Fails guidance needed  

RE: Fails guidance needed

A few thoughts:

1. Bit of a long shot, but I once realized I'd loaded 2 copies of the STL stacked in the same position prior to slicing. It wasn't immediately obvious in the slicer preview and I wound up with very similar results.
2. This looks like serious over-extrusion. Have you checked your extrusion multiplier and filament diameter settings in your slicer?
3. The distortion on the left looks like you're printing too hot. Have you verified the temp settings in your slicer?

RE: Fails guidance needed

That part should never need a brim.  If you are having adhesion problems, that is, the part coming loose during print, look at cleaning the bed with soap and water (only soap and water, no alcohol).

Also - when printing large flat parts, beyond the risk of warp, is the layers of infill for the top layer can have places that curl when printing too fast.  The curl reaches up and grabs the nozzle as it passes over, or when infill prints beyond the curl to add material.  Very common cause of major layer shift like you are seeing.   Slow down the cooling fan to 50% or less, slow down the print speed for solid infill about half. 

And - what is the material?

RE: Fails guidance needed

Thank you Bob,

1) Good idea, but no, its just a single STL that's being sliced. 2) The extrusion multiplier is 1 and the filament diameter is correct at 1.75mm.

3) Too hot, yes this figures. I wonder if the plastic has cooked in this area and expanded. Ill try it with an infill.

Thank you again for your help.

Julian

RE: Fails guidance needed

Thank you Tim.

Ive always liked a brim as it gives one confidence in the first layer adhesion and allows one to dynamically change Z without affecting the print. In this instance I thought it might be an adhesion/curl problem which is why I changed the heatbed to Powder coated sheet.

I'll take your advice and try slowing the print velocity and fan speed down, (but the wretched thing takes over a day already) mund you, I wonder if that wouldnt increase the temperature CF Bob's point above..

RE: Fails guidance needed

This being a relatively large PETG print you may want to check if the steel sheet sits flat on the heated bed. I once had a similar issue with a 200mm*200mm PETG part when the magnets were not strong enough to keep the steel sheet down when the part was trying to warp a little. I had good adhesion so the part didn't separate from the sheet but lifted the sheet up. Additional binder clips helped me keep it down and avoiding collisions/layer shifts.

The curling phenomenon that tim-m30 comes to mind, too.

It could be over-extrusion but it might also just look like this because the part warps towards the nozzle. This leads to smaller layer heights which shows as over extrusion.

RE: Fails guidance needed

Thank you Eminent TimO,

Yes, good point, curling of the part and perhaps the steel sheet. I cleaned the pei sheet and got the same result on practically the first layer. See this pic of the underside of that print.

So I have reduced the nozzle temp to 236 from 240/250 degrees, heatbed at 90, and this seems to have done the trick. Certainly for the first few layers. I have resorted to a 20% gyroid fill and apart form the odd glitch (the filament ran off the spool and managed to insert itself into the fan! This eas beautifully sensed by Prusa as a fan problem) and a few blobs, we are in business.

I've asked for a solid layer every 20 layers and we will see if this improves the longitudinal tensile strength.

Thank you very much again for all your constructive thoughts.