nanoDLP

JMG138

Member

Registered: 2017-06-06

Posts: 14

print quality - steps

Hello,

I have a weird behaviour during printing: at a certain Z level (which seems random), the thickness of the part is increasing during a couple of layers then come back to normal.

Here are some pictures which show the pb:

https://drive.google.com/open?id=1Dlf3c … dhZHxMDm3p
https://drive.google.com/open?id=0B-v7r … VOOHNNcWNN

It is like if the exposure time was increased during a few layers before coming back to normal.

I must point out that I did not have this issue before. But after a few months break in my printing and a lot of changes (build, printer architecture, FEP film, etc), I can't figure out from where that come from..

It is maybe linked to the resin level in the tank but I don't understand why.

Any clue of what is going wrong?

build #1827
Rpi3 + Stepper driver Reprap V2.3 GPIO
DLP bottom up design

Burn in layer: 2 layer, 0.1mm 8s
Normal layer: 0.05mm 4s
resin: Makerjuice SF green

no jump
no low quality layer
no dynamic calculation
no mask
no infill
pixel dimming: checkerboard 50% / 3 Pixel / 0 layer skip (but same behavior even with dimming off)

Last edited by JMG138 (2018-05-08 09:47:39)

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: print quality - steps

If the height of pieces are OK, I expect it to be LCD issue, it probably miss couple of layers or UV lamp does not get on. For DLP one, maybe shutter does not get open correctly.

JMG138

Member

Registered: 2017-06-06

Posts: 14

Re: print quality - steps

Thanks Shahin for the quick answer.

Yes the height of parts is OK.

It is a dlp printer without shutter for now. Actually, there are some range of layers undercure, some extracure, some normal. It appears  during variation of solid surface value (but not only). See attached image:
https://drive.google.com/open?id=1F1vAw … Y0O_lNFQ1n

My feeling is that it is a software issue but not sure at all. Is it possible to downgrade nanodlp?

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: print quality - steps

It is highly unlikely to be software issue as nothing changed during last year on projection sub module.
Are you using RPi version?

JMG138

Member

Registered: 2017-06-06

Posts: 14

Re: print quality - steps

Yes RPi 3.

Hovever , I really don’t see how hardware could generate such crisp/distinct steps.

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: print quality - steps

Increase lift maybe it sticks to floor on those zone for couple of layers.

JMG138

Member

Registered: 2017-06-06

Posts: 14

Re: print quality - steps

I did a try by increasing the lift as you suggest and also the wait delay (after and before).

no change. Still a clear step.
https://drive.google.com/open?id=1RsF83 … jn-9nZSovY
https://drive.google.com/open?id=1NOD1C … uap3bzsisg

it is really mysterious...

(test done with the last build 1832 and new resin)

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: print quality - steps

Could you share picture of the printer axis?

JMG138

Member

Registered: 2017-06-06

Posts: 14

Re: print quality - steps

Here are some pictures of the printer :
https://drive.google.com/open?id=1MOpMq … 9u_jF9gsiv
https://drive.google.com/open?id=1MdmoE … WkG30rRwwf
https://drive.google.com/open?id=1bAHJQ … qZEkVOrj2v

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: print quality - steps

I guess it is a mechanical issue, please check for any abnormality on movements maybe skipped steps in some sections of axis or similar issues.

JMG138

Member

Registered: 2017-06-06

Posts: 14

Re: print quality - steps

I can't feel any hard point or play on the Z axis.

I come back to the original "FEP" film I used before when the print where OK and I still have the issue.

Is it possible to downgrade the nanodlp build to the one which was available on june 2017?

Shahin

Administrator

Registered: 2016-02-17

Posts: 3,541

Re: print quality - steps

Maybe you could find older version over the net hosted on different websites, but nanodlp website does not keep legacy versions.