Sunday, April 23, 2017

Clay 3D Printing with Jonathan Keep...

When an opportunity arises to join a clay 3d printing workshop with Jonathan Keep, it should not be passed up! Jonathan describes himself simply as an artist and potter, but as evidenced by his own website, he is much more than that simple description. The breath and depth of his lifetime of work in ceramics, makes a workshop with him something much greater than a instructional 'how to' 3d print in clay. You just know it's going to be something special!

In more recent years Jonathan's exploration of digital technology, from an artists perspective, brought him to learn how to model and code in programs like Blender and Processing, creating patterns, shapes, even vessels in a virtual world. A next logical step for him was to explore how to bring the shapes to life in clay and fire into wonderful ceramic works. Learning from what the RepRap movement was sharing about 3d printing in plastics, Jonathan went about adapting a RepRap design (Rostock Delta) to print in clay, creating and sharing his own clay delta 3d printer with the world (2013).

His "Ceramic Delta" broke new ground, with it's simplicity of design and ease of construction, even with limited DIY tools and materials. The printer, specifically for printing in clay, was easily constructed, making it an attractive option for other artists, designers and potters to build themselves. The printer he launched and the desire for people to create their own clay 3d printers continues to be supported via a Google+ Community called  Make Your Own Ceramic 3D Printer.

The workshop...
What I'd like to convey here are some observations and explanations of the clay printing process, complemented with photos and videos from the two day workshop I attended. It was interesting from my perspective to be comparing the clay 3d printing process to that of printing in plastic, as I'm very familiar with plastics, but never before printed in clay. There were many parallels and some differences which I'll try capture. Also, this post is not meant as an instructional document, more a log of key processes followed and some notes along the way.

The Workshop took place at Fab Lab Limerick, which is equipped with a variety of 3d printers. One of these, the Wasp, has a 3d print-head and related air pressurised chamber for clay delivery. This is what was used for the workshop.
Jonathan setting a clay print on the WASP printer.

A simple hollow cylinder always forms a good test print for tuning in the printer.  Photo: Johanna Aaspollu.
Cylinder Diam 50mm approx.
It's all in the preparation...
What immediately stood out about printing in clay was the time given to preparation. In plastics the only setup time is in changing a roll of filament or waiting for the heated bed to come up to temperature. In clay, the preparation of the clay is everything. Softening the clay with the addition of water is a skilled process. The judgment of how soft to make it also requiring careful judgment and experience. Too hard and the the clay won't flow easily from the pressurised chamber. Too soft and the printed object won't support it's own weight and simply collapse. The best way I can convey the mixing process and final consistency of the clay is the share a video of the process in it's entirety.
Clay is cut in thin slices using wire, and dipped in water for an initial wetting. A fork is used to increase the water contact area with the clay. The complete softening process is illustrated in full in the video below (20min).
Video courtesy of Johanna Aaspollu, Fab Lab Limerick.

Note: Some clay preparation guides illustrate the use of  ethyl achohol (ethanol) as a softener, mostly in place of water. The ethanol will decrease the viscosity of the clay also. It will evaporate during the drying stage and may make softening the clay an easier process, but in discussion during the workshop it was collectively felt that for health and safety reasons we would stick with water. Good ventilation and masks would be required to work with ethanol.

Loading the clay...
My observation of clay printer designs is that there's a chamber of some sort to hold the softened clay. This cylinder typically has a piston type insert and is pressurised by air or perhaps mechanical means to force the clay out of the cylinder, through a pipe, to the print head. The clay may be directly fed to a nozzle, or delivered in a more controlled manner via an auger screw driven by a stepper motor. The WASP has a motor driven screw to move the clay through the nozzle. The movement of the print head in three dimensions on a clay printer is no different to equivalent style plastic printers.

In our workshop session Jonathan took the clay and carefully loaded it into an aluminium cylinder, adding large scoops and careful to avoid trapping any air while loading. The clean inside of the cylinder received a light coating of silicon spray lubricant before loading any clay.

There isn't a single "right way" to load clay. The important point is to avoid any method that might get air pockets trapped in the clay. The piston, in the WASP design, has two rubber "O" ring gaskets. It's important to ensure they are seated well and free of clay from any previous use.

Both end-caps of the cylinder were screwed back on, hand tight, making sure the threads were clean. The air valve was opened slowly until the pressure rose to about 4 bar, and clay began to flow through the 12mm teflon tubing, connected to the cylinder via a pneumatic style push-fitting.
Above shows the air pressure control valve which keeps the piston under force against the clay in the cylinder.
Above: Jonathan opens the air valve, increasing the air pressure to about 4 Bar. Clay begins to flow at a slow but steady pace from the connected pipe. This pipe then gets connected to the push-fitting in the extruder printhead assembly.

Slicing and tuning...
With a presumption that you are able to get a 3d model of your object to STL format, the next key step for 3d printing is to 'slice' the object. This generates a 'gcode' instruction file for the printer. There are many slicing packages to choose from, and everyone has their favorite. The fact that we were printing in clay was is some ways irrelevant to the slicing process.

If anything, configuring your slicing software for clay printing is a lot easier. You have no heated bed, nozzle temperature or cooling to consider or manage. Typically also your are printing a 'vase' or 'vessel' style single walled object, so infill percentage or pattern is not a factor. A 'spiral' or 'vase' setting is usually chosen, and that was the primary choice in our workshop also. With this setting it's usual not to have any top or even bottom on your object. If a base was desired on our objects then Jonathan quickly showed us how to press a solid disk in clay and print onto that. This over-sized base could be easily trimmed to shape later once the object was printed and allowed to dry for a while. This also saved on printing time and gave good solid bases to our prints.
Above: Jonathan shows a clay base placed on an MDF disc.

The WASP printer only came with a .5mm nozzle for the clay extruder. Jonathan's preference was for a 2mm or even 3mm nozzle for clay printing. A new nozzle was fashioned from some threaded rod and drilled out to 2mm by Michael in the Fab Lab, and it worked excellently, as visible in some of the photos below.

With experience and confidence showing, Jonathan soon has the printer working well with the new nozzle, choosing to just get it printing then play with the flow setting via the printer control panel.

An easy way to tune in the printer was to print a simple cylinder, with a .6mm layer height and ~ 1.5mm wall thickness set in Cura and see what happened. Jonathan adjusted the flow rate on the machine's control panel until a visually satisfactory result was obtained. Corrections could always be made back into Cura settings later to negate the need for any control panel changes when printing in future.

This approach taken by Jonathan may be in contrast to how you might carefully research and select settings for your particular machine when printing in plastic for the first time. But clay from a 2mm nozzle was far more forgiving of 'loose' settings. Once the Z height was reasonably dialled in the clay would take nicely to the base, and soon begin to grow the object as it spiraled around.
Above: Jonathan tuning the flow via the printer control panel.
Above: Test cylinder printing in 'spiral' mode, continuous rise in Z direction.
Video courtesy of Johanna Aaspollu, Fab Lab Limerick.
This cylinder was drawn in Blender and sliced in Cura,  Jonathan has shared  Cura settings on a Google+ ceramic printer group

Printer bed surfaces...
Jonathan recommended that an absorbent surface rather than a smooth surface was best for clay printing. An absorbent surface would absorb moisture, drying the base as the rest of the object also dried. A smooth surface under the base would prevent drying at the same rate as the rest of the object. Uniform drying of the clay is very important, I've learned. 

The Fab Lab laser cut some 200mm discs from MDF (9mm), and these proved ideal for printing on to. The printer was "zeroed" to the height of two discs, and as Jonathan explained in the following video, this meant we could choose to easily print our object with or without a base with no printer z-height adjustment needed. The discs were simply held in place with some 'blobs' of clay, and that gave a quick and efficient swap out of finished prints, welcome in our workshop scenario.

Above: Making a clay base for your print.
Video courtesy of Johanna Aaspollu, Fab Lab Limerick.

First prints...
The beauty of printing in clay, was that if your first layer wasn't good due to poor initial flow or even z-height setting, you could easily start over with a simple wipe-down and print again!
Above: Restarting a print job after poor initial clay flow.
Video courtesy of Johanna Aaspollu, Fab Lab Limerick.

Above: 5min in Blender, allowed Jonathan's experience to draw this object and move quickly to get something printing to demonstrate the process end-to-end early on in the workshop. Good strategy. Impressive result.
By the end of the two day workshop, everyone had produced some prints. Keeping in mind that many of the attendees had never 3d printed in any medium, the results were very impressive, and the workshop a great success. With the majority of the participants being from a ceramics background, students and professionals, this introduction to 3d printing in clay had everyone very excited about a new direction to explore with their clay medium. 
Above: A mix of objects printed during the workshop. The majority original creations, the lower two from Thingiverse thing:969262 and thing:1063915.
A big part of the 3d learning curve, whether you are printing in clay of any other material, is 3d modelling. Some of the workshop discussion was given to this topic, since many of the participants had no computer based 3d modelling skills. While the power and potential of Blender was demonstrated, we reverted to Autodesk Tinkercad, and in my case 123D Design to begin drawing some objects we could later print. (Sadly, both programs are now being retired by Autodesk.)  Identifying and learning a 3d modelling program that meets your needs is one of the biggest obstacles and challenges in exploring 3d printing in any material.

Above: Once fired the object is transformed in strength and appearance.

To conclude, a big thanks goes out to Jonathan Keep for giving the workshop, to the Future Artist-Maker Labs exhibition and events program for funding and organisation, to Fab Lab Limerick for hosting and providing the equipment and venue, and to the Ceramics dept. at Limerick School of Art and Design (LSAD) for firing the printed pieces. Should you care to view them, some more photos of the fired prints are posted to Ceramics at LSAD Facebook page.

Thanks for viewing.