GBX Update March 17 2021

Hi everyone! Here are the GBX R&D updates from the past month:


Hopper Gantry for Regular GBX

Last month I discussed our development of the hopper gantry. The first hopper gantry built was actually for a GBX with an XLT build frame. After finalizing that design, I altered it to fit a Regular GBX frame. Next up, Terabot X!

Updated Hopper

To adapt the hopper to the new hopper gantry, I removed the legs that previously attached the hopper to the frame. I kept a few external fins for structural support, but overall the design is more streamlined and uses less material to print.


Techmer PM Electrafil PC with CF Material Testing

Several weeks ago I conducted GBX material testing on Techmer PM’s Electrafil PC 1705 3DP pellets, which is a polycarbonate filled with carbon fiber. This material is intended for large polycarbonate prints-- the carbon fiber gives the polycarbonate rigidity, allowing it to be printed in large geometries without warping, shrinking, or delaminating. Typically re:3D uses a passive heating enclosure to print polycarbonate filament to prevent these very issues, but with the Techmer PM material, I didn’t need to use an enclosure at all.

Another learning lesson for this material is that it can’t be printed with small nozzles (0.8mm or smaller). Small nozzle sizes aren’t large enough to allow the carbon fibers to pass through their orifice, resulting in clogging and inconsistent extrusion. The quick solution to this is to simply swap out the nozzle for a larger one. Once I switched to a 1.75mm nozzle, all my extrusion consistency issues were resolved. This means that printing with this material is limited to lower resolution, but since it’s intended for larger prints, it’s probably fine :)

More information about this material, as well as other materials we’ve validated on our printers, can be found on the re:3D website here.


Maximum Extrusion Rate Calculator

Print time, print speed, and other settings are dependent on the max extrusion rate that the extrusion system can achieve, so I devised a testing method and a spreadsheet calculator to gather data around the maximum extrusion rate.

To gather this data, I hook up a laptop to a GBX via USB cable and run the printer through Simplify3D’s machine control panel. After heating up the extruder to printing temperatures, I extrude the material being tested and step up the extrusion speed until the motor begins to skip, indicating that the motor can’t supply enough torque to turn the extrusion screw. Once I have that maximum extrusion speed, I extrude the material at that speed for 200mm and measure the mass of the resulting extrusion. After gathering the data, I input it into my spreadsheet calculator, which calculates the maximum extrusion rate and the maximum print speed. As an example, here is the data for Ultrafuse rPET:

Note: the max default x/y speed listed above is not the actual max print speed, since the max print speed is also constrained by the x/y gantry system. The value shown in the spreadsheet calculator is the estimated max speed as constrained by the extrusion system.


Ultrafuse rPET Windowsill Planter Pot

In an effort to create more example GBX prints, I designed and printed a plant pot that fits on my windowsill, where my evil cat can’t reach it. The pot is printed with Ultrafuse rPET pellets and a 1.75mm nozzle. Certain aspects of the design make it ideal for printing with this nozzle size, reducing the overall print time:

  • There is no support. The notch in the center of the pot accommodates the window latch beneath the pot, and it was printed as a triangular notch with 45 degree overhangs, meaning no support was necessary
  • All walls were designed to be 3mm thick, and were printed as two solid perimeters

This print also served as an opportunity to further optimize the print settings for Ultrafuse rPET. Keep an eye out for some updated printing profiles on our Knowledge Base with the refined settings.


Please sign in to leave a comment.