Choosing extruder sizes

Could someone point me in the right direction on information for choosing which extruder size we might want?
I've searched around and can't seem to find the answer to what I assume is a pretty basic question.

I was looking at the i3XL from DIY tech shop. It asks you to choose head filament size and head extrusion size.
I assume head extrusion size is the size of each layer we will be laying down. I am also assuming that the smaller the size, the slower the print, but the finer the detail that might be possible.
I am not sure why I would care between 1.75mm or 3mm filament.

If there is a website or previous thread that discusses this I would be happy to if you could point me in the right direction. I spent some time searching and just didn't find anything.

Thanks in advance,
-Matt

Small nozzle size means more detail and precision, but as you mentioned slower print time.
If your doing down the Bowden extruder route1.75mm is the only real option, for direct drive its more down to personal preference. Depending on where you live it might come down to cost, in the UK 3mm is a lot cheaper then 1.75mm to buy so I've got no plans to change to 1.75mm any time soon.

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Quote
JoeDaStudd
If your doing down the Bowden extruder route1.75mm is the only real option,

Why? The Ultimaker is Bowden and uses 3mm filament, and has arguably some of the best prints of any RepRap-based printer, with exception to individual machines of course. The Tantillus uses 3mm as well. I have built a 3mm Bowden machine with a 300mm x 300mm build area, and it works just fine. 1.75mm filament allows for a more compact extruder, but that isn't really an advantage for a Bowden printer unless the entire printer is very compact and space is at a premium.

In the end it really is just personal preference. I have been printing for years, since back when 3mm was the only (inexpensive) filament available, and haven't seen any real incentive to change to 1.75mm. I really don't think one is better than the other in all respects. Flexible filaments are much more usable in 3mm diameter, but stiffer filaments are maybe a bit easier to deal with in 1.75mm diameter. Flexible filaments in either diameter will not work well (if at all) in a Bowden setup.

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Quote
NewPerfection

Quote
JoeDaStudd
If your doing down the Bowden extruder route1.75mm is the only real option,

Why? The Ultimaker is Bowden and uses 3mm filament, and has arguably some of the best prints of any RepRap-based printer, with exception to individual machines of course. The Tantillus uses 3mm as well. I have built a 3mm Bowden machine with a 300mm x 300mm build area, and it works just fine. 1.75mm filament allows for a more compact extruder, but that isn't really an advantage for a Bowden printer unless the entire printer is very compact and space is at a premium.

In the end it really is just personal preference. I have been printing for years, since back when 3mm was the only (inexpensive) filament available, and haven't seen any real incentive to change to 1.75mm. I really don't think one is better than the other in all respects. Flexible filaments are much more usable in 3mm diameter, but stiffer filaments are maybe a bit easier to deal with in 1.75mm diameter. Flexible filaments in either diameter will not work well (if at all) in a Bowden setup.

I was always told/heard 1.75mm was preferable on the bowden as it was lighter, didn't have as much spring and less pressure needed.
I stand corrected.

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Also be sure to read all the DIYtechshop threads. Especially the one about their hotends.

Also do to the amount of plastic extruded per step of the extruder you can get lower layer height with a larger nozzle and get better bridging at the same time. There are very few circumstances that a smaller nozzle will actually have advantages and I have personally never come across one. I have printed items as small as a popcorn kernel with a 0.5mm nozzle. The only thing I have ever seen printed that needed a small nozzle is a frog printed with a 0.25mm nozzle that was smaller than the popcorn kernel.

I have to say that 3mm is by far better for Bowden and even e3D says that 80% of its issues are with 1.75mm bowden systems.

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