<p>The zigzag is more rigid.  You can push a square into a trapezoid without putting any of the sides in compression or tension.  However, if you make a trapezoid with two triangles, the diagonal dividing the trapezoid. into squares resists an external force changing the shape of the trapezoid. Thus, the zigzag takes less material for adequate support than making squares as does cinder blocks.</p>
<p>Look at steel joist design.</p>
<p><a href="https://i.sstatic.net/Qugrt.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Qugrt.jpg" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2021-12-18T19:48:02.477Z
Steel can cope well with both tension and compression loads.  Plain concrete cannot survive tension loads, that's the job of internal pre-tensioning, aka pre-stressed concrete.
Criggie
CC BY-SA 4.0
2021-12-18T20:53:41.313Z
@Criggie True, but zigzag beats cinder blocks. The spaces serve the same purpose as cinder block spaces.
Perry Webb
CC BY-SA 4.0
2021-12-17T14:04:19.850Z
2021-12-17T14:26:15.120Z
2021-12-17T14:26:15.120Z
Perry Webb
<p>Presumably to decrease material costs, speed up printing time and reduce curing time.  The thicker the concrete, the more time it takes to cure.  You need it strong enough for the next layer by the time the print-head comes around again.</p>
<p>When the concrete is poured in a zigzag it has a thicker/wider base, meaning it can be built higher and walls can be wider before they need a corner for strength.</p>
<p>Additionally, small sealed voids in the wall improve the thermal insulation properties of the wall.</p>
<p>Last - if the wall has vertical voids with a zigzag infill between vertical walls, then those spaces can be used to run wires for power/phone/network or water pipes, to hide and protect them instead of surface mounting them inside,</p>

CC BY-SA 4.0
2021-12-18T14:11:44.700Z
not quite last.  there are also benefits to even curing from void passages.
Abel
CC BY-SA 4.0
2021-12-16T23:13:06.677Z
2021-12-16T23:13:06.677Z
Criggie
<p>Why do concrete 3D printers lay the concrete in a zigzag shape? I know pouring it in a straight line makes it unstable, but the zigzag shape reduces the contact of the top layer to the layer below. What is the advantage?</p>

CC BY-SA 4.0
2021-12-15T13:02:19.060Z
If the layers use the same zig zag, why would it reduce contact?  This seems like a normal infill method to me, but I know almost nothing about the physics of wet concrete.  The point of infill patterns is to reduce material use while connecting all the edges.
user10489
CC BY-SA 4.0
2021-12-16T06:39:56.420Z
@Aryaz just imagine the top layer as concrete block but instead using an square is a triangle due zigzag. Then the architect can continue with more and different 3D printing infill or traditional construction. The purpose of infill is to strengthen the walls.
Fernando Baltazar
<concrete-printers>
Why do concrete 3D printers zigzag?
Aryaz
# Why do concrete 3D printers zigzag?

(Asked by: username_0 on 2021-12-15)

Why do concrete 3D printers lay the concrete in a zigzag shape? I know pouring it in a straight line makes it unstable, but the zigzag shape reduces the contact of the top layer to the layer below. What is the advantage?

**Tags:** concrete-printers
> **Comments:**
> **username_1**: If the layers use the same zig zag, why would it reduce contact?  This seems like a normal infill method to me, but I know almost nothing about the physics of wet concrete.  The point of infill patterns is to reduce material use while connecting all the edges.  
> **username_2**: @Aryaz just imagine the top layer as concrete block but instead using an square is a triangle due zigzag. Then the architect can continue with more and different 3D printing infill or traditional construction. The purpose of infill is to strengthen the walls.  

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## 2 answers

### Answer by username_3 on 2021-12-17. Score: 1

The zigzag is more rigid. You can push a square into a trapezoid without putting any of the sides in compression or tension. However, if you make a trapezoid with two triangles, the diagonal dividing the trapezoid. into squares resists an external force changing the shape of the trapezoid. Thus, the zigzag takes less material for adequate support than making squares as does cinder blocks.

Look at steel joist design.

[![enter image description here](https://i.sstatic.net/Qugrt.jpg)](https://i.sstatic.net/Qugrt.jpg)

> **Comments:**
> **username_4**: Steel can cope well with both tension and compression loads.  Plain concrete cannot survive tension loads, that's the job of internal pre-tensioning, aka pre-stressed concrete.  
> **username_3**: @Criggie True, but zigzag beats cinder blocks. The spaces serve the same purpose as cinder block spaces.  

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### Answer by username_4 on 2021-12-16. Score: 1

Presumably to decrease material costs, speed up printing time and reduce curing time. The thicker the concrete, the more time it takes to cure. You need it strong enough for the next layer by the time the print-head comes around again.

When the concrete is poured in a zigzag it has a thicker/wider base, meaning it can be built higher and walls can be wider before they need a corner for strength.

Additionally, small sealed voids in the wall improve the thermal insulation properties of the wall.

Last - if the wall has vertical voids with a zigzag infill between vertical walls, then those spaces can be used to run wires for power/phone/network or water pipes, to hide and protect them instead of surface mounting them inside,

> **Comments:**
> **username_5**: not quite last.  there are also benefits to even curing from void passages.  

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