Welcome to the SeeMeCNC Community

so I have been working with a .7mm nozzle for a few days. I printed a couple of parts yesterday and last night that I had recently printed with a .5 nozzle. same STL file, same Slicer (matter control) the only difference is the nozzle size. the prints are coming out larger by a few thousands. for instance with the .5 nozzle I had to adjust in the drawing the diameter of a hole that was made for a roller bearing to sit inside. I had it dialed in perfectly with the .5 nozzle, a nice interference fit. using this same drawing the bearing hole is now too large by the amount I adjusted it, which is 10 thousands.

on another part the edge to edge diameter has changed. it is a hexagonal shape and flat to flat it is about 20 thousands bigger, just enough that I cannot mate the part with the older hexagonal shape printed with the .5 nozzle.

by changing part diameter and sizes I thought I was just correcting for thermal expansion and other oddities caused by making a part with quickly solidifying plastic. I did expect a bit of a change but not one of this magnitude.

has anyone else run into this issue? I.E. having to change part dimensions when a nozzle size is changed?

Tom C

Interior holes are largely affected by corner cutting IME. When you extrude plastic it's stretched as it leaves the nozzle, and with nothing to hold it, it will contract, so interior holes tend to shrink, the 0.7mm extrusion probably results in less overall stretching, so less shrinkage on the interior. Cooling and print temperature can make a difference here as well.
Not sure about the outside, you could be over extruding slightly compared to the .5mm hotend.

These machines are not precise machines to begin with.

The software packages that generate the g-code are even less precise.

When you have a model whose width is not easily divisible by the nozzle width, what happens? Either the layers are squished together (purposely) to some specified extent, or some tiny part of the model is truncated.

On top of the imprecise nature of the system, you have the variable of the nozzles themselves: one might be more over or under-sized than spec than the other, causing disproportionate differences in die swell, etc, errors in the extruder calibration, etc.

Basically, you're going to have to look at each nozzle as a unique slicing profile.