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bulging corners

PostPosted: 2015-Mar-Fri-10-Mar
by Snowbound
I've gotten my settings to where I'm getting consistently good prints. My one issue is that non filleted corners bulge out and i haven't figured out the setting for that.

corner issue.JPG

Re: bulging corners

PostPosted: 2015-Mar-Fri-10-Mar
by etxbkst
I'm having the same issue. I've been advised to turn down jerk/acceleration settings, which I did to no avail. I'll be watching your thread closely!

Re: bulging corners

PostPosted: 2015-Mar-Fri-10-Mar
by RetireeJay
From the picture, that looks like the bulging is happening on one axis only - either the Y axis or the X axis. Is this true? It may be that there's something mechanically loose on the affected axis (belt, setscrew that holds the toothed pulley onto the motor shaft, etc.)

Re: bulging corners

PostPosted: 2015-Mar-Fri-10-Mar
by Snowbound
That's probably not the best picture. It bulges in both directions, almost like a reverse fillet.

Re: bulging corners

PostPosted: 2015-Mar-Fri-10-Mar
by Snowbound
I don't think anything is loose. A couple of times I've gone over it making sure everything was tight and haven't found any problems.

I failed to mention, it's only the vertical corners.

Re: bulging corners

PostPosted: 2015-Mar-Fri-12-Mar
by RetireeJay
I assume that in your print preview there is no bulging...

It may seem paradoxical, but to some extent using higher acceleration values results in sharper corners. If you get the acceleration too high, you might see "ringing." On the other hand, lower speeds will help improve precision. I don't have a Simple, but there are plenty of people on this forum who have posted reasonable printing speeds for the Simple.

Re: bulging corners

PostPosted: 2015-Mar-Fri-13-Mar
by Snowbound
I'll play around with acceleration and speed, thanks. Unfortunately I'm going away for a few days so experimentation will have to wait.

RetireeJay wrote:It may seem paradoxical, but to some extent using higher acceleration values results in sharper corners. If you get the acceleration too high, you might see "ringing." On the other hand, lower speeds will help improve precision. I don't have a Simple, but there are plenty of people on this forum who have posted reasonable printing speeds for the Simple.

Re: bulging corners

PostPosted: 2015-Mar-Fri-21-Mar
by Jamie_K
I print at 30mm/s on my Simple Metal, and I saw an improvement when I increased acceleration above the default. I don't remember how high but if the velocity is low enough, then there is no real problem with high acceleration (no missed steps).

I know a lot of people recommend lower acceleration but I think lowering acceleration makes it worse. The reason is that the X/Y/Z axes respond quickly and accurately but the E dimension is sluggish, at least with the hotend that comes with the Simple Metal.

With low acceleration, when approaching a corner the firmware will slow down X and Y and E, and the physical machine will accurately slow down X and Y but E will not slow down as much as requested, so it over-extrudes when approaching a corner. Then after cornering, X and Y accelerate and E is still recovering from trying to slow down and speed up, so it will under-extrude when leaving the corner. Generally I saw the under-extrusion to be less noticeable because it is spread over a larger distance.

High acceleration "fixes" this because the temporary drop in X/Y/E speed when cornering is much shorter and so the sluggish E has much less effect. Best is if extrusion rate can be constant.

The same over/under extrusion problem occurs whenever the speed changes and the extruder is sluggish to respond. So I went a step further and set the infill and perimeter speed to be the same, to avoid extrusion speed changes at the transition.

Re: bulging corners

PostPosted: 2015-Mar-Sat-00-Mar
by Bob-StPaul
Just a simple question - this is happening on more then a single object right? (In other words - it's not the design is it?)