# Really Big Things

Matt and his team at Metrix Create Space have been working on something really BIG!  In fact, our team and their team have been engaged in a bit of a competition with our big robots.  The Metrix crew is in the lead.  A hardy congratulations to them!  AWESOME!

The Metrix crew has an old DynaCNC 1000.  We have an old DynaTorch Plasma CNC.   Both team’s robots are classic big framed 3-axis gantry robots in the 4 foot by 8 foot by 1 foot (1.25 x 2.5 x 0.5 meter) build space.

Both teams are trying to take it to the next level — something really big — FDM on a large scale.  If you’re already using a Makerbot or a RepRap, then you might be able to 3d print a door stop BUT what if you could print the whole door too?

Let’s do some good old back of the envelope “pretengineering”.  If you print with a Makerbot or a RepRap, then you are printing in mm’s with a 0.3-0.4 mm extruder nozzle.   Now imagine if your big robot ran in inches!  It’s a 25.4 scale up if you run the same G-code (from RepSnapper or Skeinforge).   Thus you need a 0.3*25.4 = 7.62 mm nozzle.   Everything else scales.

The next interesting question… What do we use for material? And where do we get THAT much material?

For inspiration check this post out:  Plastic Extruder for Growing Media

Recycled Plastics is a great choice (another form of personal recycling).   The Metrix crew is exploring milk jugs (polyethylene) as their build material!

## 4 Comments on Really Big Things

1. Thorin says:

I think the nozzle calculation (7.62mm!) might be a bit off. If you need a 25.4X flow rate, wouldn’t you need the cross-sectional surface area to be 25.4X as big?

.3mm nozzle = Pi *.3^2 = .2826 sq mm
25.4* (.2826) = 7.17 = Pi * (1.5)^2, or the new nozzle would be 1.5mm diameter.

That’s definitely big, but not on the same order as an AK round 🙂

The group with the 3D printed canoe made from recyled milk jugs seems to be heading that direction with their extruder setup:

http://www.3ders.org/articles/.....-boat.html

-T

• ganter says:

We were not attempting 25X flow rate but rather a simple scaling up of the standard RepRap system. Thus 0.4mm X 25.4
for the diameter of the nozzle was the design goal.

2. Thorin says:

I think the nozzle calculation (7.62mm!) might be a bit off. If you need a 25.4X flow rate, wouldn’t you need the cross-sectional surface area to be 25.4X as big?

.3mm nozzle = Pi *.3^2 = .2826 sq mm
25.4* (.2826) = 7.17 = Pi * (1.5)^2, or the new nozzle would be 1.5mm diameter.

That’s definitely big, but not on the same order as an AK round 🙂

The group with the 3D printed canoe made from recyled milk jugs seems to be heading that direction with their extruder setup:

http://www.3ders.org/articles/.....-boat.html

-T

• ganter says:

We were not attempting 25X flow rate but rather a simple scaling up of the standard RepRap system. Thus 0.4mm X 25.4
for the diameter of the nozzle was the design goal.