Electronics > Mechanical Engineering

Laser cutter to open sealed plastic cases.

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aargee:
Hello all,

Maybe an unusual or not wise at all application but.. can you use a laser cutter to open sealed plastic enclosures Read: sealed battery packs.

Currently, I use a 'hot knife method. The battery packs are medical in origin, sealed by plastic welded/glued joints and full of 18650 batteries.
The hot knife method is precarious as trying not to short or cut open batteries requires careful, time-consuming work. I imagine that the laser could be just as precarious if not aligned precisely.

I was wondering if I could use a laser cutter with a profile to suit the shape of the battery pack, to slice through the plastic to open them up.
I imagine having some sort of alignment jig to sit the battery in place and then run the profile.
The reality is that the cut does not need to go completely through, leaving a sliver of plastic is OK, as that can be split apart mechanically to remove.

Or is the whole idea a bit silly?

Kean:
Not silly, but I'd certainly be cautious.  Is it glued or maybe an ultrasonic weld?

First thing to check is the type of plastic (and any glue), and whether it might give off toxic fumes.

Second is that although the laser would follow an accurate and repeatable cutting path, the depth of cut with laser is somewhat uncontrolled and dependant on the material surface.  You'd probably want to keep the laser at a low power and run multiple passes to just weaken the join enough to then manually crack it open.  Personally, I'd probably do this with a jig and program on my benchtop CNC instead, as you can control the depth of cut much better.

The 18650s inside the outer case are likely covered in heatshrink and possibly other protective layers, and inside that is metal case.  So (without seeing the item) I'd guess you'd have to be very unlikely to actually hit something flammable.  The laser could reflect off the metal as well, so it must be behind something that blocks any reflected/scattered laser light to avoid eye damage.

Also keep in mind that you never leave a laser cutter alone when cutting, and always have a suitable (CO2) fire extinguisher handy.

thm_w:
Is there no way to setup your hot knife blade to only cut a certain depth?

aargee:
Yes, that's sort of the way I do it now, using a marker rather than a solid guide. But there is no good accessory to control depth - yet. I may have to craft one up.

thm_w:
Yeah make your own, maybe out of PTFE.
Stainless could also work but is a pain to deal with.

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