Uneven bolt tension for X and Y
Hi there,
I just updated to Firmware 6.4.0 and wanted to test the new bolt tension calibration via vibrations. After selecting the correct values I just got an error, that my values are out of range. After using the "old" method with app and sound frequencies I have a difference of 11Hz (maximum should be 8). Currently my upper belt is at 104Hz and the lower belt is at 93Hz.
I followed this guide and checking if my gantry has no gaps. Seems to be aligned perfectly, because both sides touch the other part, even without pressure. Then I tried to align the tension via screws. If I adjust evenly the gap between both bolts stay the same, they just increase or decrease overall. If I just adjust one screw the gap closes, but the gantry isn't aligned anymore.
After this I followed extensive adjustment guide in the end, completley dismounting my Nextruder and checking the belts. They are both showing 4-5 teeths on both sides, like the manual mentions. So this should be fine.
Does anyone have an idea how to reduce the gap between bolt tensions? Is this even a problem? My prints seems to be fine, but I don't know if they could get even better?!
Thanks!
RE: Uneven bolt tension for X and Y
With the belts completely loose, double check the gantry alignment again. Then when you tighten the belts you must turn both screws an equal amount. So you start with the left screw with 2 turns, right screw 2 turns until the belts start to get tension. Then left screw 1/2 turn, right screw 1/2 turn until the belts are in range. Then 1/4 turn left, 1/4 right, 1/8 left, 1/8 right. If the belts are too tight the loosen both screws 1/8 of a turn at the time. Never adjust the screws independently of each other.
As long as both belts are in the 90's you are fine. They don't need to be exactly 98/92hz. Trying to match that frequency by unevenly tightening the screws will bend the gantry.
Also, just like checking the air pressure in your car tires periodically, it's a good idea to check the belt tension periodically. I check it once a week.
RE: Uneven bolt tension for X and Y
Ignore the frequency of the belts.
Start with the tensioners loose and ensure that there's no gap on the gantry.
Then, tighten each screw equally until you get into range. If you're seeing a gap appear while tensioning the belts, then you're unevenly tightening them and pulling the gantry out of square. Use the same number of turns for each screw. I start with full turns to get things started, then back down to half then quarter turns.
The absolute frequency of the belts isn't important. They just need to be "in the ballpark" (close enough) while not imparting uneven tension on the gantry.
RE: Uneven bolt tension for X and Y
Thanks for your answers! Really tried hard to tighten both screws evenly, but everytime a gap opens on one side. This gap can only be closed when I tighten one side more than the other :/
Could there be any bending that causes this issue? Thinking about building a few parts again from scratch to find any issues. Was a pre-assembled Core One.
RE:
Thanks for your answers! Really tried hard to tighten both screws evenly, but everytime a gap opens on one side. This gap can only be closed when I tighten one side more than the other :/
Could there be any bending that causes this issue? Thinking about building a few parts again from scratch to find any issues. Was a pre-assembled Core One.
You should start with the "Quick Gantry Alignment" described in the yellow box of the guide you already linked to in your original post. That alignment may indeed involve bending the gantry in case it is not aligned when the belts are loose. ("2. Move the gantry halfway back along the rails. 3. Grip the gantry firmly on both ends and apply a gentle counter-force in the opposite direction of the tilt until it straightens.") You don't bend the linear rail, of course -- just the two mounting brackets which attach it to the Y drive, and which are made of rather soft metal.
After that, tighten the belts symmetrically, again as stated in the guide. Due to the balanced tension on both belts, the gantry should stay aligned during this step.
Once you are in the ballpark, you can use the belt tuning wizard built into firmware 6.4.0 to get to the right belt tensions. The wizard will continue to suggest symmetrical adjustments only, so the gantry should stay straight.
RE:
... Never adjust the screws independently of each other.
The problem / question here is: Is the non-tensioned "reference point" from which one is supposed to tighten both belts equally as accurate as the final belt tensioning. The belt assembly is ("first order approximation") a spring, so force is proportional to deflection. And sensitivity without tension at all is zero.
Without belt tension, let's say a 1 mm error in the screws will not cause the gantry to bend as it causes zero or minimal force. But this changes under tension, where the same 1 mm deflection error suddenly causes a substantial amount of force imbalance.
Asymmetrical screw adjustment to bring a bent gantry into alignment - no, the "error forces" would just fight each other. But (superficially) asymmetrical screw adjustments to maintain balance, that may be a different story ...
RE: Uneven bolt tension for X and Y
... or above rephrased: You find out only near final tension whether the starting position of the screws was correct (reminder, just 1/8 turn makes a significant difference in the Hz readings. Can you repeatedly establish starting screw position near zero belt tension to an accuracy better than that? I suspect not).
RE: Uneven bolt tension for X and Y
... or above rephrased: You find out only near final tension whether the starting position of the screws was correct (reminder, just 1/8 turn makes a significant difference in the Hz readings. Can you repeatedly establish starting screw position near zero belt tension to an accuracy better than that? I suspect not).
I started all over again and was very precise with my turns. Frame is perfectly aligned, every screw got the same amount of tiny turns and in the end I ended again with 98Hz/89Hz. I'll leave it this way since I don't experience any problems at all. Thanks to all of you 🙂
RE: Uneven bolt tension for X and Y
You can't set both frequencies precisely and also have the gantry aligned. Follow the procedures and live with whatever frequency difference you get, so long as they end up in the acceptance window of the tuning utility. In theory, turning both adjustments by the same amount shouldn't change the gantry alignment, but nothing's perfect, so at the very end I recheck the alignment one more time and tweak one adjuster to get it perfect, then re-run the tuning utility. Once you've been through it, the process takes almost not time and adjustments should be minor.
RE: Uneven bolt tension for X and Y
The biggest issue I found with the belt tensioning is the starting point as yes both belts are slack but each adjuster may not be undone by the same amount i.e. have the same mechanical starting point.
Once you have the same mechanical reference on both adjusters you apply same number of turns left and right until you get the tension into the range where the tuning app detects it, as the belts get tensioned to different frequencies there will be a slight difference in the turns on each adjuster but it is quite small. IIRC correctly it less than 1 turn.