Towards a tiny pick-and-place vacuum head

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I try to have a few different projects on the go at any time — a big, long term project (like the Arducorder), a shorter-term fun project (like the Open Source CT scanner), and a bunch of smaller weekend or few-weekend project (like the open mini spectrometer). Having a few projects of varying time scales allows you to switch projects when you’re burned out on one, and make more headway on creative pursuits when you’re at the mercy of inspiration. A project I’ve had on the backburner for some time is building a small, open source pick-and-place machine. In the past year or so there’s been a lot of interest in this space, and different groups (e.g. openpnp, firepick) have been working on designs to help folks assemble boards quickly and inexpensively. I thought I’d take a moment to show my progress on a pick-and-place vacuum head, given that I haven’t found a great deal of consolidated information on the topic.

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I confess that I’ve been thinking /very/ big and intractable on my pick-and-place project, so much so that it’s been never ending. There’s been a half-built machine in my workshop for several years that slowly sees progress every few months, largely because the project is too big — I have been trying, as a hobby, to make a factory in a single 50cm cubed machine. I designed the machine with an automatic tool changer so that it could pick up different heads, the idea being that you could pick up a mill head to mill out a circuit board, pick up a solder paste dispenser to apply paste, then pick up a pick-and-place head to populate the parts, and finally pick up a 3D printing extruder to create an enclosure for the board, all assembled by the same machine. This is of course fantastically challenging, and likely way too large a project for a single person, and I’ve only progressed as far as designing and building the tool changing head and x/y/z cartesian robot, but haven’t returned to the project to build any of the tool heads, like a vacuum head for picking-and-placing components and populating circuit boards.

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Putting together a small, working pick-and-place machine has jumped closer to the front of my queue lately. One of the most challenging things to accept as I’ve been getting a little older is that there’s only one of me, and only so many hours in the day — especially when trying to have a work/life balance. I have an interesting sensing project in my queue, but populating the board requires populating about 300 components, many 0402, extremely precisely. More than that, I’ve been working to put together a few extra Arducorders, and each Arducorder takes me 4 full days to put together — the motherboard alone tends to take about 8 hours, as it’s double-sided, full of fine pitch components, and one side tends to have to be hand soldered. All this means the process has been going very slowly, much slower than I’d like.

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I feel like inexpensive open source pick-and-place vacuum heads are in a similar place to where open source 3D printer extruders were about a decade ago. In the early days of the RepRap 3D printer project, many folks were trying to figure out exactly how one could design an inexpensive FDM extruder, and there were a lot of different designs from melting pots that were fed with shredded scraps of plastic bottles, to pinch-wheel designs that are similar to the extruders commonly used on 3D printers today. Many folks have posted great prototype designs for inexpensive pick-and-place vacuum heads, but I haven’t seen many that have been demonstrated to reliably pick up parts larger than 0603 resistors, or that have been demonstrated to reliably rotate parts into their desired orientations.

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This isn’t to say that there hasn’t been a lot of fantastic work in this space. Frequently someone will post an absolutely gorgeous pick-and-place design that they’ve put together (this one by Daniel Amesberger comes to mind), but they’re usually both expensive and intended for professional use. It’d be nice to have an easy to assemble system that was around a few hundred dollars, and that sped up the process a good deal without being intended for high throughput.

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Recently I saw a post on Hackaday describing a clever prototype pick-and-place head that uses a tiny piezoelectric vacuum pump (or “microblower“) from Murata. This design is attractive — at about 20x20x2mm, the pump is very small, and could be contained on the pick-and-place head itself, simplifying the design, and removing the need for an external vacuum pump, which are often fairly large and noisy.

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The microblower is designed to blow air rather than act like a vacuum, and so to use it as a small vacuum pump the intake ports have to be covered. I put together a small acrylic sandwich with the microblower in the middle, the blower output on one side, and a port for the microblower input on the bottom. I also found a small NEMA14 stepper motor with a hollow shaft to use as a rotation mechanism for the part. This is attractive, as the mechanical design can be kept quite simple — a microblower on one side of the motor, and a nozzle on the other to interface with the part.

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The pick-up end couples the business end of a solder paste syringe and detachable luer-lock dispensing tip (from Zeph) to the 5mm stepper motor shaft using a set of press-fit rings that I laser cut out of acrylic.

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The bottom of the Murata microblower is shown above, which is where the large inlet draws in air. The tiny hole under the inlet is about 2.2mm in diameter, which is the same size as the drill in the hollow shaft stepper. I happened to have some polystyrene tube that was nearly press fit, and just required a little sanding on either end to couple the microblower inlet with the stepper shaft. Also seen here is the microblower driver board from the Murata evaluation kit.

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The top of the microblower, shown above, is also press-fit coupled to the top of the acrylic case. I added in some sealing silicone to this aperture (as well as the wire harness aperture) after taking this picture, to ensure the highest vacuum, and best chance of success.

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An arducorder, for size. Although a prototype, and the long coupling tube between the microblower and motor could clearly be shrunk up quite a bit to reduce the overall height to just over the height of the NEMA14 stepper.

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How well did it do? Like other’s designs I’ve seen, it had little issue picking up 0603s with ease, but the real measure is how well it does with other components. Unfortunately about the heaviest I could pick up, even with some suction cups attached, was this ~4x4mm magnetometer — and even then, it was right on the edge of the pick-up strength. It could be picked up flat from the table, but not from within the tape.

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And so it appears that a microblower, while a very exciting component, is likely only useful for picking up extremely small components when used as a vacuum pump for pick-and-place heads.

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Some time ago I’d also tried this experiment using a KPV14A-6V micro vacuum pump from Clark, again without much luck. In light of this, it looks like my hope of designing a tiny, inexpensive, and completely self-contained pick-and-place vacuum head likely is still a ways off, but there are plenty of other options for vacuum pumps, if we’re willing to relax the completely self-contained constraint. Grant Trebbin has reported a good deal of success with the Sparkfun vacuum pump for his manual pick-and-place, and mentioned that he’s able to pick up around 15g with appropriately sized suction cups — more than enough for most components. So let’s give that one a try.

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I put together a quick adapter to go from the 1/4 ID tubing from the Sparkfun vacuum pump to the ~2mm diameter bore on the stepper shaft. This larger diameter tubing is far too stiff to move around, so eventually it’ll have to be sized down to something much smaller and more flexible, and the adapter mount will have to better allow for up to 180 degrees of rotation — but this make-shift coupler is good enough for a first test.

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The Sparkfun vacuum pump is capable of much more lift than the microblower, and was able to lift nearly every part that I gave it. Here a 100-pin TQFP is lifted with ease, even with the motor running at 8.5V (from 12V) to reduce the noise a bit.

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And here, the pump similarly has little issue picking up an entire bluetooth module. Definitely very promising!

I hope this has helped some folks who are also thinking of putting together their own pick-and-place vacuum heads. The microblower is a beautiful part, and were it to have enough suction, mounting it atop the stepper would make for a very small, self-contained, inexpensive vacuum head — but as it is, it looks like it’s only appropriate for picking up small passives. The Sparkfun vacuum pump definitely has more than enough suction for most of the parts that I’m likely to encounter, and after figuring out a better coupler between the vacuum pump and the stepper shaft that will better allow for rotation, it’s likely to perform quite well. My one reservation is that the luer-lock heads appear to attach slightly off-center, so that when a part rotates, it translates a little while rotating. I’m sure with a little alignment it’ll work out famously.

Thanks for reading!

15 thoughts on “Towards a tiny pick-and-place vacuum head

  1. If you’re going through all this work to make yet another DIY pick and place machine, then I’ve failed, either at communicating what our design has to offer, or in the mechanical design that people are hesitant to adopt. What I can tell you is that we do have a working pick and place head that reliably picks up any size part.. And that I’ve personally tried several iterations of the MicroBlower design already, and only recommend it for smaller parts. I’ve done several PnP retrofits and DIY designs over the years (5 or 6 by my last tally) and I can say safely that when you go down that road, you have time for little else. That’s why I started my project. So that smart guys like yourself can do what you do best.

    Anyway good luck, and if you ever need advice or want to bounce ideas around, come visit our firepick dev google group, we’ve built a great community that discusses all things PnP.

    • Hi Neil,

      Thanks for your note. I know that during the Hackaday Prize I followed your Firepick Delta project’s progress with great anticipation, and was hoping to put one together after the competition — but due to the lack of updates, I’ve continued work on my own partially-built pick-and-place machine.

      I agree with your comment that the firepick project would benefit from better communication, and if you have recently designed a working, capable, reliable, and inexpensive pick-and-place head, I’d love to have a link to the source, as well as some pictures, or a video of it in use. The last video I have been able to find of the firepick was the HDP Quarterfinals video, and there were only a few seconds of picking-and-placing in the five minute video, and only of a single 0603 resistor. I’ve visited the firepick website a few times in the half a year since then, and while the site lists impressive specifications for the machine ($300 pick and pace, components down to 0402, vision, automatic tool changing head with 4 heads, etc.), I have been unable to find any pictures or videos of the machine populating a board, pictures or details of the vacuum head assembly, or even pictures of a complete machine, except for a few of the older partially assembled promotional photos on the website gallery, coupled with a lot of renders. I’ve tried searching the Github repository and the mailing list for documentation, source, or build instructions, but if these files or information are in there, they are not easy for me to find.

      In the early days of the Reprap 3D printer project, the project maintained two blogs — one for official announcements and demonstrations from the core team, and another for many of the builders and adopters who were beginning to assemble machines and design new tool heads to post their pictures and designs on as a summary, with links to further information and source for interested folks. Maybe a similar approach might help your project — if you have a working $300 open source pick-and-place machine (or working subassemblies, like a working vacuum head), I’d love to see an easily accessible (and easy to find) resource that demonstrates it successfully working through videos, documents the build with pictures, and has links to standard source files (STL, DXF/AI, BOMs) that interested folks can make use of to start putting together their own machine.

      best wishes, and best of luck with your project!

      • Documentation and coverage of our project has been pretty sporadic since we got kicked out of the HaD Prize competition, but we’ve been hard at work ever since. If you look at our developers mailing list, you’ll see lots of stuff going on day-to-day, but unfortunately I’ve not had the time to post any of it to the hackaday page or our website. Our project is absolutely massive, we don’t just have one little board to document, or one piece of software (or just one OS for that matter). All of that complexity adds to the development time exponentially. I still feel this is the best approach, even though it’s taken us quite a while to get this far. There are others (including liteplacer who commented below) who are up and running with their DIY machines, but most of them, including liteplacer only run on Windows, or don’t have a fully modular feeder system, not to mention other details often overlooked. Anyway, I don’t mean to ramble, but we’ll get there, and I do apologize that our documentation and website are lacking info at this point. That should change soon, we’re shipping beta test kits in the next few weeks to about 100 developers on our list, and will be doing a kickstarter after that. Since our hardware is now finalized, our next big effort is to get the documentation caught up and get the software ready to be used by our beta testers.

  2. There were a few pick and Place machines in the Hackaday Prize, mine included. My machine is finished (ver 1.0 🙂 ). You can see the machine at http://www.liteplacer.com. The mechanical design files will be released soon, once I get the changes from last prototype added. Software is already on GitHub. Have a look!

  3. > I also didn’t happen to notice how the vacuum tubing is mounted to the top of the bore
    That is because I changed the (complex) design from the beta model and removed the page, haven’t had time to rewrite it to K.I.S.S.: Now, I have bore inner diameter == tube outer diameter. The plastic tube is slippery enough to turn inside the bore and sticky enough to create a tight enough seal. Even hot glue would work, we only need 360deg of turn, half a round in each direction.

    > The nylon threaded luer-lock mount looks like a very good find, too — can I ask where you source them from?

    http://www.coleparmer.com/Category/Luer_Fittings/62221
    http://adhesivedispensers.co.uk/luer.htm

    Btw: Your captha is borderline impossible to solve, and if I see it wrong, it erases the comment/reply. Arrgh!
    https://www.google.com/recaptcha/intro/index.html

    • Thanks for the links! That’s an interesting approach for the slip mount, was your complicated approach some kind of barbed slip nut or ball joint before? (Those are what I’ve been looking at the past few days).

      And thanks for letting me know about the captcha — I had no idea it was so challenging to solve, but given the ratio of blog registerers to posts since I switched, it’s likely a lot of folks are having that issue. I’ve switched to recaptcha — much easier!

    • For the swivel, I’ve been browsing McMaster and come across barbed swivel mounts (e.g. http://www.mcmaster.com/#standard-barbed-tube-fittings/=vsk0va ), and these look interesting and like they might be a possible solution. But I’ve never used one, and my suspicion is that the swivel is only movable when the nut is loose, which wouldn’t be terribly useful. But if it’s swivelable while the nut is tight, then making a mount out of one shouldn’t be too bad.

  4. Nothing new but just to re-enforce the opinions of others:

    . I am interested in a PnP machine and have been watching FirePick but Peter is dead right you guys need a video of a whole PCB being placed including setup and preferably it being reflowed. This is a minimum before I part with any cash.

    . LitePlacer also looks good but to be honest the placement at the end of your video looked a little off..

    . The Captcha is horrible here. Not only is it unreadable, but it also deletes your message !! Third time lucky.

  5. I’ve noticed the one-way valves on vacuum pumps aren’t perfect, blowing a small amount of air back out the inlet with each stroke, which limits the pick-up power. I fixed mine by adding a glass jar between the pump and head to absorb some of the pressure change – I know you’re going for small size here, but maybe if the space between the microblower and stepper motor was filled with a hollow block the suction would be improved?

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