I’ve knocked out a few prints with the PLA that was supplied with the printer, and I’ve noticed no difference in quality when leaving the lid on vs. off as specified.
What’s the reason for needing the lid off when printing with PLA?
I suspect, but do not actually know, it’s a heat-related issue. PLA is heat sensitive, and so with the top removed, the chamber is probably at a more PLA-friendly temperature, but you’d need the top on for heat containment on higher temperature materials.
Like I said, I don’t actually know, but that’s my suspicion.
What cover/lid you are talking about?
The gigantic lid on the top of the J1?
PLA mostly has issues with cooling, not with heating - as in, it has to be cooled very rapidly to avoid thermal deformation (the alternative is to keep it above glass transition temperature consistently throughout the print, and then let it cool slowly, but that brings other issues). The fan on the J1 blows from just one side, so I’ve seen overhang curling artifacts on edges opposite the fan until I reduced the bed temperature and opened both the cover and the doors. It printed very well after that.
Gotcha. That makes sense. Doesn’t sound like even adding a fan to the other side would fix the issue if you had to drop bed temp and open the whole enclosure up. Although, if it does work on one side, perhaps it would fix the other side.