Some technical aspects of 3D concrete printing

A frequently used setup for 3D concrete printing is the gantry, which allows for the printing of large structures. Here the nozzle (and perhaps the extruder) is connected to a set of rails, thus allowing it to move up and down (z-axis) and left or right (x-axis). These rails are also connected to another set of rails, which allows for motion in the y-direction. The gantry setup is used by Eindhoven University of Technology, among others.

Another option is to suspend the extruder from three arms. These arms are able to move independently from each other, thus making it possible for the extruder to move in three directions (x, y, and z). 3D Wasp uses this system.

A third approach that is often used is fixing the extruder to a robot arm. This robot arm can move in the x, y, and z directions with great precision. This system is currently used by the Huizenprinters.

In the future our buildings might be printes by swarms of drones which continually communicate with each other. They would each print a section of the building, complementing each other perfectly.

The extruder that the Huizenprinters are currently using is a tube fixed to the tip of a robot arm. A pump pumps the concrete mixture through a hose that is connected to this tube. We are working on creating separate nozzles to attach to this tube. Even without interchangeable nozzles, the extruder allows for the printing of most shapes. This extruder was used to print the elements of a banch and a canoe made completely out of concrete.

To print more complex shapes, a pump-regulated extruder can ofer a good solution. Especially for projects that need extrusion which can be interrupted during the print path, it is important that the flow of concrete can be precisely controlled and stopped. This opens up new possibilities: for example creating openings in a wall. Pump regulation, possibly in combination with a shut-off valve in the extruder, can thus facilitate bridging in 3D prints.

An alternative way to achieve precise extrusion is by using an Archimedes' screw. Extrusion takes place by turning the screw. When the screw stops turning, extrusion also stops. A nice example of this process can be found in this 3D Printhuset video: https://youtu.be/Mgi398KG1hQ

Varying the nozzle-diameter can contribute to greater precision when it comes to controlling the width and height of the concrete layers. In addition to the round nozzle that many extruders use, it is also possible to print with a square or rectangular nozzle. This type of extruder is often equipped with a rotating nozzle which allows for correct printing curves. This rotating nozzle is used by, among others, 3D Printhuset and Eindhoven University of Technology. An example can be found here: https://youtu.be/rzmzdblX75E?t=17

To go from design to print, we use the following workflow:

When working with any machine safety is paramount. When working with materials like concrete, it is also important to be aware of health and safety requirements.

Below are recommendations. Always consult the relevant authorities with using personal protective equipment.

Robot Industrial robot have been used for many years and there are safety standard available that can be used to learn how to operate a robot safely.

NEN-EN-ISO 10218-1:2018 and NEN-EN-ISO 10218-2:2018

are very important resources to read when using an industrial robot.

If you are a beginner ALWAYS run the robot in manual mode. This means the 'deadman's switch' or safety switch must ALWAYS be engaged when the robot is in operation. In accordance with the norms above, this limits the maximum speed of movement to 250mm/s.

ALWAYS maximise the space available around the robot. Should you have an error in your code, this means that you can move away easily. The robot is very DANGEROUS if used incorrectly.

We highly recommend that you have ABB training before using an ABB robot.

Pump Always read the manual and safety instructions before running the pump.

Safety goggles Concrete hoses can build up in pressure if there is a blockage. Please use safety goggles when removing a blocked hose.

Gloves When handling concrete, always wear gloves to protect your skin. https://www.pluswerkhandschoenen.nl/product/m-grip-11-540-werkhandschoenen/?attribute_pa_maten=10xl&gclid=Cj0KCQjw8vqGBhC_ARIsADMSd1DIu3C2ia7n2r4eViUl2DNhyM8YFTlAciR_Ropr1IFlzAD6ZWwFRNcaAlGyEALw_wcB

Clothing Long trousers and long sleeves are recommended.

Dust Mask Use a dust mask at all times when working close to concrete dry powder. https://www.seton-signalering.nl/halfgelaatsademhalingsmasker-standaard-dubbele-filter.html?gclid=Cj0KCQjw8vqGBhC_ARIsADMSd1Ap9_ydBfZbkiAKrX4wZuYBmkcUUEzoF6A4UbWd576xfK2gN8jIiV8aAiIgEALw_wcB&gclsrc=aw.ds

Masks with filters are recommended. Be sure to purchase the correct grade of filter for concrete.