Printing accurate holes
Hi,
I am having some problems printing dimensionally accurate round holes perpendicular to the print bed.
I know this is a common problem, and mainly due to the way the printers work, but I am looking for some advice about how I can improve matters.
I am currently printing using PLA, with a 0.4mm nozzle on an i3 Mk3, and using Slic3er PE to generate the gcode file.
Slic3er is set pretty much using the default values.
I am getting holes which seem to be consistently around 0.5mm smaller than the required diameter.
I know I could just increase the size of the holes in my model, but I would prefer not to do that if possible, as if I don't have control of the model (such as a downloaded one) the problem will re-appear.
What settings / adjustments can be made to improve the accuracy of holes in the print?
Thank you
Paul
Re: Printing accurate holes
Are you using Linear Advance?
Re: Printing accurate holes
Shrinking hole size is, unfortunately, an inherent problem with all FDM 3D printers. I once "attended" an online webinar put on by one of the big companies that sells high-end industrial printers (well north of $10,000) and they said that if you want an accurate hole, you print a hole that's slightly smaller than the desired end product and then bore it out with a tool to the precise diameter you need.
The amount by which a hole "shrinks" from the design is affected by the material you are using, the speed at which you are printing, the temperature of your nozzle, the ambient temperature, the amount of cooling air you have blowing over the print, your choice of "perimeters first" or "perimeters last", your layer height, your nozzle diameter, and of course the exact way the STL file was generated and the way your slicer treats that file. (STL files don't specify actual circles; they approximate circles with polygons.) And probably a few other factors too!
So if you don't want to bore the hole out, you simply must "oversize" the hole a bit in your model. You will find that small holes (less than 15mm in diameter) shrink more than large holes, because the "pull" on the filament going around a small radius curve is greater than the pull on a filament going around a large radius.