For testing the sand extruder I will build a 2D printer similar to my Inkjet Printer which should be able to draw two colored sand pictures.

If everything works, I can later add a Z axis to the bottom of the 2D printer print surface.

It should also be possible to print different materials with different toolhead setups like:

sand + sand for drawing pictures

sand + metal powder for metal objects

sand + clay/ceramics for clay/ceramics objects with sand supports

powder + laser for sls printing

powder + inkjet head for binder jetting

sand + glass powder for glass objects

Maybe I'm too optimistic and it will not work for any reason, but until that's the case I will share my experience with you.

Multi Material Powder/Sand Toolhead

For printing with sand and powder I built a multi material toolhead, which should be able to print with two different materials without a toolchanging sequence through a single nozzle. This has the advantage that there is no second nozzle which could destroy the depositioned layer of material if there would be any height difference between the two nozzles. There is also no time wasted for a toolchanging sequence. It should work by doing something like "coasting at end" for emptying the funnel, which is the equivalent to the pressure - and in this case the entire material in the hotend - before starting with the other material. This should also happen before every travel move and should not add more time to the printing process.

The only downside at the moment is, that the toolhead is quite heavy it weights about 2kg which will maybe require a heavier X axis for fast movements. The major part of the high weight comes from the two geared stepper motors which are necessary for driving the augers/drill bits which feed the material.

A test run of the toolhead.

A test run of the sand printhead. The flow is not steady, yet. For the next test I will look for a better auger to carry the sand.

Another test - This time I used a "normal" drill bit instead of a stone drill bit and the result is way better. Will buy another one to use both "extruders" in the next test.

Because the auger based Powder/Sand Toolhead was not really reliable I designed a paddle wheel based toolhead which works way better. The new printhead weights also less, what enables higher printing speeds.