I'm planning to build a CoreXY printer,

(Christian Werner) #1

I’m planning to build a CoreXY printer, and I’m having problems finding the ‘perfect’ low cost printable extruder. Can you find me help me find the one that matches the following criteria?
-Bowden: to keep the weight of the print head low
-Geared: to apply enough pressure for smaller nozzles even with small or TMC2100 powered steppers
-Ergonomic: quick filament release is a big wish
-Economical: 3d printable if possible, not too exotic parts, vanilla NEMA 17, ideally Open Source

It’s supposed to feed a E3D v6 1.75mm 24V hotend (which comes with 4mm PTFE tubing).
What would be your take?

(Ryan Carlyle) #2

I’ve been getting extremely good results with my B’struder design, a Kysan 1040229, and a TriDPrinting.com hardened 8mm drive gear. Thingiverse with source files: http://www.thingiverse.com/thing:711401

(Christian Werner) #3

@Ryan_Carlyle It’s a very nice design, however, with its large drive-gear diameter and without a reduction gear, i doubt that it will give the neccessary torque under all cirmcumstances.

(Ryan Carlyle) #4

What exactly are you expecting as far as torque? The Kysan 1040229 has more torque than you could possibly want with 1.75mm filament. (5.2:1 reduction planetary gearbox, 9 kg-cm rated torque, with that drive gear gives ~35 lbs pushing force versus ~10 lbs for a typical ungeared NEMA 17 extruder.) If anything, it’s at risk of blowing the PTFE tube out of the pushfits because it’s overkill.

(Ryan Carlyle) #5

Hmm, you wanted a printed-gear extruder like a Wade’s I guess. Never been a big fan of those.

(Christian Werner) #6

@Ryan_Carlyle The problem is, that NEMA17 with integrated gearboxes are much more expensive, above to the point there it’s more economical to uses a printed gearbox. At least here in Germany the price difference is like 35€ to 10€.

(Ryan Carlyle) #7

A large-ish ungeared NEMA 17 like a Kysan 1124090 (5.5kg-cm holding torque) and a Mk7 drive gear (7.1mm hob diameter to fit 5mm shaft) will give plenty of force. Same approximate pushing force as the 5.2:1 geared motor I linked, just a much heavier motor. Which doesn’t matter for bowden drives. Should fit the B’struder fine.

(Christian Werner) #8

Okay, I’m almost convinced. I’m thinking that, with 1.75mm, a direct drive extruder with a quality high torque stepper should be completely ok, at least in the most cases.
What about vanilla cheapo steppers (~40Ncm)? Do you think this would still be viable?

(Danut Lipsa) #9

i’m using Ryan’s extruder with big 10mm mk7 gear on a 1.7a regular stepper motor along with a 0.4mm aluhotend and had no problem emwith it

(Ishaan Gov) #10

I’ve heard really good things about @Martin_Bondeus ​​’s bondtech extruder. I haven’t used it personally, but I’m sure @Eclsnowman ​​ could tell you more about it. It is a proper bowden double drive extruder, but is a bit pricey, and I don’t think it has a quick filament release

(Daniel F) #11

Can recommend Bondtech, it’s very reliable. I use the 3mm bowden version for almost 3 months now, it is extreemly reliable. Not cheap but worth the money.

(Eric Lien) #12

As @Ishaan_Gov ​ mentioned I am a strong proponent of the Bondtech extruder. I have had Zero jams or feed issues of any kind in well over a year. I have three of his Bowden extruders. I print daily and have put through more than 30kg through most of them. I don’t know what else to say other than in my opinion the bondtech dual drive extruder is unmatched in performance. I have tried many many other extruders, and even design a few of my own. Nothing else even comes close.

(Ryan Carlyle) #13

The Bondtech extruder is at risk of being killed by an outstanding Stratasys patent application. (http://www.google.com/patents/US20140159273) The patent application pre-dates the Bondtech by about a year and a half. The application was publicly published right before the Bondtech inventor says he started development, and the Bondtech LOOKS like an outright knock-off, so Stratasys’s lawyers could have a strong case if they choose to pursue infringement damages. (Which seems unlikely since Bondtech is Swedish company, but you never know.) Not saying y’all should care – just pointing out something to consider. (And no, I don’t feel like getting into an argument about whether the US patent system is broken, we all know that it is.)

(Ryan Carlyle) #14

I’d say whether a 40Ncm ungeared stepper gives good enough performance will depend on the type of performance you’re looking for. In simple terms of nozzle pressure due to force/area and running speeds, a 1.75mm direct-drive extruder is about the same as a 2.85mm geared extruder with a 2.6:1 gear ratio (assuming the same hob diameter). A typical Wades ratio is ~3.5:1 so there isn’t really a ton of difference between an ungeared 1.75mm extruder and typical Wades 39:11 3mm extruder. The Wades is a little slower with a little more torque, but overall pretty similar performance profile. You can certainly go to even higher torque and lower speed by gearing the 1.75mm extruder. It just depends on whether you’re more worried about extrusion force or top retraction speed. (And whether extruder axis steps/mm is an issue, for example Marlin can’t go over 40 kHz step rate and will drop microstep level over 10kHz.)

(Christian Werner) #15

Well, thanks.
Counter-rotating hobbed bolts are certainly the best, and @Martin_Bondeus has done a great job there.
But I’m aiming at €500 total component costs, so any €70€+ system is not an option here.

(Jos van der Plas) #16

I think the Bondtech extruder design is great but I’m struggling with the pricepoint. $106 for the kit, which is just the gears/toothed bolt and a few fasteners, that’s just outrageous?

(Jeff DeMaagd) #17

Well, the pulleys and gear teeth are custom machined, I thought the machining work was impressive. I don’t think it’s possible to get gear stock quite like that off the shelf. It’s pretty clever design to boot.

I think its best use case is for the larger machines. If you’re doing a 200mm cubed machine, it might not be a big deal, but if you’re making a Eustathios or Herculien and plan to build large platters of parts, I think the Bondtech extruder can pay for itself in prevention of time and materials lost due to a random feed problem.

(Ryan Carlyle) #18

Agreed w/ @Jeff_DeMaagd . You’re paying for small production runs of custom-machined precision components, plus parts logistics, plus a premium to the creator to make it worth his time to sell them. The price is very normal for the “custom metal extruder parts” market. If you don’t want to pay for high-quality custom components, don’t buy them :slight_smile:

(Don Moss) #19

I had been using an airtripper with a Kysan 1120490 and a mk7 drive for about 18 months. Never had an issue with lack of torque driving 1.75mm filament into a .35mm nozzle with the motor current set at 1Amp.
I recently designed my own extruder based on the airtripper that is a lot easier to change filament. (I reckon it looks nicer too ;))
I had planned on moving to a mk8 drive but that will require a slight change in the design to allow for the different position of the filament from the centre of the drive shaft.
It’s a shame that I can’t post photos in the comments.
Let me know if you are interested in trying it out.
Your only outlay will be for the fixing hardware, a 608 bearing, a 623 bearing, a couple of springs and a 4mm push-fit for the bowden tube.