This site contains the specifications of the BOD 2 printer and is applicable to any BOD 2 printer. Optional items are clearly specified as such.
THE BOD2 OVERVIEW
The BOD 2 is a modular gantry based 3D construction printer, which is an improved version of the BOD 1 printer, which we used for constructing The BOD, Europe’s first 3D printed building.
The BOD 2 printer is built from 2.5m modules and can be built to customer specifications.
To match different requirements for printable areas, we can offer an infinite number of different sizes.
Figure 1, BOD2-333
The BOD 2 printer works in 3 dimensions, with the print head moving on the X-axis (side to side in the image), the X-Axis bar moving on the Y-axis (In and out of the image) and the whole XY group moving up and down on the 4 Z-columns. The gantry principle allows the printer to access any position within the print envelope and gives complete freedom of movement within the volume.
THE GANTRY SYSTEM USED FOR OTHER FUNCTIONS THAN JUST PRINTING
Because the printer uses three separate axis, the position is easy to understand for the operator and with a bit of practice, the operator can easily move the printer to any position within the printable area. This also allows the printer to be used as an on-site “crane” in addition to printing and is a great tool for placing certain elements into the building. The theoretical lifting capacity is 400 kg.
The printer can also be used to mark locations on the building site, while workers prepare the site for printing. For example the printer can mark where installations should come out of the floor, such that the electricians and plumbers can be shown precisely, where they should put installations.
TANGENTIAL ROTATION CONTROL
The BOD 2 printer has the unique possibility to – as an extra option – use a tangential control print head, meaning that the nozzle that delivers the concrete to the print rotates to always be tangential to the move direction. This allows the printer to utilize flaps to control the deposition of material which again allows smoother surfaces and thicker layers. See Figure 2.
Figure 2, tangential rotation control
The BOD 2 printer can be installed in one of two ways. The columns of the Z-axis are either bolted to the floor or mounted on four concrete blocks which are placed on the foundation or floor. This also raises the printer about a meter over the floor, adding height to the print volume, See Figure 4. The four concrete mounting blocks are not part of the price of the BOD 2 but have to be acquired as an extra item.
Because the printer is built from modules, it is easy to move, as it can be taken apart as needed. A forklift needs to be present, and this should be used to unmount the X, and Y axis and move each axis as one part, so 7 parts total. With just 2-3 people, the printer can easily be disassembled into single modules and moved with a small truck. Figure 3 shows the principle of the modules.
Figure 3, illustrating the modules of the BOD 2 printer
Figure 4, BOD2-121 with concrete block mounting (raising the printable height with app. 1 meter)
MATERIAL HANDLING SYSTEM
As an extra option, the BOD 2 can be delivered with a 4 m3 silo for holding the materials, a mixer and pump and 20-meter hoses.
These parts will be made by German PFT, which will use as a sub-supplier for this.
The mixing pump PFT XL G4 pump is placed under the silo and will automatically fill dry material from the silo as needed. The PFT then adds water and mixes the concrete to always keep the pump filled. The pump is controlled by the printer itself. The way it works is that printer has a small storage of mixed concrete (20-30kg) inside the print head. The printer continuously measures the weight of the print head and when the hopper is near empty, the printer engages the pump. The pump is monitoring the amount of material in the pump and will open the valve on the silo to re-fill dry material into the mixer as needed.
All pumps in the BOD 2 are Progressive Cavity Pumps. PCP pumps deliver a continuous flow and a typical concrete PCP pumping unit can pump the material 20m through a 25mm ID hose. Each pump unit can be changed to change the pump speed in terms of liters/minute, but also the size of the aggregates.
The pump unit supplied will be able to print materials with a particle size of up to 12 mm, but is generally designed for a particle size up to 8 mm, as this is the minimum particle sized materials to create concrete (instead of mortars).
The PCP pump unit itself is a consumable, that will be worn depending on material amounts pumped and the particle size of the materials. If worn we can deliver a new PCP pump for a price of 500 euro per piece.
Typically the pump unit will last for minimum 10-15m3 of material, and if larger aggregates are used then the pump unit wears faster.
Figure 5, the PFT XL G4 mixing pump
The material storage on the print head allows much more precise amounts of material to be printed, because the hoses delivering the material to the print head tend to expand when actively pumping. This causes a delay of material flow at the nozzle from the time the pump is turned on till material exits the hose, and when the pump is switch off, the material keeps dripping from the hose as pressure is released. However, the BOD 2 printer has a local storage and the print head has a secondary pump installed that precisely controls the amount of material that is printed with zero latency. This local pumping system also allows the printer to change speeds as needed, so to slow down near sharp corners and tight curves while speeding up when printing longer straight walls.
The BOD 2 printer is designed to be able to move the print head with a maximum speed of 1000mm/second – 1m/s.
Our previous model, the BOD 1 had a speed limitation of 100mm/s which meant that moving from one end of the printable area to the other would take up to 1½ minute.
The print head of the BOD 2 has been redesigned, such that it can move a lot faster than 100mm/sec.
Due to lack of sufficient experience presently, we cannot guarantee a print speed all the way up to 1 meter/second, but we will guarantee 10 cm/second but expects that a print speed of minimum 30 cm/second will be generally possible.
PRINTHEAD AND NOZZLES
The BOD 2 printhead has tangential control as an option and replaceable nozzles. We use 3D printed plastic nozzles that clamps on or screws onto the print head. This allows for experimentation with nozzle designs to optimize the flow of concrete and to change the size of the nozzle in minutes.
Because the nozzles are 3D printed, it is easy to try out new designs and produce nozzles for different layer heights or widths. When we printed the BOD (the building) we iterated over 26 nozzles, testing different designs to get the best possible result. We tested 26 versions in 3 weeks.
We will supply the printer with 5 different nozzles and with own 3D print equipment the customer can easily make more. The nozzles are consumables, that will wear with increased usage. Our own nozzles are 3D printed from PET-G plastic.
Figure 6, a 3D printed printhead nozzle
SAFETY / CE MARK
The BOD 2 printer and the PFT pumping system all come with a CE marking. The print head has sensors that will check for collisions at all times and the printer will go into pause mode if a collision is detected. Still, it is good operation behavior not to enter the printable area while the printer is operating. There is an emergency stop placed on each of the four z-axis columns.
The BOD 2 printer comes with our own slicer software that generates the printing program for the printer. The slicer works with .stl file input created by .stl export of normal architectural 3D drawing systems.
The software is constantly being upgraded as we gain more experience with certain prints, but there are still many unexplored possibilities.
We expect future versions of the software to enable the creation of patterns in a wall that is modeled as a flat wall to allow for explorations into artistic esthetics, not unlike what X-tree did with their 3D Printed woven counter or Siam Cement Groups woven look in their “The family cocoon” print.
Figure 7, X-tree 3D Printed woven counter
Figure 8, Siam Cement Group, “The family cocoon”
The BOD 2 is controlled by a Duet Wifi or Duet Ethernet 3D printer controller. The Duet is an open source 3D printer controller that is developed by the British David Crocker through his company, Escher3d. The BOD 2 can be controlled from a touch panel on the E-box or through a web interface. Because the electronics controlling the BOD2 are all open source, the source code is available online and the user is able to change the inner workings of the machine, the interface, and everything else about the machine.
Figure 9, The BOD 2 Touch Panel interface
Figure 10, The BOD 2 web interface
MANUALS AND INSTRUCTION
The BOD 2 printer comes with a manual that explains how to operate the system and perform daily tasks. The PFT systems come with separate manuals.
We can provide on-site installation, training and operation assistance as an extra option. When supplying such we will instruct in how to assemble, disassemble and use the printer. We will also assist with doing test wall prints. Our on-site training and installation guidance is first complete when a test wall has been made.
More training can be bought as needed.
The warranty is 1 year. Malfunctions falls under the warranty given and solving such is not charged separately.
SUPPORT AND MAINTENANCE
The PFT system is generally supported by the local PFT dealership. We will support the printer from Denmark and come on-site when needed. We provide a service contract that includes labor and parts, but not travel expenses as expenditures.
In addition, a service contract can be made as an option. The precise content of the service contract to be agreed.
As the gantry type printer we use generally is fairly low tech in terms of the mechanical parts, the need for support is limited and can for the mechanical parts be solved locally if needed. In addition, we will install remote access software on the users host computer, such that we may assist remotely with software issues, and we will travel to the user’s location when needed, under the terms described in a future service contract. Finally, we will deliver the printer with an operators manual.
Our support team consists of a.o.:
- Michael Holm, development manager
- Jakob Jørgensen, technical manager
- Dennis Werenskiold, technical operator
- Ole Ellignhausen (German), technical operator
MATERIALS / RECIPES
With the BOD 2, we can supply some test materials based on a recipe equivalent to what we used for The BOD building. However, materials should be sourced locally in general, and we will assist based on our experience and knowledge to develop a recipe based on local available materials. Our system is open source also with respect to materials meaning that it can print with various materials and recipes for making concrete.
Most importantly our system is not only able to print mortars (with a max particle size less than 8 mm), but can print real concrete with particle size up to 8-12 mm.
Our technology is NOT materials dependent, and in essence, any 3D printable material can be applied. This is also different to what some of the robot printer manufacturers offer, where they basically are trying to tie in their customers to only buy their print materials at somewhat excessive prices. We believe in open sourcing for the materials. We will advise on recipes etc. but leave it completely up to the user which materials should be applied.
Most recipes for 3D concrete printing use more cement in the mix than what is used normally for casting concrete. This is also the case for the recipe that we used for The BOD, where app. 30-35% is cement by weight. This gives us an open time of app. 20 min. before we have to print the next layer on top to get good layer adhesion.
The high share of cement was in our case needed due a.o. to the recycled tiles that we applied in the recipe. Also, please note that if an even bigger print was made, the setting time could be reduced, allowing for a lower content of cement.
Our recipe for The BOD was the following:
|Material||Quantity [ton]||Price DKK
(1 EUR = 7.45 DKK)
|Percentages by weight|
|Cement||6.12 ton||10,374 DKK||32 %|
|0-2mm sand||3.50 ton||595 DKK||18 %|
|0-4mm gravel (0-8mm)||3.50 ton||637 DKK||18 %|
|0-4mm recycled roofing tiles (0-8mm)||4.38 ton||525 DKK||23 %|
|Water||1.66 ton||62 DKK||9 %|
|Glenium sky 631 (superplasticizer)||0.04 ton||191 DKK||0 %|
|Crackstop fibers||0.02 ton||1,038 DKK||0 %|
|Total||19.22 ton||13,422 DKK||100 %|
Due to the usage of gravel and recycled tiles, the recipe we use our printed material is really like a traditional casted concrete and is stronger and more durable than the mortar like recipes used by many of the robot arm printers.The price per tons was thus approximately 700 DKK. This is around 10-20% more than the price of regular concrete for casting, caused by the relative high content of cement being used in the recipe.
The compression strength of the recipe for The BOD has been measured at 52 MPa. The tensile strength would normally be 1/10 of that but has not been measured.
The recipe for The BOD is only one of several recipes used for the printer. We also have recipes, without recycled tiles.
All recipes we have tried will be shared with our users for free and we expect the same from our users to increase the mutual learning.
We suggest that dry materials are prepared and kept it in a silo, from which the material is taken when the printing has to be done and these materials are then mixed with water in the mixer/pump.
As for reinforcements and fibers, we have used both. We used so-called crackstop fibers as an integral part of our mixture and as part of the building we 3D printed columns where reinforcements were added and then they were casted in normal concrete.
As every printer is made to order, we require 90% prepayment before delivery; 50% when ordering and 40% when the printer is ready to ship. The remaining 10% to be paid after installation.
WHY CHOOSE US AS SUPPLIER
First of all because we have the practical experience with actually printing an entire building and a building living up to the strict European building codes. Thus, it is a tested and proven system that a buyer would acquire, and from a supplier with own valuable experience.
Secondly, our printer is based in a gantry system with a much larger printable area than comparable priced robot printers, and as a gantry printer it does not have all the problems related to using robot printers (need for element printing, connection of elements, placing of the robot, robot programming skills required, need for continuous printing etc.). Our system is based on well-known software that easily converts model files to print files. Our printer is relatively low tech in the mechanical parts and with software that does not require unique skills to operate the printer other than what we can train an operator to have.
Thirdly, our system is capable to print with concrete type materials as well as with mortars, and due to the hopper above the printhead, we do not need to do continuous printing. We can print both very strong prints and finer more smooth prints, and we can do forms and shapes requiring “holes” in the print pattern.
Fourthly, we try to be very open and honest about the stage of the development of the technology and our solution, which should provide you with the assurance that we do not try to “oversell” anything.
Finally, our solution is “open source” both in terms of software and in terms of materials, and we are not excluding supplies from 3rd parties. This will allow customers to a.o. benefit from the material development going on among the large conventional construction materials suppliers.