Shifted Layers caused by ? Overheating vs Wire on UM2E+ vs Steppermotor vs Fan

[Minkeproducts 3]

Dear all,

Would anyone know what is the problem here?

 

I made 3 times a good 15 hr print on my UM2E+

The 4th time the print suddenly showed a shift on the Y-axis, almost at the end of the print

I marked the pulleys, the belts seem tight (so I did not change anything)

The 5th print, came out good. 

The 6th print showed again a shift on the Y-axis, the same way as the 4th print, also the same height

At the moment when it happened, I heard a sound, different from normal; a sound like what you hear when you connect with a usb to upgrade the firmware.

( I paused the print, and continued after a while, but the print continued to print at the wrong spot)

 

I checked the marks on 8 pulleys; they are at the same spot. All belts seem tight enough.

There are two pulleys connected with the two motor blocks I did not mark however.

The two motors can become quite hot.

The bottom heat (motherboard) seems okay; that was not really warm when it happened.

 

Would anybody know how I can solve this issue?

I know that there are more discussions about this, but some are different. I found this similar topic. Maybe somebody can have a look at my description of the problem?

Answers may also be written in Dutch. Pulleys and belts, stepper motor..., the English terminology is sometimes a bit confusing for me.

 

My conclusion so far;

-All belts and 8 pulleys seem okay

-Prints the same gcode sometimes good and sometimes with shifted layer, after quite some hours of print

-When this happens I hear a sound like a "Pòck!

 

I placed my question maybe in the wrong section, here is my original post;

 

[geert_2 553]

In the very beginning, on one of my UM2 printers, I had the Z-axis moving down a couple of times during long prints, due to overheating and temporarilty shutting down of the drivers. In mid-print it would fall down 5mm, and then continue printing as if nothing had happened. This was only on long prints, or very intensive use all day. I never had it on the X- or Y-axis, but I can imagine that it is possible too.

 

In my case the solution was to reduce current through the stepper motors. Since then, it never happened again in all those years. If I remember well this was done on the printer, via the settings menu. I don't remember the exact values, maybe from 1200mA to 900mA, or something around this? Maybe try 20% off the current value? If you go too low, the stepper hasn't enough power to move the head anymore, and you get the same problem: skipped steps. Anyway, if you would try this, be sure to write down the original values.

 

Another thing could be lack of lubrication of the rods and bearings. Or wrong oil: I once used "fine oil for sewing machines", but that quickly turned into a thick, sticky gum, almost glue, and it made head movements very hard: I could hear the printer struggling. Now I use hydraulic oil suitable for both industrial equipment (tractors, bulldozers, cranes) and fine test equipment (hydraulic lab testbenches). This oil does not dry out at all, and it collects and removes dust very well. I don't know if this is the best, but I just happened to have 100 liter surplus, so I gave it a try...

 

With the machine off, you should be able to move the head manually without much resistance, and without dead or stuck points halfway.

 

Concerning loose belts or pulleys: I think you should also check the pulleys from the motors, at the back, because they are loaded more. The other pulleys are doubled, so they share the load, but these aren't.

 

Off-topic: how did you generate that mesh-like support structure? And how does the result turn out, in close-up?

 

[Minkeproducts 3]

Good day Geert,

 

Thank you for your written advises; very clear and helpful

I will focus on all given points and give it a try, let you know when I am done 😃

I will check áll the belts, other oil, and better ventilation to start with..

 

Concerning your off-topic question; for printing the more organic meshes, like bones, skull and figurines I use Meshmixer to generate support. I do this since I started 3d printing and I am very content with it. The result in close up looks fine; I can just break away the support without a problem. (The figurine showed is a model I printed for the makers of the reconstruction, a Homo Erectus for Naturalis Leiden, made by Adrie and Alfons Kennis)

[Minkeproducts 3]