Rough z axis

Currently I’m building my k8400. At the moment I’m installing the z-axis but I noticed the bearrings are very rough. I did install them till the moment where I have to install the threaded rod. So at this moment I can still move de z axis by hand, but it is so rough it can hang by itself in the middle of the printer. Moving it by hand is very jerky. I made a movie, but the support@velleman.be email adres is not available anymore.
I hope someone (from Velleman) can help me so I can proceed my build.

If necessary, we will replace the bearings.
Please send us a support ticket.
http://support.velleman.eu
Sorry for the inconvenience.

Most likely, there is nothing wrong with the rods. Loosen the upper and lower backets to allow the rods to settle. There is some room for error, and in your case, this room for error means the rods are currently not fluidly parallel. Move it up and down until it moves fluently, and then gradually tighten it.

Sorry for the late reply due to the weekend

Yes I’m aware of misalignement, but that isn’t the problem. Even when I completely disconnect 2 out of 4 bearrings, it runs rough. A seperate bearring also runs rough but of course like 1/4 of the total roughness. My question is, is this just bad quality of all bearings or do I have a bad set of 4?

Try to get it as perfect as possible and apply more lubrication, see what that does, it may solve the roughness entirely

[quote]do I have a bad set of 4?[/quote]That is not likely…

I compared the velleman bearrings with some real industry ones and despite the fact that the velleman bearrings were really really rough I continued the build. Thinking of replacing them later…maybe with new ones or with better quality pieces

I now ran a few test runs but noticed a lot of shifting layers. So I am testing the whole system again. But I noticed that the 8mm rods have some play in the IGLUDUR linear bearrings. Is this normal?

I measured the rods they are from 7,92(!) to 7,95. The bearrings are 8.00. Velleman will probably say this is also normal but I I think this is quite a large play. I can move the rod (not only in de sliding direction) but also turn the rod in de bearing quite a lot. Does anyone know If I buy some new rods that they have better tollerances?