retraction on layer change.

[dubtec 0]

If retraction is enabled, does Cura retract on EVERY layer change, or just when required.

thanks

 

[IRobertI 520]

It never retracts on a layer change AFAIK, only when doing other travel moves that fulfil the requirements set in the expert settings dialog.

 

[illuminarti 18]

Yes, what Robert said.

 

[dubtec 0]

Thanks for the reply..

Printers 2x ultimaker original.

I've been messing about with retraction speed. and most people talk of 30-40mm/s

It sees that my Firmware has a limit of 25, which I can adjust with the ulticontroller.

so if I set Cura to 40, and it is set to 25 in firmware, is 25 the max it can go?

also would be REALLY keen to see what you guys have in your set up for xy speed, acceleration etc..

thanks in advance

David

 

[illuminarti 18]

There was a bug in the firmware that meant that retractions happened at about half of the speed you asked for. So if you set it to 40, you ended up with 20. I fixed that bug about a year ago, and many people built their own firmware to get the fix - but the fix wasn't included in an official release with Cura until January this year. Now if you're using the latest firmware, you really do get the speed that you ask for. But if you have old gcodes where the retraction was coded at 40 or more, that's going to cause a problem with the new firmware because you'll actually get 40 now, and that's too fast.

So, the default max speed was reduced to 25, so that old gcode would still work - it would be capped at 25, even if you asked for 40. However, in practice, I find that 30 or 35 is a reasonable speed with the fixed firmware, so you can change you Vmax E speed to 35, and then set Cura to retract 4.5mm at 35mm/s.

Regarding other settings, i recommend using an acceleration speed of 3000 mm/s² as the overall speed. You might also want to look at this article, regarding speed and acceleration for the z-axis to reduce z-scars:

http://www.extrudable.me/2013/04/02/the-myth-of-z-speed/

 

[dubtec 0]

Fantastic response, you really go out of you way to be helpful :wink:

 

Both machines have the latest firmware via http://marlinbuilder.robotfuzz.com/

I assume this is okay and has the bug fix.

 

I still get blobs which happens when the head lands on the next bit to print, or slightly before it.

 

I'm using faberdashery white at 230 c and tried lowering it to 220 slight improvement.

 

Ive pulled FW to 35 speed and set cura to 4.5mm at 35mm

 

both machines are now using the v3 bolt, and one has the v2 hot end.

 

I've looked at your z settings, and will see what this will do. but the main prob is the ooze between places.

edit: gr fixed link above and restored lost sentence

 

[gr5 2,178]

I've looked at your z settings, and will see what this will do.

 

Simply doubling the Z acceleration will make your blobs about half their current size. Some people call this "the Z seam" by the way.

Another fix is to print much slower - if you are really picky about how your surface looks you can get better results at massively slow speeds. Like say 30mm/sec.

 

[Daid 306]

If retraction is enabled, does Cura retract on EVERY layer change, or just when required.

 

Should be only when required, except when combing is disabled.

But, the retraction code has seen a lot of changes. So it can also depend on your Cura version. When you want to retract and when not is quite a difficult thing to get perfected.