A solution to your bowden issues



Note: Since you are here, I assume you already know what bowden and what direct drive systems are.

Every now and then – quite often actually – I see newbies asking “what are the benefits of converting to bowden” or “is it worth it”.
And then I see people answering something like this:

“It’s not worth it”

“I had nothing but trouble with bowden”

“you will have retraction problems, it’s not worth the trouble”

And my favorite:

“it requires a lot of tuning, in order to get the retraction settings right”

Right?

WRONG.

It IS worth the “trouble”, and it’s not that hard to get it right.
Yes – people DO have issues with bowden. But in fact, for the most part they are quite easy to solve in some lazy Saturday afternoon…
At least if you don’t use too flexible filaments. In which case, Bowden might not be the best choice (but it can still work).
So, let me give you a couple of tips on how to solve your retraction issues.
It works great for me for PLA & ABS, but should be valid for other regular filaments too.

  1. Pneumatic fittings. Make sure the two pneumatic fittings on the ends of the bowden tube don’t have ANY play in them when the printer is doing retractions. If they do, you will have “the bowden issues” – stringing and blobbing.
    There are two things you can do about it – get high quality fittings (not the cheap Chinese ones that came with your E3D clone :)) OR use printed fittings. Personally, I prefer & use this on the 3 printers with bowden that I have made: https://www.thingiverse.com/thing:1993384.
    It works as good as “the real deal”, but you can print it immediately, and it takes just a couple of minutes.
  2. Travel speed. It’s the KEY for reducing the stringing. Increase the travel speed and acceleration as much as your frame allows. For example, on the  Anet A6 (with stock frame & E3D v6 bowden) I use travel speed 200 mm/s, travel acceleration 4000 mm/s^2, and jerk 20.  The same on my Anet A8 (but converted to AM8).
    Yes, you read that right – 4000. I use even higher acceleration (6000 mm/s^2) on my self designed & built printer.
    Keep in mind that if you have the Anet A8, it’s frame won’t allow such accelerations – it’s just poorly designed, and easily shakes along the X axis. You might need to install some stability upgrades, but I’m not sure if it’s going to help much – that’s why I upgraded to AM8 with some custom touches from me.
    I highly recommend replacing the metal SK8UU housing for the linear bearings of the bed with printed ones. Not the bearings – just the housings. This will reduce your Y axis weight with more than 160g. If your extruder carriage uses metal SK8UU holders too, also replace them. This will save you more than 120g. All this is very beneficial, as it greatly reduces the weight of both of your X and Y axes.
    I use these holders, and they work great: https://www.thingiverse.com/thing:1172217.
    Note – these will most likely not work well with IGUS-style linear bearings, because they will squeeze them unevenly. For IGUS, you might use something like this https://www.thingiverse.com/thing:2027339.
  3. Use short but fast retraction. On all 3 printers, I use retraction distance of just 2-3mm, and retraction speed of 70 mm/s. NO geared extruders and sh*t. Also, I have set high extruder acceleration in my firmware – 7000 mm/s^2. For most prints, this retraction works very well. I’ve had rare cases, where there is some stringing with some specific models, in which case just increase the retraction distance with 2-3mm and retry. Most of the time, with such high travel speeds the short retraction works very good.
  4. You simply CAN’T just swap hotends without reflashing the firmware. For example, the stock Anet hotend uses 100k Epcos thermistor (or something similar), while the E3D v6 (and it’s clones) use ATC Semitec 104GT-2. If you don’t update the thermistor type in firmware, your temperature readings will be incorrect, and as a result you will be printing at a wrong temperature – and wonder why you have underextrusion or retraction issues.
  5. Disable the “Combing” settings for the outermost wall in your slicer.

Finally, one more tip: use high speeds for ALL print moves, except the outermost wall & topmost layer. This will allow you to print very fast, and still have smooth and shiny prints. Trust me 🙂
For example, on all 3 printers I use 30-40 mm/s for the outermost wall and the topmost layer, 100-150 for everything else, and 200 for travel. And this is not my upper limit…
Note: you might need to increase your print temperature with 5-10C if you notice underextrusion here and there. When printing at high speed, the filament moves through the hotend too fast, and might not have enough time to actually reach the temperature you have set your extruder to.

Here are some samples of my print quality with these speeds, from all 3 printers, sliced with Cura 2.7, and all printed with cheap Chinese PLA on 0.2mm layer height:

Not bad at all. The 3D Benchy was one of the first prints after I converted the A6 to bowden. It required almost no additional tweaking – I just reused most of the settings from my AM8 Cura profile.

Disclaimer (kinda): although the proposed tips work perfect for me, they might not work that good for you. Especially if your printer is poorly built, and is unable to handle the high speeds and acceleration. In which case, it’s your own fault. My AM8 can handle it very well. And I used PLA printed corner brackets everywhere for connecting the 2040 profiles, and regular ultra cheap nuts, instead of the pricey T-Nuts. Hell, I even skipped some unnecessary screws/nuts altogether… It’s not always about throwing money. Rather, It’s about making it work with limited resources. My AM8 cost me less than $40 in total…
Anyway, make sure there aren’t any loose screws or belts, and that your stepper motors aren’t skipping steps when changing direction at max speed.

 

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2 comments

    • lokster Post authorReply

      I have absolutely no idea 🙂 Zero experience with Delta printers… You can just try and see.

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