what is cura doing differently?

Hi,

I recently got a Bondtec double gear extruder that due to its weights I mounted as bowden and not as flying as before. That brought the topic of pressure and retraction back. Retraction is actually really good at 80mms & 3mm at 90cm bowden length and to minimize the layer change blobs, that are now a bit more pronounced, I wanted to get back to slic3r because it has the aligned seam option. I had abandoned slic3r some time ago for retraction and other issues and had switched first to cura engine in repetier and lastly to standalone cura.

I did a first test with slicer with the same retraction setting but the seam looked absolutely brutal, so I tested curaengine in repetier (right side) and normal cura (left side) with identical settings.


So how can the same slicer absolutely wreck the retraction in one platform and deliver decent results in the other? The slice3r results looked similar to the repetier ones btw.
What is cura doing differently that is makes the retraction so smooth? I would really like to replicate those settings in slic3r to get the additional options. I have the feeling that its a timing issue and that curahost somehow doesnt wait long enough during retraction for a blob to form, but I cant really pinpoint the issue precisly.

Cheers

Hi sungod3k
Please post a link to the full gcode from both.
I'll run them through my gcode debugger and see what we find.

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It seams that you're asking for trouble with that long of a bowden tube. I had mine only 40cm and it was such a pain that I went back to direct drive.

maybe, but then again, works well in cura. im writing a report on the extruder with more pics but it definitely works and somehow I already reduced blob on another object I just printed in cura.

I also tried that plug in for cure to retract on layerchange but it doesnt activate maybe its outdated

Sungod3k,
I've started looking at the files. Temperatures appear to be the same.

What Cura version are you using? The Cura gcode does not indicate the version inside.

The Repeteir gcode indicates it is using Cura_SteamEngine 15.01

I will make some changes to my gcode post-processor/analyzer/visualizer to recognize the way Cura identifies it's different segment types (it's recognizing Slic3r segments currently).
I like how Cura is doing it - for instance it has ";TYPE:WALL-INNER" before the beginning of a block of gcode, where Slic3r has "; Perimeter" after each perimeter line (inner or outer) - so Cura may be more specific.

Yeah we find Cura's great so tend to use it all of the time. Its very simple but the only annoying thing is when it always recalculates the print time every time you move the print a fraction.

Swapping between Cura and Slic3r, I've never managed to get my head around the cooling fan settings in Cura. The Slic3r way of doing it makes much more sense to me.

Well I compared the two in my debugger/visualizer.
Its apparent they were sliced very differently.

The Repeteir gcode used much higher extrusion rates, and higher densities - and could have been overheating as a result. It looks a mess.

Since the stand-alone Cura is better (and probably a newer version) that sounds like a better way to go.

If you are looking for Slic3r tutorials, there's a page here.

@paul interesting. yes it could look like overextrusion expecially around the layerchange point. its a shame that your cant update the cura engine in repetier like you can do it for slicer and the bigger the version difference gets the more likely are print differences as well

which visualizer debugger are you using btw?

Quote
sungod3k
which visualizer debugger are you using btw?

It's part of a suite I'm writing that includes a post-processor for:
- Pressure compensation
- First segment acceleration (works with pressure compensation)
- Coast while retracting
- Angular hops
- etc...

It has a g-code visualizer that colors the segments according to mm3/second, and graphs the mm3/sec changes. Example here. I needed this to be able to check the post-processor.

And it will have a suite of a great many Guided Calibration tools for calibrating every parameter.

Part of the process is running as many different kinds of gcode through it to understand what causes different problems.

There's still lots more work to do on it...

pressure compensation --> awesome!
guided calibration -->awesomer

i cant code but if you need testers let me know