Is binding of the installed X/Y axis normal?

Discussion in 'Build Help' started by George Hartzell, Jun 4, 2017.

  1. George Hartzell

    Jun 26, 2016
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    The subject is a bit of a rhetorical question...

    I just finished Step 4 from the Step by Step Assembly Process.

    I've noticed that there is binding on the left side as I move the assembly towards the rear. If I start with the assembly at the front of the printer and slide it back, the part labeled "Y-AXIS BACK (R)" in the "Y-AXIS REAR ASSEMBLY" image creeps back and forth on the bar, as if something is not square. By the time I get to the rear of the movement it is binding fairly tightly

    Back when I was getting started with the build (last June, in fact) I cracked that very piece and the fine folks at BigBox sent me a replacement.

    I wonder if the pair were supposed to be matched?

    Should I send the STLS for both parts off to Shapeways (or ...) and get a new pair made?


  2. Ephemeris

    Ephemeris Well-Known Member

    Nov 25, 2015
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    Short answer is the binding is not normal. It does happen sometimes and you have to tweak until it goes away. How is a longer answer than I can give right now as it's late. Stick with this problem until its resolved! Hopefully in the meanwhile someone can chime in with tips.
  3. Old_Tafr

    Old_Tafr Well-Known Member

    Mar 7, 2016
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    I am really rusty on this as it's a long while since I built mine.

    You could start from basics, check that the frame is square, don't use a tape rule or similar but some form of measuring stick.
    Checking the diagonal dimensions as these must be equal.

    Also is the BigBox on a flat surface?

    Measure the distance between the Y-Axis rods (Item-1 in step 4, ) those rods that are some 18" ish apart. If these are not absolutely parallel then the Y-Axis movement, i.e. forward and back will not be smooth, check this without the Y motor (the one on the back panel) connected so that you can feel the movement.

    Did you pack the LMU bearings with grease before fitting? either way add a little grease to the smooth rods so that you get a smooth movement with a graunching feeling. Noise and rough feeling when you move the bearing on the rod isn't good, they take a little running in.

    Are the two X-Axis rods level and parallel? Did these rods fit smoothly without too much effort into the fittings that sit on the Y-Axis rods? I found these were a tight fit so a good way to clean the holes out is the correct size drill and turn it "anti-clockwise" this sounds crazy but it works. If the two parallel smooth rods don't fit well then you could twist the whole frame.

    When my BigBox was built I fitted a support across the front as this is the weak point of the design, don't do this now as it gets in the way, I have described elsewhere how I did this.

    Measuring sticks... It is impossible to measure accurately between smooth rods with a metal rule or tape rule. The absolute distance isn't important but the fact that rods are parallel within a thou is. I made some measuring sticks with a piece of thin bamboo, with a round head screw fitted at each end. The screws allow very small adjustments so that the stick just fits between the rods. Filing a U shaped cup in the bamboo at one end is possibly better so it locates positively at one end, make sure the rod is parallel to the frame when you do this.

    Also I remember the assembly process saying don't tighten various parts until you get to "commissioning" like the fittings at the front of the Y-Axis (18 inch apart) rods. If you have tightened too soon then things will not have been set in the correct sequence.
    UlrichKliegis and Alex Stevenson like this.
  4. Greg Holloway

    Greg Holloway Administrator
    Staff Member

    Sep 4, 2015
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    As @Old_Tafr says, things are not aligned correctly....

    Loosen everything off, if it's binding it is because it's not square and the rods are not parallel. This will be fixed during commissioning. Do not tighten any of the X/Y screws or nuts.

    I also recommend reading through the whole build manual before you begin so you understand why certain things are done at certain points in the build and why some things are not done until the final stages.

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