bad quality of bottom and top layer

[basteluwe 1]

Hi guys,

I'm new to 3D printing and still do a lot of trial & error. However slowly my results get better.

This little plug came out quite OK, when looking at it from the side.

Problem is the bottom and top-layers. Bottom (feels very smooth, but looks bad):

Top (does not feel to smooth looks bad too):

I'm printing with UO+ and Cura. Material is PLA (Ultimaker) siver metallic. Layerhight 0.1mm, bed: 60°C, nozzle: 210°C.

What can(should) I do, to get a better bottom & top surface?

[SandervG 1,521]

Hi @Basteluwe,

Thank you for your post and welcome to the forums.

There is absolutely nothing wrong with learning through trial and error. That is what we have all done, and failure is a great teacher!

But luckily you can also rely on the forums to help

The side of your knob definitely looks great!

For the bottom I could suggest to level your bed a little bit higher so your first layer is really squeezed on the bed. That should help in getting that flat, smooth first layer with excellent adhesion.

About the top layer, would you say your knob is perfectly round? From the last photo it looks like it may not be... (maybe that is just the photo..)

How fast do you print?

To be sure, can you check how tight your small belts are?

Thanks, looking forward hearing from you!

[neotko 1,417]

Check this guide for circles, not round

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#circles

As @sandervg says, 99% of the time, is a belt tension issue.

To illustrate the problem. When X/Y short belts ain't tight enough, as soon one motor pushes the other direction, there's a delay on feedback to the shafts due lack of tension, this causes smooth changes of direction to show irregularities. That's why, short belts, must be tight.

Other 1% of the time, the pulleys of umo (not the best quality IMO) use to show eccentricity issues. This means that the curvature isn't perfectly circular. So when two pulleys rotate one pushes more than the other, or both get loose (micro effect). If you look at your pulleys you should actually be able to 'see' that the rotation shows changes showing that the pulley isn't perfectly round. That also can cause lack of precision on very small circles when printing slow. To fix this the best is to move to a GT2 pulley, not only is more precise (UM use GT2 on their um2-um3 but umo/umo+ uses MXL), but also you can get better quality pulleys with less eccentricity.

Remember this might not be your issue. But it illustrate why all mechanicals parts must be as precise as possible to get the best quality possible.

[gr5 2,176]

> as soon one motor pushes the other direction, there's a delay on feedback to the shafts due lack of tensio

Yes!  This is called "play" or "backlash".  You can read about it in wikipedia.  Common problem on UMO and very easy to fix.

[basteluwe 1]

Thanks to all of you for the replies so far.

Yes, you are right, my circles were not really round. I asked for that in another topic and got immediate help, which led me to the drive belts. After I put more tension on those, circles were OK. That was an easy fix indeed.

As for my bottom layers it seems more difficult. At present I print 0.3mm bottomlayer and have lately reduced speed to 20mm/s. I have leveled the bed before latest print to the nozle just slightly grabbing the piece of paper. Still not satisfying. I have a strange feeling about the amount of extrusion at the beginning of print. To me it looks like there is not enough material coming out at the beginning. Please look at the folloing picture. It schould print a skirt (3 circles) but just is a mess!

Next picture shows the bottomside, still very bad:

I'd be greatfull for further help!

Wishing you all a nice sunday,

Uwe

[gr5 2,176]

It's hard to tell if it was underextruding because the filament wasn't inserted all the way (always make sure a little filament leaks out when you turn the wheel before a print).

But if you primed the nozzle properly then this photo also looks exactly what you expect when the bed is too far from the nozzle. They say to zero it with a piece of paper but then you should turn all 3 screws another half turn or so to move the bed closer to the nozzle. You want z=0 to have the glass touching the nozzle (or even a little closer - touching with slight pressure).