Z-Offset in Dual Extruder

Hi all,

I've just been introduced to the world of 3D printers so mind me if I ask silly stuff.

I am currently in the process of assembling a 3D printer myself and have stumbled upon this question.

With referrence to this item of thingiverse, [www.thingiverse.com] (V2 or V5), you will notice that there is a Z offset between the two extruders.

May I know what's the reason behind this offset and why it is designed in such a way?

Thanks!

It seems that the different Z offset is to compensate for the height difference between various hotends (if you have 2 different brands with various heights and want to use them both in the setup).

Quote
maxiboix
Hi all,

I've just been introduced to the world of 3D printers so mind me if I ask silly stuff.

I am currently in the process of assembling a 3D printer myself and have stumbled upon this question.

With referrence to this item of thingiverse, [www.thingiverse.com] (V2 or V5), you will notice that there is a Z offset between the two extruders.

May I know what's the reason behind this offset and why it is designed in such a way?

Thanks!

Hi. The part in question is a mount which is designed to accommodate extruders of different heights. The offset is the difference between the mounting point and the tip of the nozzle from one extruder compared with another. Left to right is normally referred to as the X axis, front to back is normally the Y axis and up and down is the Z axis. Hence, if you have extruders or different heights, or a single extruder which is a different height to that which was originally supplied with the machine, then you would need to use a Z offset for the mount so that the nozzle is in the same position relative to the print surface..

Edit. It seems that drmaestro and I were typing at the same time.

Edited 1 time(s). Last edit at 05/30/2016 09:57AM by deckingman.

To expound a little, you can't use software Z offsets with multiple extruders. They have to be mechanically set with the nozzles at exactly the same height or the lower one will drag on the bed/part when you're using the higher one. When extruders have a different distance between the mounting faces and the nozzle the mounts will need to be offset. The author discusses what type of hot end one of them is for, but not the second offset version.

Hi All,

Thank you for replying to me so promptly!

So if I were to be using the same two extruders, I should be using V4(in the thingiverse post) where there is no offset right?

Is there any other reason besides this for having an offset?

Thanks!

You can't have any offset in the nozzle, otherwise the other one will collide with the bed or the part that the other one is printing.
(example take two pens in your hand side by side and place the other one a little bit higher, then try to write with the pen that you placed higher...)

And yes, if you're using identical extruders, you should use the V4

Edited 1 time(s). Last edit at 05/31/2016 11:03AM by Mr_Peace.

Quote
maxiboix
Hi All,

Thank you for replying to me so promptly!

So if I were to be using the same two extruders, I should be using V4(in the thingiverse post) where there is no offset right?

Is there any other reason besides this for having an offset?

Thanks!

To clarify and expand on what Mr Peace has just said, the tip of both nozzles needs to be in exactly the same position relative to the print surface. But in Mr Peace's analogy of two pens, if one pen were shorter than the other, then you would have to hold it lower down so that the tip of the shorter pen is in the same place as the tip of the longer pen. So effectively this would be offsetting the mounting position in the Z direction in order to get the nozzle tips at exactly the same height. So no offset at the nozzle tip but to achieve that, if your extruders are different lengths, then the mounting point relative to the nozzle tip will be different and so a Z offset for the mounting point will be needed.

Hi All,

Thanks for taking the time to reply, apologies for the delayed reply as I was having my examinations.

Consolidating everyone's input, the main purpose of the offset is to account for differences in the length of the extruder head right?

I was wondering if perhaps there was another purpose for it? Not that I know what else the offset could be for but is this the only reason (difference in lengths of heads) that it is designed like that?

Thanks!

If you have a tilting print head that raises the inactive nozzle, then you can tolerate slightly different nozzle heights, and configuring a Z offset wold be useful. Similarly if you have auto-lift nozzles.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].