Electronics > Mechanical & Automation Engineering

How to choose optimal sheet metal bending radius & k-factor

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fullmoon6661:
I'm trying to design a sheet metal enclosure, and I have a local shop that would fabricate it (laser cut + bending processes). It's a "simple" enclosure made of two U shape sheet parts screwed together with thread from the sides, the panels will be screwed on via 3D printed plastic supports. Picture attached.

The material is 2mm thick 1100 aluminum sheet.

When I asked the shop they said 2-3mm ±2mm for the bend radius. I made the first design with 3mm bend radius, but turns out the final radius is around 1.25-1.5mm after I measured, and most of the dimensions are not met except inner width. Picture attached.

I further asked the shop about the machine, the die & blade. Machine photo is attached, and their die & blade combination is: "V standard 25mm (3mm)".

How do I choose the optimal bend radius & K-factor so I get the closest result? I'm by no means a mechanical engineer and I don't want to berate the shop with novice questions, so I appreciate any insight. Thank you.

jpanhalt:
1100 is quite soft and has a recommended "minimum" bend radius .  Anything sharper may lead to cracking.  There are tables, such as this: https://www.aircraftmaterials.com/data/aluminium/1100.html 

Minimum bend depends on alloy, heat treatment, and thickness.   Minimum (not optimal) bend radius is often quoted relative to thickness.  Harder allows will have a radius of 6T or more (T= thickness).

Simply look up your alloy and any heat treatment. 1100 is often temper-0, so there is no practical minimum radius for 1/16" thickness (0.064") according to that table.

fullmoon6661:
Thank you @jpanhalt!

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