(NOW) SOLVED: Problem using variable layer heights

[bobstro]

I experiment even with the official answers. If I can't break something and make it work again, I'm usually not satisfied. Good thing for 3D printing. Bad thing for fine art.

[pjr]

Bottom stepover I think is when the model sides are sloping outwards, whereas top are sloping inwards; you should be able to have a lower value for "top" as there are usually loops (or infill) underneath.

So, when printing a model with sides sloping out, you really don't want to go less than 50% of extrusion width.

Peter

[hacker]

Exactly the thought of loops and infill made me doubt this interpretation, but then there's also vase print…

And yes, bobstro, I support your scientific approach to 3d printing.

Not so sure about fine arts, while I admit that artwork's irreproducibility increases its value, I don't think that's where the real value of fine art is and it's just a(n unfortunate) side effect. Art dealers of course should be seeing that differently. But we digress

[bobstro]

Bottom stepover I think is when the model sides are sloping outwards, whereas top are sloping inwards; you should be able to have a lower value for "top" as there are usually loops (or infill) underneath.

So, when printing a model with sides sloping out, you really don't want to go less than 50% of extrusion width.

Peter

Ah, that makes sense. I'll try to tinker with it some. EDIT: I've realized I really do need to create a style for each nozzle profile to keep it simple. I'm re-starting with a 0.40mm nozzle with layer thickness set to 0.05mm min, 0.32mm max and 0.20mm 1st layer, with 50% top and bottom stepover. So far, no complaints from KISSlicer when slicing with these settings.

If I set 1st layer to a percentage, does it use a percentage of the nozzle size or layer height? I assume nozzle size.

My primary goal with adaptive layers is finish. I'm printing a rounded surface, and want as few steps as possible to appear in the top surface. I believe increasing the top stepover value will keep steps between layers smaller, hopefully avoiding the "topo map" appearance. I've noticed that all of the Variable layer height presets for Prusa use 50% for both, except Variable Full Range which uses 0.2mm for both. I'm curious why that one's different and what the impact is.

For anybody playing along at home, I've attached the STL of the test part that I'm using.

[pjr]

Percentage of extrusion width.

Nozzle size is a relatively new feature in KISS and is used to calculate the Preload.

It is possible to set the extrusion width to relatively stupid values (relative to nozzle size), but that is entirely up to the user. Using a "fixed" extrusion width makes modelling so much easier

Initially, when "adaptive" layers were introduced, percentages were not an option. So the "Full Range" profile (which I no longer use) was set up with actual values. Now you are going to ask why I don't use it.... Simple answer is that with Preload enabled, I get better results with smaller ranges. Preload is not quite perfect and needs a different value for 0.05mm and 0.32mm layer heights. I think it's to do with the differing nozzle pressures, but I am not the "expert" in this (or any other) area

Although PR mention that minimum layer heights are 50 or 70 microns I do believe that 25 microns (or even lower) is a possibility (haven't had time to test on the Mk3), as long as you can keep the speed up and maybe implement 1/64 micro-stepping (M350 E64 - it automatically changes the E-steps/mm). One day I will find time to check it out.

Peter

[bobstro]

Percentage of extrusion width.

Great, thanks. I hate not knowing what values relate to. I've realized setting up a profile for each nozzle size using explicit values will be a lot less confusing as I go along. I'll just put in my desired (0.20mm) value.

It is possible to set the extrusion width to relatively stupid values (relative to nozzle size), but that is entirely up to the user. Using a "fixed" extrusion width makes modelling so much easier

I've been sticking with 120% of nozzle width just as a convention. I've read that you can use up to the width of the nozzle itself, but I haven't tried going any wider yet. For small stuff, precision is more important but I can see that being useful for big, beefy functional prints with larger nozzles.

Initially, when "adaptive" layers were introduced, percentages were not an option. So the "Full Range" profile (which I no longer use) was set up with actual values.

Ah, makes perfect sense.

Now you are going to ask why I don't use it.... Simple answer is that with Preload enabled, I get better results with smaller ranges.

Sorry, are you saying you used smaller ranges for variable layers with Preload, or don't use variable layers with Preload? I haven't gotten into preload yet. Results are very nice so far!

Preload is not quite perfect and needs a different value for 0.05mm and 0.32mm layer heights. I think it's to do with the differing nozzle pressures, but I am not the "expert" in this (or any other) area

My immediate quest is to figure out variable layers, but I do want to go down the Preload rabbit hole at some point. As a bit of a lark, I printed my test piece (the swoopy tank) using variable layers with a 0.60mm nozzle. Small detail was lost of course, but I was impressed that the curved top surfaces looked smoother than those printed using Cura's adaptive layers with a much smaller nozzle. Steps are only visible for the top 3-4 layers. The transitions between lower layers is nearly seamless -- STL-like. I was impressed.

Although PR mention that minimum layer heights are 50 or 70 microns I do believe that 25 microns (or even lower) is a possibility (haven't had time to test on the Mk3), as long as you can keep the speed up and maybe implement 1/64 micro-stepping (M350 E64 - it automatically changes the E-steps/mm). One day I will find time to check it out.

I've printed at 40 with no issues, but didn't do any particular adjustments. I wasn't aware of M350, so will add that to my ever-growing list of things to check out. Interesting note about the speeds.

Thanks for your help guys. I think I'm getting the hang of KISS now.

[pjr]

Extrusion width. I use the nozzle width for perimeters and a tad wider for infill. Personally I would not extrude more than +25% unless I wanted something really strong and then print quite slowly.

Yes, I use Preload and I find that works better with limited layer height ranges, which is why you have the three limited ranges in my profiles.

Adaptive layers are very nice, but for most of the models I print, they always seem to want to use lower layers and I want the print to be fast

With lower layer heights, you can run into the minimum extrusion value where KISS will automatically speed up the print. Problem is keeping the pressure in the nozzle so that extrusion is consistent; I think something like 50 steps per second is about the lowest I would want to go, so it's good to be able to change the E-steps on the fly. The other issue is step interpolation by the Trinamic drivers; when you get below a certain step count, interpolation goes out the window Auto steps is somethign that PR plan to build into firmware, but until they do, then work-arounds are necessary. Currently the firmware will handle 8, 16, 32, 64 and 128 micro-steps.

Peter

[hacker]

Reading all that gave my unrelated thought of having extrusion with defined as a percentage of nozzle diameter and therefore being per-nozzle. Of course, this thought somewhat solves the setup/ui challenges associated with different extrusions for different nozzles, but not actual slicing challenges (what are they if any only Jonathan knows).

[bobstro]

Bottom stepover I think is when the model sides are sloping outwards, whereas top are sloping inwards; you should be able to have a lower value for "top" as there are usually loops (or infill) underneath.

I noticed something interesting in the generated gcode:

Code: Select all

; unsupported_stepover_mm = -65
; supported_stepover_mm = -50

Going by these names, I think the different values will be used depending on underlying support or lack thereof. That would certainly make sense. It would be nice to have an authoritative answer!

So, when printing a model with sides sloping out, you really don't want to go less than 50% of extrusion width.

I was thinking about this when I had a bit of epiphany: This will be a big help when printing filleted corners on the underside of a print. I'm doing some experimentation, but I'm hoping that using a larger "top" (unsupported?) value will result in smaller slices with more overlap, improving filleted edges. I've done a test print with 50/50 and the fillets look good. A 6.5mm overhang also printed better than I've achieved without supports before, but still suffered a bit at the edges. I'm going to try using variable layers with a larger nozzle printing big functional parts. I'm hoping it'll use fine layers for dealing with fillets and overhangs, yet still use thick layers for regular surfaces, giving me a good compromise between appearance and strength.

I'm really curious to see what a 1.00mm nozzle would produce with these settings. Maybe later this week...

[pjr]

Extrusion is slowed down for the "unsupported section", much like bridging and the fan is increased (proportionally, according to amount of support) based on the Material/Flow Adjust/Cool and Material/Fan/Cool settings.

Peter