Enclosures for your prototype
william chan
Posts: 1,326
Guys,
Making molds for plastic casings is always a big investment for low volume products and prototypes but in the end, it may not look nice enough to fully commercialize it.
Then you have to make a nicer version2 mold and version3 molds with even more investments.
Anybody got better ideas for low volume enclosures?
I heard some people can make fibre glass casings in low volume ( 10 pcs per order ) for quite low costs.
Is it true?
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Making molds for plastic casings is always a big investment for low volume products and prototypes but in the end, it may not look nice enough to fully commercialize it.
Then you have to make a nicer version2 mold and version3 molds with even more investments.
Anybody got better ideas for low volume enclosures?
I heard some people can make fibre glass casings in low volume ( 10 pcs per order ) for quite low costs.
Is it true?
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Comments
Vacuformed plastic shapes are quite reasonable and easy for DIY - just use a vacumn cleaner and heat laps. But you really cannot get square boxes, mostly bubbles.
Fiberglass is quite messy. But if you really have a complex shape and can build a mold, it will work well. The original can be shaped with clay [noparse][[/noparse]like pottery clay], then the mold can be erected around the clay model. Is that really worth it for only 10 items? It seems a lot of work to me.
Regarding fiberglass, there are several different production technologies that are used to make boats, furnature, greenhouses, and more. The traditional is to use fiberglass cloth, but there are blower machines that mix the resins, chop the fiber, and blow it into the mold. For big things this is fine, but I cannot imagine a small chasis.
A lot of people use plastic boxes from stationary stores. Or food storage containers. These can also be used for molds to be copied into harder, stronger material.
Audio amps used an ugly chasis covered by a beautiful solid wood box for many decades.· The front was a solid brass sheet with silkscreened printing.· Seems to me that there is nothing wrong with doing that again.
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"Everything in the world is purchased by labour; and our passions are the only causes of labor." -- David·Hume (1711-76)········
Post Edited (Kramer) : 10/16/2007 12:37:48 PM GMT
I'm sure you can't use food containers or aluminum tubings.
I guess that's why most Parallax products don't come with a casing.
Where to buy the Vacuformed plastic material? What are "heat laps"? Can we blow the plastic into a mold to get square shapes?
Anybody knows how much does a metal casing like the USB Oscilloscope costs?
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-Phil
It's a really simple process. Heat a sheet of plastic till it's soft and stretchy then suck it onto a mold.
Marty
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Lunch cures all problems! have you had lunch?
I think they can be used to enclose PCBs.
Anybody know where to buy those plastic liquids?
and how to handle them?
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http://www.tapplastics.com/shop/category.php?bid=33&
·
Twisted Pair....
Post Edited (Twisted Pair) : 10/17/2007 3:36:36 AM GMT
Where are the pictures of your sample plastic enclosures?
How much do you charge for plastic matchbox sized enclosures?
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"What about those clear plastic liquid that you pour over dead butterflies and beetles to make ornamental keychains."
I used to use this stuff all of the time when I was in prosthetic research and development. We called it "Sea-gull-hearts" <--- I will try to get the correct name for you by the end of this week. That stuff works well for encapsulating electronics... the "trick" is to put a light coat of varnish over your electronics before you seal it in the epoxy though, and some wire insulation can be affected (becomes rubbery and swells) by the epoxy. I would also recommend using as little promoter (catalyst) as possible... the slower you allow the Epoxy to harden, the "clearer" it will set when it's dry, otherwise you can get bubbles or a yellowish tint.
BTW) It wasn't cheap, I remember that stuff going for about $30 a gallon.... anyway, I'll find out, I can call someone that I used to work with by the end of this week and find out the proper name and $$ amount.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Twisted Pair....
I am looking to make a SX board powered by wind blowing from an air conditioner.
The plastic box should about the size of a matchbox but maybe double the thickness.
I want to double-side-tape this box to the bottom of an air-conditioner but near the airflow.
It should have a lightweight propeller (plastic ?), either facing the wind, or a water mill type of propeller mounted at the side of the box where the top section of the mill is blown by the air.
The reason why the casing needs to be thicker so that the propeller can turn freely without knocking anything.
Inside the box, the propeller's shaft is glued to a super strong magnet which will then induce current in a static coil to charge up a supercap which powers the SX board.
Can you recommend the best casing design for this proposition and please quote your fee as well.
Thanks.
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Since you will have a small Axial and radial load applied to your enclosure with the prop, a wall thickness of about .090" should support this load without any problem. I have a mold already made for a small plastic Enclosure that you might be able to use for your project. It has mounting ears on the sides, no board standoffs, internal press fit cover and is about twice the size of a matchbox. The draft angle is two degree's. If you could use this Enclosure, I could sell it cheap since the mold is already made. You could cut the mounting ears off if not needed and use sealer on the cover to make the box weather proof. I assume that you will drill your own holes to fit your needs. After I know more about your Enclosure requirements, I can give you a Quote. How many will you need ? I will measure the box dimensions and take a few pictures today and of coarse I will post them here.
Twisted Pair....
All the pieces could easily be cut to length on a regular cutoff saw with the right blade for aluminum and then be cleaned up with a file in a few hours. It would be a lot easier and cleaner than casting. And aluminum would not affect the magnetic field.
It doesn't really matter what you choose, you are going to have to drill holes in all these processes.
Epoxy resin is expensive. Google 'West system epoxy' to get an idea. They provide a wide range of resins.
I don't think vacumn forming will provide you with the right shape or strength in such a small design. And, it really is too small for fiberglass.
There are a lot of premade boxes that would work, but some may be more costly that making your own.
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"Everything in the world is purchased by labour; and our passions are the only causes of labor." -- David·Hume (1711-76)········
Post Edited (Kramer) : 10/18/2007 9:58:24 AM GMT
The epoxy is much more than I thought.· It's called Siegleharz (OB 617H21=4,600) and the cost is $98.30 for the liquid, but the Hazard shipping is almost $30.00
This is for a 1 Gallon metal can.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
I'm still searching for more photo's of my Plastic Enclosures but haven't been able to locate them. I did however find the smaller box that I mentioned in my latter post to you. Here are a few quick photo's of that box. It's about twice the size of a matchbox. The Dimensions are, 3.00"(L) x·2-3/8"(D)·x 1-1/2"(H)....
Twisted Pair....
Allied Electronics has them, I think Newark might also.
www.alliedelec.com/Catalog/Indices/Products.asp?sid=4717F38070617F&N=4294964092+4294958596&Ne=2671
Most of the enclosure manufacturers offer to do customization if you need commercial quantities. This might be useful once you finalize your design.
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- Rick
Looks like this problem is too difficult to solve..... I am almost giving up
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Don't give up !!!! You've only just begun the Hardware Engineering phase of your project. Without Specifications or a Drawing from you, I have conceptionaly visualized what you need and I have made a simple drawing of a box with a Prop and Shaft. Is this what you have in mind ? Adding the hardware to an Enclosure is not that hard with the right components. Keep the Faith....
Twisted Pair....
It seems like the wind-generated power will be the most challenging part of this project. Of course, we don't know what your application will be, so there may be other challenges that we're not aware of. I would think a prototype enclosure is the last thing you should be worried about.
I assume you are planning to drive a small motor from the propellor to make it a generator. You may want to consider using a small electrical cooling fan as your generator. You should use one that has brushes, or you could modify a brushless motor to make it an alternator. If the generator does not generate a high enough voltage you will need a circuit to increase the voltage.
Can you tell us a little more about your application?
Dave
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~~ dRu ~~
Your drawing is what I have in mind !, except for some minor details.
1. I am expecting to mount the box in such a way that the wind would be perpendicular to the shaft, that means that the propeller blades should have small anemometer cups or at least some flat paddles to effectively catch the wind.
2. On top of that, I think we need at least 4 blades on the propeller in case the blades become parallel with the air flow and won't start turning.
3. We probably would need a very small bearing to hold the shaft, to make it smoother.
4. The other problem is that if we double-side tape the box to the bottom of an air-conditioner, the propeller would touch the air-conditioner, so we need a somewhat flexible ( but not too flexible ) bracket to mount the box a in such a way the propeller can turn freely and optimize the positioning for wind catchment.
The bracket will be double-side taped to the bottom of a wall mounted split air-conditioner.
5. The box should be match boxed sized, transparent, and the propeller can be made smaller a bit.
Can you design such a box, including the propeller and bearings ?, in quantities later?
Dave,
The SX board and other peripherals will only use about 1 to 2mA of current on average, b'cos the SX is mostly asleep.
It is also OK for the board to totally power down due to insufficient voltage on the supercap, and then power up again when the air-cond is running.
I usually find that a small motor is difficult to turn, this will make the propeller big and difficult to start turning.
That's why I'm deciding on a small magnet turning inside a coil that is mounted on the PCB itself, making the propeller as free-turning as possible. I estimate the peak to peak voltage from the coil to easily reach 5v, to be passed on to a bridge rectifier. I wouldn't worry about the electronics, I think we have enough know-how.
I hope to surprise everyone in the forum when the project is working....
Dru,
Thanks for the info. I may need it for my other projects.
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Post Edited (william chan) : 10/24/2007 1:35:58 AM GMT
What if your fan is positioned in such a way that the airflow went through your box or enclosure?· Picture a standard computer fan, or the blades of a standard computer fan connected to a small stepper motor... <-- The Stepper motor is your generator.· Use a frame similar if not the same as the one used for the computer fan.
To get your "power" out of your stepper, locate the common terminal that is your negative... Depending on the number of phases and the type of stepper, you will need a diode for each phase.· Connect the anode of each diode to·each output phase, connect all of the diode cathodes together, that is your positive terminal.· Try that and give your stepper a spin.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
I can design whatever you need but a drawing would give me a better idea of your component dimensions etc. I don't think that a matchbox sized Enclosure will be large enough to house your hardware....For example, the bearings for an 1/8" shaft would be 3/8" (OD) x .1250" (W). That is a small bearing and is smaller than a dime...There are smaller bearings and bushings but you get·the idea....I like Beau's idea but it means a larger enclosure to house the Fan. I have attached two more concept drawings much like what Beau has suggested....
Twisted Pair....
I am scared that the stepper motor will have difficulty starting up due to the higher torque required to turn it.
If the Fan.jpg is used as the enclosure itself, where do I mount the PCB?
Twisted Pair,
Do you prefer to design the propeller or buy a ready made plastic propeller? I guess for the 1st design, a sideways
propeller is difficult to source.
The second design is possible, but we still need a bracket to mount the box about 3-4inches away from the air-conditioner so that the louver swing will not touch it. Can you draw this flexible bracket as well?
For the third design WC3.JPG, we can double side tape the box to the bottom of the air-conditioner but since the fan is small and its position is inflexible, it might not catch any wind if the louver is set to an unfavorable position.
What does 3/8" (OD) x .1250" (W) stand for? Sorry.
I think WC2 with a 4 inch flat bracket is possible, but if the box size is too big, it may block the airflow and reduce the efficiency of the air conditioner.
Thanks a lot.
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Post Edited (william chan) : 10/24/2007 10:36:15 PM GMT
The 3/8" (OD) is the outside dimension of the bearing and the .1250" (W) is the width....I will re-draw whatever you need but at this point I need more information from you. Can you supply a picture of the air-conditioner and a rough hand drawing/dimensions of the components that you will use ? The coil and magnet are most important as I already have the size of the chip. This will allow me to calculate where the components will go in the Enclosure. Once I have this information from you, We can move forward. Send this information to me by Email at, Twistedpair@suddenlink.net ....
Twisted Pair....
Post Edited (Twisted Pair) : 10/24/2007 3:18:13 PM GMT
I will post them tomorrow.
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Twisted Pair....
I have posted some pictures on the other thread titled "Propeller powered Propeller".
Have you read it?
Thanks.
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