How to mount PCB to plastic project box

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dqsis
 
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How to mount PCB to plastic project box

Post by dqsis »

A "novice" question:

I am trying to recreate the solar charger (wearable) project,
As stated in the manual, the PCBs (eg PowerBoost) are screwed into the 3D printed box via Philips screws.

However, the mounting holes on the PCB have no threads!
How is then the fitting/mounting achieved?

And more generally, what is the best way to attach PCBs into plastic boxes?
A couple of photos would really help me understand.

Thanks iin advance!

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Franklin97355
 
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Re: How to mount PCB to plastic project box

Post by Franklin97355 »

However, the mounting holes on the PCB have no threads!
The screw is smaller than the hole in the PCB and threads into the box holding the PCB between the box and the head of the screw. If you can't use screws you can use double sided tape, glue or hot melt.

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adafruit_support_mike
 
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Re: How to mount PCB to plastic project box

Post by adafruit_support_mike »

The screws pass through the PCB and bite into the standoff.

There are two main ways to use screws in a project. One is to use self-tapping screws that cut their own thread through wood or plastic as you screw them in. They're fast and easy, but tend to strip the hole if you remove the screws too many times.

The better option is to use threaded brass inserts that melt/press/screw/glue into the standoff, and regular screws. The inserts will last indefinitely.

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dqsis
 
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Re: How to mount PCB to plastic project box

Post by dqsis »

Hello again.

I still have a hard time understanding how to mount the PCB using bolts in e.g., the solar power bad 3D printed box.

In the CAD file, the PCB holes have a diameter of 3mm. The holes in the box have also a diameter of 3mm.
The specified bolts are #4-40, hence have a diameter of less than 3mm (approximately 2.7mm).

In that case, how are the self tapping screws "bite" in the box'es standoffs or the PCB? (depending on screw insertion direction).

Thanks in advance!

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adafruit_support_bill
 
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Re: How to mount PCB to plastic project box

Post by adafruit_support_bill »

Please post a link to the tutorial you are following.

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dqsis
 
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Re: How to mount PCB to plastic project box

Post by dqsis »


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adafruit_support_bill
 
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Re: How to mount PCB to plastic project box

Post by adafruit_support_bill »

Most fused filament printers tend to leave holes slightly undersized. If you design them to the exact screw diameter, your screw threads will have something to bite into. That may be what the author intended here. I will check.

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pixil3d
 
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Re: How to mount PCB to plastic project box

Post by pixil3d »

Hi there,

Although we could apply threads to the holes in CAD, most FDM 3D printer aren't capable of printing them even at a low layer height. Since the standoffs are printed layer by layer, it's just easier to tap your own threads using screws (#4-40 wood screws for tapping, machine screws for mounting).

We intentionally set the diameter of holes in the standoffs to 3mm because the tolerances tend to be tighter after printing. It's about ~0.2mm shrinkage in the hole, so it becomes ~2.8mm. This happen with 3D printers like the printrbot simple metal, flash forge creator pro and ultimaker 2.

I recommend using wood screws to tap the threads, slowly and as straight as possible. Here's a video on some tips for designing standoffs.

https://www.youtube.com/watch?v=NHIrTtLCnEo

PS: We may do a video tutorial just on this topic. Thanks, hopes this helps!!

–Noe

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