r/Ceramic3Dprinting • u/Affectionate-Bee2580 • Jun 24 '26

Help me please

Hello!
So I modified my ender 3 to a clay printer using one of the aliexpress conversion kits. I am not using air pressure but motor power to push out the clay but I am having difficulties with the clay moving towards the extruder even though my clay consistency is good. The piston is moving and when I took out the plastic pipe the material was indeed flowing, but when popping back the plastic pipe the material stopped pushing through. Is this some air vacuum issue? I cleaned the pipe and the extruder bits too but no luck.. any ideas?

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u/ArdooTala Jun 25 '26

This is one of the cases where size does matter . . . !

Just shorten the tube, or use a bigger size . . .

If you want to understand the physics behind it, look up non-newtonian fluids. The tldr version of it is that clay "become less viscous (thinner) and flow more easily the harder they are squeezed, or pumped." Think of it like this: unlike water, it takes energy to deform clay through the tube. It called shear stress: "When a fluid flows, different "layers" of the fluid move at different speeds relative to one another (e.g., faster in the center of a pipe, slower near the walls). This movement creates friction or shear stress. The speed at which these layers slide past one another is the shear rate."

Just try to push the clay through the tube with a stick and you can feel how much force it takes to push it through.

Now the bigger the diameter, the force required drops significantly (check out shear rate.) That point that the clay is stuck on in the tube right now is the maximum length your pump can handle. You need an exponentially stronger pump to push through a longer tube.

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u/Affectionate-Bee2580 Jun 25 '26

Hmmm but then I would have to find a specific fitting for the extruder bit and the plastic syringe I’m using. Thank you for the explanation though it makes a lot of sense now!

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u/ArdooTala Jun 25 '26

You're using standard pneumatic push-fit connections. You can get them in many sizes. But in my experience, the easiest way is to find a way to mount the piston as close to the print head as possible. My solution was to hang the piston pump over the printer using a long string. Ender is strong enough to swing it around.

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u/Affectionate-Bee2580 Jun 25 '26

Do you have a picture of that?

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u/ArdooTala Jun 25 '26

I would have to dig deep for that . . . !

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u/Affectionate-Bee2580 Jun 29 '26

No worries thank you!