Just started building the K8200.
I’m finding that the bed support carriage does not run freely along Y rods despite multiple adjustments. Individual linear bearings run fine but when lock to bed support plate start to bind. Have confirmed that Y rods are parallel to each other. I get the impression that there may be a very slight curvature in the bed support plate along the Y axis which tilts the linear bearings out of true alignment with the long axis of the Y rods when the bolts are tightened.
Has anyone had similar problems? Help much appreciated as I’ve got a long way to go yet!
I’m not sure I understand what the problem is exactly… your bed starts to bend when it’s slid over both rods? If you place both rods next to each other on a flat surface, are they bent?
Mind you that it is normal that it feels a bit ‘scratchy’ when you move the carriage over the rods. It won’t be like the shaft of a pump that moves silently and smoothly. Shouldn’t lock or bend anything either 
Many thanks. Sorry if my post was a bit unclear!
The bed support plate isn’t bending on movement and as far as I can judge from holding the rods themselves against a flat surface they are not bent.
It’s just that the bed support plate when assembled on the y rods doesn’t run smoothly and certainly not as smoothly as I would have expected. However from what you have said maybe this is normal.
I found the movement to be rather disturbing, because it feels like the carriage is scratching the rod. But this is normal and will get a lot better over time. The carriage should not get stuck though, the movement needs to be smooth in that aspect.
Apply silicone grease spray regularly on all metal rods.
Thanks. That’s very helpful to know and reassuring!
i have a can of wd40 next to the printer and use it allot to keep it all smooth
I have the same problem - Individual linear bearings run fine but when any are locked to the bed support plate the bearing starts to bind. It seems that the bearing case distorts under tension and in turn distorts the bearing. I have applied bearing grease but still the same problem. There seems to be a design fault with the bearing support case.
I now have all bearing cases very loosely secured and additionally held in place with super glue. Working fine.
Same issue here; I was already thinking of disassemble this part again (although I am busy with left Z “arm”).
With this arm there are more problems: one of the lock nuts was missing the blue plastic to lock the nut.
But got that from a DIY store, putting me back €0,04 
But more disturbing is that from one of the bearing one ball came out. Just saw it lying on top of the bearing.
Hopefully I can get this replaced.
Same issue here, two bearings lost their balls (balls were in the bags, so not damaged during mounting…)and now are as lumpy as possible. In my case it were the bearings on the Z-axis (bag number 19). As for tough running, left to right it flies (belt not yet attached) front to back is scratchy but in a smooth way… (I mean the same all through).
Update, bearings fall under warranty and Velleman is shipping out replacements. Thanks guys !!
Also noticed that the X and Y axis run quite smoothly when I do not short the stepper wires. As soon as I short those, it becomes very bad. Logical I guess, since I am creating electric loops in the steppers…
I found during assembly that the Y and X axes didn’t move as smoothly as I liked/expected, especially after I had tightened all the bolts (they moved very nicely when they were loose).
I also found that the motors didn’t move very well when the wires were shorted… fine when they were disconnected.
Once all complete and in use, the X and Y axes all moved fine - the stepper motors are pretty big and powerful. I had no missed steps or problems, and that was with the recommended motor drive voltage (0.425V).
This should be noted in the manual when instructing the user to check that the carriages run smoothly. Like: “just make sure the leads to the motors aren’t shorted”.
I was this close to taking apart the entire X–Y assembly at 2:30 am last night when I couldn’t get it to consistently run smoothly. I must have shorted the leads every now and again, cause it ran smoothly for a while, and them kept sticking. I thought I hade gotten some metal shard stuck in the motor or similar.