A special thanks to our friends over at the Het Nieuwe Instituut over in the Netherlands. They prompted us to pull out the frostruder, calibrate the machine and come up with some new recipes for open source cookie baking. Details about the show can be found below.
Exhibition PLASTIC, Promises of a Home-made Future
At Het Nieuwe Instituut in The Netherlands
http://www.hetnieuweinstituut.nl/en/plastic
Working Specs
1 Syringe 60cc or ml [they are the same unit folks].
Working pressure range 40-65 PSI depending on the thickness of dough mixture.
Cookie dough build plates: 1/4″ or 6mm thick aluminum plate. These should be pre-frozen before printing. Pull the build plate from the freezer just before printing to ensure good bed adhesion. [Think wet tongue on a frozen flag pole].
![Layer Resolution [Initial Testing]](http://depts.washington.edu/open3dp/wordpress/wp-content/uploads/2014/12/OctoCookie.png)
Layer Resolution [Initial Testing]
Recipes:
Vanilla Short Bread Cookies
1/2 Cup Flour
1/2 Cup butter
1/2 Brown Sugar
Teaspoon of Vanilla
Ginger Bread Cookies
1/2 Cup Flour
1/2 Cup butter
1/2 Brown Sugar
Teaspoon of Water
1/2 Teaspoon of Ginger
1/2 Teaspoon of Cloves and/or Cardamom
Chocolate Cookies
1/2 Cup Flour
1/2 Cup butter
1/2 Brown Sugar
Teaspoon of Water/or Vanilla
1-2 Teaspoon(s) of Cocoa Powder
The thicker cookies are tricky to cook fast enough to harden without burning them.
STLs
Frostruder Cap
The file below is the stronger version of the quick change cap, re-designed after the two failure mode were discovered.
http://www.thingiverse.com/thing:609952
Bunny Face Cookie
http://www.thingiverse.com/thing:609969
How the bot works
After sitting on the shelf for a year long break “little red” has been refurbished and is back at it again with more spunk and nothing to lose. This peppy little bot has Cupcake brains on a Prusa frame, we are talking some old school Gen3 Makerbot boards, ReplicatorG [GUI] and a python script called frostforge. How does it work? the python script frost forge modifies the G-code pulling out all the extruder commands and replacing them with commands to turn the fan on and off. A three way solenoid valve is wired where the fan would be. This solenoid now regulates the pressure to the syringe.
![You run the python script in the Command Prompt [Terminal] It generally looks like this.](http://depts.washington.edu/open3dp/wordpress/wp-content/uploads/2014/12/IMG_0366.jpg)
You run the python script in the Command Prompt [Terminal] It generally looks like this.
Solenoid ON [Cookie dough comes out]
Solenoid OFF [Residual pressure from the syringe gets vented]
Simple right…? Just ignore the colloidal substrates, advanced fluid mechanics and food chemistry that is happening in realtime… as the pumping of the syringe kneads the cookie dough.
What you need to know is the pressure in your syringe should be below 65PSI, and generally the compression volumes will change 3-6 ml. What does that mean? If you have 10 ml left of cookies dough, then you have essentially Zero ml of cookie dough left. Now your laptop and bot are happily getting sprayed with cookie dough.
Frostrusion is not always the smoothest or cleanest process.
Troubleshooting
Common problems frostruding.
Clogging- Particulate is too large.
Solution- Sift ingredients more or use a finer powder.
Most common ingredient to clog the syringe is the brown sugar. It clumps more than most other ingredients other than fresh ground ginger
Poor extrusion: Either the syringe is clogged or the cookie dough is mixed too thick.
Solution: Check the syringe for clogs… if no clogs, then add a 1/4 teaspoon of water to the dough and mix thoroughly.
Warning do not turn the pressure above 65 PSI
1st failure mode: The clamp and the syringe flange both fatigue quickly at ~70 PSI
2nd failure mode: These polypropylene syringes can’t handle 80 PSI chamber pressure.
Poor Bed Adhesion: Z-axis should be one layer thickness from the bottom of the bed before extrusion.
Solution: Extrude a bead of cookie dough, and Zero the Z-axis to one bead width from the bed.
[See end of bloopers video for an example of poor bed adhesion.]
Baking Process
The baking process is a more complicated to maintain resolution. Remember butter melts… which can destroy the print resolution. The goal is to cook the outer shell to hold the cookie together as the inside cooks. The less water the better.
The cookies are kept in the freezer overnight to help remove the excess water.
The cookies go on to the top rack under the broiler.
As the outside cooked fully the inside becomes molten.
Once the surface starts to brown/harden remove the cookie from the oven.
Cookies will have a light char or browning. And a re-freeze and re-bake may be necessary. Re-bake @ 400F on the lower rack to fully cook thicker cookies.
more on 3D printing cookie dough here
Tags: 3d printed bunny cookie, 3D printed cookies, 3D printing cookies, 3D printing food, bunny cookies, cookie dough recipes, frostration, frostrusion, paste extrusion, printed cookies, syringe printing
You can prevent the syringe cap from ripping apart by adding holes to the side in which you insert M3 bolts. Look at the one I designed for an example, never had the caps failing and used them at 6bar pressure: http://www.thingiverse.com/thing:21074
The cookie dough recipe overcomes static friction at lower pressures, but has a greater lag time for extrusion. [this leads to two failure modes]
The first failure mode had the syringe flange and syringe cap failed simultaneously. It was resolved by making the tolerances tighter and changing the printable orientation.
Parameteric quick change frostruder files: http://www.thingiverse.com/thing:609952
The second failure mode is that the syringe itself can explode above 65 PSI. The fatigue under the drastic pressure changes of the solenoid turning on and off cause the polypropylene do form stress cracks [common in injection molded polymers]. The syringe eventually explodes within 0-2 hours of this rapid high pressure pulsing. It is dependent on the delay between pressure applied and material extruded.
This can be resolved by using a stronger syringe, a metal syringe, or by lowering the pressure requirements of the printable medium.
I believe the folks at http://unfoldfab.blogspot.com handle this pulsing problem by eliminating all of the retract calls in the G-code. It allows pressure to be continuous which requires that the print also be continuous. This is a good work-around, but some of the current projects require retract commands.
6 bar = 87 psi
Working pressure is
45-65 PSI
3.1-4.5 Bar
or
3.0-4.4 Pa [Atmospheres]
Thanks Bowman, BTW ‘the folks at http://unfoldfab.blogspot.com‘, that’s me/us 😉
I see you print your cap in the other direction, good to know that that solves the issue there too. In regards to the failure of the syringes, never seen a syringe break in such a way as you describe. But you’re right to point out that we design our files around the problem although I’ve been playing lately with pulsating a valve rapidly to create patterns. The off cycle is just a fraction of a second to create a small indent, the on cycle is between 1-5 seconds. So that is a lot of cycling and so far haven’t seen breakage happening there. My syringes in the 60cc range are BD Plastipak. I’ve recently upgraded to Techcon industrial 300cc syringes that sit in a full metal jacket. They are designed to handle this (and cost about the same…) and the increased volume gives a smoother more stable output with air pressure. But you’ll have more air to repressor if you intend to switch air on and off.
Yes I have been following your work since 2012, it is good to see the separate ideas evolve in parallel.
Thanks for the syringe information, a good metal jacket will allow our PSI to higher, which could speed up print time, or allow a thicker medium to extruded.
I think the syringe breakage is caused by a strange property gluten in the cookie dough. I had never seen it before, but I have run ~50-100 cookies this month. I found the gluten in the dough would increase in elasticity the longer it was pumped from the syringe, this is would create a greater lag time before extrusion as a print continued. The focal point of the pressure seems to cause stronger pulsing, swelling/flexing of the syringe, and print spray. So I embedded a diffuser in the syringe cap. [If you look down the nozzle in the file there is a triangular diffuser] It resolved most of those issues.
This is different when we extrude things like clay the pulsing tends to separate the aggregate from the medium forming chunks. These chunks eventually migrate at the nozzle tip causing it to clog. Have you run across this behavior with the clay slips you are using?
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