Z-Layer Height...
Let's start with an accurate representation of my current mood concerning the following issue:
Today I was 3D Printing some blast gates allowing me to selectively redirect the vacuum airflow between my various Devices in my Maker Space Basement so all of them can have their dust and/or shavings handled by a single Dust Collection system without constantly shuffling the hose from one to the another which gets annoying like REALLY fast.
For those interested - The System also consists of 3D Printed Y-Splitters but those were of no issue.
Whiiiich couldn't be said about those blast gates required to be 3D Printed in pieces and then assembled.
The left picture shows how they were printed on the Bed requiring the least amount of assembly and support material - The latter which couldn't be avoided. The right one shows the assembled ones ( some of which I had to shim with paper glued in between )
My main issue here lies with Z-Height accuracy... As can be seen with the right picture the 4mm thick Slider gets sandwiched between the two halves used to establish a screw in connection with the hose. Upon finishing the Print it ended up with a thickness of 4.1mm ( "not great, not terrible" ) since it was a value that has been accounted for and would have worked if all parts had behaved like this - Which they didn't.
On the Hose connecting parts, the area making contact with the support material ( and housing the Slider ) was initially calculated with a 2x 2.10mm gap for a total of 4.2mm which would have cleared the Slider but It ended up requiring to be bumped up to 2x 2.5mm for a theoretical total of 5mm. Theoretically, I should now have almost 1mm of space to work with but the Slider JUUUUST fits through.
Both parts reference from the same Bed surface but the Slider ends up being 0.1mm too high whereas the bridging of the Hose Connector is 0.4mm too low - WAT!?
RE: Z-Layer Height...
I hate to be flippant, but you have't provided any clue as to what tools you are using to create these parts. Cura? S3D? J-Placovik-Custom-Slicer?
What printer? (assume MK3/S due to forum this is posted in, but...) What material? Print conditions? Enclosure? Printed in Winter somewhere near the Wall?
Z-height has one variable: Layer 1. Everything else is pretty much fixed by the lead screw. N turns equals n height. Unless the firmware has somehow decided to reset the factory multiplier, it's going to be hard to get the wrong height. Did you change the hot end to a Volcano or Skeeter and burn your own firmware?
As a diagnostic, have you printed the simple 25 mm test cube?
RE: Z-Layer Height...
Another point: since you are using supports, did you compensate for filament droop and adjust interface spacing accordingly?
Getting flat accurate bridged surfaces is tricky.
RE: Z-Layer Height...
Sorry, the late reply... Outlook keeps putting Prusa Forum Mails into the Spam Folder xD
Yea... More information!
I'm using the current Prusa Slicer with a KIT Prusa i3 MK3S and no modifications ( except for a different Dial Knob ) to either the Hardware, Software or Firmware.
The Printer sits, without immediate enclosure, in a normally opened, when operating, Closet and is using Prusament PLA Jet Black with the Prusa Slicer default temperature settings.
Generally speaking, I'd say that dimensions are on point except for the +0.1mm added to the 4mm Slider piece ( I'd argue that's good enough for a non-industrial FDM Printer? ) and in hindsight possibly caused by the uneven structure of the Powdercoated Springsteel Bed? Before printing the P.I.N.D.A. recognizes the Mountains while during measuring the Caliper measures the Valleys?
I haven't done any changes regarding support material ( other than enabling it ) or filament droop ( ?? )... How should I go about that to improve my situation?
RE: Z-Layer Height...
It looks like your printing on the textured build sheet? If you are then to get a correct height you need to compensate for the filament thats squeezed into the textured surface.
Its better to use a flat PEI build sheet if your after close tollerance pitting parts as you have
RE: Z-Layer Height...
The PINDA actually ignores the hills and valley, instead sensing the inductive change caused by the metal underneath.
But you are correct that layer 1 - while set to 0.20 mm in slicer can be 0.1 to 0.3 mm due to layer 1 calibration, the value set during Live-Z adjustment. Some schools say to set Live-Z so that layer 1 is 0.2 mm thick. Other schools say adjust Live-Z so parts stick. It's a personal choice, and leaves a variability that must be considered when making parts that require mechanical accuracy. I'd use a smooth sheet for such parts to maintain some degree of accuracy and confidence I could get 0.2 mm as intended.
Default support material uses 0.2 mm as the interface gap. This, droop will be - ta da - up to -0.2 mm. This makes that section of the part 0.2 mm lower than designed.
By changing support settings, you can reduce the support clearance and regain part accuracy. Depending on surface, there are tricks to maintain accuracy and support removability... but I doubt there is a one-stop solution for all cases.
RE: Z-Layer Height...
As for what I call droop: think of a rope bridge. When connected to two points, the weight of the rope causes the rope to droop. The same thing happens when the printer lays down an unsupported trace of filament. While we'd like to think the filament cools, hardens, and becomes a perfect flat unbending piece of plastic; it doesn't. Instead, it will droop until it cools enough to become rigid, or until it contacts whatever is below it.
This block of settings control how supports are built under an overhang: critical settings are interface layers and contact Z distance. In a perfect world the interface layer is a flat surface spaced contact-Z-distance below the below the part overhang. Thus, as the nozzle begins printing the overhang, the extrusion will form a string starting at the closest edge of the overhang and will extend out, cooling, and droop until it hits the support interface. In some cases the extrusion has cooled enough to not adhere to the interface, other times it is still melt and welds quite well. And thus the troubles begin.
RE: Z-Layer Height...
Before printing the P.I.N.D.A. recognizes the Mountains while during measuring the Caliper measures the Valleys?
The PINDA as said only works on the steel sheet its self. The powder coating is on top of that and cant be picked up as its not sensed by the inductive pick up (PINDA). Prusa have done there best to produce as flat a power coating as possible but the power coating is not flat. Therefore you need to compensate for that.
I print on to a textured sheet which has a deeper hole pattern than the power coated sheets have so i have to set up to allow the extra filament to squeeze down into the bottom of the holes to create the pattern i need as a surface pattern. For any parts that i need to fit together i always us a flat PEI sheet.
RE: Z-Layer Height...
The PINDA actually ignores the hills and valley, instead sensing the inductive change caused by the metal underneath.
Posted by: Robin
The PINDA as said only works on the steel sheet its self. The powder coating is on top of that and cant be picked up as its not sensed by the inductive pick up (PINDA).
Is there an echo in the room? lol.
RE: Z-Layer Height...
"As said".
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
RE: Z-Layer Height...
Who said? I was reminded of a bot that was echoing comments ....
RE: Z-Layer Height...
I guess I ended up jaded from using my Form² requiring a lot less thought for how things need to be modeled, oriented and printed...
In the meantime, I got myself a MMU2S to possibly address some of these issues with PVA Support Material Interface Layers.
Obviously, I bought it before reading the Forums and the shit ton of complains people seem to have with it but my first two prints dabbling with lettering on the first two layers appeared to have worked fine - I will though replace the Prusa provided Filament Buffer with something else as it's not doing what it's supposed to do and also a Royal P.I.T.A. to work with - Especially in my Printers confined location >_<
Will probably have to look into other mods as well addressing possible issues with the F.I.N.D.A. Probe Hole getting clogged.
Thanks for the recommendations! I'll see what I can do with them =)
RE: Z-Layer Height...
Some people are geting god results with PETG supports for PLA models, and PETG is both less expensive than PVA, and easier to work with, you may consider trying this as an option.
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK