Ideas why my design dimension is different then print?

[vrema01]

I am doing some testing to make a woodworking jig and I noticed that the size of a cylinder in Sketchup, ends up printing slightly smaller. I am new to making my own 3D models for printing, so just curious if I should expect this or if there's something I can do to fine-tune my printer. I am using Sketchup Pro 2022, Ender-3 V2 3D Printer, exporting using SLT Export plugin, and slicing using Ultimaker Cura.

The piece I am printing is a cylinder that is 19.70mm in Sketchup and its actual size when printed is 19.61mm. Should I expect to have the print be exact or should I just adjust my expectations?

In advance, thanks for your feedback.

[Rich O Brien]

Because SketchUp use segmented edges to create curves your result could differ...

Try increasing your segments when drawing...

[vrema01]

Thank you, Rich. I just ran a test print with a circle (cylinder) with 128 segments and it worked perfectly. The biggest challenge I had was resizing the object since I need the final cylinder to fit in a 20mm hole (Festool Multi-function Table). Now that I have it working, I will be making some guides for my workbench. If you have any pointers on how to quickly resize my objects down from CM to MM? I have to work in a larger size to allow that many segments.

[Dave R]

When I model for 3D printing I model with Units set to meters and work as if they are millimeters or inches depending. I export the .stl using Model Units and import into the slicer using millimeters or inches as appropriate. Since the .stl is unitless, there's no need to scale down. Here's an example from a model I finished up today. Note the dimensions of the pin are in meters in SketchUp.

Screenshot - 10_15_2022 , 7_16_16 PM.png

And in the slicer:

Screenshot - 10_15_2022 , 7_18_37 PM.png

FWIW, I would suggest when drawing arcs and circles, use a multiple of 12 for the number of sides.

[vrema01]

That approach works great. Thank you for sharing. Now I want to know if there's a unique style or plugin that setup your dimensions for that pin drawing. A style or plugin that helps create the extended guidelines/boxes for measurements and changes the color. I have trouble reading my measurements while in the workshop; maybe a different color and bold-faced text would help.

[Box]

Looks like you've picked the 5 minutes when Dave's asleep to ask.
My guess would be he has used Thomthom's Draw Bounding Box to create the guide geometry.
https://sketchucation.com/pluginstore?pln=tt_draw_bb
As for colour and size of the dimension text, you can set your default for that in Window/Model Info/Dimensions
Or adjust them after the fact in entity info, individually or as a selection.

Something else to keep in mind with 3d printing.
Different material will shrink different amounts, so the finished size often depends on what material you are using.
It is often better to make things slightly bigger or small and manually adjust the size if you need a perfect fit.
For example sanding down an oversized plug to fit, or drilling and taping a small hole to the right size. By printing a blank hole you get a wall thickness that is drillable, rather than drilling through a 'solid' which is usually filled with a network of fill.

[Dave R]

Box is right on all accounts, as usual.

[Box]

Spot on with the 5 minutes at least, the rest is just hearsay.