Z axis top brackets, of P3Steel, differ between v1.x/2.x and v4

  • I have been studying the differences between version 2.x and version 4 of the P3Steel frames - in particular the AC08 bracket at the top of the frame which secures the top of the smooth bars and threaded rods of the Z axis on both the left and right sides. Here is the laser cut parts, for version 1.x, showing the part labelled as AC08:

    Laser cut parts for P3Steel v1

    Version 1.x/2.x has the AC08 bracket with two holes, one for the threaded rod and one for the top of the smooth bar (from the lasercut image):

    P3Steel v2 Z axis top bracket

    However, in version 4, the corresponding top Z axis bracket only has one hole for the smooth bar and just an indentation for the bearing which holds the top of the threaded rod (from Twitter):

    P3Steel v4 Z axis top bracket

    Here is a close up of the diagram from the google docs repository, listed in the v4 section on the RepRap Wiki page for the P3Steel, which shows the bearing assembly just apparently "resting" against the indentation:

    Close up of P3Steel Z axis top bracket

    Here is the bracket shown with the bar and threaded rod (again, from google docs):

    P3Steel v4 z axis top bracket

    Does anyone know why the top of the threaded rod is not secured by a hole, as it was in version 1.x/2.x? It just does not look particularly well secured.

    Under the list of version 4 changes, see 2. Frame versions, it is mentioned:

    The extruder no longer hits the Z axis top bracket

    Is this the reason why the change has been made?

    I don't know about the specific design of this printer, but constraining the rods at both ends is considered bad practice. If the leadscrew is somewhat non-straight, then with both ends constrained the wobble is transferred to the carriage, whereas with the top end free the top end wobbles, transferring less force to the carriage. But that doesn't explain an apparently floating bearing.

    @TomvanderZanden - I understand why that would be true for designs that employ, the less precise, threaded rod Would that also be true for designs which use lead screws, instead, as they are meant to be of a higher quality?

    What do you gain by constraining the end even if it was perfectly straight?

    @tjb1 - I am not sure, probably nothing... But it seems to me (as a complete novice) that having a "loose" bar/rod end seems a bit insecure, and, for want of a better word, somewhat "untidy".

    @TomvanderZanden - I have added an update that agrees with, and expands upon, your comment...

    @tjb1 - I have added an update that (sort of) explains that I had hoped that by constraining the end, that wobble would have been reduced - which could be the case, although other issues would thereby arise (such as increased motor wear)...

    @Greenonline You might consider adding your "update" as an answer rather than as part of the question.

    @TomvanderZanden - I did consider doing that but... It would be mere supposition on my part, and not a definitive answer. The real answer would need to come from either the designer or someone connected to them, I guess. I have contacted people around the designer and invited them to comment/answer, but that appears to still be "pending"...

    @Greenonline, when you constrain both ends you take most of the movement you seen at the top and force that movement to the center (where the Z axis is riding). When you leave the top open, the rod is only constrained by the motor connection and the nut on the Z axis which allows it to move at the top assuming your motor connection is flexible. I really fail to see what you hope to gain by fixing the top?

    Greenonline I agree with @TomvanderZanden that you should move your "update" to an answer. I think your rationale and references are sufficient to consider it a quality answer. If understand your hesitancy; but. if we had to wait for the actual designer to answer questions like this then most would never get answered. Also your answer will not preclude theirs. Finally, part of the quality of this site is that questions get answers; so, moving your response to an answer improved the quality of the site.

    @markshancock - done :-)

  • I've just seen this right now, I'm Alvaro Rey, the designer of the p3steel v4 mod. The change was made, because with previous versions with the extruder homed, if you go up in the Z axis, the extruder motor could hit the Z axis top plate. So, in order to avoid that, I just changed the design.

    The bearing in the z axis is not necessary but some people prefer to use it, in order to avoid wobble in the threaded rod.

    Anyways, I designed a printer part to fix the bearing in the Z top plate.

    Excellent! Many many thanks for getting back to me, Alvaro and answering this question. And welcome to SE.3DP by the way... it is a real pleasure to have a designer onboard! :-) BTW, do you have a link to the new printer part, which will fix the bearing?

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Content dated before 7/24/2021 11:53 AM

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