3.5 liter chocolate extruder

Testing begins tomorrow! Planning initial test with pancake batter because I can control viscosity by varying powder to water ratio, and it's a lot cheaper than chocolate.



http://milwaukeemakerspace.org/2015/07/making-a-plunger-for-a-chocolate-syringe/

Haha, a total new way of making yoda shaped pancakes.
How about eggs? With a dual extruder you could print separate white and yellow

Is there a heating element inside the tube? It´s pretty hard to keep it clean, I guess?
-Olaf

I will be wrapping the outside with heater wire and insulation, and using a PID controller to regulate temperature. I haven't decided if I'll melt the chocolate inside the extruder or melt it outside and pour it in. Melting it inside the syringe will be a very slow process because I can't let heater wire get too hot or the pipe will get damaged. Ultimately an aluminum or steel pipe will be a better way to go, but for test purposes PVC will do.

The whole thing comes apart for easy clean-out. Running hot water through it should melt any chocolate residue and allow easy wash out with detergent.

I'm not sure how to deal with air bubbles in the chocolate yet, other than just inverting the whole thing and pushing them out with the plunger. I don't know if the viscosity of the molten chocolate will allow the bubbles to rise or if they will stay suspended in the chocolate. The viscosity changes rapidly over just a few degrees, so maybe warming it beyond extrusion temperature to debubble it, followed by a cool down period to final extrusion temperature/viscosity will be in order. A vibrator may help, or maybe I can use vacuum degassing.

I have devised a so far untested scheme for cooling/solidifying the chocolate as it comes out of the extruder nozzle. I'll be testing that after I'm satisfied that I have a workable extrusion process.

First test an unqualified success!



Edited 1 time(s). Last edit at 07/04/2015 04:59PM by the_digital_dentist.

Hmm, where´s my comment about bubbles?
I made a proposal to use a vent in the piston, that lets air pass, but closes, when a solid paste tries to pass through.

google search

Anyway, from the video I´d say it partly works, but the extruded amount of choc will become unpredictable, when you use a DC motor for it. From the sound in the video I could tell, it slowed down, when it started to compress.
In the nozzle you could use a pressure release valve. Only, when a certain pressure is reached, the paste can pass. This way you won´t have a dribbling nozzle.
With a pressure sensor you could add a way of control to the process, too.
-Olaf

That demo was running at 50-100X the speed that will be used in the final printer, so I am not too concerned about the slow down under load. That slow down occurs when the chocolate starts extruding, and I think it will remain more or less constant once it does because the inside of the syringe will reach an equilibrium pressure between the push from the plunger and the venting at the nozzle, assuming that molten chocolate is an incompressible fluid, which may or may not be the case, and I can get all the air out before extruding. I would have preferred a stepper motor to drive it, but couldn't figure out how to calculate the amount of force required push the chocolate through the nozzle, so I couldn't calculate the motor torque required. The next generation extruder will use a stepper.

The whole thing will be inverted in operation (dramatically reduces floor space required), so if the air is able to rise in the chocolate, it will be vented before the printing starts. I think air will mainly be a problem if I melt the chocolate in the syringe by adding solid chips. If the chocolate is melted outside the syringe and then poured into the extruder air will be much less of a problem. If air bubbles can't rise in the chocolate at print temperature, I may run a cycle at higher temperature to thin it and let air rise, maybe with a vacuum pump connected to the nozzle, then let it cool to print temperature.

The printing device I have planned now will operate at a more or less constant extrusion rate, and will not do any retracting until the "print" is finished. I won't be attempting anything like a full-on FDM printer. Yet.

The air/goo valve is a nice idea, but assumes that all the air in the syringe forms a single bubble that will arrive at the valve before the chocolate does. If some of the chocolate gets there first, the valve stops working and you still have a bunch of air in the syringe.

This is all speculation. We'll see how it behaves soon enough.

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The air/goo valve is a nice idea, but assumes that all the air in the syringe forms a single bubble that will arrive at the valve before the chocolate does. If some of the chocolate gets there first, the valve stops working and you still have a bunch of air in the syringe.

In my dissapeared post I proposed the valve for a syringe, that isn´t filled completely with choc when you insert the piston. Then there would be a lot of air, I assumed.
-Olaf

You mean they don't make chocolate filament??????

They do, but someone at the factory keeps easting it just as fast as they make it

Ah! The evil chocolate pushing Dentist. Tisk, tisk.

After some basic tests and adjustment, I plan to make cordials filled with Mountain Dew and Gummy Bears....

...and leave them in the waiting room??? Did you take a Hippocratic Oath or a Hypocritical Oath?????

No, just good business sense - get the customer to come back over and over and over again!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

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rhmorrison
No, just good business sense - get the customer to come back over and over and over again!

Please dude, patient is the preferred vernacular, not customer...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Update: I tested the turntable screw drive mechanism today:

Chocolate printer screw drive test

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Looking forward to watching its first prints. It must be a huge machine...

It's pretty big. Right now it's assembled by just pounding the PVC pipe pieces together with a rubber mallet- it is too big to fit through normal doorways when assembled, so it will be kept as a "kit" to allow transport.

I have a friend helping write code for the controller right now, and we're working feverishly to get it ready for the Milwaukee Maker Faire. It may make its first ever print at the faire, though I'm reluctant to haul it out if I don't know for sure that it's working.

I have to make a new plunger for the extruder- it seems that the silicone I used shrunk a bit in the couple months since I made the first one and it doesn't fit very tightly in the extruder pipe any more. I'll be printing the mold and recasting that part this week.

Edited 1 time(s). Last edit at 09/14/2015 10:06AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Less than two weeks, I read. Good luck with your work!