Black burnt mark on print out

[jin1219ca 0]

Hi,

Just finished assembly of UMO+ and started testing for a few days. For every print, there would always got some black burnt mark on somewhere of the print out. Sometimes there is only some blacks, but sometimes you can see it really kind of burnt and dissolved. Can I know how to solve this? Is it because the bottom layer doesn't stick to the bed so the prints got uneven base and swing a little bit then the nozzle touches the print? Any suggestion would be appreciated.

Also, can suggestion for the proper temperature for PLA to be stuck on the bed better?

One more stupid question, how to remove the material? I dialed back the feeder gear but it didn't work.

Thanks.

 

[jameshs 42]

same question in another thread.

temp depends on the material - 220 first layer for bed adhesion (glass with PVA) then as low as it will go and print reliably (this is what I use for colorfabb PLA/PHA)

Remove by opening the feeder and pulling when the head has been at temp for a few seconds, or cold pull for nuclear (look elsewhere for instructions)

 

[ultiarjan 1,223]

I find pla to stick to the bed just fine anywhere from 50 to 70 degrees (mostly use 50) most important is to keep the glas clean. I just wash it with soap and warm water now and then... and dont touch it with your hands. ..

[chrisr 18]

I find pla to stick to the bed just fine anywhere from 50 to 70 degrees (mostly use 50) most important is to keep the glas clean. I just wash it with soap and warm water now and then... and dont touch it with your hands. ..

 

The special cloth you can buy which is for cleaning spectacles and camera lenses is excellent for removing any traces of grease from the glass. It literally makes the glass "squeaky clean" = good for adhesion :-)

 

[jin1219ca 0]

Hi,

Just uninstalled, wiped out the residues, and tightened them last night but still got some leakage from the heater block bottom to top of the nozzle. I will take them apart again and try to tighten it harder. Thanks for all the inputs here.

 

[jameshs 42]

careful on the tightening - you can break the nozzle brass tube easily.

adjust all the threads so you are getting a brass to brass connection at the nozzle and then good seal the other end too.

I make sure I do the last tighten with the whole assembly 'hot' to make sure it is all seated - a firm grip on the heater block and a box end wrench means I have not broken any yet!

 

[jin1219ca 0]

Hi,

Redo the whole tightening again, but still got leakage immediately. I'll try to get thread seal tape tomorrow and try if it works. Thanks for the feedbacks here.

By the way, since the temperature will hit 220 degree easily, is the tape durable under such heat?

 

[jin1219ca 0]

Just found the leakage was from the bottom of the brass pipe/top of the heater block, and then dripping down to the nozzle and then ends on the print. So I think tightening the connecting of these two parts might work, let's see..