Here are some basic rules, tips, and tricks to design a printable model in ceramics.
Minimum wall thickness 3 to 6 mm
Minimum details 2 mm
Accuracy ±3% deviation, adds 1 mm of glaze
Maximum size 340 x 240 x 200 mm
Clearance 4 mm
Interlocking or enclosed parts? No
In 3D printing, wall thickness refers to the distance between one surface of your model and the opposite sheer surface.
The minimum wall thickness of your design is defined by the size of your object because the wall thickness defines the strength. In general, larger parts need to be stronger. If the sum of the dimensions of your object is between 120 mm and 200 mm, you should use walls that are at least 3 mm thick. When the sum of dimensions is greater than 201 mm and smaller than 300mm it is advised to use a minimal wall thickness of 4mm. When the sum is larger than 301 mm and below 400 (above is not printable) the walls should have a minimum thickness of 6mm. These minimum wall thicknesses are a general guide but keep in mind that large pieces should have thicker walls. Clicking on the left image will show you a small overview of the values.
The maximum wall thickness is a lot easier. If your walls stay below 15 mm in thickness, you will be fine. Larger sections will generate too much internal stress causing the item to crack or even break.
Minimum and maximum size
Due to the machine size and the processability of ceramics we need your design to have a minimum size as well as smaller than the maximum size. The minimum size is set because smaller items are more difficult to glaze. The maximum size is defined because of the building volume of the machine and the characteristics of the material.
Unlike other technologies where a specific bounding box is given; here you need to do some math and add up the 3 dimensions of your object. If this sum of X, Y and Z dimensions is between 120 mm and 400 mm, you are good to go. Objects where the sum is below 120 mm or exceeds the 400 mm are not possible for the moment. The maximum dimension in one of the directions is limited to 340 mm because the machine size is limited to 340 mm x 240 mm x 200 mm.
Because it’s easier to make a thicker piece than a really thin item, we want your design to fill up at least 5% of the bounding box. Thicker pieces cause fewer problems in production and transport because they are less breakable. You might think that this minimum fill percentage increases the price drastically but unlike other technologies the price for ceramics is determined by the surface area. This means that you don’t get penalized for using larger wall thicknesses as much as with other 3D printing techniques.
Minimum feature size
A feature should have a minimum size of 2mm to come out nicely. The glazing reduces the definition of the features in the piece because it adds a layer of maximum 1.5 mm of thickness on top of the piece.
For an even application of the glaze it’s recommended to avoid sharp edges by all means. It’s advised to apply a fillet with a minimum radius of 2.0 mm to sharp corners. Also joining faces should have a minimal radius of 2.0 mm.
Minimum feature opening
Due to the glazing process, too small openings can get closed by the glaze. Therefore the minimum feature opening size is 5.0 mm. For hollow parts the part must have an opening for powder removal that is at least 10 mm in diameter. Enclosed areas might not have glaze applied since it cannot reach these areas. So make sure that the openings are large enough so that the glaze can be applied.
The necking effect
Try to avoid the so called necking effect, were you go from a thick to thin area in your design. This will create internal forces in your design that could cause the object to break during production or afterwards.
Thin struts cannot be attached to large unsupported sections. Try to imagine what happens when gravity is applied to your design to avoid problems. This explains why large sections should be lower in the part and cantilevered struts should be less than 20 mm long. One example for figurines is that the head is firmly attached to the body and that they are stable and have a base.
To glaze or not to glaze
In order to do the glazing parts you need to have an obvious base because your design will have to stand or rest inside of the firing oven to become strong and get a glaze applied. This will result in an area were no glazing will be applied. In some cases the object can be hanged during the process but this will still leave a mark of unglazed ceramic.
Due to the nature of glazing some geometries may cause uneven distribution of the glaze on pieces because the glaze flows at firing temperatures. The glaze will add thickness to features on pieces. The glaze can add up to a maximum of 1.5 mm of thickness to the piece. An example of this is the bottom of the inside of a cup where the glaze will be thicker than on the sides.
Unlike polyamide, it’s impossible to have moving parts in a ceramic design. Pieces that "fit" together are difficult, but if you have to design this please keep a clearance of 4 mm.
Engraved text and surface details
When placing embossed text on your design you need to have a minimum point size for raised text 36 points or 12.7 mm (0.5 inch) and have at least 2 mm sticking out. For engraved text you need a little larger text due to the glazing. It’s advised to go for a minimal size of 60 points or 21.2 mm (0.83 inch) and have them at least 3 mm sticking inwards.