billyd wrote:ps I typically print something like a 20mm square about 3mm high with about 20% infill and 4 layers top and bottom. I adjust my extruder steps/mm until my top surface is perfectly smooth with no gaps. I leave extrusion multiplier at 1 for all prints. Make sure you measure your filament diameter exactly and get all other information controlling plastic flow volume correct. After you do this your prints will always be perfect as long as you measure filament diameter accurately for each spool.
pss if the outer measurements of the cube are wrong your printer's x y or z steps/mm might have to be tweaked (assuming your plastic flow is perfect). It also could mean you are printing too fast or with too much acceleration.
Thanks. Here is my 20mm test cube with my multiplier set back to the default 0.9
As you can see, the top layer isn't perfect in the top left and bottom right corners of the face. The corners also seem to be a little bit bulbous. As for the dimensions, X=20mm and Y = 19.85mm. Acceleration is down to 200mm/s
Only some of my filaments seem to under extrude, so I can I get away with just adjusting the multiplier or do I have to change the steps each time?
No only change the steps/mm for your extruder once. And if you get it such that you are getting a perfect top surface without gaps and no bulges then you are all set. The only thing you should change from that point on is your filament diameter to match your filament that you are currently using. Again I leave the multiplier at 1 for every print. Not a fan of changing that number ever. If you have your printer and everything else set up correctly that number should be 1 and your prints will come out perfect.
Your curved corners are a result of your firmware for your printer and poor pressure control of the extruder. My Taz 5 used to print corners like that using the stock marlin firmware they provide. I have upgraded it to newer marlin firmware downloaded from github and now my corners are sharp and walls vertical (along with a ton of hardware upgrades too numerous to mention). I don't recall what printer you are using but the issue you are seeing with those corners is firmware related and difficult to control with S3D. There are a few parameters you can alter is S3D to help with those issues a little but they don't work that great (coasting and other pressure controls of the extruder). They typically cause more problems than they solve. See if you can find better firmware for your printer controller.