Bad surface on larger (>75mm Diameter) prints, while smaller (<~75mm) surfaces print fine.
More Details and Imaged - https://imgur.com/a/NXjRQMv
Hoping I can get some advice on how to address this issue I'm seeing.
The printer seems pretty well tuned on most prints. Benchy and Z-Axis prints seem to indicate that things are pretty well aligned. I'm getting good first and subsequent layers. No real artifacts on smaller prints.
I tried to print a larger item with a large flat surface. Thingiverse - https://www.thingiverse.com/thing:621711 model of a garbage can. In the images, you can see the artifacting when on the outer edges of the horizontal surfaces.
I initially thought it was some sort of harmonic vibration, so I stopped the print and restarted it when the printer was sitting firmly on a concrete floor. Exactly the same issues, in the same place.
Any thoughts as to what might be causing this? And how to fix?
Re: Bad surface on larger (>75mm Diameter) prints, while smaller (<~75mm) surfaces print fine.
On larger prints you'll start to experience problems that don't show up on smaller prints. So long as you're printing Benchy-sized pieces, a lot of settings and limitations never come into play. I suspect you're starting to print large enough pieces that several printer and filament limitations are starting to become apparent:
1. You're probably getting up to the maximum speeds you've specified in print settings. On smaller parts, acceleration and jerk settings typically keep actual print speeds to far lower than those specified.
2. The E3D V6 hotend itself has a maximum amount of material it can process, measured in mm^3/s. The V6 is advertised at 15mm^3/s, though 11.5mm^3/s is a more realistic "real world" setting. Volumetric throughput is measured as Layer Height X Extrusion Width X Speed. The combination of settings you use should stay below roughly 11.5mm^3/s for repeatable good results. On with a 0.40mm nozzle printing 0.48mm extrusion widths at 0.20mm layer height, you can print at up to roughly 120mm/s with PLA. Filament viscocity comes into play as well, and with PETG, the recommended throughput drops to 8mm^3/s, limiting those speeds to roughly 83mm/s.
To fully answer your question, you need to share more about your settings, notably the filament type, nozzle size, layer height and extrusion width you're using.
As a quick test, try simply slowing the print down. Using the knob on the front panel, dial speeds way back, to something like 50%, and see if print quality improves. If so, you know you need to make some simple slicer adjustments accordingly.
Slice the model, then view it in Slic3rPE's preview mode. Change the View option at bottom-left to see what speed and volumetric flow rates are coming into play in the problem areas.
Rather than try to calculate speeds that will work with different filaments and nozzles, I suggest throttling speeds using the Max volumetric speed settings in Slic3rPE. You can find these under both Print and Filament profile options. Try tweaking those and observing the changes that it makes in preview mode. More notes here.
Re: Bad surface on larger (>75mm Diameter) prints, while smaller (<~75mm) surfaces print fine.
Fantastic, thank you for the reply.
I will absolutely try the speed and see if it changes the result.
To answer some of your Q's:
Let me run some tests tonight, and see what it tells me.
Thanks you for the completeness of your response.
Re: Bad surface on larger (>75mm Diameter) prints, while smaller (<~75mm) surfaces print fine.
@bobstro - you were 100% correct about the speed/flow rate. I mean, I have a rule - always trust a muppet, I should never have doubted.
Here is the same piece, printed after applying your recommendations.
Perfection.
Thank you very much for the input. Not only have you made my prints higher quality, you have also provided me with some serious knowledge.
Re: Bad surface on larger (>75mm Diameter) prints, while smaller (<~75mm) surfaces print fine.
We're here to solve the problems the world doesn't have!
@bobstro - you were 100% correct about the speed/flow rate. I mean, I have a rule - always trust a muppet, I should never have doubted.
Thank you very much for the input. Not only have you made my prints higher quality, you have also provided me with some serious knowledge.
There's a lot of great information here on the Prusa forums and from the 3D printing community in general. I'm trying to compile all my notes into useful pages. I've got some notes on volumetric throughput here and using Slic3rPE's preview mode here that might be helpful. The Max volumetric speed setting in Slic3rPE really sets it apart from other slicers (except KISSlicer!) and was the biggest "secret" I discovered when trying to master larger prints and nozzle sizes. My thoughts on the illusion of speed here. Good luck and have fun with it!