Clay for 3D printing

An overview of clay for 3D printing, including guidelines on clay preparation and clay recommendations.

This article is adapted from jonathan reservations: HTTPS : //wikifactory.com/@jonathankeep/clay-for-3d-printing

Clay for 3D printing

All clays can be used for 3D printing, but some clays print better than others . What you are looking for is a less sticky clay that has a good texture and dries quickly . If you use a printer with a screw print head, do not use anything that is too rough, otherwise the screws will be worn.

Extruding 3D printing with clay is no different in process than the traditional way of using clay. In printers, soft, malleable clay is shaped by accumulating layers of clay . One coil is built. In contrast to ceramic 3D printing, computer-guided coil construction is almost better described. Following the practice of processing in clay, the objects are thoroughly dried and then hard-burned in a kiln. If a glaze coating is required, the glaze is usually applied after the first firing and then the object is fired a second time.

Here is a video tutorial: How to Make a Correct Clay Mixture for Eazao Ceramic 3D Printer.

Clay type

Pure red clay is usually sticky, and if you have a printer that feeds the clay through a thin tube through it, the fluidity will be poor. If your print is stagnant and starts many times, the clay can also become very messy. Fine red clay also dries slowly. Sandy red clay or red clay mixed with other clays works better.

A good amount of 0.2mm barrier frost clay clinker  or  clinker appears to  work well. Clinker reduces the viscosity of the clay and typically passes the system better. Clinker also provides more structure to the mix to help printed forms stand up. Loose clay can also dry faster and more evenly . Many suppliers indicate on the packaging label how much clinker is in the clay . Refined loose stoneware clay is a good starting point .

I want to print a lot on porcelain because I want you to get enamel from porcelain. However, the shrinkage of porcelain is so high that it is not the most rewarding clay. Porcelain is not very malleable or sticky, so it extrudes well and dries quickly.

Additives

I am not involved in clay additives such as deflocculants, desiccants (such as alcohol) or stiffening materials (such as paper fibers). There may be advantages, and I don’t recommend that you don’t try to use them, but without them I would do a good job and try to keep it simple. Basic clay is such a lovely natural material, and I don’t think you want to use it too much.

Excessive  flocculation is  certainly not good. If the clay becomes thixotropic, it will become more liquid when stirred, then it will not work in screw print heads, and even with DC extrusion, the clay will not delaminate well. By using soft (alkaline) water, especially porcelain clay, accidental flocculation can occur. The solution is to mix a small amount of vinegar into the clay (5 ml per 10 kg of clay). It is a logic to use clay that is ready for slurry casting. This clay can be used for 3D printing after flocculation, because this clay has less water, but it will encounter thixotropic problems. Avoid slipform clay.

In Italy, we did test with bioethanol when working with WASP. I think the drying speed of the clay may be advantageous, but when I return to the UK and work in a closed space, there will be too much smoke, so I did n’t Follow up on this. We mixed bioethanol and water in a 50/50 ratio, then added it to plastic clay to soften it into a paste. I prefer to use photography lights or heating lights to keep the amphibians warm, or use a heater to help dry work when printing.

Clay consistency

The clay used for extrusion 3D printing must be soft enough to be fed by the machine, but not too soft to support itself when stacked. There is no easy way to determine this consistency, but what looks like hard toothpaste is a good guide. The clay surface looks just wet, not saturated.

Different clays have different characteristics, and absorb different amounts of water to soften, so it is difficult to provide accurate amounts. It comes down to how it feels, and I still think it’s wrong. Borrow the clay analogy, but if you beat a small amount of prepared clay down, you want it to look like a healthy cow pat. It would be too soft if the pile slipped like a cow pat from a cow just grazed on fresh spring grass. If there is no concession between the layers when you break up a lot of clay, the clay may be too hard. Like I said, you want healthy beef pat quality.

Hard or soft soil

Pressure from compressed air or mechanical tamping is used to force the clay through the system. Under pressure, water is extruded from the clay mixture, and the higher the pressure, the more often it occurs. So while it is logical to use hard clay to keep the print from collapsing, it will require more pressure to get it through the system. The result is that you will dehydrate more and the clay in the bulk container becomes harder. The more non-clay particles (such as sand and clinker) in the clay, the easier it is to push out the clay. Coarse clay dehydrates faster than very fine clay.

Harder clays can also cause printed layers to not stick to each other and delaminate or crack. This is more likely to occur on curved shapes than on vertical shapes, so again, different working styles may lead to different working methods. I tend to use soft soils that require a pressure of 3 to 5 bar to get it through the system. The closer the clay block is to the printhead, the less pressure is required.

Wet and dry mix

Clay can be prepared from wet clay bags or dry powder clays intended for use on pottery wheels. Clay particles are described as platelets, and water acts as a lubricant between the plates. It is this structure that makes clay plastic, and different types of clay have different platelet sizes. Very fine clay is more viscous than pure red clay, and it is not as effective in extrusion printing as larger platelet clay (such as porcelain clay).

Although you can quickly soften the clay with water, it can take up to a day or more for water to penetrate the finest particles. As a result, the clay mixed today will be harder tomorrow and even remain in the plastic, not because the water has evaporated, but because it has been further absorbed into the mixture. Therefore, softened and wet clay is more suitable for immediate use than mixing directly from the powder. Freshly mixed clay with dry powder usually has a slightly granular texture and lacks plasticity, which will lead to better printing results. If you do mix from dryness, the clay should age as long as possible before use, preferably days or even months.

Coloring mud

Printing with dyed  or colored clay is no problem  . Light-colored clays (so the colors will show through) are also best served with ceramics, so choose clays that print well first. It is important to mix the colors thoroughly so that you can soften the clay well enough to sieve the mixture and then let it dry. Different natural colored clays can be mixed together to get more earthy yellow.

If you put the clay in a clay container for printing, you will find that once the clay is extruded, there is no obvious difference between one layer and the other, that is mixing. This is because the material moves faster during the extrusion process and drags on the outer surface. In order to get clear two or more color prints, each color requires a clay container and a print head. See project by   Tom Lauerman @tom .

Clay shrink

Different clays shrink differently. As the clay dries and the water evaporates, the clay shrinks, but once fired, it shrinks further in the kiln. The higher the temperature, the more the clay shrinks. Generally, clay shrinks equally in all directions, but when using 3D printed shapes, the degree of shrinkage in the vertical direction is greater than the shrinkage rate in the horizontal direction. I think it has something to do with the layers compressed together. As a guide, the clay of the stoneware shrinks about 13% in the vertical direction and about 8% in the horizontal direction. The content of the ceramic pieces in the vertical direction is as high as 20% or more, and the content of the ceramic pieces in the horizontal direction is as high as 16%. When transmitting to 1220 degrees Celsius.

We use kaolin for 3D printing and sinter it in an electric kiln at 1260°C. Compared with the printed model after sintering, the content of the ceramic pieces in the vertical direction is as high as 22% , and the content of the ceramic pieces in the horizontal direction is as high as 11%. .

Soften a bag of clay by hand

Cut the clay block into thin slices (1 cm) with a potter’s wire cutter. Use a kitchen fork to cut the surface of each slice as much as possible, then immerse the slices in a bucket of water and stack them. What you are doing is being exposed to as much water as possible. If you have planned ahead and can leave a whole slice out (covered with plastic), the clay should soften well. If you want to get in the car immediately, you should set the slab and break the clay with a fork. Then it’s time to get your hands dirty, squeeze a small amount of clay together, and keep stirring with your hands. You may need to spread the clay before tearing it with a fork and adding more water.

I work on a non-porous board, an old kitchen cabinet shelf is fine, and I press water on it with a sponge. Continue manual stirring until you have the correct consistency and the entire pile of clay is the same. Mixing by hand can make you feel any lumps. For good printing results, the clay paste should be completely smooth. Any inconsistencies in texture will appear as coarse / fine extrusions on your print. When mixing clay, you should avoid trapping air bubbles in the paste. Scraping several layers of paste with a cup-shaped hand, and then breaking it into a pile, seems to work well.

There is a basic video  here of  making a batch of clay by hand.

Mechanical clay preparation

With degassing mixer of any person  we are very  lucky, because these expensive devices clay studio doing very well. These machines will mix powder and may also add chopped plastic clay. I also saw the bagged, cut plastic clay mixed with excess water in a pasta mixer to a hard paste-like consistency. You need a strong mixer. In my opinion, mechanical mixing is only suitable for mass production, because the time required to clean the machine afterwards exceeds the time required for manual mixing.

For the mixing of bulk powders, I used a biaxial mixer for construction workers, such as plaster. This will only blend to a much softer consistency than I want to print. I then peeled the mixture to dry slowly to the desired consistency. This also makes the mixing time older. I will apply this technique to a large number of clays. The batter is stored in plastic bags and I will mix each batch manually before use-preferably with my hands stuck in the clay.

Clay printing works well

porcelain

In the UK, I successfully printed Royal and Special porcelain from Valentine Clays. I have tried Valentine’s Parian Body, known for its transparency, but found that the unglazed sintered results looked like printed white plastic. More serious, however, is the appearance of cracks within a period of time after coming out of the kiln, which is usually a sign of tension in the clay. I have given up on using Parian.

In France, I use Limoges porcelain as much as English porcelain. Limoges porcelain is a case, in which case I will add a little vinegar to the mixture to prevent it from becoming thixotropic.

Clay recommendations

(UK) Scarva Earthstone Professional White Porcelain Stoneware PF700-available from many suppliers.

(France) Ceradel White Stone Porcelain CG811-of which the proportion is very high, 0-0.2 mm clinker / soft ceramic.

(Spanish) Sio-2 Artemis White Stoneware 164-ARTE- Available in Potclays, UK.

Note: This clay can solve the requirements that cannot be achieved in clay extrusion printing.

(Sweden / Denmark) Red 1122-available from cerama.dk and cebex.se

Note: Charlie Stern used this clay very successfully.

3D printed clay receipt

If you look at the details of the clay bag explained above, you can start to understand what makes a good clay printed receipt. You are looking for alternative ranges in the form of clay and clinker.

JK Print Mix

Hyplas 71 ball clay 35

Grolleg Chinese Clay 20

FFF Feldspar 15

Fine white mica (0-0.2 mm) 30

Bentonite 2

Note: To print resistant works, half of the Molochite will be of medium grade (0.5 mm).