Hole sizes not right

I am using an Airwolf 3D printer and it's Repetier on Gen 6 board.

If I print a box, the outsides are within 0.01mm of the size I make them but if I then put a hole through it side to side or top to bottom then the hole is always a bit smaller than I make them.

As an example I just made a Gopro tripod mount and wanted a hex inset in the bottom for a 1/4-20 nut. The nut outside measures 10.9mm (flat sides) so I made my hole 11mm yet it printed 10.69mm

Not sure how my outside can be so accurate but a hole never is. It's not just this object but any I make 'or' download. Yes anything I get off Thingiverse does the same (so it's not my 3D software). I have been using various versions of Slic3r and now am using the latest. I use Repetier host to print and like I mention the machine (gen 6 board) has repetier on it. I am a hardware guy so I am not Savoy on the firmware, software whatever it's called on the printer board.

So would there be a setting for this in Slic3r? Or the firmware on the gen6 board or what?

Any help would be appreciated as I am tired of guessing how much larger to make holes.

Thanks

for holes i normally just reach for a drill bit and hex holes are a whole different story, just about the only solution is to make them bigger assuming things like steps per mm on all 4 axis is correct

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So is this a pretty normal thing then for all printers? If so, maybe there is a formula to calculate the proper size.

if you calibrate your steps per mm with a calibration cube with a square hole in it, measuring both the inner hole and outer hole, then you can get it to the point where rounded holes are prettty close but even then just swapping filament can throw it out again,

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reduce flow rate.


if you use skein forge there is a feature called stretch.
borrowed from bits from bytes wiki:
[wiki.bitsfrombytes.com]

you can also try kisslicer. it seems better at calculating distance on inside as well as outside perimeters. here are its settings: [www.kisslicer.com] can be downloaded here [www.kisslicer.com]

if using slic3r reduce flow rate on inside perimeters. I'm not 100% sure how to do that but i think it is in advanced settings. change it to say 80%

other things that effect small holes are: loose belts, belt tension helps here, and precise nozzle hole calibration. some nozzles are over sized 0.5mm=0.55mm 0.35mm is actually 0.4mm.

I actually found a pretty good article on it here [hydraraptor.blogspot.com]

The only "flow rate" I see in Slic3r is for bridges. I do see a function called Extrusion multiplier that I have no idea what it's function is, maybe that's it.

But from that article it looks like there is no one single cure/ Maybe one day they will find a calculation and put it right in the slicer.

Thanks!

Extrusion multiplier , this is correct to adjust flow rate.

Since I have re-calibrated my extrusion rate in the firmware, set the correct filament width (it was a bit wider than 3mm) and have re- and re- and re-calibrated my X, Y and Z and E over and over again I now finally have correct hole sizes. It's kind if a drag to try different settings, but in the end for me all I needed was to calibrate and calibrate some more

I find it easiest to calibrate my printer, then print one of the many items on thingiverse that has a load of different size holes or hex holes. That way you can just find what nominal size gives you the correct fit. I'm not sure there is a perfect way to calibrate a printer, since you have to know exactly how the plastic will shrink (which is contained by infill on external perimeters, but not internal ones), which depends on the filament, print speed, and temperature. Heating the nut up or pushing it straight into the still-hot print works pretty well too. Also nophead's polyholes work nicely too.

If you calibrate correctly using slic3r you can get inner holes to be about as acurate as OD dimensions. Thats assuming they are not true arc holes but more square sided holes.

set the slic3r settings to 1 perimeter , 0 infill and 0 solid infill and set the width settigns to automatic. Basicly you want to print a single wall shell. After slicing go find the g-code file and open it. In the header comments will be listed the single wall extrusion width. Print your object and then measure the width of the single wall printed. Compare that to the measurement listed in the g-code. If its not exactly right then adjust the extrusion multiplier in slic3r and reslice and try again until it measures exactly what it is supposed to.

Thanks for all the info. When I get a chance I will do some testing with the "extrusion multiplier". Any idea which way I need to go with it? It's at 1 now (was default) so maybe start off with .8 or something?!?

Start off at 1 and then follow the instructions i posted. If the single wall width is thicker than its suposed to be you need to go down on the multiplier. Heres an example : width is suposed to be .35mm , it actualy measures .32mm . So .35 divided by .32 = 1.09. So you enter 1.09 as your multiplier in Slic3r. Just divide what its suposed to be by what it actualy is and thats your multiplier number.

Thanks

Hello,

Quote
GITRDUN
If its not exactly right then adjust the extrusion multiplier in slic3r

I'm using Slic3r 0.9.8 on Linux (Ubuntu) and haven't found any "extrusion multiplier" setting anywhere in the GUI.

Would that be "Default extrusion width"? It's under Print settings tab, Advanced.

Thanks.

NormandC Wrote:
-------------------------------------------------------
> Hello,
>
>
> If its not exactly right then adjust the extrusion
> multiplier in slic3r
>
>
> I'm using Slic3r 0.9.8 on Linux (Ubuntu) and
> haven't found any "extrusion multiplier" setting
> anywhere in the GUI.
>
> Would that be "Default extrusion width"? It's
> under Print settings tab, Advanced.
>
> Thanks.

Second option on the Extruders panel. At least it's there on Mac version.

BTW it had no effect on my issue and could not see that it made any difference no matter what the setting.

Please explain what you consider the "extruder panel". The only thing remotely related to extruders is as per attached screen capture, and there is no "extrusion multiplier" option.

If you could post a screen grab of your slic3r it would help greatly.

Thanks.

Click on the "Filament Settings" tab. It's in there.

I could have swore I checked everywhere...

Thanks.