Extruders and Hot Ends – Direct vs. Bowden etc.

I’ve been working on my 3d printer design and collecting parts for my upcoming build.

I’ll be using two independent IDEX style heads.

My original plan was to use two Chimera clones, for ease of mounting, and to only use one nozzle from each chimera. That, along with two Bowden style extruders.

I have since realized that the Chimera clones all have PTFE liner all the way into the heat tube, so I won’t be able to use that at the temperatures I want to for some Nylon and / or Nylon CF filaments I want to use (would be nice to be able to go up to about 300 deg C max). I haven’t found any all metal Chimera heat tubes on EBay, although I have found many all metal V6 type options.

All this research has cause me to rethink some things and led me to think that perhaps I want to use a direct drive setup.

My printer will have a printing area of approximately 12” x 24” in X and Y and around 30” in Z.

Looking at some larger 3d printers like this one:

[www.youtube.com]

and this one

[www.youtube.com]

and this one

[www.youtube.com]

and this one

[www.youtube.com]

they all use direct drive non Bowden setups.

Whereas it seems that many other printers, like the BCN Sigma and countless others use a Bowden setup.

I’ll be using quality size 15 linear rails for my printer, so I am not as concerned about the extra weight of a direct drive system as I would be if I were using V slot rails and wheels for example.

So I’m now looking at using a setup similar to the E3D titan extruder with all metal volcano style hot ends for 1.75mm filament. I noticed the Chinese knock offs have been having some issues where the internal components aren’t made correctly so they don’t work as is shown in the video below:

[www.youtube.com]

I also noticed that there is a separate type called the “Tevo titan” which has a bit of a different design and appears to have many users? Not sure if I like that all the gears are made of plastic though, but it is definitely a different design. Notably, the stepper shaft doesn’t rotate inside the plastic arm like it does on the genuine E3D Titan, so I think I like the Tevo design better? You can see how it goes together here:

[www.youtube.com]

So currently I’m thinking of two “Tevo Titan” extruders feeding two Volcano type all metal clones in a direct drive configuration. But I don’t know if this is the best choice.

Any thoughts or advice would be appreciated.

I can't pitch in much on the hotend side of things, since I've only used Mk. clones and V6 clones personally. I can however pitch in on why those larger machines use direct drive though. The drawback of bowden systems is their hysteresis/backlash, this backlash is proportional to the length of the bowden tube. With a relatively small machine like the BCN Sigma, the backlash isn't too bad. On a bigger machine though, you need a longer bowden tube which means more backlash which can get out of hand. Bowden tubes also have a fair bit of friction which again gets worse as the bowden tube gets longer.

Before you consider direct drive, think about how it will work in an enclosed printer ( I presume Nylon also needs an enclosure? )
What is the max. environmental temp of a Titan? The stepper will heat up the Titan housing a lot, too.

What about remote direct drives? ( Flex3drive, Zesty Nimble )

I recall e3d saying somewhere (I think it was in one of Tom's videos) that the titan gears are fine for inside a heated enclosure for things like nylon and polycarbonate, I could be wrong. There are always all metal alternatives I guess. Remote direct drives have the same issue as bowden tubes on bigger printers, a longer flex shaft has more friction (stick/slip effect) and more backlash. Plus as your printer gets bigger, your gantry gets heavier, and the weight of the direct drive extruder gets less significant compared to the weight of the gantry itself, so the weight savings of bowden and RDD extruders become less significant.

I like how people find extravagant ways to minimize the weight of the hotend assembly. I've seen some folks even filing down the heater block to save couple of grams.
I also find it paradoxical to file down 1g of aluminium from the heater block but keep the NEMA17 motor on the hotend assembly.
There's always a plus and minus to any kind of approach. I understand having a heavy piece of metal on a CNC because it uses lead screws to everything. But in my opinion stressing out the elastic in nature (even reinforced ones) belts with a backlash from heavy object stopping back and forth is not the right approach.

If you are going to be printing slow, you can opt for Double D's (teh pun!)
For faster speeds you should consider Bowden, or at least Lead Screws.

For flexibles there's no way to avoid Direct, I can agree on that.

Regarding Stepper motors and heat, I recall someone mentioned they are designed to work with temperatures exceeding 100*C.
Reprap wiki has this http://reprap.org/wiki/NEMA_Motor

Quote

Maximum operating temperature:
A: 221 °F (105 °C);
B: 266 °F (130 °C);
F: 311 °F (155 °C);
H: 356 °F (180 °C);

P.S. "site:forums.reprap.org Direct Bowden" in google gives me more than 10 pages.

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Proud owner and maker of build from scratch FDM 3D printer [forums.reprap.org]

First off, a big thank you to everyone who has responded so far!

Quote
Trakyan
I can't pitch in much on the hotend side of things, since I've only used Mk. clones and V6 clones personally.

And what has your experience been with the V6 clones? Good, bad? Do you ever wish you bought the genuine E3D?

Like I said I was originally thinking two Chimera type clones but only using one nozzle on each, if only for the ease of mounting compared to a V6 type.

Quote
Trakyan
I can however pitch in on why those larger machines use direct drive though. The drawback of bowden systems is their hysteresis/backlash, this backlash is proportional to the length of the bowden tube. With a relatively small machine like the BCN Sigma, the backlash isn't too bad. On a bigger machine though, you need a longer bowden tube which means more backlash which can get out of hand. Bowden tubes also have a fair bit of friction which again gets worse as the bowden tube gets longer.

That makes sense. I'd buy that explanation. Still not sure if my machine will qualify as "big" or "medium" sized. Was also thinking of running a bowden tube to the filament roll even with a direct drive over the hot end....thoughts?

Quote
o_lampe
Before you consider direct drive, think about how it will work in an enclosed printer ( I presume Nylon also needs an enclosure? )
What is the max. environmental temp of a Titan? The stepper will heat up the Titan housing a lot, too.

I do plan on making an enclosure, but to my knowledge, Nylon doesn't need a heated bed. I plan on using garolite / phenolic. Some of the really $$$ commercial printers made for nylon and nylon CF use garolite / phenolic and don't even come with a heated bed.

So even with a higher nylon temp at the nozzle, I am thinking the temp inside the enclosure would be about the same as if you were printing ABS even if I go with a heated bed.

Might want to print in ABS or something else so I haven't ruled that out.

Quote
o_lampe
What about remote direct drives? ( Flex3drive, Zesty Nimble )

I'll have to look into those, this is my first 3d printer build so I'll need to look up what they are. Thank you for the suggestions.

Quote
Rossos
I like how people find extravagant ways to minimize the weight of the hotend assembly. I've seen some folks even filing down the heater block to save couple of grams.
I also find it paradoxical to file down 1g of aluminium from the heater block but keep the NEMA17 motor on the hotend assembly.
There's always a plus and minus to any kind of approach. I understand having a heavy piece of metal on a CNC because it uses lead screws to everything. But in my opinion stressing out the elastic in nature (even reinforced ones) belts with a backlash from heavy object stopping back and forth is not the right approach.

If you are going to be printing slow, you can opt for Double D's (teh pun!)
For faster speeds you should consider Bowden, or at least Lead Screws.

I agree, but "heavy" is a relative term. And I haven't figured out how relative it is to this project yet.

Lead screws can be very slow or very fast depending on the lead of the screw (distance traveled per rev), the voltage of the power supply (higher volts = better stepper performance at higher speeds), and the characteristics (speed vs torque graph) of the stepper. If I were to go all out I'd use ballscrews with a lead in the vicinity of 10mm to 25mm . 5mm ballscrews (or leadscrews) driven off a stepper motor running at 12V is probably going to give you a very very slow machine IMO. Of course, for the Z axis of a 3d printer it is preferable to have a small lead, but not necessarily so for X and Y.

Many industrial cartesian robots use linear stages that are belt driven. And they move around weights that compared to a 3d printer gantry are very heavy, all day long, at very fast speeds, with high accuracy. Of course those belts are an inch wide and more heavy duty, so I definitely see your point .

For my build I'll be using 9mm belts (already bought them from POWGE on EBay). I'll also be using a setup similar to the Buildlog.net 2.x laser design. That is to say the gantry will move via a single Nema 23 dual shaft motor connected to 8mm steel shafts in pillow block bearings to rotate the pulleys at each end (each end will have a 9mm belt).

You can see the concept in this video:

[www.youtube.com]

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Rossos
For flexibles there's no way to avoid Direct, I can agree on that.

I do plan on using some flexibles, but not the super squishy kind, more like hard rubber, at some point.

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Rossos
P.S. "site:forums.reprap.org Direct Bowden" in google gives me more than 10 pages.

What's the fun in that? Plus I would like to hear back if possible from anyone using the specific setup I'm contemplating of the TEVO Titan, vs the Regular Titan, vs the Chinese Regular Titan Clone (from what I've seen doesn't work because they messed it up).

If I go with a Titan setup, I can always use it as either Bowden or Direct Drive with some simple mods in the future.

I am hoping that Digital Dentist will chime in, I went back to his blog and noticed his setup on his custom printer is direct drive...

Also, I read in this thread:

[forums.reprap.org]

that someone had to change to a bigger stepper to get their Tevo Titan to extrude properly, wondering what a good motor choice would be for this extruder? Because they do sell motor + extruder kits on EBay but the Chinese are notorious for not matching components in their kits correctly.

Thanks again for everyone who has replied so far!

@Rossos, I don't think leadscrews are much good for fast printing.

@Don McLean, They've worked fine for me so far, no real issues. I've never used the real thing so I can't say if there's any performance boost I'm missing out on. The hotend I'm using is an all metal clone if it matters. My only complaint is that the heater cartridge is a mission to get out, it could be the hole was undersized to begin with or the heater block deformed over time from the grub screw or I'm an idiot and over tightened it. As for the reverse bowden (from filament roll to extruder), I can highly recommend. Did it on my printer because beforehand you could see visible under extrusion when the extruder had to yank filament off the roll when it moved away from the spool. That and the slack it gave when it moved back towards the spool would sometimes cause the filament to come off the spool or tangle. That being said, dunno how much friction there would be on a printer that size and if it would cause more issues than it solves. PTFE tube is fairly cheap, would be worth trying at the very least.

Re: Chinese Regular Titan Clone (from what I've seen doesn't work because they messed it up).

I bought an original E3D Titan lately and it also didn't work from the beginning.
I could fix it, but it felt, like they were made from the same source as trianglelabs'. ( without final quality control )
Those Chinese cloners might have worked out their issues in the mean time. If not, their return policy is often very generous ( ebay shops try to avoid any negative comments )

Edited 1 time(s). Last edit at 04/24/2018 03:26AM by o_lampe.

lost the will!!!

Edited 1 time(s). Last edit at 04/24/2018 03:44AM by jinx.