This is an external spool holder designed to interface with the Flashforge Inventor 3D printer. It may also work with the Flashforge Dreamer and the Dremel Idea Builder. In order to complete this project, you will require a 5/8 inch round wood dowel of desired length and a piece of PFTE filament tube (3mm inner diameter, 4 mm outer diameter).
The external spool holder can hook and rest on any of the three sides of the 3D printer (left, right, and back) and allow for the 3D printer lid to be closed even if only installed on one side. I recommend the printing of the filament guide and the use of a piece of PFTE tube to prevent the filament from cutting through the printer.
I have embedded a very thin (0.25mm) film that barely touches the rollers of the bearings to act as a skirt/brim for them. It is very easy to remove post-printing. I still recommend enabling an 8mm skirt/brim around the external perimeter of the parts. In order to prevent defects in the rollers caused by excessive tension in the filament, I recommend positioning the bearing end of the part closest to the side of the filament spool used for the printing.
Step 1: Measurements
I took several measurements of the top of the Flashforge Inventor 3D Printer frame and of the distances between the grooves located on the upper sides of the printer so that the spool holder could properly interface with the printer. I measured the dimensions of the tabs that hold the lid in place so that the lid could properly close over the spool holder bracket. I measured the outer diameter of the largest filament spool that I owned so that different filament spool sizes could be supported. I measured the diameter of a round wood dowel I owned and the outer diameter of a PFTE tube that I owned so that I could embed it to a filament guide part.
Step 2: Initial Designs
I drew a basic 2D profile of one spool holder bracket and extruded it to a reasonable thickness. In order to make the design aesthetically appealing, I tried to use dimensions that are multiples of other dimensions used in the design. Since the outer diameter of the PFTE filament tube was 4mm and I wanted to add 1mm of material around it, I used 6mm and multiples of 6mm (12mm) for several design features. Having some knowledge of the printing characteristics of my 3D printer, I estimated the required tolerances and ensured that I oriented my model so that it could print without added supports. In my original versions, I did not have the tabs to hold the lid.
Step 3: Prototype Prints
I made five prototype/partial prints in order to verify the fit of specific areas of the spool holder and get a working bearing. The first trials were close but unsuccessful so I had to tweak the designed tolerances. I realized that successfully printing a bearing is an art; a lot can go wrong, even if the design is good. I experienced issues with the PLA of the cylinders in the bearing deforming. Mounting the filament spool used for the printing on the side closest to where the bearing is located on the build plate seemed to have fixed the issue with I believe was due to excessive tension on the filament when traveling quickly to the far edge of the build plate and printing details.
Step 4: Final Print and Assembly
Once I got two decent prints, I cut the 5/8 inch round wood dowel and PFTE tube to desired length, assembled, and enjoyed a great filament spool holder.
When using brittle filaments, such as the Proto-Pasta Carbon Fiber HTPLA, do not feed the filament through the PFTE tubes/filament guides and do not close the lid. Otherwise, the filament will break as the carriage moves closer to the PFTE tubes/filament guides.