ganter on May 25, 2015

It seems like everyone is getting on the DLP bandwagon in the 3D printing space as of late.  While we have known about DLP 3D printing (i.e. vat photopolymerization process – ASTM F2792 − 12a)  for some time, we had chosen to stay away mostly due to resin issues.   Over the past few years, many new resin formulations have become available and many are both low in odor with toxicity within reasonable limits (in fact several resin systems are open sourced).  When you combine the improved resin systems with substantial activity in crowd funding sites and IRC chat, we decided to jump in to see what all the flashing lights were about.  We purchased a couple of systems and have been exploring both overall print system and resin concepts.


{One of our tet-ty bears under production using a test DLP system}

The left image is the exposure phase (about 1 sec).  The middle image during the peel and re-position phase (about 1 sec). The right image is a completed tet-ty.   It’s exciting to see the speed and quality of this process – no wonder everyone is excited.

ganter on May 22, 2015

We have been experimenting with creation and printing of structured and unstructured tetrahedral meshes over the past several months.  Our work has just been for fun and experimentation.     It currently involves multiple steps through different software systems (we are working on reducing what’s required).  Please notice that the animals are completely filled with tetrahedral structures (it is not simply a surface shell structure).

We are pleased to present:


{ a tetra-saurus rex}

tet_bear2{a tet-ty bear}

We will be posting more tet-ty creatures as our work progresses.

ganter on May 15, 2015

The Open3DP site received the following this week:

Hi Open3DP,


We are happy to tell you that CGTrader community has named you The Best Website For 3D Printing News out there!


CGTrader asked their 180 000 community members to vote for the best 3D online resources, software, tools and designers.  Qualitative and quantitative surveys were answered by 662 designers and they chose their favorites in the industry.


For more information on this award and other categories please check out: CGTrader page

Thank you!

ganter on April 28, 2015

Dear Readers,

Thanks for your patience.

After a bit of work,  we are running on new campus level servers.   This mean MUCH better up-time and automatic backup — hopefully more reliable service for you.

For a short time, there will be a redirection page (but that will go away in the near future).

BUT the real reason that we moved to campus level servers was SECURITY.   We were just getting tired of folks on the internet attempting to break into our little server.   Our failed login file was about 2GB each day.     When that failed, they were running DNS and flooding attacks.   I believe that will be done very soon.

I hope you all look forward to more OPEN material from us.

Yours … Open3DP team.


The Autodesk Spark team has done something quite unusual in the world of commercial 3D printing companies (3D Systems and Stratasys, please take note).  The Spark team has brought out a DLP style printer called the Ember which employs photo-resin technology.


{from lemoncurry group}

The Ember system is a bit on the high end in terms of cost (coming in at about $6000).   It is a bit out of the price league for home consumers but possibly within the scope of prosumers and small companies.  Unlike almost all 3D printing companies, Autodesk promised that they would not use the “razor blade model” for consumables (according to Duann Scott).     They have come through!   Autodesk released PR48 under CC-SA.

Thank you!

To get all the details, please check out their post on the spark blog:



ganter on March 6, 2015

by Kat Steele

Seattle Handathon

Students join forces to hack 3D-printed prosthetic hands

 Seattle’s first-ever “Handathon” brought together students, faculty, and clinicians last weekend for a 24-hour, hackathon-style challenge to build better 3-D printed prosthetic hands.  The event included two dozen participants from the engineering and prosthetics & orthotics (P&O) programs at UW-Seattle, UW-Bothell, and Seattle Pacific University.

 TheBeginning  The Beginning

 Teams were challenged to improve the latest open-source 3D-printed hand design, the Raptor Hand – from functional improvements to crazy design ideas. All teams had access to a CAD lab, 3D-printers, tools, actuators, electronics (Arduino, electromyography, etc.), and enough pizza, coffee, and treats to keep them energized for 24 hours.

 At the end of 24 hours we were amazed at the designs and improvements the students had developed.

The winning team, Dexterity, had two P&O students on the team and focused on function and comfort. They modified the thumb to provide more degrees of freedom and allow multiple types of grasps. To improve comfort, they incorporated a neoprene sleeve.

TeamDexterity Team Dexterity

 The second place team, Myo, used an Arduino with electromyography to create a locking mechanism for the hand. The current hand design lets users open and close the hand by flexing and extending their wrist. However, if you want to hold onto something for a long period, you have to keep flexing your wrist. To reduce fatigue, Myo created a simple mechanism that could lock the hand into a specific position triggered by electromyography.

Congratulations to all the participants! Over the next few weeks designs will be uploaded to the E-nable community to let others continue to build and innovate on the open-source designs. From Seattle, we challenge more groups to take hackathons from programming to physical devices!

The Handathon was organized by Dr. Kat Steele, a UW assistant professor in mechanical engineering and students in her Ability & Innovation Lab, along with Mark Ganter, a UW professor of mechanical engineering; Sue Spaulding, a UW teaching associate in rehabilitation medicine; Pierre Mourad and Ivan Owen at UW Bothell; and Adam Arabian at Seattle Pacific University.


 Karla Vega incorporates the actuator for Myo’s locking mechanism.

ganter on January 27, 2015


{Prequel update:  the UW press team produced a nice version of this story that is a little less technical}


We would like to take a moment to share with you some very exciting news on our research front.    When different research teams partner together amazing things can and do happen.    This research paper is available free for about a year compliments of A.J. Boydston.     Click on the paper title below to read the paper.

We promise more AM related details and results soon.

3D-Printed Mechanochromic Materials

Department of Chemistry and Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195 United States
ACS Appl. Mater. Interfaces, 2015, 7 (1), pp 577–583
DOI: 10.1021/am506745m
We describe the preparation and characterization of photo- and mechanochromic 3D-printed structures using a commercial fused filament fabrication printer. Three spiropyran-containing poly(ε-caprolactone) (PCL) polymers were each filamentized and used to print single- and multicomponent tensile testing specimens that would be difficult, if not impossible, to prepare using traditional manufacturing techniques. It was determined that the filament production and printing process did not degrade the spiropyran units or polymer chains and that the mechanical properties of the specimens prepared with the custom filament were in good agreement with those from commercial PCL filament. In addition to printing photochromic and dual photo- and mechanochromic PCL materials, we also prepare PCL containing a spiropyran unit that is selectively activated by mechanical impetus. Multicomponent specimens containing two different responsive spiropyrans enabled selective activation of different regions within the specimen depending on the stimulus applied to the material. By taking advantage of the unique capabilities of 3D printing, we also demonstrate rapid modification of a prototype force sensor that enables the assessment of peak load by simple visual assessment of mechanochromism.



For those not familiar with the field of chemistry and the ACS journal, when you see “Supporting Information” in the text click it for another paper’s worth of research result details.
bowman on January 17, 2015

When a part takes 15 hours to print and it breaks, a little chemistry can come in handy. Besides, who doesn’t want take two parts and want to stick them together. Want to know if/how to solvate a polymer? Skip the gnarly home cocktails of ABS & turpentine and learn how to make a good chemical bond below.


Chemical Bonding:  Adhesives to English description

[Acrylic] =>Super Glue [Cyanoacrylate]–  water [a weak base] on the surface of the part neutralizes the stabilizer [a weak acid] in the super glue and causing to set quickly [aka anionic polymerization]

When to use Super Glue [cyanoacrylate] generally if it has the word acrylic in the name. Cyanoacrylate and acrylic [PMMA, MMA, etc]  based polymers can get good bonding at the molecular level.


[ABS, PVC, HIPS] => Acetone and Methyl Ethyl Ketone [MEK aka 2-Butanone] will dissolve both ABS and PVC and chemically rebuild the joint in a less ordered manner as the solvents dries. It essentially adds enough chemical energy to allow the polymer to move around an re-order itself for several minutes before the polymer runs out of energy and sets.

More explanation here: ABS plastic & Solvents: 4 good ideas

Sidenote: Acetone can often instantaneously dissolve polymers with lots of styrene. Styrene [Benzene] groups are prone to ring opening. This is when the benzene ring breaks open and releases a fair amount of energy. ABS will not have this behavior, but it is good to do a test piece before address other styrene polymer eg. “High Impact PolyStyrene”[HIPS]


Flexible Materials


Bonds to other silicones.

Rubber and Latex

Both rubber and latex are important for 3D printing allow parts to be designed with flexible joints, gaskets, sleeves etc. Rubber cement can work surprisingly well.  However latex and many robust rubbers need to be primed or dissolve with N- heptane is a good solvent for latex and most rubbers.  Bestine makes a good rubber (with N-Heptane)  cement that can bond to both.

Polyurethane [PU]

Ninjaflex is a good example of a flexible polyurethane. Polyurethane based adhesive can bond on a molecular level with polyurethane parts. Gorilla glue is cheap effective and readily available, flooring and wood finishes offer a mixture for finer applications.

Polypropelyene [PP]

PP [#5] will fuse to most of the polyethylenes. It is fairly solvent resistant, but polyurethanes will interact with the polymer.


It is best to avoid these polymer solvents

Nalgene /Poly Carbonate[PC] – Methylene Chloride dissolves this along with a long list on MeCl based cocktails. [Which means use gloves, goggles, proper ventilation and/or a good respirator] A better alternative for polycarbonate friction fusion. PC has a pretty good friction/heat fusion like PLA.

PolyLactic Acid [PLA] can be dissolved in Bases like, weak concentrations of Lye and Isopropyl Alcohol … however this mix can cause damage to the nervous system. [Which means use gloves, goggles, proper ventilation and/or a good respirator]


These polymers just don’t dissolve. [except with superacids and other complex chemistry.

Kinetic bonding– polymers that can’t be chemically bonded easily, can be fused with ultrasonic welding or with high heat. Layer to layer fusion with heat is one of the main principles that many 3D printers  rely on.  The extrusion temperature for the polymer is also the welding/fusion temperature. Parts can be bonded manually with the appropriate application of heat.

These polymers are all extremely resistant to acids/bases and solvents.

#1 Poly Ethylene Terephthalate [PET]

#2 High Density Poly Ethylene [HDPE]

#4 Low Density Poly Ethylene [LDPE]

High Molecular Weight Poly Ethylene [HMWPE]

Teflon [PTFE]



Five rules to help a reader answer their own solvent questions.

There are some solvents you should avoid, teratomas [tumors] and liver toxicity are not worth it. Don’t risk your health and  don’t waste your time.

[Chemists out there… stop cringing at the gross generalizations… the DIY folks will be fine].


Rule 1: Read the back of the label… that is where the real information is.

Business often gets in the way of industry information by creating catchy buzz words and brand names.  On the back of any product there should be a list of ingredients. This will inform the reader about what family of polymer, adhesive, etc that a product belongs to. The if the warning labels and ingredients don’t explicitly tell the contents check the MSDS sheets for the product. Often the name of the solvent with sound similar to the material name…[Thank you scientific naming conventions]

e.g. cyanoacrylate (super glue) & methylmethylacrylate (acrylic)


Rule 2: Like dissolves Like… this is one of the universal axioms that holds our universe together.

Greasy things are solvated by greasy things, polar things are dissolved by polar things. Think oil and water, they don’t really dissolve each other, they create an emulsion. Where does your polymer lie on the greasy to polar spectrum.


The polar functional groups allow plastics to be solvated by polar solvents like acetone or MEK.

The polar functional groups allow plastics to be solvated by polar solvents like acetone or MEK.

Thanks again Wikipedia you are worth every penny.


Rule 3: Acid Base Chemistry Exists… Deal with it.

Things like PolyLactic Acid are dissolved in Bases like, weak concentrations of Lye and Isopropyl Alcohol.  Get cozy with the periodic table. The electronegativity arrangement and electron shell information comes in handy. Polar groups bond to polar solvents. Hydrogen bonding is the giant electromagnet of the polymer world. This means water [super polar] and alcohols [polar but greasy] are good at dissolving things. Why does acetone work well? It is so tiny it fits into most small polymeric crevices. It has a free proton due to resonance, but it is still greasy enough to hang out with the other cool polymers.



Water is extremely polar


Acetone is tiny carbon chain. It is known as a polar protic solvent. It can handle proton swapping because of its free electrons, it’s electronegative character.


Alcohols refers to OH [the oxygen and hydrogen bonded] on a carbon chain. Alcohols tend to be bulkier and slower for solvation they are common in SN1 and SN2 reactions.

Rule 4: Wikipedia and Google images… Learn to love them

Rule 3 describes a substitution reaction. SN1 or SN2 reactions are chemistry “terms” that will help improve search-ability for the necessary solvents.  It will be important to be able to classify similar solvents and plausible way for chemistry to happen.


Rule 5:  Read the MSDS sheets…Methyl Chloride is not your friend … and neither is Toluene.

If toxicity is this obvious head the warnings,

If toxicity is this obvious heed the warnings.


Always check Section 3 for health factors

Always check Section 3 for health factors



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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



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]

Layer Resolution [Initial Testing]


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 hard to cook fast enough to harden without burning them.

The thicker cookies are tricky to cook fast enough to harden without burning them.




Frostruder Cap

The file below is the stronger version of the quick change cap, re-designed after the two failure mode were discovered.


Bunny Face Cookie


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.

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.




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

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


The clamp top and the syringe flange both fatigue quickly at ~70 PSI

1st failure mode: The clamp and the syringe flange both fatigue quickly at ~70 PSI


These polypropylene syringes can't handle 80 PSI chamber pressure

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 are kept in the freezer overnight to help remove the excess water.


The cookies go on to the top rack under the broiler.

The cookies go on to the top rack under the broiler.


As the outside cooked fully the inside becomes molten.

As the outside cooked fully the inside becomes molten.


Once the surface starts to brown/harden remove the cookie from the oven.

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.

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



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Eamon McQuaide on December 17, 2014

As the complexity of the part increased from our initial support design study :, the support we originally made was no longer suitable for use, as it would get trapped within the lattice structure we created, and be impossible to pull out. Now things are getting interesting..



We noticed two things from our prior experiment:

1.  We wasted time and filament making solid support.  We needed to turn the support into a shell to reduce heat, and wasted material.  This will also make it easier to break out later.

2. We needed to add thin sections in the support to make it weak enough there to break apart to get it out.

Here is what the completed part looked like from the bottom:



You can see now that the support was hollowed after it was designed in by using a “shell” command in Solidworks. We used a .5 MM shell thickness, which was a bit overkill.  It could have been done with .3 with equal success. The gaps between the part and it’s support was consistent with the last setup.  You can see in the foreground that there was a built in stress riser (thin spot about .05 MM thick) up the middle to aid in breakout, and the results were the support came out in two equal pieces.  The results were excellent!