Looking For A Bowden Extruders Update

I haven't heard or seen any big eureka blog posts or youtube videos that say the Bowden extruder system is a solid improvement over Wade's or Greg's Accessible Wade's extruder. Have the oozing problems been unanimously fixed by retracting filament in the z axis? Are there any downsides left at all with the system? Does anyone actually know if it really provides a speed advantage over the motor-on-x-carriage extruders (not theoretically, because it should theoretically, but experimentally)?

Ultimakers can print up to 300mm/sec.
Retract does not work well with bowden extruders which is why a high print speed is very helpful.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

So then, the oozing problems are solved just by printing really fast, and maybe retracting a tiny bit?

No, just by printing really fast.
Retraction does not work well do to the hysteresis effect.
To do this properly you need a darwin/makerbot style machine where the x & y axis moves the head (hotend) and the z axis moves the table.
The Mendel design moves the bed in the y direction and do to the mass of the table plus object you can never achieve the same speed as when the hotend is moved BOTH X and Y.
WITH a BOWDEN extruder of course so the head (hotend) is as lightweight as possible.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

rhmorrison Wrote:
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> No, just by printing really fast.

In my experience printing really fast also means having a lot of pressure inside the hot end and without retraction, getting extra plastic output after starting a non-printing move. How does printing really fast help with this?

And by "fast", do you mean velocity or acceleration? Because Mendel can move at 300 mm/s just fine...

Very fast moves when not extruding reduce the amount of ooze.

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[www.hydraraptor.blogspot.com]

Sure... I noticed a big difference when I replaced the FiveD firmware with Marlin and it permitted the 200-300 mm/s travel speeds. Instead of strings there was just a small blob at each end of the move and some harmless loose sputters on the way. But that was still never as good as what you get with properly working retraction.

nophead Wrote:
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> Very fast moves when not extruding reduce the
> amount of ooze.

ttsalo Wrote:
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> Sure... I noticed a big difference when I replaced
> the FiveD firmware with Marlin and it permitted
> the 200-300 mm/s travel speeds. Instead of strings
> there was just a small blob at each end of the
> move and some harmless loose sputters on the way.
> But that was still never as good as what you get
> with properly working retraction.

So then, just to be clear, very fast moves (and possibly using Marlin) helps, but doesn't completely solve the oozing problem with the Bowden extruder, and if you want to have oozing completely under control the best way with a Mendel at the moment is to use retraction with a non-Bowden extruder?

Using low layer heights also helps reducing stringing with a bowden.
Slower extrude gives less filament pressure accumulated in the tube.

I also tends to prefere cleaning strings, which detach easily, rather than the blobs resulting from retraction, which need cutting and/or sanding to get removed. So I tend to avoid using retraction, depending on the printed part shape. The skeinforge "Comb" module helps a lot there to reduce the amount of strings.

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Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.

I have been thinking about the advantages to a Bowden after seeing the reprap pro use the same style:
[reprappro.com]

Since the push seems to be using multiple or mixed colors for prints, I can't help but wonder whether the Bowden style will be dominant in a year or two once things settle out. I can imagine that having a 3 color mixer + white or black would probably require a Bowden style because having 4 motors on the X axis would probably be too heavy, right?

I've been thinking about mounting an optical mouse camera (or two) onto my extruder, with the intention of using it to detect both missed steps, and slipping filament, so that both conditions can be reported in pronterface.

It occurred to me that with a bowden extruder, the same camera could be mounted at the hot end, and used to measure (and possibly correct) hysteresis, improving retraction.

It'd take a heck of a lot of math to do it right, and it'd have to be done in real-time to get it correct, but you could approach a standard extruder's print quality without adding significant mass to the bowden.

Yes I had the same thought. I think it would need to see the tooth pattern generated by the hobbed bolt so maybe the idler would need to be hobbed as well so it goes all the way round.

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[www.hydraraptor.blogspot.com]

I think a "laser" optical mouse may be able to track unmarked filament - they do a fine job of tracking something as nearly featureless as frosted glass.

... in a German bot-project we used the sensor of a normal optical mouse as camera - it reads an area of 19x19 pixels and displays it like a normal camera with a special software, one of the users developed then and posted with c-sources (AFAIK).

If you're interested, I can try to find the old threads and software, but there sould be some more similar solutions around the mouse-sensors out there too ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Ok I finally had some time to make video showing how far bowdens have come (At least Tantillus).


This is printing at 100micron layers, at 30mm/s with 180mm/s travel and 9000mm/s^2 acceleration. It uses 4mm of retract at 40mm/s (limited by firmware) with a retract acceleration of 10,000mm/s^2

I have done no post processing. This is how they look after printing.









See more printed with a bowden at [www.tantillus.org]

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Those pictures of the frog are gorgeous! I have never heard of a tantillus printer before but it definitely made me take a look. I wonder how well this would come out on a prusa or mendel max.

ambiguousphoton Wrote:
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> Those pictures of the frog are gorgeous! I have
> never heard of a tantillus printer before but it
> definitely made me take a look. I wonder how well
> this would come out on a prusa or mendel max.

I printed the following model on a MendelMax using No retraction at all (The orange one has no retraction, the white was with 1.2mm retraction)
Normal Greg/wade Extruder, J-head nozzle.

This model will be more challenging for a Bowden based extruder than the Frog.

It would be very interesting to see this printed on a Ultimaker or Tantillus, as soon as I get my Tantillus up-and-running I will print it out.

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[richrap.blogspot.com]

I had not looked in the plastic extruder forum for a while because it had been reset so I did not see it had new comments.

I did actually print that Voroni tower but never posted pics. It is a real challange for almost any printer but even more of one for a bowden machine. Since printing it I have increased retraction speeds so much I am sure it would come out even better (Now it retracts at 55mm/s with the retract accel at 10,000mm/s^2 and default E accel at 10,000mm/s^2).



Edited 1 time(s). Last edit at 07/10/2012 04:14AM by Sublime.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Thanks for the Voroni tower pictures Rich and Sublime. Those are some gorgeous prints you have there. I should try printing one, it seems like a badge of honor among rep rappers!

PS- Rich and others, this is tangentially related to print quality but I have read about Prusa's new i3 printer with a vertical X axis that should be stiffer:
[www.youtube.com]
and I also saw this vertx x-axis where it has a double pulley system to supposedly double the X resolution:
[reprap.org]
If such improvements were really better (which I am unsure of) I wonder if a vertically adapted quick fit x carriage would be the ideal setup.
[www.thingiverse.com]

Here are the changes I made to upgrade the Bowden & drive system:
Bowden upgrades
Drive upgrade
My next project is an improved extruder (hot end section)
Bertho