Explain Tolerance Settings?  

RE: Explain Tolerance Settings?

I have the same questions.  I have not found a simple answer and probably have 20 or more tabs open on my browser for this question alone.  Much depends on what you want and actually need.  Finer detail, smaller nozzle.  I just received some 0.2mm nozzles for some projects that are only a few mm thick.  I just did a test on my printer as I was concerned about accuracy and found that over 200mm, I get 200.45mm on both X and Y axis as most of my prints were smaller than what they should have been.  I had done some adjustments to my machine and that may have changed things.  I also was using the beta version of the slicer for the latest tests.  I have also found out that one change may affect another variable.

There are online videos and also guides.  I found this one through searches and from posts here.  Print Tuning Guide There was another site but it has announced that it may be closing down.  I really doubt there are any single guide since there are so many variables that can affect the precision.  Including your own machine.

RE:

Chris,

I was wondering about this as well and did some testing. I made a test block and added square dowels of 7mm/.1mm, 5mm/.1mm, 5mm/.5mm, 5mm/1mm (Size/Tolerance). These are all the same depth. The tolerance value seems to only impact the hole size as each of my 5mm dowels are the same size. It is worth noting that the dowels are not measured along the side of the square but appear to be based on the diagonal.

RE: Explain Tolerance Settings?

Here is a hasty (pretty ugly when zoomed in) print of that cut. The 7mm dowel just barely fits. Its super snug and probably not what I would want to use. The 5mm/.1mm does not fit, the 5mm/.5mm is a good fit and would hold well but still be removable, the 5mm/1mm falls out but would have plenty of room for glue. I imagine some of the fit issues are related to attempting to print small parts in general so the larger dowels you use, the more likely of a good fit. For my printer and the somewhat small dowels I use, I'm sticking with .5mm-1mm tolerances for gluing. 

RE: Explain Tolerance Settings?

An update to my post about accuracy.  I have improved it since my post in 2023 through more experimentation and testing.  Prusa Slicer has also added some features that help.

Tolerance settings are also dependent on how well your printer is calibrated.  If you don't have your printer and filament calibrated, you have to compensate for that in your designs which can be a problem, if you forget to make that compensation.  I prefer to be able to design something that is accurate from the start and hopefully the printer will get it correct.  Over the time that I have had the printer, I have learned to calibrate it for precision with minimal if any fine tuning after the print.

My procedure is not complicated, just time consuming and required for every roll of filament.

1.  Measure filament diameter at multiple locations and enter the average into the slicer.  May not be important but I do it anyway.  Step 3 may compensate for this.
2. Temperature tower and enter in the temperature you want to use.
3. Extrusion wall thickness - Prusa extrusion multiplier calibration  I found this to be important in my tests.  I don't use the cube but an octagon that I designed.  I have a very precise micrometer (4 decimal point) for this procedure.  I may do this 3 or 4 times to get a very close average to the expected wall thickness.  My model is a good size for mixing small amounts of epoxy so they don't just go to recycling.
4. Calibration cube.  30mm or 40mm object.  I found one that does circles and bridges and a few other tests.  I use this to enter shrinkage factor.  Shrinkage factor is in the Normal Mode > Advanced > Shrinkage Compensation.  I do multiple tests until I am in the precision I want/need. I used to use the multiplier in the slicer to compensate.  I don't have the link handy at this time.
5. Extra shrinkage calibration if I am using the filament for something larger.  Created a custom calibration target for X and Y and a separate one for Z of 200mm in size.
6. One thing I do for precision prints is change the slicer to do perimeters first.  This is under Printers > Expert Mode >  Perimeters and fill > External perimeters first.

Only things that have an issue is where bridging is involved and that is hard to control.  I have printed holes vertically for steel rods in ASA-CF and they are a very snug fit with no gaps or slots to allow any movement.  Just an air hole.

Of course, in your designs, you have to compensate to ensure there is a tolerance for snug or loose fit or to allow air to escape from a closed cavity if you are inserting something that is tight.  If using an adhesive that is thick, you need to allow air to escape or a gap for the epoxy.

FWIW, I have only used a 0.4mm nozzle at any time.  I have a 0.2mm nozzle but have not used it.  I am still fighting with quality of very small prints.  I know it is cooling and temperature settings for both the nozzle and build plate.

On a side note, when I first got into 3D printing, I was afraid to use filament, due to the cost.  I have learned that the cost of filament is cheap if you do a proper calibration and don't have to reprint because the printer isn't calibrated.  A few calibration objects area well worth the time and cost.  I probably wasted more money on failed prints, when I started, in an effort to save money.