Erik's Bowden Extruder

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Erik's Bowden Extruder

Release status: unknown

Erik's bwoden extruder - img 1495 display medium.jpg
Description A fast Bowden extruder design
License GPL 2.0
Author ErikDeBruijn
Contributors
Based-on Darwin
Categories Bowden Extruders, Extruders, Cold End
CAD Models Thing:2221
External Link Original Blog Posting

Contents

Преимущества подачи Боудена

Кабель Боудена позволяет уменьшить массу экструдера и, таким образом позволяя быстрее двигаться каретке, уменьшить тряску вашего принтера, меньше потреблять энергии и, что важно: быстрее печать! Обычно механизм, который продвигает нить в горячую часть (там, где плавится нить) находиться непосредственно на верхней части экструдера. Это создает колебания при быстром движении головки, которые можно увидеть в результатах печати, слышать и чувствовать, когда ваша машина трясется при печати. Если механизм привода нити поместить на неподвижную часть 3D Принтера, ее можно толкать в трубку. Для этого применяют трубку из ПТФЭ (тефлона ™), потому что это скользкая: тефлон имеет меньшее трение с пластиком. Это уменьшает износ и потерю энергии. Другой конец трубки подключают к горячей части экструдера.

Концепцию использования Кабеля Боудена было предложено и впервые Ed Sells. Посмотрите его блог здесь [1]

Benefits

The lighter the extruder is, the quicker you can move the toolhead(s), e.g. when you're not extruding. The machine will need less current to run the motors and it reduces stringing when not extruding. Even more so, it reduces the moving mass of the X-axis so much that a much simpler and lighter Cartesian bot is possible. The steel rods wouldn't necessarily be needed, allowing a much larger ratio of self-replication. The Bowden cable itself could be printed in several modules that snap together. This guide could be lined with telfon-tape (available in every hardware store) that can be replaced when worn.


Drawback

The Bowden cable system has one major drawback: Hysteresis. The plastic filament will compress in any extruder, but putting pressure on such a long length of filament will multiply the effects of this compression, leading to springiness. The flexibility of the PFTE tube exacerbates this problem.

It is potentially possible to control this problem, perhaps with an encoder just above the hot end. Software might also be able to reduce this problem, but would require (maybe lengthy) calibration.

A stepper-based extruder is required if no encoder is used.

Implementations

Several couplings have been suggested to affix the slippery PTFE at either end:

Snap fit Bowden.jpg Captive-nut-Bowden.jpg

From left to right: Snap fit Bowden coupling, Captive nut coupling


Bowden hints and tips

  • Gives you slightly less control over how much thermoplastics are output where, but:
  • It decouples the extruder drive mechanism from the moving mass in the printer.
  • By doing this it greatly reduces the mass, allowing much faster motion and less oscillations at the surface of the objects' exteriors.
  • It also allows you to use a decent plastic driving motor or more 'space consuming' complex gearing arrangement. This makes sure that you can not only speed up motion, but also output more plastics. So this is especially a good way towards faster printing.
  • It can help make printing slightly more reliable. If the nozzle orifice is jammed for just a short while (e.g. too close to a part of the object that curled up a little bit), without the Bowden extruder the drive mechanism will have stripped the filament and not recover because it loses grip when it has stripped it too much. With the Bowden extruder, short blockages are not causing failure of the build. This is useful when you're just starting with printing, because you may have some problems getting large objects to stick to the platform very well.
  • Reversing the extruder motor very quickly allows you to have less oozing. The beneficial effect of reversing is more pronounced for the Bowden cable setups than for regular extruders.
  • Fast changes in Z-height are helpful if you don't want to get a small seam where it changes layers. So make sure your bot can go fast in that direction too, or optimize it to have zero oozing.
  • The Bowden extruder is not as helpful if you have a fixed printing head (or moving in Z-only) and a XY-moving platform. There are still, however, multiple advantages to be gained even in these cases. By physically separating the extruder from the hot end you eliminate potential physical incompatibilities between the two, it becomes much easier to disassemble and fix either component in the event of failure in one part, and you eliminate the problem of the hot end potentially melting the extruder body.