Bowden tube clamp for Ender 3 style printers (hotend side)

Small upgrade restricts bowden tube movement, addressing jamming after retractions. Works with Ender 3 style printers.
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updated December 21, 2023

Description

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Backstory:

Ever since I upgraded my Ender 3 Pro with the Mellow All Metal Hotend, I've had a significant problem with jamming. Initially, I thought it was due to heat creep, but after hours of research, I discovered that the bowden tube gets loose on the hotend side. Pressure pushes the tube out of the cooling block instead of pushing the filament through the nozzle.

It's easy to observe during retractions—simply put a piece of electrical tape around the tube just above the coupler. If it's moving, you've got a problem. Trimming a few millimeters of the tube works for a while, but then the coupler cuts a groove in the tube, and the problem returns.

I got tired of dealing with this, so I designed this model to solve it for good.

Disclaimer:

Since I'm using the Mellow All Metal Hotend (a clone of the Micro Swiss All Metal Hotend), I designed this upgrade around it. It should work with all similar hotends with a flat, plastic coupler. While the original hotend with a tall, metal coupler should theoretically (barely) fit, you may have a problem accessing the screw behind it to install this upgrade.

Working Principle:

It's really simple—this upgrade clamps the bowden tube above the coupler, limiting its ability to move. As it also limits the rotation of the tube during movement, it should prevent the teeth in the coupler from digging into the tube and cutting a new groove.

Additional Hardware:

  • 2 M3 heat-set inserts (I use 6mm long ones, but shorter should work fine)
  • 2 M3 8mm bolts (button head or socket head; if you use an additional sandpaper strip around the tube, you may need 10mm long ones)
  • (Optional) 8mm wide strip of fine-grit sandpaper

Printing:

I printed mine using PLA and a 0.4mm nozzle with a 0.2mm layer height, but any reasonable combination of nozzle size and layer height should work. PLA is fine, as everything sits way above anything hot, but you may use any material you want except flexibles.

Installation:

Before you begin the installation, you need to press in two heat-set inserts using your soldering iron.

You don't need to completely uninstall the bowden tube from the hotend. First, remove the small plastic clip from the coupler. Next, loosen two screws holding the upper carriage wheels about 2mm. You need to use a small wrench to hold the nuts holding the wheels to prevent them from spinning.

When there is a gap big enough, slide in the mount from the top and retighten two bolts holding the wheels. Check if the carriage moves properly left and right. You may need to readjust the eccentric nut on the bottom wheel if the carriage is too tight or too loose.

Next, align the bowden tube with the groove in the mount and attach the second part of the clamp using two M3 bolts. Don't tighten them yet. You may put a little strip of fine sandpaper around the tube before clamping to help hold it in place. Now push the tube all the way down into the hotend and while it sits firmly at the bottom tighten the bolts carefuly. Reinstall plastic clip on the coupler and the mod is completed.

WARNING:

Under no circumstances should you tighten the bolts all the way to the bottom! You WILL crush the tube and cause blockage! One or two turns of the bolts are probably enough. If you see the tube moving during printing, just add ¼ of a turn. If you want to be extra safe, you may remove the nozzle before installation—you can then pass a piece of filament up and down during tightening the bolts. Then, when you feel even the slightest increase in drag, back up the bolts a bit.

Happy printing!

This small mod really helped me with my jamming problem. I've never had much luck with pneumatic couplers and try to avoid them at all or work around them. I genuinely hope someone finds this little upgrade as helpful as me :) Happy printing!

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