Having trouble with a print - "ring effect" when printing holes

[astrodenny 0]

Hello,

I started printing an assembly for this snap together robohand from thingiverse:

http://www.thingiverse.com/thing:92937

Printing with Black PLA

Retraction on

Temp: 220

Layer Height .1mm

20% Fill

Print speed 50 mm/s

Travel spee 100 mm/s

For centered holes, there is a ring effect that occurs around the hole itself.

Also, in the case of the first image, it seems as if the hole protrudes along the surface.

I'm having trouble figuring out if this a mechanical issue or settings issue. Are my x-y melts too tight causing backlash?

 

[olivierc 2]

Are my x-y melts too tight causing backlash?

 

I'd say it's the opposite, they are not tight enough. Also, it might be the short belts linking the steppers to the axis, they are the one causing the more backslash to me

Also the print looks pretty ugly from the side, you should try lowering the temperature a bit

 

[astrodenny 0]

Thanks Olivier - I'll try doing that. I just adjusted my short belts before the print, so this could be be it. Just to confirm, if my short belts are too tight, would it cause backlash? What if they are too loose? I remember seeing a post on this but can't find it.

 

[gr5 1,235]

You guys need to learn definitions:

Backlash (see wikipedia) also known as "Play" means the belts are too loose is evident in that when you change directions, the head doesn't change right away because the belt is so loose.

What you are describing is sometimes called "ringing". It happens when either the head or the platform is vibrating at a resonant frequency.

If you tighten or loosen the belts it will change the frequency of the head. Tighter means higher resonant frequency (closer together). If they are so close together that it's invisible then that's a good thing. Looser belts lower the frequency of the ringing (waves farther apart). Slowing down head movement will also make the ringing get closer together and fade out sooner.

If it's the bed that is doing the vibrating you can add a weight to the bed to lower the resonant frequency - so low that again the waves will be invisible.

The ringing affect is a tiny tiny error in the surface position but very very visible because the surface is normally so perfect. If the surface isn't shiny (dull) then it's also hard to see the ringing - you have to hold the part up to the light in such a way that part of the "waves" on the part reflect and part don't.