Slic3r question

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Slic3r question

Postby keos » Wed Jul 31, 2013 9:40 pm

In Slic3r under printer settings under retraction under Lift Z: what happens if you put 0 for values....

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Re: Slic3r question

Postby blah_59 » Wed Jul 31, 2013 11:39 pm

During retraction, the Z axis will remain at the current height (without lifting, which is normally the default). Having it lift a little helps it not run into anything as it moves, in case you extrude a bit too much plastic or Z height is off a bit, etc. And, if it strings it strings vertically more so it doesn't bridge things you didn't mean to bridge.
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Re: Slic3r question

Postby cvoinescu » Thu Aug 01, 2013 12:45 am

What blah_59 said. Just to be clear, "retraction" refers to moving the filament backwards. Optionally, it can also lift the Z axis as it retracts the filament.
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Re: Slic3r question

Postby keos » Thu Aug 01, 2013 7:08 pm

Guys could this have an impact on how layers are printed, the reason i am asking is because i adjusted the bed for the second time and i am still getting gaps in the print like if the layers do not bond to each other.
also i have a mini computer fan attached to the extruder to cure the plastic as it prints the layers. After printing several layers i start hearing cracking noises and that is when the layers start to separate . is like icebergs breaking apart :lol:

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Re: Slic3r question

Postby cvoinescu » Thu Aug 01, 2013 8:16 pm

No, that setting is unlikely to have anything to do with it. It affects only what the printer does when it stops extruding, moves to another location, and resumes extruding -- and then it moves up, sideways, then back down to the same height. The bulk of your print is done in long, continuous movements, without retractions, so it shouldn't matter.

I remember your problem, and everyone guessed that
  • your Z was misconfigured: it moved more than commanded, that is, too many steps-per-mm for the given motor, leadscrew and microstepping setting. That was supported by the fact that, if I recall correctly, your parts were way taller than they should have been, but you also claimed that jogging it moved it the correct amount; or
  • your extruder was not calibrated correctly and extruded less than needed. More possibilities here:
    • too few steps-per-mm;
    • wrong filament thickness programmed into the slicer (e.g. 3 mm but you're using 1.75 mm);
    • messed with the "fill factor" (not sure what it's called in Slic3r).
I still think that Z or extruder misconfiguration is what's going on -- I mean, what else could it be?
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Re: Slic3r question

Postby keos » Thu Aug 01, 2013 8:49 pm

cvoinescu ;

* your Z was misconfigured: it moved more than commanded, that is, too many steps-per-mm for the given motor, leadscrew and microstepping setting. That was supported by the fact that, if I recall correctly, your parts were way taller than they should have been, but you also claimed that jogging it moved it the correct amount; or
* your extruder was not calibrated correctly and extruded less than needed. More possibilities here:
o too few steps-per-mm;
o wrong filament thickness programmed into the slicer (e.g. 3 mm but you're using 1.75 mm);
o messed with the "fill factor" (not sure what it's called in Slic3r).


* z moved more than it commanded - the problem here was that the drivers were getting hot, so i added a fan to cool them out and this worked .... no problems here any more
* extruder is now calibrate .... no problems here any more
* fill factor- i tried 40 %, 60%, and even 100% but realized that i do not need 100% so i went back to the suggested values.

I am planning to take the gantry off and re-setting everything again and also t find an easier way to adjust the heated bed because when the heated bed is mounted on the printer the center adjustment screw is a pain to reach.
Any thoughts....

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Re: Slic3r question

Postby cvoinescu » Thu Aug 01, 2013 10:28 pm

I'm not talking about that fill factor. That should not affect adhesion too much, at least not along the perimeter. In Skeinforge, there's a "packing factor" (recommended value between 0.85 and 1.0) which directly affects how much filament gets extruded, on top of all the other settings. I don't understand the reason of its existence very well, but, apparently, it should be different between ABS and PLA. The explanations I found were diverse and contradictory.

Anyway, if such a fudge factor exists in Slic3r, maybe it's set wrong. It should be easy to tell whether you're not extruding enough plastic to get good layer adhesion, or there is enough plastic but it doesn't stick because it's extruded too cold (or you're cooling it too quickly with your fan). In any case, try to increase the temperature and throttle down the fan that cools the print (PLA needs a little cooling; ABS should be fine with the fan off).

And some nitpicking: "curing" involves a chemical reaction (such as polymerization); your plastic merely suffers a phase transition, not a chemical change -- it solidifies, it does not cure.
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Re: Slic3r question

Postby keos » Thu Aug 01, 2013 11:12 pm

Thankx a bunch
cvoinescu
i will try it tonight. will disable the fan i am using to cool down the print and see what the results are. by the way i am using ABS at this point....

thankx
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Re: Slic3r question

Postby blah_59 » Thu Aug 01, 2013 11:35 pm

The fill factor in slic3r that cvoinescu is referring to is called "Extrusion Multiplier" under the Filament tab. Default is 1 and normal values are between .9 and 1.1. I agree with cvoinescu that it's either cooling too fast or not enough plastic.

If turning the fan off doesn't help (my gut says it should help because of the cracking noise) then try bumping the extrusion multiplier up or decrease the filament diameter a little (same thing just a different field). If you want more plastic you can lower the filament diameter, raise the extrusion multiplier or raise the steps per mm in firmware (probably marlin).
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Re: Slic3r question

Postby cvoinescu » Thu Aug 01, 2013 11:45 pm

blah_59 wrote:The fill factor in slic3r that cvoinescu is referring to is called "Extrusion Multiplier" under the Filament tab. Default is 1 and normal values are between .9 and 1.1.

Thank you. That's the one. (Not familiar with Slic3r, as you can tell.)
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