Parking aid enclosure

[jsc]

Here's an enclosure for a parking aid sensor I've been working on for a little while:

parking-exterior-sm.jpg (68.78 KiB) Viewed 11707 times

parking-enclosed-sm.jpg (124.19 KiB) Viewed 11707 times

Very simple case with stand offs, a battery compartment, and some slots/tabs to stay together:

https://github.com/jinschoi/parking/blo ... e/case.stl
https://github.com/jinschoi/parking/blo ... re/lid.stl

Here's a video of it at work: https://www.youtube.com/watch?v=eTVb-AUKWIc

Designing 3D printed enclosures around electronics, rather than the other way around, is just so much more civilized.

I got some sagging on the bridge, I think maybe I'm printing bridges TOO slow now, and slightly faster might be cooler. Has anyone nailed down their bridge settings yet?

Also, my slot/tab closure, while it works, isn't super secure, and a little bit fragile. Suggestions on mechanical fasteners for box-like objects?

[Dale Reed]

Hey, Jin! Nice job! What CAD tool did you use to design it? If it was OpenSCAD, could you post the .scad file for it? I'd like to use it as the starting point for a case I'm designing for a slightly larger electronic project.
Dale

[jsc]

DesignSpark Mechanical. I could have done it in OpenSCAD, except that getting chamfers and rounds is currently a bit of a pain. Also, I began the process by roughing out the two boards and the connector, using both measurements from the PCB design file and from calipers, then using that to design the enclosure around. It was conducive to using a visual CAD program.

The rsdoc file is in the github, but I am in the process of reworking it to make it slightly nicer. For one thing, it was my first design in Imperial units (because PCBs are laid out in inches), and it made me uncomfortable; I'm more familiar with metric units. So I'm redoing the whole thing as metric, and moving the grooves around a bit, etc.

If you don't use DesignSpark Mechanical, or even if you do, I'm not sure this design would be useful to you directly. It is easy enough to recreate it in whatever program you use. I wanted to have a mechanical latch, but the two long mortise and tenons seem secure enough for now. The bridged shelf is hard to print cleanly, for some reason I always get a few saggy strands at the forward end; I'm trying it with manual support just for that portion now.

[Dale Reed]

Jin,

Thanks for the feedback. I was wondering how that was working out for you. I was going to go with a 5-sided box with posts and holes for screws and a 2-level rim at the top, for the bottom half of the enclosure, and a flat top with countersunk holes at the corners for flathead wood screws at the corners. Based on your experience, I think I'll stick with that. My internals are nice in the I can have flat ridges of various heights in the base and the lid to hold the battery assembly and the PCB in place. I'll use some rectangular holes for the keys, which will have a brim at the bottom to keep from coming out and will be held in place by the return spring pressure from the tact switches underneath.

This one will entail a massive number of measurements for placement of the holes for the keys (43 of them!!!) and the LCD display. Fortunately I can get a lot of the spacing straight from the PCB software.

Dale

[jsc]

Please share your completed design when you have it. I'm interested in seeing how people solve different design problems. I think, with enough examples of particular enclosures, that it wouldn't be too hard to come up with a customizable "generic" project box that is good enough for many things. Better than getting a one size fits all one from Radio Shack anyway.

I think countersunk screws is a fine idea, but I wanted the enclosure to be openable without a screwdriver. The boards themselves mount using the standard #4 screw, but I sized the standoff holes to self tap, which works fine.

I started by roughing out the dimensions of the board+connector+sensor as a few rectangular cubes, with any parts that stuck out more than usual (like the transducers) added. Working around a however crude representation of the board makes things a lot easier.

[jsc]

The revised enclosure. Not too much different, redone in metric units and the slot and rail attachment is hidden internally now.

[jsc]

More enclosure action for a revised version of my parking sensor. I wanted a more positive closure action, and mechanical snaps seemed fiddly and would take more experimentation than I wanted to invest. I had a bunch of small neodymium magnets sitting around though, so I put in posts to hold them in the box with matching ones on the lid, and they worked great. The lid snaps into place and is held securely.

If anyone has done any designs using mechanical snaps, though, I'd love to know of any guidelines you've learned.

I think I will get in some battery clips next time and try to integrate the battery holder into the enclosure instead of relying on the box from Radio Shack. Who knows how much longer they will be around....

[ADam]

Suggestions on mechanical fasteners for box-like objects?

I've been using thread forming screws for plastic from McMaster-Carr.

http://www.mcmaster.com/#thread-forming-screws/=vamknj

[jsc]

Thanks, those could be useful. I've found, though, that I can get even regular machine screws to tap plastic if the holes are sized properly. I was more referring to printed mechanical clasps/tabs.