[time-nuts] pick and place problems/design
albertson.chris at gmail.com
Sun Jun 26 21:52:24 EDT 2016
Yes, I found that machine. There is work on going to get openPNP software
to work on the liteplacer. So that machine will soon have all the
capabilities of every other machine using openPNP.
What has changed recently is that vision is so cheap and easy. You can
buy a ready to use USB connected hi-def camera for under $10 and some have
interchangeable lenses with M7 threads and you buy quality M7 lenses with
metal housings for about $20. OpenCV makes vision software not so hard to
do as it was.
But a cheap person like me says "I have a milling machine" so I don't need
to buy yet another X,Y,Z positioning machine. I put that on the end of a
long list of projects I'll never get to.
On Sat, Jun 25, 2016 at 10:06 AM, John Swenson <johnswenson1 at comcast.net>
> There is a "hobbY" pick and placer called LitePlacer that meets a lot of
> your criteria.
> It works on cut strips, not reals, it will handle random placed parts on
> the table top, but so far I don't think it automatically figures out what
> they are. But you can put a bunch of one part in one area, another bunch of
> parts in a different area etc. But for most parts you just leave them in
> the cut strips taped to the table.
> The cameras read the holes in the tape and use that to figure out where
> the parts are. The first one it grabs from a tape it takes it over to an
> upwards facing camera to make sure it gets rotation correct and knows
> exactly where the pins are.
> It even has the white melamine table.
> I haven't bought one yet, but I'm strongly considering it.
> John S.
> On 6/24/2016 10:11 PM, Chris Albertson wrote:
>> The ideal hobby use pick and place machine would be very different
>> from a commercial machine. Lets say I want one board made. What I
>> want to minimize is my time. With a conventional machine by FAR most
>> of my time is spent setting the machine up. In fact setup is so slow
>> that for smaller PCBs I could do it with tweezers in a fifth of the
>> time needed to set up the machine.
>> So a hobby machine must be designed such that you could get it going
>> in nearly zero time. In the ideal case you drop the parts all mixed
>> up, (but right side up) in a small tray. They are mixed and in random
>> orientation. then you give the machine your PCB design file (not a
>> special pick and place file) and then a vision system IDs the parts.
>> Today vision is dirt cheap.
>> But the 3D printer needs one more degree of freedom. It must be able
>> to rotate the part (or the PCB) as it is unlikely the part on the tape
>> or tray only needs translation to the PCB, likely ration is required
>> in almost all cases.
>> I think a hobby machine would only be successful if it could reduce
>> the setup time to nearly zero and for that it would need a really good
>> vision system that could hunt down randomly placed parts. It would
>> have to work pretty much like you or I would do the job manually. But
>> we have software like openCV and good "board cams" with M7
>> interchangeable lenses for $35. A vision system actually saves a ton
>> of money because the machine need not be so precise as vision closes a
>> feedback loop.
>> Also how many hobbyists are going to have reels of parts? I might buy
>> some parts by the dozen but most no more than about 4 or 6 at a time.
>> I don't want a large machine. It should have a working surface, a
>> white melamine table about 12 inches square and I place the PCB to be
>> stuffed and all the parts on the same foot square table at any random
>> location then press the "go" button. The camera scans the table.
>> This kind of machine would be horrible for production work but a one
>> foot cube machine that required zero setup is what most of us want.
>> Going a little farther. I'd like this SAME machine to actually make
>> the PCB too. A 3D printer could route the copper and drill holes and
>> print the solder resist plastic too.
>> On Fri, Jun 24, 2016 at 8:56 PM, Attila Kinali <attila at kinali.ch> wrote:
>>> On Fri, 24 Jun 2016 13:59:58 -0500
>>> "Graham / KE9H" <ke9h.graham at gmail.com> wrote:
>>> Lots of problems to be solved...
>>> Most of these problems are easy:
>>> How do you take loose parts or cut tape or tape reels
>>> You don't. No loose parts with any kind of pick&place machine.
>>> As for cut tape, these can be taped on an empty reel to make
>>> them compatible. Everything has to be in a tray, reel or similar.
>>> and get the right
>>>> part out, and into the chuck, oriented in the right direction?
>>> Orientation is defined by the reel/tray the parts come in.
>>> This is also documented in the datasheet, usually.
>>> How many different kinds of parts, sizes, shapes, pin counts, IC
>>>> footprints, can you handle at once?
>>> As many as there is space around the machine :-)
>>> How do you know it is the correct part?
>>> You put it manually in the right feeder and double check that it
>>> fits the programming.
>>> How do you know where the "+" end, or "pin 1" is?
>>> This comes with the orientation of the part in the reel/tray.
>>> How do you know that there actually is a part in the chuck?
>>> Your trays are guaranteed to be non-empty by manually loading them.
>>> How do you know the part in the chuck is oriented the way you expected
>>> The manufacturer guarantees that the reels/trays are loaded correctly.
>>> How do you know where the footprint on the circuit board is located? (to
>>>> few thousandths.)
>>> This is provided by the pick&place file. Usually its 3-5 digits after the
>>> decimal point, when using mm. But as I wrote before, you don't have to
>>> place part hyper exact. Being within 0.1-0.3 of the pitch of the part
>>> is usually enough. Surface tension does the rest.
>>> How do you know the part left the chuck and ended up where you intended
>>>> to be?
>>> You dont :-)
>>> The way how this is checked is either a pre-solder and/or post-solder
>>> inspection. This is either done manualy or using a camera system where
>>> computer compares the PCB to the picture of a known-good PCB.
>>> As this is ment for a small volume and hobbyist system, doing the visual
>>> inspection manualy is good enough and more than fast enough.
>>> Attila Kinali
>>> Malek's Law:
>>> Any simple idea will be worded in the most complicated way.
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