Virtual Pottery Wheel

We recently made a video from the Virtual Pottery Wheel that is part of Unfold's L'Artisan Electronique installation. We have already a slightly better version where you need to manually spin the wheel to spin the virtual model vs. the automatic rotation in this video but no video yet of that.

Video - Jonathan Keep

Excuse the quality of the video but I hope it can give some idea of the processes I am going through to print pots. To ensure a good flow of clay ooze during a print I remix, blend just enough clay to fill a syringe for each print. The video does not show it but the syringe is attached to an air compressor, you can see the air hose, and it is set at about 3 Bars of pressure.

Clay - Jonathan Keep

While it is early days in my ventures with ceramic printing the impression I am getting is that the clay qualities desirable in more traditions pottery techniques hold true for printing with clay too. So far I have tried porcelain clay, then a blended buff stoneware clay, a ball clay, a red terracotta clay and a black firing clay. The general rule of thumb with clay is that the whiter it is the less plastic and malleable it is. What is known as ‘short’ clay. The darker the clay, the more sticky it is and often the more plastic and able to bend before breaking. The converse is, the whiter the clay the higher the temperature it can be fired to before distorting. So porcelain is higher fired and stronger than say red earthenware red clay. There is always a payoff and that is why most clay bodies are a blend of a number of materials.

Another factor I expect will influence our choice of clay for printing will be particle size. Short clay tends to have large particles, sticky clay small particles. But then fine sticky clay dries more slowly than white less plastic clay. To support the weight of the clay as it builds up the print must dry quickly but to unsure the layers stick together and bend both qualities are desirable. To further complicate the particle size issue a range of larger particles give structure to clay wall and gives rigidity to a soft clay structure. So often crushed, already fired clay, or what potters call ‘grog’ is added to a clay body. As the ceramic printing head/syringe I am using has a 1.5 mm nozzle I have used a 80# sieved grog, adding about 10% in dry weight. Whether grog is helpful in printing clay only more experience will tell. My gut feeling has been to include grog from the start to help give a bit more structure to the soft printed clay but also as clay powder is very fine the grog gives a bit of ‘tooth’ when mixing the powder with water. Different clays naturally contain slightly different proportions of clay to water for the same consistency. As a guide I have been printing with mixes of 2.5 – 3 parts dry clay mix to 1 part water.

‘Volcanoes’ – ave size 9 x 9 cm (Experiments in modelling with ‘sculpt mode’ in the 3d program Blender)

• Porcelain clay printed well but if it is too dry it goes ‘cheese’ and the extrusion breaks apart, and too wet it cannot support itself and collapses, so consistency is vital. Porcelain prints are the only objects I have glazed so far and the print layering texture looks ok through the glaze.
• The two buff clay were best to print with. The stoneware clay is gritty anyway so I did not add grog. The other buff clay is a ball clay that offers plasticity without being too sticky. The ball clay print quality is finer and more pleasant than the stoneware clay.
• The red clay printed ok as well but depending on what type of glazes you want to use and what temperature you are going to fire to a red earthenware clay might not be desirable.
• The black clay, although it looks great fired did not print well and was very difficult to work with. In preparation the surface dries easily and it is difficult to avoid small lumps in the mix that block the printing head. It was difficult to get the slurry consistency correct. It went from being to dry for the compressor to push it through the syringe to being too wet to stand up during printing with very little water added. I did get a reasonable dark brown ‘ant hill’ print out of a 50/50 red clay, black clay mix.

‘Ant hill’ forms – ave height 13 cm (Experiments in modelling with ‘metaballs’ in the 3d program Blender)

Working Method - Jonathan Keep

Having just got my first printed ceramics outof the glaze firing I thought it would be a good time to offer a post on my current working method. On and off for the last ten years I have been using 3D computer modelling programs, mainly as a tool to train my visualisations memory and explore new forms. Using numerical transformations the computer can generate forms I would not otherwise conceive of. Scaling, particularly uneven scaling or scaling only in one direction I have always find interesting. The human eyes aptitude for responding to symmetries is another area I have explored both in 2D and 3D software. Morphology and the evolution of form is a third technique I use. The 3D program can calculate the transition from one form into another offering the possibility to capture a new form at any point along that transformation.

Recently I have started using Blender, an open source 3D program that offers great possibilities and I can see myself spending a lot of time with it. Unfortunately the most recent version does not yet have .stl export, the file type used to convert to code that the ceramic printer understands. So saved as .obj files I do the conversion to .stl in Netfabb Studio. What is useful in Netfabb is that the surface area of the form is given so I can make the necessary adjustments to make sure I will be able to print the object from one 60 ml syringe of clay paste. The saved .stl file is then opened in the BfB Axon program and finally the form is cut up to make a g-code file that goes on a memory card ready for the printer. The BfB Axon program has a minefield of settings that are required when using a self made printing head as with ceramics. This is another posting in itself and while I am still trying different syringes ( I want to be able to hold a greater volume of clay for each print) it will be a while before I know what my settled ceramic print head settings will be.

Three stages in preparation for printing – Blender, Netfabb and BFB Axon.

Morphology of glazed printed porcelain forms – height 9cm each.

Simple glazed printed porcelain scaled forms – 6 to 3 cm high.

Shipping robots

I unpacked one of our printers that came back from an exhibition in Abu Dhabi last november and found that two of the four corners where completely loose, thats four grub screws for each corner that popped out of their place so now the vertical bar slides freely in the corners.
Funny thing is that when I unpacked them in Abu Dhabi, the crate was damaged and not very rigid anymore but the printer wasn't. I fixed the crate before shipping back and now it is the opposite.

Looks like I will need to take this one apart and reassemble correctly again, he was a bit wobbly in the first place...

And I will need to look into ways to better pack the machines, I always fill the crate with foam. Also on the bottom there is 3 cm foam in which the feet are plugged so the foam sits flush with the horizontal bottom bars. Will need to look into ways to improve this.

So fellow robot travelers, how do you ship your machines?

Kilns part 1: OpenKilnController

Last Christmas I got a small, almost new 8 liter kiln from my uncle who owns a large dental lab. He got it when he bought a whole lot of material in a liquidation and it was to big for them. Small for us is large for their industry, they use tiny desktop kilns, maybe 250 cc that fit a few tooth in them. The only problem was that it was only the kiln with the heating elements and no controller, thermocouple or relays. Buying all the necessary gear through our local pottery supplier would have made us ± 600€ lighter! So having a little tinker ethos I figured that it would be easy to build something yourself using an Arduino as a controller and a Solid State Relay to switch the 2 Kw elements. Not being such a great programmer or electro-engineer I dived into google thinking that this must have been done before considering the prices of commercial controllers,  some code would probably be available to get you started. Well, google turned op close to 0 hits so apparently there are not enough potters with programming/engineering background or hackers that like clay? After doing lots of research, driving to holland to pickup some old analog industrial temperature controllers, thermocouples and relays, requesting manuals for gear from the 80s from japanese companies I finally threw in the towel and bought a 300€ controller kit that was a perfect fit for small kilns like ours. I found this kit through all the googling (so never a waste of time) and figured that it was not worth it to continue my search for a DIY solution since I really lack the skills to pull it off from scratch. The ST222 kit I bought included a controller, thermocouple and relays and was made buy the UK company Stafford Instruments. So here's our inferno in a box.

I still love the idea of a DIY kit controller, I calculated the costs of a DIY solution to be around 150€ (Thermocouple 60€, Arduino 30€, SSR 30€, Display for Arduino, buttons etc 20€) which was a quarter of the initial commercial solutions and would allow you to preprogram all curves from a computer instead of using the awkward interfaces of commercial solutions and even monitor the kiln with plotted curves on the computer. The solutions on the market are really basic in functionality. While the 300€ controller was a sweet enough deal for our small kiln I still think a DIY controller would be very interesting for larger kilns. So I hope someone wants to pick up my mission for the OpenKilnController.

Here is what I have found so far, kiln controllers are PID controllers (I never heard of them, remember my lack of skills) and they appear to be very common in industrial control systems.  There is already a pretty decent PID library for Arduino. (http://www.arduino.cc/playground/Code/PIDLibrary) that could be used as a starter. The hardware is straight forward as mentioned above, you need a thermocouple as analog sensor, the Arduino with PID library as controller and a SSR as switching mechanism for the kiln. The tricky part looks to be the 'tuning' of the P, I and D parameters.
I also found some rforum posts over at arduino about DIY Arduino PID controllers so at least some people tried like PWillard.


UPDATE: While typing this post I revisited the forum thread I mentioned above and apparently GlennD did build a kiln controller for a glass fusing Kiln. Unfortunately only after I bought the ST222.

Introductions - Jonathan Keep

Jonathan's post (Read An Englishman in Antwerp bellow first):

I am an artist potter based in Suffolk, England and for some time have been interested in studio based 3d ceramic printing so to find out earlier this year what Unfold have been doing was a revelation. Eager to replicate their system I visited Claire and Dries and now have my own RapMan oozing porcelain paste in my UK studio. With a desire to continue Unfolds generosity in sharing knowledge I plan to post my printing progress on the Unfold-fab blog to keep all the information in one place on the web.

My RapMan supplied by Bits from Bytes, Somerset UK is version 3.1.0 loaded with software 4.0.2. Building the flat pack went ok and I had it moving in three or four days. Not interested in printing plastic I have not put the print head together. Wanting to concentrate on printing clay I got on with putting that together.  My ceramic printing head is very cobbled together with bits of gas kiln equipment as I am well aware that there are still lots of development work to be done and so I just wanted to get started to develop from experience.

My starting point is, as developed by Unfold, a 50/60 cc plastic syringe held in a self made cradle attached to the RapMan printer head mount. The syringe is then pressurised from an air compressor -  that I fortunately already had as I have a spray gun for glazing. The one thing I had to go shopping for was the 1K Ohm resistor that bridges two points of the unused print head cable connector plug on the printer control board. This gets RapMan software to think a pen tool is fitted.

Differences from Unfold –

• I am using a manual switch at the printer head for air pressure control rather than an electronic solenoid valve. This is for simplicity and so far has worked well as I can stop and start clay ooze as I want.
• I am using a 1.5 nozzle size as my prints are single walled. My thinking is to duplicate conventional pottery coil building techniques. I have set the Z (vertical axis) increment to 1 mm. So a syringe takes about 20 minutes to empty/print and a tall form can be about 10 cm.
•  I am printing onto pre prepared wades of clay so do not print a base. This does mean I need to get into the gcode in text editor and cut out some code.
• I use a (not very good) hairdryer as I print to stiffen up the form as more clay gets layer on. 

It has been a week since I got clay oozing and the learning curve has been steep but things are happening and the development put in by Unfold has been invaluable. In which direction all this might go I do not know as ideas and possibilities keep coming but I am making pots. There are still lots of problems, with gcode, with how RapMan behaves, with the limitations of the syringe size but I have a tool I understand and can customise to my ends and that I feel has fantastic creative potential. 

There have been post on how to fill a syringe; well I have to add to that. Having a wall mounted clay extruder in my studio I made a simple turn and lock fitment to take the syringe on the base plate. I fill a plastic bag with the clay paste (my mix is 1 water to 2.5 porcelain clay powder) and stuff the bag into the rather rusty extruder. Put in the plunger and extrusion arm and pull down. Result filled syringe, and so easy to attach the next syringe for a fill.

For further information on Jonathan’s work see – www.keep-art.co.uk

Thanks for sharing Jonathan!