Extremely annoying Z layers missing - costing time and money

[lamb_proto 0]

I've had my machine for about 14 months.

For the last few months it has an intermittent fault where it misses a Z layer (or maybe several) at a height of about 20mm from the bed. this is approximately every 3rd or 4th build but is random so I cannot tell until a build fails.

Parts easily break at the fail point.

I've done factory resets, unloaded and loaded material and cleaned and lubed the screw but the problem always seems to come back when it is least convenient.

I think others may have this problem but I've not seen a fix. I imagine Ultimaker will recommend buying lots of expensive spare parts.

I'm an industrial designer. Although the machine is useful it is getting to the point where I cannot rely on it,

does anyone know what this might be? failing that can anyone recommend a professional machine that actually works?

[SandervG 1,522]

Hi @Lamb_proto,

thank you for your message and welcome to the forums!

Do you perhaps have some photo's of what the fault looks like? That always helps a lot when isolating the problem.

Have you followed or done any of these recommended maintenance tips to your Ultimaker?

Did you also clean the Z-rod?

In any case, without having seen any photo's I would recommend to give your threaded Z axis a good clean.

A PTFE coupler which is down to its last breath probably won't cause a repetitive failure around 20mm, but just in case, have you ever replaced your PTFE coupler?

Looking forward hearing from you.

[gr5 2,293]

Photo of a few prints. Is it always the same spot? Most likely it's related to Z movement. It is getting hung up. With mostly equal probability it could be the Z screw, the Z nut, the Z rods, or the Z bearings. It's possible it's also other things like an overheating Z driver - it might shut off for 1/4 second due to overheating and your bed could drop a tiny bit. For example it could be 20mm from glass is where things start to get too hot. But if it gets "good" again above 20mm then it's probably mechanical.

Slide your bed up and down many times by hand with power off trying to feel if you can detect the bad spot.

To separate rods from screw issues, remove the screw. With power off, remove the Z motor and screw and pull it out the bottom. Slide the bed up and down and without the stepper involved any problems are VERY noticable.

A quick hack fix/test is to put a heavy weight in the back of the bed. 1kg or 2 pounds is about right.

If the problem comes and goes then often a very thorough cleaning will help. Many people have bought a new Z nut of higher quality and that has helped many people. Many others replaced the vertical rods or the bearings which fixed their issue. It's hard to say for sure.

[gr5 2,293]

Oh and you shouldn't need any (or EXTREMELY little) oil on the rods. They have ball bearings inside. Sometimes it helps to take those out and clean the ball bearings with wd-40 and then dry thoroughly and re-lubricate with a drop of oil or less than a drop.