converting to a Bowden style extruder - help!!!

Ok - I recently finished my prusa I3 - Im starting to like it better than the original design.
However.....
Since I now have the added rigidity I want to print faster, and it seems at 100mm p/s the x will eventually skip. I am using the finer belt and machined pulleys from ultimachine. so I know its not because of a badly printed pulley and the belts are tight.
So I was thinking about going to a bowden style remote extruder. I printed adapters to hold the tube and got it all mounted up. It seems like I have too much coming out now due to the "springinness" of the cable.
Any tips on getting the extrude set better?
Im obviously loosing the precision over the extrude and retract.
Thanks!
Jeff

Odds are that you will have issues until you can get the acceleration up to 3000+ and then you will need to make the extruder retract a lot faster 40mm/s+ and then you will need to increase the retract distance to 4-6mm. Then you need to stop using any default values you have for extrusion width and set it to match the nozzle diameter if using a J-head. If you are using another hotend you will need to set the extrusion width to 0.05mm more than the hotends rated diameter. After all that you will be getting good results but will still want better. That is the point you have to move onto a different slicer. Right now you have the choice of Kisslicer that has wipe and Cura that has a function to slow the extrusion before the end of the path being printed.

Edited 1 time(s). Last edit at 12/16/2012 06:33PM by Sublime.

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wow! Thats quite a mouthfull!!
ok - lets start slow...
so Im NOT to use slic3r any more?
I am using a .35 j head, and MOSTLY slicer default values. .25 layer height 1mm retract @15mm...
starting point??

I forgot to say you also need to turn up the jerk settings higher than normal for a Prusa. The key is to not slow down and let the pressure release. With the jerk and accel setting low you end up slowing down around corners which results in blobs.

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You can use Slic3r but is has NOTHING to deal with the hysteresis in the bowden cable that the other two have. To use it just make the changes I mentioned above and you will get good results. But in the end you will still want even better results and have to switch to one of the others.

Also you may want to use Slic3r 0.7.2b as it has a lot less travel and retraction then the newer versions. Also it has better layer alignment then the newer releases.

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Wow - talk about relearning everything I know!! LOL!

ok - Im game for a diffrent slicer - Kiss or cura....better?

Parabolic Wrote:
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> wow! Thats quite a mouthfull!!
> ok - lets start slow...
> so Im NOT to use slic3r any more?

Start with it.

> I am using a .35 j head, and MOSTLY slicer default
> values. .25 layer height 1mm retract @15mm...
> starting point??

This will be an issue. The larger the layer height the higher the flow rate needs to be. This results in higher pressure and more blobbing. To extrude that much cleanly you will either need to slow down (boooo) or print with lower layer heights which reduces the flow rate. I find 0.2 is OK starting point. The retract is an issue too, I would increase it to 4mm and as fast as it will retract. Tantillus uses 5.5mm of retract @ 40mm/s and the retract acceleration is set to 10,000 which is the highest it will go before defaulting back to the default value.

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Kisslicer is good and makes nice code but the terms it uses are strange and it is missing some features like fan speed control until the next release. It also has the issue of being closed source and designed for BFB machines and now a lot for Replicator owners. If you can handle all the settings it would probably be best to use Cura as it gives the most control and the best code at the price of slicing speed.

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If im going to eventually end up having to switch slicers - id rather do it now then waste a whole bunch of time messing with slic3r.
So im going to download cura now and try to plug in those values u recommended as a starting point.
I didnt realize that .25 is too thick of a layer...

Good info sublime, I have a printer that I'm converting to bowden and will find this information priceless, thanks for sharing.

Parabolic - you should be able to move your X carriage way faster than 100mm/s! People tend not to print too much faster than 100mm/s on non-bowen setups but it is quite typical to have a travel speed of 300mm/s. Perhaps you have too much friction by misaligned guides/rods? It's worth checking out before you move to a bowden setup.

the only way to get extreme speed is to increase the voltage. do this cautiously and with expensive electronics. Pololu will pop like pop corn if not set right. i would prefer something with voltage and current control to motors. but essentially increased voltage increases performance.

also, what nozzle size are you using. and are you using 1.75mm feedstock? those will help with the required print speeds and forces required to print thru a bowden system.

what kind of hot end are you using? even a 400g mass can half your max speed.

Well, Right now I have a Prusa I3 built with a frame (not a plate), and all the printed parts off of josephs GIT hub - however, I am running a j Head adapter with a wades on it. Thats why I figured Id try a bowden setup - although im running 3mm stock. Ive only done 1 partial print with the boweden and it looked like a hot mess because of my retract and speed settings.
I started messing with cura last night - yeah thats going to be quite the learning curve...

ok - well, Ive been messing with CURA all day - starting to get quicker and cleaner prints. however...
I just noticed that my bridging is very spotty...im going to try and slow that down to like %30 or something - hope that fixes it.
also noticed that its printing mirrored from what its showing on the screen... which is the correct orientation...anyone seen this before?

im now printing at a .15 layer height at 120mm p/s which I like.... now just to fix these other issues..
oh, and whats up with the infill on this? its like a random cross hatching instead of even spaced lines...is that to save material? is it still as strong?
Jeff

Parabolic Wrote:
-------------------------------------------------------
> ok - well, Ive been messing with CURA all day -
> starting to get quicker and cleaner prints.
> however...
> I just noticed that my bridging is very
> spotty...im going to try and slow that down to
> like %30 or something - hope that fixes it.

I use 25mm/s for my bridge speed

> also noticed that its printing mirrored from what
> its showing on the screen... which is the correct
> orientation...anyone seen this before?

This sounds like your firmware. Are you sure it ever printed the correct way with slic3r.

> im now printing at a .15 layer height at 120mm p/s
> which I like.... now just to fix these other
> issues..
> oh, and whats up with the infill on this? its like
> a random cross hatching instead of even spaced
> lines...is that to save material? is it still as
> strong?

As strong as Hex? No. As strong as Slicer rectilinear? Maybe.

I would use the hex infill.

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It should be stronger than rectilinear because it effectively creates an extra solid outline by moving the ends of the zig-zags so that they meet. SF has always done it that way, see: [hydraraptor.blogspot.co.uk]

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jamesdanielv is on the right track as far as voltages are concerned, I run 24V and it allows much more headroom as far as how much power you get out of the motors. Sublime can chime in but I believe he specs a higher than 12V power supply for the tantillus.
The pololu drives can take up to 30V, using the same motors, RAMPS, etc and get more performance out of the machine. However you have to change the resistance of the hotend and heated bed. I run dual power supply's 12V for the heated bed and 24V for everything else. My next machine will have a 24V heated bed however and just one power supply.

I run the entire Ramps set up off of 15V without any changes to the Arduino or Ramps. It gives a faster frequency on the current chopper which allows for faster step pulses before you lose steps. The higher the voltage the faster possible until you run into the 16mhz limit of the Arduino. I choice 15V because the Ardunio voltage regulator is rated to 19v but has a suggested limit of 12v. I found that 15v caused the regulator to heat up enough that I did not want to go higher without a separate regulator board.

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