BONDTECH Extruder Filament Guide by EE_Maker

Last crawled date: 3 years, 1 month ago

When I updated my BONDTECH BMG extruder to a DIRECT DRIVE setup, I found that I needed to develop a way to deliver the filament into the top of the extruder. I finally decided to use about 1 1/2 feet of thin wall (4MM OD, 3MM ID) poly tube similar to a BOWDEN setup. I mounted the input side of the filament feed-tube to the printer frame just above the spool holder, and then slipped the feed tube into the top of the BMG extruder using it's normal 4mm bowden tube coupler. While this got me started, I soon found two small issues.

Since the ID of the thin-wall tubing is large (3 mm), the 1.75mm diameter filament easily slips through the tubing and on into the DIRECT DRIVE extruder. This is good! However, unlike its thick-wall Bowden tube counterpart, the thin-wall tubing (4mm OD, 3MM ID) is less rigid and therefore more prone to kinks and bends near the top of the BMG input port fitting as the carriage moves about. These kinks can pinch the filament and cause findup which can interfere with proper filament feeding.

Also, every time a filament change is needed, the feed tube must be removed from the BMG extruder entry port fitting. Since these tube fittings are not really designed to handle lots of in-out operations, over time, they can wear out and jam up. This is not usually a problem for BOWDEN setups (as the BOWDEN tube is not removed during a filament change) but becomes is a problem for DIRECT DRIVE setups.
To solve these issues, I designed this Filament-Guide-Support part that slips on (and off) of the BMG filament tension release arm to provide support to the poly filament feed tube. With a simple friction fit over the tension release arm, It holds and positions the guide-tube perfectly above the extruder entry spot. Pot fitting wear is eliminated as the thin wall tubing does not actually have to enter into the extruder tube-fitting at all. Further more, when a filament change is needed, the Guide-Support and poly-guide-tubing "combination" simply slips up and off of the extruder tension arm providing easy access to the filament itself.
This is a simple part to print. If you use a similar setup for your BMG DIRECT DRIVE EXTRUDER, this little guy might just help you out as well! Take care and stay safe!