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Extruder Printer Head for Concrete

Posted by teh.stig 
Extruder Printer Head for Concrete
April 12, 2016 06:19PM
All,

Hello and thank you everyone for supporting this great community! I've just embarked on a journey to build a large-scale printer, large enough for housing, that prints concrete. I'm an engineer, but totally new to 3D printers and robotics. I've started by buying a RepRap kit, which I will assemble and put together, and hope to learn a lot about "building a printer" in general. From there, I will scale up to other materials and larger platforms. While I'm building my RepRap, I've been researching some other teams' projects that have successfully accomplished this mission (e.g., Andrey's Build, Lund University's, and Contour Crafting / China).

My basic "experiment" step-by-step plan is to:
1) Build RepRap
2) Build basic extruder such as Lund University that does not move, and dial in concrete extrusion [I've got a concrete expert helping me with mixtures]
3) Dial in larger 3d printing platform [I've got someone who has built larger scaled printers before that will help me with this]
4) Design more robust extruder design such as Andrey or Contour

With all of that said, are there any smart minds out there that are familiar with some other builds (perhaps even open-source) I should read and get help from? Does the basic plan seem to make sense? Are there any specific resources on "building big printers" I may not know about and should read?

Lastly, if anyone is interested in helping, please let me know.

THANK YOU
Re: Extruder Printer Head for Concrete
April 27, 2016 03:19PM
I hope your project goes well! I think it's fascinating - that's why I'm commenting.

Just a few observations.

Scaling up a printer involves much more costly components and care, because of the need for:
- increased rigidity
- more powerful motors and more sophisticated motor drivers
- closed loop
- a faster controller (32-bit)
- longer cable runs for sensors and motors
- changes to extrusion for increased output and pressure management

Do you have funding?

Plus for this project you will need more sophisticated/different and therefore custom slicing software.

I think developing this is a full time job for at least 5 individuals (programmer, materials scientist/test engineer, electrical/CNC engineer, structural engineer, machinist).

Just getting the extruder right will be a big challenge.
I think getting the outside smooth (like Contour Crafting is beginning to do is important), not just for looks but for structural integrity, water-tightness, and maintainability. I've seen other videos where a deployable smoothing blade was used.

In one video I see walls made with a zigzag inner core - but are the zig-zags actually bonded to the outside walls? Since concrete has little "pull" strength, will these hold? Can fiber be used to strengthen these walls? Making sure the structure is actually strong (and won't crumble in an earthquake) is critical. These are some questions you will need to answer before governments will approve this build technique.

You haven't mentioned the reason for this pursuit - Educational? Philanthropic (houses for the poor, etc...). Commercial?

Since you are starting from zero, I'd recommend visiting the various teams that have been working on this for a while, and collaborating. Hopefully there are not yet patents that will cause problems...


My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!
Re: Extruder Printer Head for Concrete
April 27, 2016 04:06PM
Hey Paul, thanks for the reply - see below:

Quote
Paul Wanamaker
Scaling up a printer involves much more costly components and care, because of the need for:
- increased rigidity
- more powerful motors and more sophisticated motor drivers
- closed loop
- a faster controller (32-bit)
- longer cable runs for sensors and motors
- changes to extrusion for increased output and pressure management

Do you have funding?

Plus for this project you will need more sophisticated/different and therefore custom slicing software.

I think developing this is a full time job for at least 5 individuals (programmer, materials scientist/test engineer, electrical/CNC engineer, structural engineer, machinist).

Just getting the extruder right will be a big challenge.
I think getting the outside smooth (like Contour Crafting is beginning to do is important), not just for looks but for structural integrity, water-tightness, and maintainability. I've seen other videos where a deployable smoothing blade was used.

In one video I see walls made with a zigzag inner core - but are the zig-zags actually bonded to the outside walls? Since concrete has little "pull" strength, will these hold? Can fiber be used to strengthen these walls? Making sure the structure is actually strong (and won't crumble in an earthquake) is critical. These are some questions you will need to answer before governments will approve this build technique.

You haven't mentioned the reason for this pursuit - Educational? Philanthropic (houses for the poor, etc...). Commercial?

Since you are starting from zero, I'd recommend visiting the various teams that have been working on this for a while, and collaborating. Hopefully there are not yet patents that will cause problems...

Software: What are you basing that off of?
Funding: I'm self-funding at this point in time, and will later seek investors
Development: I can agree with the larger, and more sophisticated team. At this point in time (short term) I'm "taking the ball as far up the field myself" as I can. In long-term, the team will be built out. Are you interested?
Contour Crafting: They're no doubt further along in that regard. I'm not sure how much of it was done for aesthetics, and how much was done for structural reasons
Wall Structure: I believe just "self-bonded" together by touching each other and then drying. Fibers can be added to the material mix. CC has done tests on their walls and they've been strong. From my understanding, extremely strong. With that said... it's hard to judge the "test of time" when first prints were just a few years ago
Pursuit: The pursuit at this point I'd say is mostly educational, with an eye on turning commercial. With that said, as you mention, governments/politics will be a big hurdle for the commercial side (which is why it's not a primary focus at this point in time).
Legal: I've hired outside counsel and the results have not stopped me yet. Others do not seem interested in collaborating at this time -- if there are hobbyists that would like to help -- I'm all ears
Re: Extruder Printer Head for Concrete
April 27, 2016 08:10PM
Quote
Paul W
Plus for this project you will need more sophisticated/different and therefore custom slicing software.
Quote
teh.stig
Software: What are you basing that off of?

My background: I've been writing software for 20+ years, and have been working on a post-processor suite for Slic3r with multiple pressure compensation and acceleration related features, as well as Guided Calibration (as time and health permits).

You will not be able to use an off-the-shelf slicer to create the tool paths.
One example is the Zig-Zag "Infill". For strait paths it's simple, but not so when it must conform to a curved path. Almost all slicers set up a grid of infill that does not rotate with contours - unsuitable for your task. There was a slicer from India that could do this, but I think they folded. There are other unique features you'll need I'm sure - so - a custom slicer.

I think you will not be able to use off-the-shelf firmware either.
You must be able to stop and restart a "print" at any point - as you can't throw out a house out at 60% and start over... This is very difficult with reprap. The closest I have come to this (after a jam) was to measure the height of the print, edit the gcode to remove all below that layer, and continue printing from there - very far from foolproof. It would be handy to be able to position the extruder head at the exact restart point and have it continue from there. If you use closed loop (perhaps with LinuxCNC) then you might be closer to being able to do this - with some additional custom software. If it can not do this, and if the interface between old and new material is not perfect, then the structure is compromised - not acceptable for a building. Am I right?

Quote
teh.stig
Are you interested?

It would be quite fascinating, but unfortunately I am not available.

I think your basic research steps are a good start. It will be very interesting to see your progress! Please keep us posted.


My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!
Re: Extruder Printer Head for Concrete
February 08, 2017 04:44AM
Hey everyone,

teh.stig: did you make any progress with concrete extruder? What kind of material feeding do you plan to use?

I´m also thinking about making large machine which can print buildings from concrete. I´m going to test, if it is possible to feed concrete with some sludge pump.
Re: Extruder Printer Head for Concrete
February 08, 2017 04:51AM
btw. have you noticed Apis Cor

I like this type of construction. It seems very simple and efficient to me.
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