Let's do some engineering! I will tell you something about tolerance. Before I start, please check the previous article if you are not familiar with this topic.
Tolerance is an essential feature of drawing for every kind of engineering. In this case, we will see how we can use the tolerances on 3D Printing. (Using some mathematics) Instead of trying and failing, we can hit the target by some mathematical calculations.
In this scenario, I draw an open box with 70mm length and 12.6mm width. The thickness of my mobile phone (iPhone SE, similar to iPhone 6 and 7) was 7.6mm, and the length was 67.1mm. Firstly I gave a 2mm thickness for the four walls, which means it would be 4mm smaller from the width and the length:
==>> 12.6-4= 8.6mm (thickness) and 70-4=66mm length.
**First Problem: The thickness was better, but the length wasn't; because when I SHELL the box, I forgot that it would be smaller than the first draw.
**Second Problem: On the first drawing, I didn't calculate the tolerance. There are two tolerances: Filament accuracy and printer accuracy. (I know it is a little bit boring, but we can make it fun:D) I opened the "Blue Print Drawings" (I will talk about it in the following articles) on Fusion 360 and draw the critical dimensions. Then, I used my vernier to measure the real dimensions. In this case,
*Step (1): I found the tolerance of the filament&printer combination:
1)Real Length: 69.1mm, Drawing Length: 70mm, Accuracy: 69.1/70=0.987
2)Real Inside Width: 8.7mm, Drawing Inside Width: 8.6mm, Accuracy:8.6/8.7=0.987