Author Topic: low volume custom pcb enclosure  (Read 8968 times)

stern0m1

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low volume custom pcb enclosure
« on: January 29, 2017, 11:24:45 PM »
Im looking for leads for affordable low volume  custom plastic pcb enclosures.  I designed the CAD files. Im looking for some way to have my CAD files manufactured.

Injection molding- seems to start at least $1500.
3d printing- seems for my files something like $10 a piece.


Thanks
It all started with a Moteino!

ChemE

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Re: low volume custom pcb enclosure
« Reply #1 on: January 30, 2017, 08:27:59 AM »
I would think the cheapest way to make this happen would be if Felix could justify the mold costs and have a bunch injection molded.  Not sure if he could reasonably expect to sell a few thousand of them to help defray the mold costs.  The molds are so expensive b/c they cannot be made from Al.  They have to be milled out of high-strength steel to handle the pressures exerted by the molten plastic (not that I've explored this before :) ).

Felix

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Re: low volume custom pcb enclosure
« Reply #2 on: January 30, 2017, 09:02:51 AM »
There's the possibility to make silicone molds for less than huge volume production. They can still produce a very nice case at a fraction of the cost of metal molds.
I am making a case right now for another project, silicone molds, and I'm very eager to see the outcome. The design and tweaks and proto prints/adjustments has been running for a few months now, not exactly very fast but it's a somewhat complex case. I will talk about it and details when/if it will be ready :)

Anyway for amateur level casing, you can use makercase to make some very cheap and easy lasercut-able cases. I used that for all cases I offer with MotionMote, SonarMote etc. They look very decent and from a little distance they look quite professional.

I have several Moteino type/sizes now so which one would it make sense to make a case for?
If I make one for the small Moteino then people will ask for a bigger one for MoteinoMEGA. If I make one that accomodates both then they will complain it's unnecessarily big for use with regular Moteinos.... the endless debates of usability vs manufacturing cost :)
Then I'd have to sell thousands before I get my upfront money back, not really a model I like to run by :)

ChemE

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Re: low volume custom pcb enclosure
« Reply #3 on: January 30, 2017, 10:20:30 AM »
I would think if you only offered one size (which I would) it would be for a 2xAAA battery shaped mote.  I'm beginning to go down the road of making my own in case you don't ever get to it and my PTH AAA battery clips will arrive later this week.  To my mind, for all the different projects we use this platform for, 2xAAA LiFeS2 batteries clipped to a board with a 328p and RFM69CW/HCW and if it can fit a PCB antenna in a waterproof/dustproof little enclosure would be incredible.

WhiteHare

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Re: low volume custom pcb enclosure
« Reply #4 on: January 30, 2017, 10:55:13 PM »
3d printing- seems for my files something like $10 a piece.

I'm assuming you mean $10 each in material cost alone (i.e. the cost of the plastic filament)?  I hadn't realized that 3D printing a custom  enclosure would be so expensive!  What are the dimensions of your enclosure for which that is the estimated cost?

executivul

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Re: low volume custom pcb enclosure
« Reply #5 on: January 31, 2017, 09:12:23 AM »
ABS is about 20USD/kg, PETG is also a good option.
A cheap 3D printer (200mm/200mm/200mm~8"/8"/8") is 200-300USD.
If you have the time to fiddle with 3D printing yourself it's a great opportunity  ;D

I have one and I'm printing the panels for custom lightswitches in my home.



WhiteHare

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Re: low volume custom pcb enclosure
« Reply #6 on: January 31, 2017, 04:55:47 PM »
Thanks for sharing the photos, executivul.

So, about how much does one of those enclosures (an empty one) weigh?

executivul

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Re: low volume custom pcb enclosure
« Reply #7 on: February 01, 2017, 04:35:52 AM »
If you have the 3d model of the box you can use a free slicer (Slic3r, Cura) to slice it for 3d printing setting a 0.4mm nozzle and 0.2mm layer height (most used ones) or 0.8mm/0.4mm LH, and see how much material is used and the time it takes to print one. The machine draws about 200-250W/h so you can estimate energy bill too.
Just watch a few yt videos about slicing for 3d printing :)

WhiteHare

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Re: low volume custom pcb enclosure
« Reply #8 on: February 01, 2017, 11:15:04 AM »
That's a useful answer.  Thanks!

By the way, one quick thing I've always wondered about that relates to 3D printing cost of material: suppose the unused filament at the end of a roll is not enough to complete an entire 3D print.  In actual practice, what is typically done with it?  Is it thrown in the trash as leftover waste or instead somehow spliced to the start of a new roll so that all of it gets used? 

The OP never gave his dimensions but says printing an enclosure costs $10.  So, ballpark, that would be 500g of material.  By inference, that sounds like a pretty large enclosure.... much larger than what would be needed for most Moteino motes.
« Last Edit: February 01, 2017, 11:20:18 AM by WhiteHare »

executivul

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Re: low volume custom pcb enclosure
« Reply #9 on: February 01, 2017, 02:49:18 PM »
ABS density is 1.04g/cm^3, so 500g ~= 500cm^3, at 3mm wall thickness it means 1667cm^2 that is a cube with 165mm(6.5") size.
Maybe the OP said $10 including manufacturing costs, 3D Printers tend to be slow and printing is a hit or miss job, so prices for the customers are a bit high, that's why I advised him to get his own printer if he has the time, skill and nerves  :P

LE. the math is for 3mm thick 100% infill walls, if you use 3 inner/outer layers and 30% infill you could double the size.
« Last Edit: February 01, 2017, 02:50:59 PM by executivul »

WhiteHare

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Re: low volume custom pcb enclosure
« Reply #10 on: February 01, 2017, 05:37:46 PM »
As a point of comparison, I recently purchased 5 of these black plastic project boxes for $4.32:  http://www.ebay.com/itm/201633631645?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Ignoring shipping costs, that makes them about $0.87 each.  For many, if not most Moteino sensor projects, they're plenty big enough.

Each box weighs in at 34g on my kitchen scale.  That's about 4 grams more than the advertised 30 grams, so for the sake of being conservative, let's go with 34 grams.

Unfortunately, I'm missing the key information as to whether or not it's ABS plastic, but if it is ABS, then based on weight alone the printing cost (assuming solid walls) would be $20*0.034= $0.68.

Anyhow, it seems like roughly a wash either way.  With 3D printing, though, at least you can get exactly what you want.




executivul

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Re: low volume custom pcb enclosure
« Reply #11 on: February 02, 2017, 05:14:40 AM »
With 3D printing, though, at least you can get exactly what you want.

That's the key factor, you get standoffs, customs cutouts, vents, whatever you want and you get it in a few hours not weeks  ;)

TomWS

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Re: low volume custom pcb enclosure
« Reply #12 on: February 02, 2017, 08:01:04 AM »
The cost of plastic in 3D printing is virtually nil, the real costs are the design and print times.  If you do your own design, you control those costs, and, if you have your own printer, the printing runs unattended so, if you have an UPS to keep it running during brief power outages and can leave it running for as long as it takes, you can make literally anything.

The attached photos are of a prototype of a drip valve, printed in PLA, at a total plastic cost of $0.33 (approximately 1.2Meters from a 1KG spool that cost $25 and contains 880 Meters of filament).  I don't recall exactly how long it took to print, but I believe all 5 parts took a total of about 3 hours and can be printed in a single run (actually there is room on my printer bed for probably 4-6 sets of parts).

You don't need ABS unless the piece is going to be exposed to a harsh environment (temperature or high humidity) and I haven't used ABS yet since I don't have an effective means to filter/vent the styrene fumes - yet.  I can print PLA in my office unvented...

Tom

Felix

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Re: low volume custom pcb enclosure
« Reply #13 on: February 02, 2017, 08:26:53 AM »
@TomWS - nice print, looks really good compared to other 3d prints I see online.
What printer do you have? Any customizations?
What's the project you are showing, looks very interesting (if you can share)?

TomWS

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Re: low volume custom pcb enclosure
« Reply #14 on: February 02, 2017, 09:28:17 AM »
@TomWS - nice print, looks really good compared to other 3d prints I see online.
What printer do you have? Any customizations?
Prusa I3 MK2, no mods to the HW or SW, minor tweaks to the filament and print parameters to improve adhesion to the base.  These were done on the mid-quality setting (0.2mm layer thickness).
Quote
What's the project you are showing, looks very interesting (if you can share)?
This is an inline drip valve that's intended to irrigate small regions like window boxes, herb gardens, etc.  It requires an upstream valve and pressure reducer if the source is residential water supply, but should work well for rain barrel setups.  Naturally it's battery operated with an expected battery life of 2 or more years.  I'll share the project when I've deployed it.  I have the second version of the prototype running, but waiting for warmer temps to start setting them out.  I 'may' include the 3D print files, not sure yet.

Just for fun, I'm attaching another project I just finished.  This is an antenna rotator for an HD TV antenna mounted in our attic.  It uses ESP8266 so probably won't post here.  It has 4 different printed parts (2 PCB mounts, drive gear, antenna post gear, and, to support the world famous LowPowerLabs SOT-23 breakout board, the 3 axis mag sensor holder that positions the center of the mag sensor directly over the drive gear).

Tom