Fwd: [kc-fabricators] RepRap + Bioengineering = Awesome.

[Bryan Bishop]

From: Jordan Miller <jrd...@gmail.com>

Date: Sat, Jul 7, 2012 at 8:05 AM
Subject: Re: [kc-fabricators] RepRap + Bioengineering = Awesome.
To: "kc-fabr...@googlegroups.com" <kc-fabr...@googlegroups.com>

thanks Greg!

I call it the Baricuda Extruder

I tried to keep it simple... it's redesigned based on MakerBot Frostruder ideas-- i used a glass syringe that I can heat with nichrome and measure with a thermistor, driven by air pressure (that's where "Baric" in Baricuda comes from). Though these items are not rated as food grade, heated glass is still food safe and has a steel luer lock tip so you can choose your steel nozzle. steel is food safe. still trying to figure out the regulatory burden for food grade stuff but I think MakerBot just ignores the potential issues so we should be pretty good as is.

I just posted all relevant design iterations, experiments, details, and source files at:

http://blog.reprap.org/

http://www.thingiverse.com/jmil

http://www.github.com/jmil/Baricuda

And they made me a reprap core dev now! such an honor :)

the sugar glass formula I used is in our paper but has a special sugar called dextran added. But don't worry, any sugar glass or chocolate will work. A simple sugar glass is sucrose (table sugar) mixed with corn syrup (concentrated glucose solution). you just need to find the right temp depending on how much water you left in the mixture (a candy thermometer works great for getting things going -- indeed my first feasibility experiment was done in my kitchen :-D). the glucose prevents the sucrose from recrystallizing (opaque, powdery) and gives you a stable glass (crystal clear). this has been known for literally a hundred years in the candy industry but took me a while to dig up the details and some trial and error to get things working (but thats where the fun comes in!).

for heated liquid extrusion, don't try to get precise air pressure, that is hard/expensive to do. Better to just take your air pressure as fixed (ours is 40 psi max) and then adjust temp of your sugar with high precision (which is easy) to its optimal glassy state. Temperature controls viscosity which therefore controls extrusion rate at a fixed pressure. our sugars extrude well at 110 degrees Celsius after being heated past the hard crack stage (155 degrees Celsius, to boil off most of the water you initially dissolve them in).

Some sugars burn faster than others so you may have trouble if you are doing 8 hour extrusions (burned sugars have viscosity that is changing with time as they caramelize unfortunately) but for the most part you should be good.

and cleanup is a cinch! just use water for sugar to redissolve everything. but don't add water to cleanup chocolate. chocolatiers just use heat to melt everything and wipe off to go for another round.

cheers,

jordan

On Jul 6, 2012, at 11:13 AM, GregY <bigg....@gmail.com> wrote:

Ok Jordan, that was damn cool.  You just gave me an idea on how to plumb air through a part that I couldn't get the struct right on.  Never thought about melting away some of the material.  I could also use the sugar as a support material for fine features.

What was your nozzle and sugar method for extrusion?  Were you using cane sugar melting through the hot end with a plunger for pressure control?

Greg

On Monday, July 2, 2012 5:40:27 PM UTC-5, Jordan Miller wrote:

thanks guys! As you know I'm an avid listener on here :D

If anyone wants a copy of the paper just gimme a holler here: jsmi...@seas.upenn.edu

cheers,
jordan





On Jul 2, 2012, at 6:36 PM, Luis E. Rodriguez wrote:

> http://www.youtube.com/watch?v=9VHFlwJQIkE
>
> Luis E. Rodriguez
> Are you a Maker?
>
>
>
>
> On Sun, Jul 1, 2012 at 11:41 PM, Rob Giseburt <gise...@gmail.com> wrote:
> Jordan Miller is using a RepRap to engineer living tissues for regenerative medicine: http://www.hive76.org/how-to-innovate-in-science-with-open-source-technology
>
>   -Rob
> —
> MakerBot Operator
> Member of CCCKC Hackerspace
> Member of KC Fabricators Google Group
>
>

--
- Bryan
http://heybryan.org/
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