need help on layer separation issue on big object

I am having layer separation problem printing big object (23cm high) using lulzbot HIPS, which take about 24 hours.
I am using 0.5 nozzle, bed temp =80c with enclose box to keep the heat.

I have a completely opposite idea to help layer separation.

  1. use higher bed temp to transfer the heat to higher layer.

  2. use bare minimum heat to make sure that the object will have similar temperature.

which option do you think is better?


.5mm nozzle? Sounds like an upgrade, I just finished with a 50mm high 3+ day print with a .35mm nozzle and my layer adhesion was good setting at .20mm layer height (57%), PLA temp at 206c with the following speed settings in SLic3r: 50, 20, 50, 60, 55, 45, 50, 60, 30, 200. The object printed correctly with no layer separation. Getting the “squish” height was what really helped, I made a circular calibration test to allow me to set my height over the entire plate, while it printed I adjusted my plate leveling screws (after setting Z according to the manual) so that the first parameter layer was equal across the edges of the plate with the extrusion squish adjusted to “perfect” according to the booklet that came with the TAZ 4.

You need some good lighting on the TAZ plate to set up your print, if the first layer is correct, the temps are correct then your model should be fine, I set my temps at 208c extrusion/70c bed first layer, 206c extrusion /65c other layers for PLA, default to 200% extrusion rate for fist layer in Slic3r.

So for .5mm yours would be .28mm layer height to follow the same accuracy I used allowing for excellent layer adhesion even on tall prints, you’ll have to play with your temps a bit, so that the flow rate from the extrusion nozzle leaves behind a nicely bonded first layer without upper layer separation. Watching and adjusting your upper layer adhesion via flow rate on smaller models with pronterface on while printing allows you to dial in/adjust your filament extrusion temperature a degree at a time till you get the flow rate you desire and the bonding you need. Higher temp = higher flow rate and better layer fusion, lower temp = slower flow rate, lower layer fusion with separation possible if too low. I’ve noticed some temperature based flow variance in different spools of PLA, only a few degrees C, but slightly higher temps were indeed better than lower temps for properly bonded upper layers.

As for your printing, above 30mm little heat is transferred to the upper portion of your model, the bed should remain on if you want to help avoid edge curling, I use constant enclosure exhaust, at temps around 75-80F in my enclosure box and have gotten good results. I have noticed that the models are more flexible overall with higher bed temps until cooled.

I hope this helps,