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S5 belt not tightening

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Posted · S5 belt not tightening

I tried tightening my S5 belts per the instructions in this Ultimaker video. However, this only yielded a ~10% tightness improvement, and they are still hanging slack. In addition, the set screws do not screw all the way back in. What are my options at this point?


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    Posted · S5 belt not tightening

    Did you use the proper diameter hex tool?  These set screws are incredibly tight and so if you use the wrong tool you can strip it. 


    You want a metric, 2mm hex screwdriver.  You want a flat end (not a ball end).  In fact it's good to have both types of hex drivers (ball end, and normal) for these printers.  The ball end lets you come in at an angle.  The flat ends hold screws in mid-air nicely.  I don't think the ball ends are strong enough to tighten these.


    When you loosened the pulley, did it spin on the shaft?  Can you double check that?  If not then something is wrong with the spring inside the sliding blocks.


    You can buy an entire sliding block/belt kit (I don't think you can buy the belts alone).  Or you can take apart the offending block and there is a spring system.  It's quite difficult to get the block apart, and it's tricky to get it together with that powerful spring in there.  That's why they sell them as assemlies.


    The assemblies do not include a pulley.


    You can get a pulley from your reseller.  You can buy them also on the internet but I don't recommend that.  Many have the center hole badly aligned with the pulley.  Even just 0.1mm of offset of the center hole on the pulley means you will have + and - .1mm errors on the positioning of the walls of your parts.

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    Posted · S5 belt not tightening

    I used the Ultimaker-provided flat-head 2mm and still seem to have stripped the screws while screwing them back in. 


    The pulley did not spin on the shaft when I tightened it. Given that, do I want to buy something like this? Or do I need to buy a replacement pulley as well? (For what it's worth, I think the issue is the pulley slipped a tooth, not excessive slack.)



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    Posted · S5 belt not tightening

    I'm asking if the pulley was able to spin on the shaft when you *loosened* it.  My first guess is that you didn't loosen the pulley enough and it didn't spin to balance the tightness of the belt.  This is issue #1.


    Issue #2 is repairing that pulley.  Well maybe you can leave it as is and loosen the other pulley on the same belt.  It doesn't matter which pulley you loosen.  Just be much more careful this time to not strip the set screw.  Push the print head around until the set screw is most easily accessed with the hex driver.  Insert fully and as perpendicular as possible.  It takes quite a bit of force to loosen and you want to use even more force to tighten later on.


    Make damn sure the pulley spins freely on the shaft and that you can get good tension.  If not then and only then should you buy that from dynamism but now realize you need to probably loosen both pulleys to get the old belt off and the new one on.  I'm not certain.  You might be able to do it with one pulley still connected to the rod.


    I should warn you that most people do NOT tighten the set screws enough later.  Everything seems fine but they go to print and the pulley slips a bit on the shaft and each layer is printed with a bit of offset.  So if you have this issue then you didn't tighten the set screws enough.


    If it turns out you need to get that pulley off then you should by a screw extractor.  Google it.  They are reverse threaded drilling bits that drill into the center of the screw in CCW direction and eventually get a good "bite" and pull the set screw right out.  You'll need to replace it with a new set screw.

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    Posted · S5 belt not tightening

    Thank you very much for all your advice here! This is extremely helpful. The second print ringing gets worse, I'll just invest in the replacement pulley, as I've followed your instructions above to a T.  

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