Need some guidance for designing for 3D

[WobblyHand]

I want to design a box to house my custom ELS control board and display. I can do this in FreeCAD, but I need some practical guidance on wall thicknesses and ways to add fasteners. For instance, how thick should the back of a box be, where some GX16 connectors are entering? 2.5mm ok? What about box wall thickness? The box really isn't structural, except perhaps for resisting any twisting in the rear by the entering and exiting cables. The lid to the box will have a built in bezel and opening for a touch panel display. On one wall, I guess I will make some pockets for magnets, so the box will stick to the top of my head stock. How are fasteners attached? Are there special inserts? I will print some bosses in the bottom to retain the PCB. The walls will have a lip to receive the cover.

Rough dimensions of the box are around 5" x 7" x 1.5". I have silver PLA which looks pretty nice, and black PETG. Haven't printed PETG yet, that's another adventure for me. The sticky on 3d design seems to point to a dead URL...

 

[TorontoBuilder]

Yes use bosses where you will fasten any connectors, and heat staked inserts for screws so that you can use thinner walls yet still have strong connections. Ditto for the aviation connectors.

Box wall thickness should be fairly substantial but use low density infill because tall thin walls are prone to breakage under constant use.

Dial in your printing temps, my first PLA boxes did not hold up to heavy use, they split at the layers on the thin wall sections when I went to drill holes I'd forgotten to just model. I'd go PETG black, shows fewer oily fingerprints.

Below you can see how I modeled material for heat staking inserts at the corners, but I eventually just made full height pillars the depth of the box for fastening the cover. Because it needed support material anyway.

I inset the cover BTW to better support the front of the box and allow a thinner wall.

Bosses in the side to heat stake inserts to screw on legs. I added a feature to kae sure the legs remained fixed at a permanent angle for better viewing. I printed the entire back thick enough that I did not require bosses for the wire glands.

In the end I made this box out of black PLA solely for prototyping and replaced it with a diecast aluminum box once i had everything worked out. If I'd made it just slightly thicker and in PETG I'd have kept that. But I had stringing with PETG I haven't resolved yet.

Let me check my thicknesses in fusion and get back to you

 

[Ken226]

Heat set inserts are popular and easy to install, using a soldering iron.

 

[jwmelvin]

I generally design wall thickness as a multiple of my intended layer height (for bottom walls) or nozzle size (for perimeter walls). For a lot of things, 1.2 or 1.6mm wall is ample; that would be printed solid as 3 or 4 perimeters.

 

[TorontoBuilder]

Okay, so my wall thickness is ~4 mm, the back is a little thicker. I think I used 40% infill and minimum 2 external and internal walls IIRC

Legs 4 mm. Cover is the same 4mm, while the wall extension to make the inset for the cover is 2mm, printing adjusted so this part is solid infill.
Note my control box was meant to be picked up and moved around often and therefore required to be more rugged than something mounted rigidly to a surface at the back

 

[TorontoBuilder]

I generally design wall thickness as a multiple of my intended layer height (for bottom walls) or nozzle size (for perimeter walls). For a lot of things, 1.2 or 1.6mm wall is ample; that would be printed solid as 3 or 4 perimeters.

I designed for my wall layers and course nozzle size... which is why I arrived at a weird dimension that is not standard imperial or metric.

IF only I'd made my design parametric I would have been able to share it with wobbly

 

[WobblyHand]

I designed for my wall layers and course nozzle size... which is why I arrived at a weird dimension that is not standard imperial or metric.

IF only I'd made my design parametric I would have been able to share it with wobbly

Based on everyone's info, that is what I am trying to do. Make important stuff multiples of layer depth and nozzle width. Put this in a spreadsheet into FreeCAD so all this stuff is written down and I can see what I did! Parametric design is great, but it's a bit of work.

 

[TorontoBuilder]

Based on everyone's info, that is what I am trying to do. Make important stuff multiples of layer depth and nozzle width. Put this in a spreadsheet into FreeCAD so all this stuff is written down and I can see what I did! Parametric design is great, but it's a bit of work.

Parametric is really not that much work, if you start from scratch with a base sketch and plan ahead thinking you may want to make a box maker.
When I did my design it was a one off prototype just to allow me somewhere to hold a display, wire connectors and a few switches and potentiometer.
You should do this as parametric design... you may wish to revise your design

 

[WobblyHand]

Parametric is really not that much work, if you start from scratch with a base sketch and plan ahead thinking you may want to make a box maker.
When I did my design it was a one off prototype just to allow me somewhere to hold a display, wire connectors and a few switches and potentiometer.
You should do this as parametric design... you may wish to revise your design

I'm expecting quite a few redesigns! LOL. Integrating in info from my PCB and display has been painful for me. Don't have a heck of a lot of mechanical design experience, so this often doesn't go as smooth as I'd like it.

 

[TorontoBuilder]

I'm expecting quite a few redesigns! LOL. Integrating in info from my PCB and display has been painful for me. Don't have a heck of a lot of mechanical design experience, so this often doesn't go as smooth as I'd like it.

Start with a good sketch with constraints and dimensions.

That way if you need to revise the box you can revise the base sketch dimension and the box design changes to match the new dimensions