layer height - big cude

err meant 'big cube'

hello everyone.
i am up to step one of the repreap calibrartion - trying to print the small box at different layer heights.
not much sucess (see photo) - seems 0.2 for my 0.4 nozzle is the best of a bad bunch
thought i would try to print another bigger box that the people I bought it off supplied.
holly macarony batman (see photo). not sure what i did but it came out well.
questions:
1. should i continue to try to print the little box, is there any obvious reason the big one comes out better the the small one.
or should i move straight on to the Infill test now.
2. what is the moral of the story - what does changing the layer height mean - do i always leave it at .2 now or is that some info
into something bigger down the track.
3. the big box i think is suppose to be 50mm cubed - it measures 50.8 in the x and y dir and 49.8 in the z dir.
4. not that i'm too worried about finest (am trying to print prototypes for a new product, each print will be destroyed with each test) but the last photo shows that i got some good solid layers and then normally 2 wiggly ones. luckly the wiggle wasn't big enough and the good ones stuck to it later on.
does this info help me (you) set and further parameter to get better prints??

anyway i'm excited
thanks roger

Edited 1 time(s). Last edit at 11/06/2012 02:19AM by rogerw.

I suspect it's a cooling problem. Try the small one again with a fan blowing on it after the first layer has printed. Using a fan has made a massive difference to my prints and I can't understand why they're not standard.

Edited 1 time(s). Last edit at 11/06/2012 07:21AM by MarkMarsh.

+1 for the fan, I have tried to print the single-walled cube several times and succeeded yesterday by blowing on it during the print, was quite dizzy after 16 mins...

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Prusa with cast PU parts, RAMPS 1.3, Wades extruder, J-Head hot end

If he doesn't have a fan, he can improve the quality of the small cube by turning on the cool option in slic3r with the option to slow down the print to a minimum of 20-40s per layer.

thanks all will try that when i get home - seem to be going quite well printing some other bigger stuff

still at work - have bought a little pc fan
is the theory that on the big cube the layer has time to cool before it comes around again and deposits the next layer and that is why it is working better.
whereas the smaller one the plastic has not cooled when the next layer quickly comes around again.

also was reading another post and had this
Parameter: layer height
Description: .....
Safe value: (nozzle diameter) * 0.8
Optimal value: (nozzle diameter) * 0.5. Shoult be multiple of Z steps. Example: ...

mine is 0.2 for 0.4 - which sounds right
but what about the Z steps - what are they and how do i find out what mine are?

Yes on allowing the previous layer to harden before the next layer.

Layer height must be less than the nozzle diameter to ensure layer adhesion. I'm not sure about the optimum of a ratio of 0.5. Where did this come from? I don't see this in parts printed on commercial printers.

As far as making layer thickness a multiple of the z step size, I don't see why this should be so. There's another thread on this topic: [forums.reprap.org].

thanks brnrd
saw this written (as an example) in this post:
Starting work on an Online Calibration Wizard, need pictures of your fails and faults
will read the other post you suggest
thanks
roger.

Edited 1 time(s). Last edit at 11/06/2012 07:31PM by rogerw.

brnrd
yes I agree - a steps smaller than half a bee's dick
roger

brnrd Wrote:
-------------------------------------------------------
> If he doesn't have a fan, he can improve the
> quality of the small cube by turning on the cool
> option in slic3r with the option to slow down the
> print to a minimum of 20-40s per layer.

This can cause the radiated heat from the hot-end to melt the object since it stays right over it all the time. Insulating the heater may help if this is the case.

Fans are great for PLA but with ABS it's pretty easy to make weak, crumbling objects by overcooling the previous layers. So, beware...

I have found printing multiple copies at the same time the most reliable way to print very small things.

ttsalo Wrote:
-------------------------------------------------------
> brnrd Wrote:
> --------------------------------------------------
> -----
> > If he doesn't have a fan, he can improve the
> > quality of the small cube by turning on the
> cool
> > option in slic3r with the option to slow down
> the
> > print to a minimum of 20-40s per layer.
>
> This can cause the radiated heat from the hot-end
> to melt the object since it stays right over it
> all the time. Insulating the heater may help if
> this is the case.
>

That's true. But for the thin-wallled cube that he's trying to print, this is not a problem since the nozzle is moving continuously around the perimeter only. It would even work even if he filled the cube.

hi everyone,
last nights progress
did a print very slowly (5mm/s) to prove that if the layer cooled then it would fix the problem - it did (was happy).
went to 10mm/s and started getting the prob again
start up the fan and 10mm/s was ok
15mm/s was ok
(have paused at this point in time to make a bracket to hold the fan - see other threads)
will keep going back to my original 30mm/s
have added photos for others reference.

like ttsalo idea of printing multiples - will give that a try too

(should all this info be added to the wiki calibration page - seems harder to print this tiny cube than a bigger one)

roger.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.