I was doing a 30+ hour-long print with the new Dual Extruder v2, using PLA and PVA. Because of the design, the machine was laying down a significant amount of PVA before even starting the PLA. The repeated flexing of the PLA where it enters the head resulted in it breaking, which of course ruined the print job.
Also, PVA filament is very limp, and I wanted to hold it upright so it wasn’t entering the print head at an angle.
In response, I decided to design and print a head-mounted filament guide retainer. I present it here for everyone’s free use and modification. I was in a hurry, and I knocked out the design in about three hours, so it could still use a little refinement. If I get around to doing that I will post updates. In the mean time, this one is functional.
For mounting, I decided to use the main print head retention screw. I took out the stock one and replaced it with another that is M3 x 25mm. This leaves a number of threads sticking out the back for the bracket to mount to:
(By the way, note the black PLA filament that is white from fatigue where it enters the head).
The underside of the bracket follows the contours of the X carriage and the extruder frame, and that takes care of positioning and allows just the single retention nut. I used a vertical slot rather than a hole, which allows the bracket to be lifted upwards to access the extruders by just loosening the kep nut. There is a circular depression that is the size of the kep nut washer, so that locks it in vertically when the kep nut is tightened:
The filaments pass through 4mm holes that are counterbored 6.35mm by 12.7m deep on the top to accommodate the filament guides. They need to be a friction-fit to hold the guides in place; honing them with a 1/4" drill bit made it work perfectly. Here’s what it looks like installed:
I am attaching an stl file, and also a step file in case anyone wants to modify the design. Improvements that need to be made:
-A slight enlargement of the mating surface where it meets the head and the carriage, to make it less of a snug fit.
-The filament holes are not quite perfectly aligned.
Comments are welcome, of course…