I've lived off of TommyDee's B2B print head design for quite a while and I've been extremely pleased with it but I ran into a couple of issues recently. I sold a few converted Cube3s to friends and my boss (I know...). My boss, whose nickname is now "Hulk smash", had zero 3d printing knowledge and managed to destroy multiple B2B print head components and clip the end of a print tip off with snips . Another friend came across a small batch of used cartridges cheap and really wants to swap colors/materials frequently. It's been my experience that the B2B print head is rock solid until you start pulling the print head out, it can be done safely but it's a 3d printed component and will have a short life with this kind of use. So with these two circumstances giving me headaches I went to the drawing board.

*Disclaimer - I found these modifications to be fairly involved/difficult with tools that I have - a small lathe and "ghetto bench mill" (heavy duty drill press with a XY table). I wouldn't recommend attempting this with just a hand drill. I also had to design quite a few jigs, some of which are still being refined. So this won't be a how-to... yet. But... If you're interested in helping test this design further and comfortable mailing a print head and aluminum feed assembly to me, I'm happy to convert yours for free and mail it back to you.

Right from the beginning I knew that preventing destruction of the PTFE tubing by frequently rotating the P2C fitting barbs around it had to be solved. Unfortunately, my initial plan to simply release the PTFE tubing and lift prior to twisting the print head on/off isn't possible. Once connected and loaded, it's locked in tight. Once the print tip is heated though, it releases and the filament can be removed easily. I was able to come up with a solution that uses custom g-code files encoded to Cube3, enhanced versions of what MajorOCD posted to his site. I created two varieties, one specifically for swapping filament then purging and another for purging only (at max temp). I created these for both sides of the printer and in all 3 cartridge types available. Happy to share my Google drive folder with anyone interested in checking them out (PM me your email address).

I have S3D so I use an ABS cartridge to print everything. All of my Cube3 profiles (PLA, PETG, PLA+, Silk PLA) use material code "136" - the printer never knows the difference. With this design though, it would be very easy to leave print heads in place and hot swap between modified cartridges. I have an INF cartridge modified and I am excited to finally see what the OEM slicer can do with it. I need to find something really challenging on Thingiverse for this test (and then when disappointed after 60 hours of printing, ratchet it way back ).

How I am rolling now.... I am very happy with early testing and how well the filament swap g-code files work. I'm using 480mm long 2x4mm PTFE tubing. I recently measured a full OEM feed assembly and found that a 470mm long tube will make a modified assembly that is exactly the same length (feed assembly to print tip).

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I am using Initeq M6-1.0 threaded inserts for 3D printing. I found them highly recommended and cheap on eBay. You use a soldering iron to melt them into the cavity. I am very impressed with the strength!
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The two halves of the head will try to separate while inserting, so I melt the fitting into place while the head is in a printer. Once it's cooled slightly, you need to split the halves as the fitting is fused to both halves. Waiting until it cools completely makes this harder but still takes a bit of strength while warm.
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The print heads with the rubber coating are hard to cleanup in post processing. Obviously, a few too many attempts to make this one look good.
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