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Feature request: Lift Z for first n layers only

Posted by tml 
Feature request: Lift Z for first n layers only
February 19, 2013 05:56AM
I have recently discovered the absolutely superb "Lift Z on retraction" feature of Slic3r. I'd like a way to configure this to happen on the first n layers only.

Long version:
The problem I solved with this feature was that the molten PLA was oozing a bit which caused serious problems on the first layer if the object being printed had tiny or really thin parts (like a 2mm sized thing or a support structure generated by slicer) along with other printed "islands".

What happened was that the printer printed these tiny squares and lines first, then went on with printing other stuff but kept the head travelling between the pieces. During travel, despite retraction, the hot end was oozing a bit. During the travel the head often travelled over the already printed tiny parts (which have a really small surface area and so, bad adhesion). It often happened that the ooze sticked to these parts, and because of the bad adhesion, the head ripped them off the printing bed and pulled them with itself, completely runining the print.

The Lift Z on retraction feature solves this problem, as even a minimal lift (0.2mm in my case) lifts the head up enough so that the ooze can't touch the printed layer any more. On the other hand, these liftups and liftdowns increase the travel time a bit, which results in more oozing.
The problem I described above is only critical on the first few layers, when the pieces are not sticking to the bed properly yet. My experience was that once a small piece survived the first few layers without being moved away by the head, it completed even without the Z lift. So, I was thinking, it would be beneficial print time and quality wise if there was a setting that would allow me to instruct Slic3r to do the Lift Z magic on the first few layers only.

Edited 1 time(s). Last edit at 02/19/2013 05:57AM by tml.
Re: Feature request: Lift Z for first n layers only
February 19, 2013 06:53AM
Solve the problem of the oozing rather than ask for another feature. I'm really NOT trying to be mean but can't think of any other way to put this.
Re: Feature request: Lift Z for first n layers only
February 19, 2013 08:03AM
Odd I do the opposite. For things with a small base area I hop between islands, but not on the first layer. They are only prone to being knocked off when they get tall compared to their base. Having said that I don't have any ooze.

Re: Feature request: Lift Z for first n layers only
March 01, 2013 04:13AM
This is getting requested by many parties. I think it's only needed with badly calibrated machines. Adhesion problems and oozing problems should be fixed on their own, so I usually tend not to encourage workarounds to problems that have to be fixed at their origin...
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