Getting rid of the bowden tube. Idears and discussion

[jonask 0]

Hi everyone,

i am often using filament witch is more like 3 mm then 2.85 mm.It often gets stuck when i am doing fast extruding or a lot of retractions because the feeder deforms the filament. Also the best retraction settings between 2.85 mm and 3 mm changes.

So it would be cool to have a kind of bowden tube witch adjusts to the filament diameter.

So i came up with this Idea:

 

I think its explaining itself. I used 6 mm softair balls. Its designed for 2.8 mm diameter, but because of the gap it can widen itself if the filament gets bigger.

 

What you think about this?

cheers

Jonas

 

[DidierKlein 729]

Looks interesting,

I guess you intend to have one of these every few centimeters ? The only thing i see is that the filament could be bended out of the path so you would probably need to have them one next to another with a distance small enough to prevent this but not to small to still have the effect of the "ball bearing".

You would probably still need a piece of bowden in the feeder and one before the head.

 

[jonask 0]

I guess i just have to try it, to see how much space is possible between the elements.

luckily i have bowden tube with 4 mm inner diameter, witch i would use for the feeder and the head.

In further constructions i would also need something to attach everything to the head and feeder. It should be possible to make something that doesn't need short peaces of bowden tube anymore.

 

[woofy 12]

I assume you mean one long extrusion here anchored at both ends like the existing bowden, rather than multiple segments?

An alternative idea is https://www.youmagine.com/designs/ultimaker2-on-the-top-extruder-mod by Gregwar

 

[jonask 0]

i would use two strings of filament and attach them somehow to both ends, and make multiple segments between them, like in the last picture of the first post.

The question is how much space is the maximum between the segments, so that the filament wont bend. The downside is this eliminates the use of flexible filaments. But if the space have to be really small, even with normal PLA, i should look for another solution than lots of single elements.

I like the idea of overhead extrusion, but i guess that the extra weight effects print quality on average speeds ?

 

[woofy 12]

I like the idea of overhead extrusion, but i guess that the extra weight effects print quality on average speeds ?

 

Everyone seems to say so, but I'm not so sure of that. My Up printer uses a head mounted extruder and produces excellent quality prints. Also at the MACH exhibition at the NEC last month I saw the Leapfrog creatr. This has two extruder motors mounted on the head. Didn't see it printing though so no idea on quality. It may need an acceleration tweak on the UM but I see no insurmountable problems.

I had been considering Gregwar's design.. . then Ian comes along with the Dragnet and teases with a head mount version :-P

 

[Daid 306]

Also at the MACH exhibition at the NEC last month I saw the Leapfrog creatr. This has two extruder motors mounted on the head. Didn't see it printing though so no idea on quality.

 

It's low quality. But that has little to do with the feeders on the head.

 

[nallath 1,124]

Just spray some teflon spray in your bowden tube. That will probably solve most of you problems with retracting.

 

[jhertzberg 19]

I disconnect one end of the bowden, hold it vertical, put one drop of sewing machine oil in the top, let it run down, then reconnect and feed filament. I can then print in FlexPLA (slowly). I think your design might act like a spring during fast retraction.

 

[eldrick 65]

It would be easier to just buy better-quality filament.

 

[jonask 0]

Of course it would be easier, but where would be the fun? :mrgreen:

also i got like 3 kg left of the not-so-good-quality filament :???:

I think what i am planning wont work, but i will try it anyway. If it fails i will gonna look a bit deeper in the overhead extrusion.

 

[illuminarti 18]

The point of the Bowden tube is to constrain the path of the filament so that the input movement at the motor end is exactly reproduced at the nozzle end. Any 'give' in the system to accommodate larger plastics as needed is probably going to defeat that - and especially cause problems with retractions.

Similarly efforts to put the motor on the print head seem counter productive - that specifically defeats the UM design philosophy of minimizing the head weight, to allow faster accelerations and more precise head control.

One option that might work would be to put the extruder on a tripod over printer, and have a more or less straight Bowden going down to the head, so that there's a lot less stress on the filament, and no need to fight the natural curvature as much.

[nick-foley 5]

Yeah, I have two of my machines setup with an overhead bowden. My primary motivation was to make the machine easier to feed from a wall-mounted spool, but there seems to be a minor improvement with retractions and filament problems due to the shorter bowden. It is an extremely easy mod to make, though it certainly makes the entire machine much less compact:

 

[nallath 1,124]

An option would be to put a small stepper motor on the head in addition to the big feeder motor. Does increase the weight, but not as much as the heavier stepper motor.

 

[DeathMachine 23]

I like this type of Idea. Any more info on how well it works?

I leaning more toward a cart.

https://www.schooloutfitters.com/catalog/product_info/pfam_id/PFAM46559/products_id/PRO60755?sc_cid=Bing_COP-TD5000&CAWELAID=320012570000034832

And putting the filament into a box, like.

http://www.thingiverse.com/thing:954675

Any input would be great.

Thanks Ed

[bondtech 25]

If you use the Bondtech Feeder it have much higher feeding force with minimal deformation since it uses 2 drivegears, works as good with 2.85 as with 3.0 mm filament.

Please see www.bondtech.se for more information.