were used to insert screws into the wooden base. This occurs on the outside screws that attach the Jetson mount to the right wooden base. This is only needed for those two specific screws because they are so close to the edge of the base. Carefully using a larger drill bit to add the two small counterbores should be enough.

Additional holes may be added for attaching electronic or other components as necessary.