Sketchup STL file dimensions wrong

Hi All,
I am having a bit of a weird issue and I hope someone can help me. In Sketchup I designed a replacement cover for a light that I broke, the dimensions were 160 x 160 x 70 mm. I exported to STL with the Sketchup plugin. I was just about to print it when I noticed that the GCODE produced by slic3r said the object was 172 x 172 x 69.9 mm. I confirmed this with a GCODE viewer and worked out that the STL measurements in X and Y were somehow at 1.07 times what they should be. In the end I reduced the X, Y sizes and re-slic3d it but I am baffled as to why this happened. I exported the STL in both ASCII and Binary and set the units correctly to mm and every time the X and Y were larger by a factor of 1.07.
Any help would be appreciated.
Thanks
Mike

Hello Mike,

I may be wrong, but I think Slic3r includes the skirt in these dimensions. The skirt's default distance from the object is 6mm all around, which would explain why the outer dimensions are reported as 172 x 172 instead of 160 x 160.

As for the total height, it depends on the layer height set in your settings. To get exactly 70mm you may try to play with the first layer height by multiplying the total of layers minus one with the layer height, and subtracting 70 from this value to get the first layer height.

You might be able to verify this
In any case, have you actually measured your printed part? I would bet it printed smaller, nearer to 149 x 149mm which is the factor you reduced it to.

Cheers,

Normand

AHEM, yes.
Thanks Normand,
I believe you may have a point there. Thanks for the update. Luckily enough the light cover is a little flexible so it still works but your right.
A pure rookie mistake.
Thanks
Mike

No problem!