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Aeroengineer
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Re: Trading speed for size and accuracy
Aeroengineer   6/26/2014 11:04:33 AM
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Max,

Here are the sizes I would recommend for the poll cm listed first, and rough inch sizes listed in parenthesis:

 

10x10 (4x4)

15x15 (6x6)

20x20 (8x8)

20x25 (10x12)

30x30 (12x12)

 

Aeroengineer
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Re: Desktop Pick & Place: the big picture
Aeroengineer   6/26/2014 10:51:22 AM
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That is great advice if it will work for the board needs.  A lot of my boards are very space constrained, and 0402s are the smallest I feel comfortable working with without having a lot of rework.

 

I have seen a manual pick and place machine over the last few days that has looked pretty interesting for doing smaller components.  That seems like an interesting concept, and perhaps something that could be part of the modular approach that we are looking to use in this project.

zeeglen
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Re: Desktop Pick & Place: the big picture
zeeglen   6/26/2014 10:46:03 AM
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@Aeroengineer improving the throughput for hand assembling SMT boards.

Design in the largest components that fit on the board, 1206 are a lot easier to manually handle than 0402. If ICs come in more than one package size use the widest lead pitch available.  Use the widest copper etch possible for physical robustness.

Aeroengineer
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Re: Desktop Pick & Place: the big picture
Aeroengineer   6/26/2014 10:21:59 AM
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On a side note, I would love to hear any other comments that you might have on improving the throughput for hand assembling SMT boards.  I am sure that there are valuable lessons that can be learned while we are contemplating these next steps.

Aeroengineer
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Re: Desktop Pick & Place: the big picture
Aeroengineer   6/26/2014 10:19:15 AM
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Carl,

 

I appreciate you input, and yes it is ambitious.  Here are some of my personal motivations behind it.  I usually travel a lot.  I also have a handful of hobby boards that I produce.  The problem is that when I am home I do not want to spend the time building a bunch of boards by hand when I could be with my family.

 

So, I looked into what it would cost to have these boards assembled for say 100 or 1000, and the cost was on the order of $10-20 per board.  The boards only have 10 components on them, and they can sell for about $15, and have $5 in BOM costs.  This makes it financially not viable. 

 

But if I have a machine that costs me $500, and in my first round of 100 boards, this means that the cost to me was only $5.  This is an acceptable cost, and gets paid for in the first round of production.  At 20 boards, it is at least break even with having it outsourced.  So from a cost perspective, it makes sense.

 

Now that the cost perspective makes sense, the time also falls in line.

 

For a person that only does 1 small board per year with under 20 components, then this may not be for them, but if they do a single board with 200 components, then there is value in having a machine that is more likely to place the correct components more accurately.

cabatear
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Desktop Pick & Place: the big picture
cabatear   6/26/2014 10:06:32 AM
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I've read through all of the various posts and comments so far, and learned quite a lot!  But I gotta say:  a fully automatic desktop pick and place with the kinds of parameters you're talking about is a pretty ambitious way to go about addressing the need to populate a few prototypes once in awhile.  While there would certainly be a "cool!" factor having such a machine, perhaps a more practical approach would be to simply improve the method of manually populating boards so that it is less tedious and more efficient.  I researched this challenge a couple of years ago and came across a great product from Abacom called EZpick, which we now use.  In fact we use it for low-volume manufacturing as well, in combination with low-cost laser-cut mylar stencils from Pololu, and a retrofitted toaster oven for reflow.

Carl

Aeroengineer
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Re: UNC hardware rocks!
Aeroengineer   6/24/2014 9:38:48 PM
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I have come to peace with both systems of measurement.  Each has their advantages. As you mentioned, you can get a whole lot of common hardware in Inch.  Many scientific calculations end up being easier to do in metric except when it comes to derived units, then it can be just as hard because you never remember what the derived units actually are in their proper combination of units.

 

McMaster is one of the greatest stores ever.  Here in the states, they have great service and a lot of things at a reasonable price.  There are a handful of other sources I use, but they are a big one.

salbayeng
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PCB Size poll
salbayeng   6/24/2014 9:29:02 PM
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OK, If I exclude two huge LED lighting PCB's.

And include all my boards over last 3 decades, and include 4 colleagues I have worked with. All of these individual PCB's will fit in the 15cm x 20cm size.

(From an economic perspective, being able to load 20cmx25cm sub panels is better for production runs, but this is not the question being asked). 

So that's 5 votes from Oz for 15cm x 20cm  (you might want to discount the votes a little, as we are unlikely to be buyers) But I guess it's statistics you are after . 

Note that 16cm is a common extrusion width for enclosures. And that by number alone, half of the PCB's would be under the 10cmx15cm. (also revenue earned from PCB's is related to area)

salbayeng
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UNC hardware rocks!
salbayeng   6/24/2014 9:06:49 PM
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Some may say I'm a big fan of metric, but you can't beat UNF & UNC for quality hardware. I've just spotted on the solar blog http://csirosolarblog.com/page/6/  , about 3/4 way down

26.Each heliostat and its components are held together with 55 bolts – for a total 24,805 bolts in Solar Field 2 alone.

Most of these we airfreighted in from McMaster-Carr, including fasteners you just can't buy over here: 10-32UNC Stainless Hitensile thread forming hex head screws to precisely align the "origami" frames. 3/8UNCx1/2 flangehead ZP bolts with matching serrated nuts. 3/4"UNF x2" ZP for the bearings. And AN526C1032R8 for attaching actuator brackets. 

Aeroengineer
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Re: AS5xxx encoders
Aeroengineer   6/24/2014 8:50:35 PM
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It sounds like you too have had a lot of fun in your day.  With your frequet references to astronomy, I am guessing that you work in a rather specific field.  Though it seems too that you may have some not just ground based hardware, but space based hardware to your name as well.

 

We are going to do a poll about the build area size.  I was going to pretty much use a cut down list from Seeed Studio as it seems to offer a rather extensive set of size options. 

 

http://www.seeedstudio.com/service/index.php?r=site/pcbService

 

Do you have any other size options that you do not see here that you would like to see on the list for inclusion?

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