Herniating Syringe in Cracker Dough Printing Project

Hello folks,

I’ve been attempting to push through a custom dough – and when the pressure builds, I have great luck extruding it. However, yesterday, the new sturdy syringes that I grabbed from Structur3d appear to be deforming and herniating.

That material was custom tuned to make extrusion more predictable than most “doughs” – it is actually closer to a cracker material – no yeast or leavening, doesn’t spring/expand, at least noticeably, and maintains the same threadwidth after being deposited. Steady heat over time hardens it without causing to leap, spring, rise, or whatever the correct baking term is for expanding when heated.

I’m trying to sort out what the next step should be – between adjusting the dough softness (softer than silicone, as far as I can tell – but am attempting to gauge if it hardens under compression in a way that makes it behave differently than silicone), the M92 E1000 setting (for UM2, thus UM2 not + series), ambient temperature (again, no rise in the dough, so am hoping that no additional contributors to pressure are happening at room temperature), or other factors.

Here are photos of the syringe.

Here’s my current drop-in Start.gcode style header:

`G28 ; home all axes
G1 Z5 F5000 ; lift nozzle


M302 ;Allow cold extrusion
M92 E10000  ;Increases extruder steps (required to turn Discov3ry)
M500 ;Store new temporary M92 settings
M501 ;Set temporary parameters to current M92 settings
G21 ; set units to millimeters
G90 ; use absolute coordinates
M82 ; use absolute distances for extrusion

G28 X0 Y0                     ;move X/Y to endstops
G1 Z30 F1800.00        ;move the platform down 30mm
G1 X110 Y110                  ;move X/Y to centre

M107  ;start with the fan off

G92 E0    ;zero the extruded length

G0 F7200.000000 X53.023 Y37.752 Z0.400

Could really use some help and advice!

I suspect this has to do more with the rheological properties of the cracker dough than the syringes.

The materials that are ideal in paste form for 3D printing all exhibit some degree of shear thinning. What this means is that applied pressure causes the material to relax a bit and flow.

In doing some searching on research for doughs, it seems that the ideal cracker dough exhibits zero shear thinning. So while this kind of dough formulation would make great crackers, it appears it is less than ideal for 3D printing.

Adding other agents to the dough can improve this characteristic and make the material more “flowable.” These agents can include cellulose or pea fiber (see research paper here, http://www.doiserbia.nb.rs/img/doi/1450-7188/2015/1450-71881546029D.pdf). It is possible adding a bit more fat can also achieve better flow properties, so lard, coconut oil, or butter should work well in small quantities.

We are checking out some ingredients tweaks like you mentioned – thanks for these detailed notes and the link to the paper!

These details were really helpful for us. We started experimenting with butter and lard, and creaming/not creaming as style of mixing the ingredients, and have managed to pull out a huge range of material properties from this dough. Now we are wondering if dual Discov3ry units might help us to find food-forward approaches to strengthen the results. Thanks for the help!

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Awesome! Dual Discov3ry units could yield interesting results beyond regular mixing. This might have more interesting results for holiday treats. For example, you could print alternating layers of shortbread and marzipan, then bake the resulting cookie to get a nice blend of flavors.