Is it really that difficult to get consistent good quality large prints for working parts?
This is a thread that I had started before and this particular reply is where I thought I had sussed it after lots of helpful info from forum members which I’m very grateful for.
So since then I have made some changes to the design, and before attempting to print in PC I wanted to print in PLA as supposed to be easiest to print and didn’t want to waste my PC on a prototype.
So printed with all the same setting as the last successful print in the link above except I changed to 0.28 layer height but left the first layer at 0.2. For no particular reason just didn’t change it.
The this happened at layer 2.
So re tried setting first layer to also 0.28 and it was fine until further into the print where the problems started. FYI I was using 5% gyroid infill as was only a prototype. Looking at the issues present I’m wondering whether the low % infil contributed to some of the problems due to bridging over not much infill.
I dont need to explain all the problems you can clearly see from the photos.
With regards to the corners lifting I know brims are normally helpful but there isn’t room due to the size of the print and also glue is an option but I’ve had success before with out glue so what’s changed
Temperature maybe? With regards to lifting corners. Maybe it’s a bit drafty or simply cooler where your printer is, this time of year compared to a month ago.
Rule of thumb: layer height should not exceed half of nozzle diameter.
Nozzle 0.6, layer height should be smaller than 0.3
Nozzle 0.4, layer height should be smaller than 0.2
Nozzle 0.2, layer height should be smaller than 0.1
The corners lifting aren’t just aesthetic. As they lift, they can actually cause extrusion issues on the next layers that migrate slowly layer by layer across the print. For warpy filaments:
-Make sure chamber is 45c or above before starting the print. Set the bed heater to max, and aux fan to max. Wait until chamber is 45c, then start the print.
-Make the bed 5c hotter than the specs of the filament call for
-Use “Vision Miner Nano Adhesive.” Nothing else. For me it has worked magic on large warpy prints when no variety of glue sticks, hairspray, etc… would.
-Use no fan for first 5 layers, and the least you can get away with for the rest of the print (only on very short layers, or overhangs)
-turn off aux and chamber fan completely (excepting the use of aux at the start to heat the chamber)
I used to get major warping with engineering filaments. I tried tweaking every slicer setting… including infil. It all helps, but with these steps I can use whatever infil I want.
Ohhhhh… I misread. I will say though, I did just use vision miner on a PLA print yesterday that warped the first time and proceeded to have lots of messed up layers. Fully fixed it. I’d give it a shot and see what it fixes.
As a rule of thumb the max layer height should not be much more than 60% of the nozzle diameter.
And that still goes hand in hand with the extrusion width.
For thicker layers you also want a wider extrusion to get a proper layer bond.
Having said that…
Calibration is most vital, even with so many defaults seemingly working fine - the devil is the detail(s)…
Studio is close but not fully there yet when it comes to printer/filament calibration results providing consistency.
You can do the math in terms volume coming out and length extruded.
If you then just play a little bit with the volumes you can see how massive the impact is once the volume goes up or down.
Too much in terms of flow ratio and especially solid layers can turn into a rough mess.
Not enough and infill, layer/bed adhesion suffer.
If you want consistent result no matter what type of filament you use for a model than it all start by properly calibrating those filaments.
And I learned my lesson many printers ago and for very fine or very thick layers I do separate flow ratio calibrations and save that as a different filament profile, e.g. Ali PLA THIN.
Too sparse of infill, though I think your next few top layers would have cleaned it up pretty well, I’ve done a fair few prints with very little infill and relied on bridging to make the top work out.
I find adaptive cubic is pretty good for these situations, or even support cubic with a higher infill.
Gone back to 0.2mm infill and seems great at the min.
Only thing I’m wondering if I can improve on is the bridging over infill it has alot of gaps in it still and then subsequently the bottom layer on top of infill has gaps also. Can I increase the flow ratio of bridging and bottom surface to improve? Or slow the bridging speed down?
You on the right rack
Low infill means the bridging needs to be as clean as possible and strong enough.
Otherwise the solid infill layers above can make a little mess that accumulates to a failure.
There is dedicated test models to get the bridging work a good as possible and for the longest distance possible.
But if infill is your main concern and not supporting large free hanging areas…
You can change the nozzle temp for the bridging but you can change the bridging flow ratio and speed
If I am not mistaken even the overlap/anchor length.
Create a test cube that is slightly larger than the max length required for your low infill rate bridging.
E.g.: If the longest bridging lines would be about 8mm long make it a 10 to 12mm cube.
Lower the height of the cube to about 3mm and print it with no infill.
Observe how the bridging is laid down and how it behaves.
A lot of sagging can be addressed by a slight increase in bridging speed.
Severe gaps between the bridging lines can be limited by increasing the bridging flow rate a bit.
Here’s the catch 22 though:
You can optimise things for two totally different types of bridging - STRONG AND FLIMSY, the later looking almost like thin silk lines.
What’s the difference ?
Strong bridging is great whenever you know the next layer comes out good enough.
A little lower on the flow though means the bridged surface can come out with a bit more tolerance.
Meaning where the bridging goes once infill lines there will be less filament be pushed down either side of this single wall - limiting the bumping on these spots on the next solid layer above.
But it also provides a slightly larger layer gap - resulting in a slightly rough looking next layer but it won’t stick out of the surface.
Means there is fewer chances of the solid infill causing a build up that is dragged along.
On the far and flimsy end of this you create very thin bridging lines that with have gaps between them as their line width will be less than the nozzle diameter.
Those however will have next to no sagging…
So the solid infill layer on top comes out even smoother as long as the bridging holds…
A balance act but well worth tuning …
The bridging might end up rather slow compared to the rest of the print but if it means the solid infill comes out smooth …
