Ok guys new printer build question.
My current setup is a 1.75 bowden drive. I know with my new printer I want to run dual extrusion but I can’t decide between bowden or direct drive. I know I don’t usually print at higher than 50mm/s most of the time but I still have a little concern of two large Nema 17 motors being flung around and how it affects the print quality.
On the other hand bowden allows for a much lighter print carriage but I wouldn’t be able to print flexible filaments.
Will definitely go with 1.75 but any suggestions / comments as ti which drive system to used would be greatly appreciated.
Thanks,
Griffin
@Mark_Rehorst
you should give examples to illustrate this kind of answer 
… And printing flexible filament with a bowden is totally doable, you just need to print slow and have the correct extruder. Here’s an example:
Dual direct drive is an extremely common printer configuration for small/medium size printers. (Look at the 100,000 or so Replicator 1/2/2x and clones like FlashForge on the market.) They do have some ringing because the 8mm rods aren’t quite as stiff as you want for that much moving mass. But at low speeds, it works just fine.
It depends a lot on how big you want to go – the longer the linear stages, the harder it is to make them stiff enough.
Bowden you can have the 2 heads closer together. You lose the distance between the two heads in printing width. Another option is to have a direct drive and bowden on one carrier would add the least weight but retain a direct drive while using bowden for the 2nd head. The biggest problem however with dual heads is to get both nozzles level as it needs to be exact or it will drag the nozzle through your print.
@Michael_Scholtz
Even with a dual direct drive you could have both hotends close together. Place the 2 nemas side by side and then place both hotends in the middle of the carriage. You only need change the rotation direction of one of the steppers.
Typical NEMA 17 dual-direct-drive nozzle spacing is 33-35mm. Which in my opinion is about perfect, since it gives the material coming out of one nozzle some time to cool before the other nozzle runs into it. You also want the nozzle spacing larger than your print / wiper structure spacing. Although that’s less important now that S3D has those nice print-hugging ooze shields.
Thanks for all the suggestions. I would only do direct drive for the purpose of printing flexible filament. However, if printing flexible 1.75 with bowden is possible, even at a slow speed I would prefer bowden. I think that that lesser mass would be beneficial.
I do want to spread the nozzles apart from eachother for good cooling but will most likely use an ooze shield when doing dual extrusion.
Anyone think this is a bad idea?
If you are really concerned with weight, maybe use Geared Nema 14 stepper motors for your extruders instead of bulky Nema 17s, you may save ~100g per motor
@Michael_Scholtz @Sven_Eric_Nielsen Or just just a dual color hotend like the Chimera or Cyclops from E3D or the Diamond hotend.
Basically I’d say it comes down to how big your printer will be and whether you’d rather have speed or the ability to print flexible filament. If your printer is going to be extremely large (~more than 12x12) then you probably don’t want all the weight of a direct drive system on the longer rails. My suggestion would be to go with a CoreXY style system so you have the option to use direct drive or bowden. I’d personally start with a direct drive system to start with probably a Chimera hotend and keep upgrading as I see fit until the extruder carriage gets too heavy and then make the switch to bowden.
@Adam_Steinmark I really like the Chimera hotend and will most likely go with that. The more people talk about weight the more it bothers me though. I like having the ability to print fast if I want. I almost exclusively print PLA and if I do flexible I will just run the speed down.
I really think I might be going with the dual bowden.
@Griffin_Paquette Some have said you can print flexible with bowden but it really takes an extremely well fine tuned machine. I still think then its hit or miss. You might be able to get by with SemiFlex though.