1

Hi all,

I’ve been informed recently that slicing software should not print beyond the boundary lines of an object, and should automatically compensate for the line thickness by coming in from the boundary by a required amount. This means that the exterior dimensions should be the same dimension as what it was designed to. However, I have found this not to be the case with Cura - objects designed to interlock don’t fit because the female and males parts are not the dimensions designed to. Is it true that slicers should bring the printed line half the line diameter in? Is there a setting in Cura that I’m missing?

2

Basically there is much more to it than “the slicer should just do this”.

There are things like the expansion/shrink of the filament after it is extruded.

There can also be issues with the steppers not being calibrated exactly that could throw the dimensions of just a bit.

Over/under extrusion can play a part.

I would google about interlocking parts not fitting. Also look for printing small holes and dimensions. There is plenty out there that can help and answer questions.

3

Consider this.

I believe that the only compensation CURA does is to run along the STL line from the outside of the STL line.

My outside diameters are always pretty close to what I’ve drawn.

However:

Inside diameters are always approximately the Nozzle width too small.

I compensate by making bores and inside diameters 1 nozzle width different in size.

I see this exact question a lot.

In the end the answer is always the same.

It’s a bit of a pain to design for this fact. But until the 3D printing Slicing software actually does what you are thinking,

The facts I’ve given above are I believe absolutely true of All 3D printing Slicers.

Just my 2 cents worth.

4

What is the gap that you have designed between the famale and male parts? My sugestion is to have this at 0.5mm (not less) for a standard 0.4mm nozzle.

Usually the walls of the 3D printed parts is not perfect due to the FDM process. Try sanding just a little both interlocking parts (in the area of the interlock), but carefull to not overdue it, the target is to remove the bumps that remain after 3D printing, not to reduce all the surface. This works great for me.

5

Thank you; This is interesting and definitely a pain as at the moment I’m using a ‘surface’ made from an object a to extract from object b, so there is a female part the same dimensions as the male part. Having to model a different object for the female part will be a bit of a pain. I’ve been given some advice to use holes with compressible dowels which I think will be the path I go down, but if the hole itself isn’t equally out-of-tolerance along its circumference, then the compressible dowel will push the two parts out of alignment.