Hi,
these days I observed a strage behavior of my heating bed during 3d prints:
when the plate start to move, the rear part (in the direction of movement) lowers while the front edge is raised. Or to say: the whole plate tilts like an accelerating car, who’s rear dives.
We talk about probably 0.3 - 0.5mm, maybe more; so easy to observe by eye (and difficult to measure).
The resulting effects are visible in the way, how brims are printed:
:
one half (left/right in the direction of Y movement) is thinner (because the printed brim is on the elevated front/rear half of the plate) and vice-versa - and mirrored pattern on the other half (front/rear) of the plate.
(I hope, this description makes any sense )
This is on a Snapmaker A350T and I suspect a mechanical problem as root cause.
From a first visible and light pushy check the plate is well mounted to the lineare drives and is not loose.
But before dismounting everything with questionable outcome:
did anybody observe similar things before or are there any suggestions or tips what to look for when investigating the root cause and checking components ?
This is the notorious z-wobble of the Y-axis linear rails. It has been an issue for a long time, which Snapmaker has apparently refused to acknowledge, and is a fault in the design of the linear rail modules (it can eventually affect the X and Z axis modules as well). The underlying cause it that the bearings inside of the linear rail modules are loose and/or worn. There are 5 options to fix it:
Contact Support to purchase replacement modules (expensive)
Disassemble modules to tighten the bearings (not a guaranteed fix)
Disassemble modules to replace the bearings
Install DIY support rail modification
Install Snapmaker official bracing kit (SM advertises this as additional bracing intended to support the 200W CNC module rather than a fix for the wobble, but they took their inspiration for it from the DIY support mods and originally released it due to owner request/complaints about the wobble, but then refused to offer it free-of-charge to anyone with the issue - shoddy and unsupportive of them, no pun intended)
Note: #1-3 should be considered temporary fixes, as it will eventually happen again. If you choose any of #2-5, you should consider #3 as mandatory along with it in order to retain full integrity of the modules. #5 is probably the most efficient solution, but will cause the permanent loss of some of your z-height build volume, and the longevity and reliability of the kit is not yet fully tested since it is a new product just released within the past few months. #4 has numerous solutions developed by various users/owners, with varying degrees of mechanical aptitude and modification required; you can find most of them here in the forum using the search term “support rails.”
In my case, my A350 purchased new in April 2021 suffered this issue around the 6 month (approx 900 hours of use) mark. I was so infuriated with the poor quality engineering across various aspects of the machine that I didn’t touch it for about 3-6 months. When I finally got around to messing with it again, option #5 didn’t exist at the time, so I ended up going with #3-4 combined. That was more than 2yrs ago, and it has not been an issue since.
Excellent advice above.
As said, if you go for solution #4 then you really need to do #2 or similar too, because otherwise you will only be hiding a problem that will get worse.
The official cure for #2 (page 13):
You should first search for others’ tips and opinions here on the forum on the official method.
Also here (same info without having to dowload):
@Mxbrnr thanks a lot for your very detailed explanation and directions to go !!
Based on your reply #4 made huge step forward on my prioritized list of projects
I’ll work on #2/#3 right now to bridge the time until #4 can be completed.
@Boxkite thanks a lot for sharing the guide and link. So far I didn’t search for this kind of information since I didn’t expect problems like these after just about 4 months of operations.
)
