Help with printing issue

[steve220]

I'm hoping the group can point me in the right direction to help me fix an issue I'm having. Corners on square items bulge a little and I'm getting some ringing around holes in objects. Can you point me to the appropriate settings to minimize these issues? Using the standard PLA settings from S3D for the M2 (revision E).
Here are some pics.

Notice I had to shave off the bulge so the bottom cover of this piece (Not Shown) would fit.
Thanks for any help!

[3dPrintingMD]

Ringing - Have you lowered the default acceleration? That would be the first suggestion to minimize that. It is always present, you could also reduce your printing speed and movement speed, that should help as well.

Corners - I'm going to assume that one of the corners is the starting/stopping point, and its usually an area that is thicker due to this. Are you noticing that on each corner? Safe to say the model doesn't have it that way ?

[Jules]

Yes, it's the acceleration, (not the speed) that causes 80% of that effect.

You can lower the acceleration the Startup Script by using the code below:

M201 X1000 Y1000 ; lower default accelerations

The other thing that causes that ringing is movement vibrations - the only way to deal with that is to use Nema17 dampers on the machine....insta did a writeup on what they are and how to install them in the Modifications section.

viewtopic.php?f=10&t=2552&hilit=nema17

[steve220]

Thanks, I'll try those things. I actually have the dampeners, but haven't installed them yet. The extra bulges are on all four corners of the box. In fact, they seems to show up on most edges as shown on the object here as well:
http://www.thingiverse.com/make:264296

I'll reduce the acceleration and see how that works. Thanks!

[Jules]

The nozzle cannot lay down a perfect sharp corner, when it stops in place and changes direction, it over-extrudes a little bit. If you round the corner just a little bit in the design, you will get a less bulby corner....the nozzle will not have to slow down and stop to turn, it will just follow around it, extruding more evenly.

It seems weird to have to round a corner to actually get a sharper corner out of the deal, but it does work, because of the forces acting on the melted plastic. Try a test case and see.

Or the dampers also help with that - you ought to go ahead and install them if you have them. (Really makes things a lot quieter too.)