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I have been looking to buy a new extruder. One of the options I have seen comes in "right handed" and "left handed". What does this mean? How can I tell what my current extruder is, so I get the right replacement?

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  • $\begingroup$ can you provie a link to such a setup? It might be a case of mirrored setup (If mounted with the motor in Y and the gripping side going "down", is the motor left or right?) or it might be a case of the pinning (does the motor rotate clockwise or counterclockwise with this pinning?) $\endgroup$ – Trish May 13 at 16:25
  • $\begingroup$ Opposed to some some views, the orientation sometimes does matter. E.g. it depends on the access to and positioning of the extruder motor. I guess you operate remotely considering you tagged bowden, so look at the current extruder and how the shaft turns to extrude filament. Please add your machine and extruder setup and a photo would be very welcome! $\endgroup$ – 0scar May 14 at 11:13
  • $\begingroup$ Quick clarification on my end: gripping side means the side that moves the filament. $\endgroup$ – Trish May 14 at 11:23
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This is an example of a right handed extruder setup:

Right Handed Extruder Setup

And this is an example of a left handed extruder setup:

Left Handed Extruder Setup

I believe that you can can choose whatever one you favor. With the right handed setup, you will be pushing down the red part with your right hand when inserting filament. With the left handed setup, you will be doing the same thing but then with your left hand. Personally, I favor the right handed setup (my right hand is my dominant and stronger hand). But, you should be able to choose whatever one you like! Be sure to check it will work with your printer though (extruder holder & hotend).

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  • $\begingroup$ It seems to me that if the stepper is rotating clockwise, then the right handed setup would "push", and the left handed would "pull". Depending on how the stepper is mounted and the layout of the machine, this could be important when choosing which to go with, as it might only be feasible to mount the stepper one way. $\endgroup$ – linuxdan May 13 at 23:31
  • $\begingroup$ With an un-keyed cable, the stepper wiring can be rotated (at one end pins 1-4 mapping to 4-1), to reverse the direction. Of course, it can be done in software too. $\endgroup$ – Sean Houlihane May 14 at 11:39
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The short answer to identify what extruder type you have is the rotation of the extruder gear.

CCW rotation to extrude = right-handed extruder

Detailed explanation is below.


In addition to the other answers, the right-handed designation comes from math and pysics convention that has become a well known mnemonic in engineering practice:

Right hand mnemonic

or in its physics coat,

right hand rule in physics

The Right Hand Rule: Figure (a) shows a disk is rotating counterclockwise when viewed from above. Figure (b) shows the right-hand rule. The direction of angular velocity ω size and angular momentum L are defined to be the direction in which the thumb of your right hand points when you curl your fingers in the direction of the disk’s rotation as shown. reference

In a right-handed extruder,

Right Handed Extruder Setup

you place your thumb of your right hand in the direction of the shaft (so pointing it towards yourself in the image of the extruder above) to see that rotation in the direction of your curved fingers leads to extrusion of filament (in counterclockwise direction).

For a mirrored extruder they call it left-handed extruder.

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  • $\begingroup$ i'm not quite sure why "the right hand rule" should have any meaning here $\endgroup$ – darth pixel May 14 at 8:35
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    $\begingroup$ @darthpixel because it is a math/physics convention: a rotation is given as the rotational axis and the speed of it. "10° per second around X" means it rotates with that speed counterclockwise around the X-vector. A "lefthanded" extruder spins - mathematically speaking - around the -X vector. $\endgroup$ – Trish May 14 at 10:54
  • $\begingroup$ but it's not connected to left or right handed extruder. L, I and omega are also not very needed in terms of the question - What makes an extruder right handed? you could also incluse 2*pi*r as it's also loosely connected but it won't help here. left handed means this and right handed means this - why to make things overcomplicated? rotation direction is not really what defines left/right handed extruder $\endgroup$ – darth pixel May 14 at 12:14
  • $\begingroup$ Sorry but it is. Do you think it is called because you operate a right-handed one with your right hand? :) $\endgroup$ – 0scar May 14 at 12:39
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    $\begingroup$ Righthanded: The shaft of the motor and the rotation vector (According to right hand rule!) both point out. Lefthanded: the shaft poinsts out while the rotation vector points in. $\endgroup$ – Trish May 14 at 13:40
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It usually doesn't matter whether you get a right-handed or left-handed one. The reason the two different variations exist is because some people use a dual extruder setup. If you have two extruders it is convenient to have them be mirror images of each other (as this makes them easier to install in use with the filament release lever pointing out to the side). If you have only a single extruder, it doesn't really matter, unless there are other construction restraints.

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when thinking about righ-handed extruder or left-handed extruder it's good to know that there is no magic or any other science rule behind this naming convention. it's just an arbitrary explanation which can be unfortunately misleading. in fact there is visual explanation of this left / right handed name and it doesn't have anything to any "the right handed rule" mentioned in other answers.

it's just this

enter image description here

no physics... no magnetism... no induction... no vectors and no formulas

the other answers present pictures of LH and RH extruders which are of course fine but be careful - there are universal extruders which can be both L or R handed.

like this one

enter image description here

as this extruder has fully fixed filament path and there is no restriction which direction the filament should go - there is no way to describe it arbitrarily

it is left-handed when it works as left-handed and it is RH when it works as RH

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  • $\begingroup$ +1 for the picture comparing the two at the same time $\endgroup$ – Greenonline May 15 at 9:10
  • $\begingroup$ @Greenonline thanx :) in terms of the answer - the picture is worth 1000 words so it was obvious to have both on one picture. as i tried to explain in my other comments in this thread - why to add unnecessary and misleading pseudo-scientific value if just such simple picture will explain it all $\endgroup$ – darth pixel May 15 at 9:31
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    $\begingroup$ Hmmm... I think both explanations are good. It's nice to have a simple explanation, but it is always handy to have a scientific one too, for greater depth, when needed. :-) Sorry, I got so carried away writing my first comment that I forgot to vote. LOL. $\endgroup$ – Greenonline May 15 at 9:34

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