Frostruder Media Observations

I don’t have a frostruder myself, but have learned a few things from those who do. Aparently, one problem is that the frosting continues to extrude after there is no longer force being exerted on the plunger syringe. One idea is that there were air bubbles in the syringe from loading the frosting and the solution is to be better at packing.

I wanted to give it a try, so I removed the plunger from a syringe loaded it by vacuuming through the nozzle with a pump. The loading process went perfectly and there were no bubbles to speak of. I gave the plunger a push and out came some frosting. Success! Well, not really. After I stopped pressing the frosting continued to extrude. Why?

The frosting itself must be compressable! This makes sense since the frosting is a bunch of ingredients whipped and mixed together.

I then set up an experiment to observe the effects of air within the frosting in which one glob of frosting would be placed in an evacuated chamber while another would remain at 1 atmosphere of pressure (first image).

After the chamber was evacuated I could see that the test glob had expanded (second image), presumably from air within the frosting. The test glob collapsed as it was brought back to 1 atmosphere of pressure (third image).

I feel this supports the idea that air within frosting causes continued extrusion.

Possible Solutions
. A valve at the end on the frostruder to regulate frosting extrusion.
. Find an incompressable frosting-like material.
. Don’t use a plunger. Pump air behind the frosting and return it to 1 atmosphere when the frosting should stop extruding.
. Pull the plunger back to bring the pressure withing the syringe to 1 atmosphere.


4 thoughts on “Frostruder Media Observations

  1. I think there is a engineering motto to do best by not adding, but what you can take away. Pulling back the plunger may be better then the valve, since it is already there. I can assume that it would be easy to program. But, the amount you pull back needs to be a constant. If you find that with different frosting’s the amount you pull back is variable, then go with the valve, or the pump air idea.

  2. I think the option about pulling the plunger back should be easy. You could do something easy like attach a plastic rack gear to an extended part of the plunger and just make it reverse when you are done. The issue will be with “pre load” as there will be some time between when you engage the nozzle and when the frosting starts flowing. It seems to me like you might need some sort of frosting flow sensor.

  3. Another consideration is that objects compress under a given pressure by some factor of their current volume. As the volume of frosting remaining in the syringe decreases, the distance which the plunger would need to be pulled back decreases.

    Maybe use a soft frostruder tip that can be squeezed shut. That should be simple enough.

  4. Hey Charles,

    I don’t think this is a frosting media problem, but rather a fluid mechanics problem. Water, which is not compressible, will also exhibit this same problem when plunging a large area/volume through a tiny hole. Microfluidics people will tell you the same experience. I think it is a combination of the housing distending very slightly with increased pressure as well as back-pressure from the high friction going through the tiny hole.

    The solution could be to warm up the frosting a bit so it is less viscous, and will have lower friction.

    An enormously more complicated solution would be to make a microfluidic peristaltic pumping mechanism à la Steve Quake.

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