Maximum nozzle diameter

Hello, this is my first post.

So - I need crude 3d printer to print relatively crude, radius 10mm at min, big (600x250 mm) and flat (6-8mm height) parts, on cardboard. And parts should stick to it.

Is it ok to use 2 or 2.5 mm nozzle for 4 mm abs/hdpe filament ? Or it should have good reduction for better pressure build-up inside extruded ? I had seen in one post of successful using of 1 mm nozzle. But, could it be made even bigger ?

Stanislav

If you intend to print in plastic, say ABS, everything needs to scale up. The melt chamber will need to be quite large, in order to melt at a useful rate. The filament (assuming) will need to be wide. Might have a look at plastic welding systems for inspiration.

jcabrer Wrote:
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> If you intend to print in plastic, say ABS,
> everything needs to scale up. The melt chamber
> will need to be quite large, in order to melt at a
> useful rate. The filament (assuming) will need to
> be wide. Might have a look at plastic welding
> systems for inspiration.

i thought the hot zone should be as small as possible for fast extruding, so the filament can be pushed with more pressure in the hot zone

Actually its a common mistake, but the pressure rises if the tube diameter increases and not the other way around, at least regarding to water (one of the main reasons why some irrigation systems fail - the tubes aren't just thick enough and the pressure is lost on the furthest sprinklers...)

no i mean something other, if the hot zone is long, the filament will be soft, long before it will be extruded, this soft filament can not build up pressure on the nozzle if its pushed, this is why we have stainless steel barrels with active cooling (stainless steel conducts heat bad) or with PEEK

With larger nozzles you will have a higher throughput of material. With a small heating volume like you use for 0.5 - 0.2mm Nozzles you will not be able to melt the material for a 2mm nozzle fast enough. You need more volume (preferably larger diameter not length) to liquify the filament sufficently fast.
You can just enlargen the nozzle diameter to 2mm, but you will need to go slow then.
I tried up to 1mm with my Merlin Nozzle and it worked fine, i had to limit speed a bit though.

Cheers
Björn