Incorrect Inner geometry sizes

[dmon123]

Hi all,

I am a new user of Simplify3d and am going through learning 3D printing. I have a Prusa i3 which is working beautifully. I have printed several thingies including a geared key chain very well.

I am now trying to design parts (in FreeCad and OpenScad) and am having a funny issue. So I created a 20x50x10mm bar. I then added a 5mm in diameter circle, a 5mm hexagon (each side of the hexagon is 5mm) and an equilateral triangle (each side is 7mm) and I then pocketed each of these shapes into the bar (5mm).

I then printed 3 cylinders (5, 4.8 and 4.6 x 10mm), 3 hexagonal bars (5mm, 4.8mm and 4.6mm x 10) and finally 3 triangulars bars (with sides 7mm, 6.8mm and 6.6 mm x 10).

After printing the holes are not the original sizes!!! So I can fit very nicely the 4.8mm cylinder in the circle, the 4.6mm hex bar into the hexagon and the triangles dont fit at all

My settings are sort of normal for PLA.

All settings in mm:

PLA 1.73mm
Nozzle 0.4
Extrusion multiplier 1.06
Extrusion Width 0.48
Layer height 0.2
Top and bottom solid layers 3
Outline/Perimeter 3
Infill 20% Rectilinear
No support
198 deg C hot end
64 deg C bed
Hot End and Extruder fans on

I am looking to print some enclosures with pins to go into sockets for locking it and cannot get the sizes right...

Any help would be greatly appreciated.

Many thanks,
D

[CompoundCarl]

Could be a lot of things - over extrusion, thermal expansion, even STL model tolerance. If you print parts that need to fit together a lot, it's probably a good idea to add some tolerance to the gaps between parts

[zemlin]

Take a look at the information I posted in a thread about my 'Calibration Cross'
viewtopic.php?f=9&t=6130

Print one of these things with no scaling and no horizontal offset. Then measure the part and enter the numbers into the spreadsheet. With that you can adjust the values for horizontal offset and X,Y scaling to minimize the errors.

While it's not perfect, it gets parts very to where they are designed, both internal and external dimensions.

[dmon123]

Sorry for the late reply. Busy at work

I will try your post and see how it goes.

Many thanks for the replies.

D