NEW MATERIALS: Viscous Liquids & Flexible Solids >

Viscous Liquids

 

Recently TNO researchers have developed a print head that can handle viscous liquids. This allows computer controlled 3D printer to work with stronger objects.

Currently DIY 3D printers can build complex objects by extruding tiny droplets of liquid plastic through extruder but the printed objects are often not strong enough. To be able to print with a conventional print head, the material must be thin liquid and that means the monomers (long molecular chains, the building blocks of a plastic) is short.

“After curing the product is often brittle and fragile,” says Dr. René Houben of the Department Equipment for Additive Manufacturing of TNO.

To solve this problem Houben designed an entirely new print head, suitable for a mixture with much longer chains. The maximum workable viscosity is around 500 mPas (millipascal seconds, the unit of viscosity), similar to thick motor oil.

Houben presented his work at the end of September at the University of Twente.

Most home color printers work with “drop on demand” method: nozzle spits out ink exactly when required. For viscous liquids it does not work like that. For pressing “ink” through the nozzle you need a high pressure of a couple of hundred bar.

Houten made a so-called continuous inkjet to create a continuous stream of droplets. Once in motion only a much lower pressure is needed. The basis of the print head is a metal cylinder with a nozzle of 80 microns in diameter.

Inside the head, just above the nozzle, there is a cylinder with a piezoelectric crystal vibrating at 20 kHz and an amplitude of about 100 nm to ensure a stable flow of liquid.

The liquid is set to vibration and it breaks just below the nozzle at some twenty thousand identical droplets with a diameter of about 140 µm, with a speed of approximately 10 m/s.

In this printing system selective passage of droplets is essential – otherwise it would only be a flat printing. Existing continuous printing usually give droplets a small electric charge and bend them in the direction of a discharge chute. Most plastics, however, are non-conductive.

 

“It is possible to add conductive materials, but this changes the composition, which is usually undesirable. Think of materials for medical implants or displays, in which the material composition is very close, “says Houben.

 

He found an unusual solution: a fine stream of air from a syringe shoots unwanted droplets away. It sounds easy, but the on and off of an air flow of 20 kHz was not feasible.

Therefore TNO researchers developed a fine mechanical system with a continuous airflow – to set the droplet stream within 20 µs and can only shoot single drop out.

“We believe this is the way to get the fastest building speed. We strive to minimize the time that a print head does nothing”, says Houben.

A plastic block that is printed in layers by three heads in three colors: blue, red and transparent plastic. Photo: TNO

Besides 3D printing of relatively strong plastics, the print head has an unexpected application: making milk powder. Milk drops can be rapidly turned into powder by using spray drying in high spray towers.

Source: deingenieur
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Flexible Solids

Fabbster uploaded a video of 3D prints of flexible material made on a Fabbster 3D printer. Fabbster uses a special material concept: SDM – stick deposition moulding.

The extruder of the printer is fed with special sticks developed by the fabbster team. These sticks are characterized by a cogging-shape on their sides. They are made by injection molding technique and thus are extremely precise. This innovation offers some major advantage over circular filament that is subject to slip.

The sticks are automatically fed to the extruder via a supply magazine. The result is a precise dosage of the melt. Also they can be easily combined to produce an object in various colors and materials.

^In this video, Fabbster showed objects printed using sticks made of flexible material and compared the print with ABS plastic print

Source: Fabbster

 

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3DPrinted Customised Electronics…

ARTICLE SPECIALIST KNOWLEDGE LEVEL  > > > >4 >

‘Using printable electronics and rapid manufacturing processes, a more local consumer electronics industry is born. In this system, people select their electronic products online.’

There lay the basis  of the London Royal Collage of Art’s O.Update project by Hannes Harms, Alex du Preez and Peter Krige.

They conceive the increasingly likely premise that in the future, consumers will select their own electronic products online. They will browse through an online database of electronic products and customise the objects they wish to have. The database can then link them to their local store.

At that local outlet, technicians will assist the customer in manufacturing their unique products using 3DPrinting, laser cutting and acid etching. In this way, objects are only manufactured on demand – this system could localise electronics manufacturing and reduce electronic waste.

Products can constantly evolve through update cards. While an update is available a new printed electronic card is sent to the customers and the old electronic cards are sent back for re-manufacture or recycling.

Here is how they conceive their project, ‘O.Update,’ to materialise:
O.Update, Hannes Harms, Alex du Preez and Peter Krige

Materials: Wood Filament > > >

Advertised as looking and even smelling like wood after printing, this 3DPrinter wood filament can be grinded and painted as per conventionally formed wood commodities. By alternating 3DPrint temperatures it’s even possible to produce tree rings. 

This is a big step forward for the home 3DPrinting sector, particularly as one of the major limitations that has been cited over the last year of rapid hype expansion for additive manufacturing has been the low breadth of materials available for the cheaper varieties of printer that are more likely to find themselves on the desk tops of the masses.

That which widens applications widens appeal, that which widens appeal widens potential market, that which widens potential market widens the window of opportunity for 3DPrinting to fulfill it’s publicised, now almost prophetically projected, rise into a revolutionary technology.

TECH SPECS:  The wood is 3mm Diameter, comes as bundle of 500g as per the featured the picture. The material is especially designed for RepRap and similar 3DPrinters. No heated bed is necessary. Recommended extruder temperatures 185°-230°C.

Materials: Is ABS Safe? > > >

There are two plastics most commonly used in home 3D plastic extrusion printers: ABS and PLA.

 
PLA, also known as Polylactic acid or polylactide, has a rather pleasant aroma when heated, sometimes described as “waffles” or “honey”. Along with its lack of warping, the aroma makes for a very satisfactory 3D printing experience. 
 
ABS, also known as Acrylonitrile butadiene styrene, with chemical formula: (C8H8)x· (C4H6)y·(C3H3N)z), has a very different printing experience, particularly when your 3D printer is poorly ventilated. Its smell is very sharp and sometimes can burn your throat if you breathe too much of it.
Coughing can occur and we’ve often heard stories of folks with scratchy throats after a long ABS print operation. While ABS can warp during printing, it does produce strong models that can take a beating.
 
But is it killing you? What happens when you breathe it in? Is it poisonous? Does it cause cancer? We took a deeper look by examining its Material Safety Data Sheet, a document that must accompany any industrial substance. According to the MSDS: 
 
Emergency Overview:
  • Solid pellets with slight or no odor.
  • Spilled plastics create slipping hazard.
  • Can burn in a fire creating dense, toxic smoke.
  • Molten plastic can cause severe thermal burns.
  • Fumes produced during melt processing may cause eye, skin and respiratory tract irritation. Secondary operations, such as grinding, sanding or sawing, can produce dust which may present a respiratory hazard.
  • Product in pellet form is unlikely to cause irritation. 
 
Chronic/Carcinogenicity: 
None of the components present in this material are listed by IARC, NTP, OSHA, or ACGIA as a carcinogen. 
 
We also checked Wikipedia, which says: 
 
ABS is flammable when it is exposed to high temperatures, such as a wood fire. It will melt then boil, at which point the vapors burst into intense, hot flames. Since pure ABS contains no halogens, its combustion does not typically produce any persistent organic pollutants, and the most toxic products of its combustion or pyrolysis are carbon monoxide and hydrogen cyanide.
 
 
There you have it: apparently ABS is, relatively, safe for 3DPrinting. Just don’t set your models on fire or sand them into a fine dust. We imagine you could poke yourself in the eye with a stray filament, too. Nevertheless, we think suitable ventilation is necessary, if only to remove the irritations. 
 

3DPrinted Bikini Beachwear > > >

The N12 bikini claims to be the world’s first wearable “print”, with all of the pieces made directly by 3DPrinting – and they snap together without sewing. The bikini was designed by Jenna Fizel and Mary Huang of Continuum Fashion.

Named after the material it’s made out of, Nylon 12 is created by a laser in the printing process that layers plastic so it bends without breaking. Nylon 12 is strong, flexible and 3DPrintable with an impressive thinness of 0.7 mm (0.027 in).

The material is innately waterproof so it’s ideal as swimwear and according to the designers it actually becomes more comfortable when it gets wet.

A process called Selective Laser Sintering (SLS) is used to achieve the complex geometrical design which combines circles connected by tiny strings.

“The bikini’s design fundamentally reflects the beautiful intricacy possible with 3DPrinting, as well as the technical challenges of creating a flexible surface out of the solid nylon,” says Mary Haung.

The bikini is a starting point, 3DPrinted dresses, zipper included, have been manufactured in a similar way. As the technology developed the range of clothing that can be made directly from digital designs, without any sewing and on one machine continues to grow rapidly.

Here’s  Mary Haung’s talk on the future of fashion and 3DPrinting at NEXT Berlin 2012:

3DPrinter Breaks Resolution Record > > >

Researchers at the Vienna University of Technology (TU Vienna) have made a major breakthrough in speeding up the astonishing “two-photon lithography” 3DPrinting technique.

The high-precision-3D-printer at TU Vienna is orders of magnitude faster than similar devices, opening  up completely new areas of application, such as in medicine.

A model of St. Stephen’s Cathedral, Vienna (credit: Klaus Cicha)

A larger version of St. Stephen's CathedralLondon Tower Bridge – Distance between the towers: 90 µm (credit: Klaus Cicha)
Distance between the towers: 90 µm

‘Setting a New World Record:
The 3DPrinter uses a liquid resin, which is hardened at precisely the correct spots by a focused laser beam. The focal point of the laser beam is guided through the resin by movable mirrors and leaves behind a polymerized line of solid polymer, just a few hundred nanometers wide. This high resolution enables the creation of intricately structured sculptures as tiny as a grain of sand. “Until now, this technique used to be quite slow”, says Professor Jürgen Stampfl from the Institute of Materials Science and Technology at the TU Vienna. “The printing speed used to be measured in millimeters per second – our device can do five meters in one second.” In two-photon lithography, this is a world record.

This amazing progress was made possible by combining several new ideas. “It was crucial to improve the control mechanism of the mirrors”, says Jan Torgersen (TU Vienna). The mirrors are continuously in motion during the printing process. The acceleration and deceleration-periods have to be tuned very precisely to achieve high-resolution results at a record-breaking speed.

Photoactive Molecules Harden the Resin:
3DPrinting is not all about mechanics – chemists had a crucial role to play in this project too. “The resin contains molecules, which are activated by the laser light. They induce a chain reaction in other components of the resin, so-called monomers, and turn them into a solid”, says Jan Torgersen. These initiator molecules are only activated if they absorb two photons of the laser beam at once – and this only happens in the very center of the laser beam, where the intensity is highest.

In contrast to conventional 3DPrinting techniques, solid material can be created anywhere within the liquid resin rather than on top of the previously created layer only. Therefore, the working surface does not have to be specially prepared before the next layer can be produced, which saves a lot of time. A team of chemists led by Professor Robert Liska (Vienna) developed the suitable initiators for this special resin.

Because of the dramatically increased speed, much larger objects can now be created in a given period of time. This makes two-photon-lithography an interesting technique for industry.

At the TU Vienna, scientists are now developing bio-compatible resins for medical applications. They can be used to create scaffolds to which living cells can attach themselves facilitating the systematic creation of biological tissues. The 3DPrinter could also be used to create tailor made construction parts for biotechnology or nanotechnology.’

Abstract and images from: http://www.tuwien.ac.at/en/news/news_detail/article/7444/