Is 3mm filament on the way out as there seems to less colours compared to 1.75 when browsing suppliers on eBay?
Yes. It won’t disappear but 1.75 seems to be the Vhs.
3mm still has its purposes, for things like FilaFlex - but generally 1.75 has become the standard. Some of those reasons include things like chinese manufacturers reselling plastic “welding rod” as filament, with things like ball bearings inside them. When 1.75 was introduced, it was pretty much guaranteed to be extruded for 3D printers and 3D printers alone.
Our sales data on hotends shows a gradual decline in 3mm and an increase in 1.75mm. Interestingly the number of 1.75mm Bowden hotends we have sold has grown hugely proportionally to the others. I attribute this to the popularity of delta type machines that invariably use 1.75mm bowden extruders.
@Sanjay_Mortimer Can you share your approx sales ratio 3mm to 1.75mm ratio overall? It really does seem the market is moving to 1.75mm, at least what I see from shopping for filament. I currently use 3mm, and as I consider a new hotend (almost certainly one of yours 
I need to figure out what diameter to get. I’m leaning towards sticking with 3mm for now, as I have a fair bit of filament. I’m coming to the conclusion that I will end up using both diameters at some point, and that 3mm won’t go away completely, so moderate further investment in 3mm won’t be obsolete soon.
@Roy_Franz last Sanjay had hinted at was something like a 4:1 ratio of 1.75 hot ends to 3mm…and I’m sure that’s increasing.
Thanks all, I will prepare for a 1.75 move as my 3mm runs low
@Roy_Franz @ThantiK From v6 sales data it’s 7:3 1.75 to 3mm.
We sell 1.75mm bowdens more than 1.75mm directs at a ratio of 4:3
Thanks @Sanjay_Mortimer . I need to make up my mind so I can give Nylon a try. I guess I’ll just need to practice swapping extruders/hot ends on my printer
I thought people were seeing the same tolerances with 1.75 as 3 but since it’s smaller diameter it is a larger percentage compared to 3. Can anyone confirm or deny that?
@Mark_Taraba From my looking around that is what I have seen. Claimed tolerances for 1.75mm filament are most often the same in absolute terms (usually +/- 0.1mm iirc), which results in a larger relative cross sectional area variation compared to 3mm. I’ve been trying to understand why 1.75 is gaining popularity, but I’ve had a hard time finding “good” reasons for it. @ThantiK comments about low quality 3mm on the market early on is one of the better reasons I have heard. It also allows for using simpler direct-drive extruders. I would also think that the lower extrusion force required would help bowden setups, along with being more flexible. So many unsubstantiated, or just plain wrong, statements are made regarding the advantages of 1.75mm it makes it hard to have an informative discussion. Whatever the reasons are, it seems to be past the tipping point, and where the industry is going. At some point simple availability of filament becomes reason enough to pick 1.75 instead of 3.
… Or to buy a Filabot and make your own 3mm filament I guess.