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Pronounced corners - advice?

Posted by ardia 
Pronounced corners - advice?
December 22, 2011 12:08PM
Hi all,
I've recently completed my Prusa build (thanks to nophead for the super plastic parts!!) and today it was completed with a heated bed.
I tried to tune Skeinforge (the latest version, "help->Version" shows 11.12.19).
I went from what is seen here: to here: .

To get to the second result, I reduced the amount of material deposited by increasing the feed rate (keeping flow rate constant).

It looks somewhat good, but I;m jealous of Nophead's results now that I have seen them :-)

So, I have these problems that i would like to correct with any advice I can get:

1. The corners are pronounced, as seen here: . Also, the start of each layer creates some extra material to accumulate, creating even more excess material:

2. There is a problem with the dimensions. The test cube is 20x20mm but my result is 19.8x19.8 (including the pronounced corners) or 19.4x19.4 if I measure at the middle, leaving out the corners that carry more material. How would I compensate the difference? I do have the firmware (Teacup) configured on X and Y steps per meter as they can be calculated by theoretical numbers. I'm afraid that if I change my fill rate then I will have excess plastic. Any suggestions?

Thanks for reading!
Re: Pronounced corners - advice?
December 24, 2011 10:50AM
It may be an oozebane problem. Lower the travel constant.
Re: Pronounced corners - advice?
December 26, 2011 08:43PM
I had the same issue with pronounced corners. My solution was to change firmware. I was using Sprinter FW, but after reading through the forums, it seems Marlin FW produces smoother perimeters. This has certainly been my experience. I've almost doubled my perimeter speed and have almost no buldge at direction changes.

As toehead stated, oozebane may also work, but I've done little with oozebane so I can't speak to that.

You may want to try sfact instead of skeinforge. In my experience, it has been much easier to setup and gave me better results.

As for dimensions, I'd double check your x and y steps/mm.

Good luck!
Re: Pronounced corners - advice?
January 03, 2012 02:57PM
Yup, time to move to Marlin. With Sprinter, you'll see corners like that unless you print perimeters at 25 mm/sec or slower. With Marlin, you can go much, much faster and still see better quality.
Re: Pronounced corners - advice?
March 16, 2012 02:26PM
Argiris => I'm curious if you tried Marlin or not to solve this issue yet.

I'm using Teacup on Gen7/Prusa + Skeinforge and having EXACTLY the same issue with corners. The Z-step corner looks especially ugly (similar to yours) , but the other corners also bulge undesireably .
Re: Pronounced corners - advice?
March 17, 2012 05:25PM
Hi, I've not yet found the time to change the firmware. The issue has been somewhat diminished (not eliminated!) by using SFACT. I think it is easier to tune than Skeinforge. If you want I could pass you my settings for SFACT to see if there is any impovement in your setup. What certainly helps, at least the z-step extra material, is to set the clipping to a higher value (I use 1.25) and increase the withdrawal of the filament in the firmware. The default value was 289 steps as I remember, but I increased it to the equivalemt of 2mm (use your steps_per_m_e to find the correct value). I don't have picture to post right now.
Another reason for not changing the firmware yet is that I'm indimidated with the number of settings I have to change, certainly in the firmware but also the SFact.......I've postponed it until there will a big timeframe is open :-)
Re: Pronounced corners - advice?
March 20, 2012 04:16PM
Switch to Marlin + pronterface and look for a sample skeinforge settings that they have shared.
Re: Pronounced corners - advice?
March 26, 2012 01:36PM
I ended up switching to Marlin - although it is superior to Teacup in several ways, it didn't actually "solve" this bulging corners issue - that has to do with speed & acceleration. One thing that did help significantly though was to turn on "Radius" in Skeinforge. Use a value of "2" times perimeter width and an intermediate flow rate of "0.75" and it works quite nicely to both reduce frame shake and corner defects.

Attached is a photo of a print on the left using Teacup @ 30mm/s and on the right using Marlin @ 75mm/s with rounded corners.

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