GBX Update October 25 2020

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


Crammer Rev11 In Progress

The Crammer, or Active Feeding System, is a 3D printed feed throat with a motorized auger screw that conveys material into the Gigabot X extruder. The Crammer was developed for use with print materials that have difficulty flowing into the Gigabot X extruder, namely regrind with irregularly size flake like rPET water bottle flake, or TPU pellets or regrind, which have a tacky texture that makes the particles stick together and not flow well. 

In the past month, design updates have been made to the Crammer to future integrate it into the Gigabot X printer. Changes include:

  • Updating the clamp mechanism for attaching to the feed tube
  • Extending the top of the Crammer feed throat to match the standard feed throat
  • Adding wire holders for wire management


Gigabot X Instructions

The Gigabot X Enclosure Assembly Instructions are available for download from re:3D’s Knowledge base here: GBX Enclosure Assembly Instructions. All build volumes of Gigabot X printers can have an enclosure added on to them, which enables printing with higher temperature materials or materials prone to warping, such as polycarbonate, ABS, and LDPE. The enclosure consists of polycarbonate panels on all sides of the machine except the top, with is covered by bellows that allow the X and Y movement of the hopper gantry during printing. The enclosure passively traps heat within the build volume during printing, creating build volume temperatures up to 60C. Gigabot X printers can be purchased with an enclosure, or a printer without an enclosure can be upgraded to have one after the initial purchase.

The Gigabot X Hopper Gantry Assembly Instructions are currently under review for final revisions. Although these instructions will be exclusively internal for use when assembling Gigabot X hopper gantries, they may become externally available if Gigabot X is ever sold as a kit.


Updated Knowledge Base Articles

A few GBX-related articles have been updated on the Knowledge Base:

The Knowledge Base is searchable database of instructions, troubleshooting tips, and other helpful information for 3D printing successfully.


Testing with rLDPE

This past month, a recycled LDPE regrind underwent GBX Material Testing Tier 2: Extrusion and Tier 3: Print Optimization. Extrusion testing includes extruding at increasing speeds until the motor torques out or skips, indicating that the motor cannot provide the torque required to extrude the material at that rate. For this rLDPE material, the maximum extrusion rate was 0.56kg/h. The material was also extruded for 200mm for 5 trials, and  the extrudate was massed to quantify the material’s extrusion consistency. The average extrudate mass was 17.5g, and the standard deviation was 0.34g, which is 2% of the average. Further testing with a variety of materials is necessary to establish the threshold for a reasonable standard deviation.

During print optimization testing, a calibration cylinder, a Moai, and a plant pot were printed. Bed adhesion was tested with a bare bed, PVA Glue, Magigoo PA, Magigoo PC, 3D LAC, and Magigoo PP, and Magigoo PP was the only adhesive that improved bed adhesion. Bed adhesion was achieved with a combination of Magigoo PP, heating the bed to 90C, and increasing the nozzle temperature to 155C. Although adequate bed adhesion was achieved, warping forces pulled the part off the bed for larger parts. Warping was partially mitigated with a brim and printing in an enclosure, which was successful for the Moai, but not the larger plant pot model. 


Plant Pot that warped off the bed during the printing process, resulting in a failed print.


Nozzle temperatures were optimized to 155C / 140C / 100 C (bottom/middle/top). One thing to note is this material showed signs of bridging in the extruder, which is when the particles partially melt and stick together too high in the extruder. Moai Trial 8 on the left had a cyclic pattern of over- and under-extrusion, resulting in stripes along the height of the part. In Trial 9 on the right, the top heat zone temperature was decreased from 105 to 100C halfway through the print, and the stripes disappeared. Therefore, keeping the top heat zone at a low enough temperature is crucial to consistent extrusion.


Moai trials 8 (left) and 9 (right). Trial 8 was printed with the top heat zone set to 105C, and exhibits a cycle of over- and under-extrusion throughout the print. The top heat zone temperature was reduced to 100C partway through Trial 9, resulting in a transition from the inconsistent extrusion also present in Trial 8 to a more consistent extrusion rate.


Intermittent nozzle clogging issues with the 0.8mm nozzle suggested possible contaminants, but switching to a 1.2mm nozzle caused nozzle clogging issues to disappear.

Due to the warping issue, small parts or parts that are 5 layers tall or less are recommended for printing with this material. Mixing with fillers or a more rigid material may mitigate the warping issue. This material is printable in limited applications, but warping issues prevent printing larger geometries. Magigoo PP and an enclosure are essential for successful prints.


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