I am planning on buying a cheap 3D printer to get into 3D printing, but the printer I'm planning to buy only takes 1.75 mm filament, I was wondering if it might be possible to change the hotend of that printer or something to take in 3.0 mm filament, the reason I want to use 3.0 mm filament is because it is cheaper than 1.75 mm filament.
First it really depends on your printer / extruder. That said generally 1.75 mm is cheaper and much more common.
If one were to change the hotend, likely you will need to replace most or all of the hot end. In the case of my personal hot ends, when I did this conversion I had to replace both the tube and the PETF lined mouth. I did not have to replace the tip, core, or the thermsister.
My advice is to pick a different printer. You see 3 mm on older extruders like J Head direct gear from around 2012-2013 and Bowden style (like the Ultimaker) use 3 mm (actually 2.85 mm).
Possible yes, advised, no.
It can be quite straightforward to convert from 1.75 mm to 2.85 or 3.0 mm, but it requires to buy hardware specifically for larger diameter filament. Nowadays, in 2020, Ultimaker is still using 2.85 mm filament which is not more expensive than the smaller diameter (at least not for the premium brands I'm using). I converted to the larger diameter filament years ago to be able to exchange filament with an Ultimaker 3E I maintain and manage.
To convert to a larger diameter, you need to be aware of
- the pros and cons of the various diameters
- increasing the stepper motor torque to be able to extrude the filament; larger diameter filament requires much more pressure than smaller diameter filament; the easiest way to do that is reducing the speed (and as such increasing the torque) of the extruder using a belt drive or gear reduction
- buying specific parts for your hotend, e.g. heat sink, heat break, etc.
- modify the steps per mm for the extruder
Thingiverse has always been a great starting point for me for larger diameter filament extruders; my own custom extruders are based on such designs. It is perfectly possible to convert to a different filament diameter, but, it requires some money, time, elbow grease and engineering from your side.
I had my printer Anycubic-Chiron converted from 1.75 mm filament to 3.00 mm, as it is big enough to handle bigger filament and the printer itself came with two sizes of the heatsink - the other fit to 3.00 mm filament.
In addition, I changed my extruder to a "Bulldog" extruder kit for 1.75 and 3 mm filament plus the PTFE tube and had to change the metal tube (heat break) between the heatsink and the hotend.
However, the conversion failed, the filament gets stuck on multiple points. I found many blogs describing this similar issue. The only possible solution is to increase the heat up to 270 °C at which my printer also fails. As the thickness of 3.00 mm filament prevents the heat to reach the middle of it. That's why it spools on the beginning only of printing then stop. There is no way to continue.
So, the problem is with the hotend, being mostly designed to suit 1.75 mm filament, not the printer itself.