Manual PnP DIY Build - Page 1
Forum section: electronics / general

author: Harvs
author_rank: Super Contributor
timestamp: December 03, 2016, 11:53:29 pm
content: This is my first attempt and a manual PnP, not quite finished but I'm not over joyed with it yet.Problems with this setup:- The rails are too heavy.- The rails aren't smooth enough. Feels like there's slight undulations in the ball bears that make getting the part into the final position difficult (0603 parts).- It's difficult to see small parts. I've been playing around with USB cameras like in other DIY builds, but so far having the camera at an angle (even at a very shallow angle holding the pen and camera together) without stereo vision makes it quite awkward. I'm not convinced about how a camera could work well with this sort of setup yet.

author: KL27x
author_rank: Super Contributor
timestamp: December 08, 2016, 08:25:08 pm
content: QuoteI have never used a PnP like yours, but here is potentially a way to get around the need to rotate the needle.Instead of rotating the needle, make a small circular tray that rotates, freely, and set that next to the component pickup area. If you need to turn a part 90/180 degrees from how you pick it up (or just straighten a part a few degrees because it went wonky out of the tape, as can often occur), you move the needle over the tray. Set down the part, manually spin tray to where the part is oriented the way you need it to be, then pick it back up. I use something like this for manually placing SOT parts - except I dump like 200 parts into it, and the bottom has ridges to flip the parts, too, so it's pretty big, like 4" across, and has a thrust ball bearing built in. It is very fast. For this purpose, you are only needing to use the very center to hold just one part; a little dias less than an inch across would be all you need. Small enough circumference, perhaps, that you can get a complete rotation with one turn of the finger along the side. A couple discs of acetal/HDPE/Plexi and a nail would do it, along with some sort of heavy base or hot snot to secure it in place.If you don't need to rotate the entire pickup tool, you obviously gain a lot of leeway into how it's built. Using a bent needle, you could potentially have same type of unobstructed view as with a hand-held manual pickup tool.BTW, nice pics. Looks great.

author: Harvs
author_rank: Super Contributor
timestamp: December 11, 2016, 02:50:34 am
content: Thanks I'll try out building a quick rotary tray and see how it goes.

author: KL27x
author_rank: Super Contributor
timestamp: December 11, 2016, 05:26:49 am
content: I think the ball bearing might not be necessary, if your tray is small enough to get complete rotation by hand. But in case you need one, what I did is just route a concentric 1/8" flat-bottom groove in the bottom plate (of HDPE), making a circle about 5/8" in diameter and about 123.5 mills deep after debur/polish, then drop in about 8 or 9 1/8" steel balls. It will spin for a good few minutes. Easily > a full rotation with a flick of a finger. All done with simple router table and a nail. But you will need a small clearance plate to get the circles that small. The hard part was the deburring.Another method that worked ok was to route the entire surface of the bottom plate away, by just a few mils, except for a small sub 3/8" diameter circle of HDPE in the center and a small rim around the outer edge. Then route away most of that outer rim so it's just a series of evenly spaced nubs. Then sand down the nubs with 400 grit to round them off and lower them by a mil. A little graphite on the center bearing area, and it spins ok. Just good enough in this case, but kinda meh, really, compared to the ball bearing. The nubs are there to prevent excessive tilt when you press on the tray, of course. 1/8" nail for the axle.Practically, I think tray maybe needs to be larger than 3" diameter (or made of heavier and higher tolerance material for a smaller tray), for such crude bearings to work, though. For the rotational inertia. Hopefully, you don't need to go there. Heck, you might come up with a better solution for a tiny tray, like a gear or banded pulley system with a separate knob.Also, thx for keeping an open mind. I think it could be good. Always thought there was too much going on with the right hand with these manual PnP machines.

author: DTJ
author_rank: Super Contributor
timestamp: December 11, 2016, 06:50:12 am
content: That's quite interesting.I've been thinking of a similar project but using a mechanical micro-manipulator for final placing of the parts so as to allow a camera or microscope to be directly over the part/pads.The manipulator also has mechanical reduction built into it to allow finer placement and reduction of hand 'shakes'.http://www.singerinstruments.com/solution/mk1/Could you add a rotary axis to your placement part in the carriage ?

author: KL27x
author_rank: Super Contributor
timestamp: December 11, 2016, 07:26:42 am
content: QuoteNot sure what exactly you mean by "placement part in the carriage." Or even if you're addressing my post about a rotating tray. I think something like this, but smaller, could be quite useful in conjunction with that micro-manipulator. I would imagine if you're using a lot of parts, you would want to continue using regular tape feeder mechanism, though. And just have a small tray as intermediate stop for orienting all your parts. My process is for batching a lot of the same part in one go.Seeing might help. Might be awhile before the vid is up. It looks like I'm in a hurry. Cuz I wanted to limit upload time without having to do any editing, lol. It's also time to cut my fingernails.https://youtu.be/SlRDVNUBYx8Orange tray is a Lyman primer flipper, BTW. When you run out of right-side-up parts, you give it a shake.I have also machined a precision cut tape vice for holding small sections of cut tape without doublestick making 10% of the parts stick. And for placing small numbers of a lot of different parts, like a one-off prototype, that might be useful. For batching lots of SOT, this is way better to me. It seems redundant to take the parts out of the tape, then orient them all over. But dealing with cut tape and botched pickups and parts that disappear when you hit the edge of the tape and advancing the tape just wastes so much time.

author: DTJ
author_rank: Super Contributor
timestamp: December 11, 2016, 08:52:17 am
content: When I hand place I do much as you do in the video except I have the PCB on a small rotate table and spin that for alignment.My comment about adding a rotary axis to the placement carriage..... I'm assuming you have a vacuum pickup in the vertical hole of the carriage part and that you move the carriage to the parts, pick a part and then move over the pcb and place the part. If you could spin / rotate the pickup then you could align the parts to the pads. Maybe that's not an issue when loading from cut strips but it is when loading from loose parts in a tray.As a side note your rails and bearings look the same as the ones I used in a cnc router I've built.

author: KL27x
author_rank: Super Contributor
timestamp: December 11, 2016, 09:21:02 am
content: Ahhh.. ok I am not OP. And his pnp pickup rotates like everyone elses' (I presume). I was suggesting this as a means of removimg that rotation system, so he could get a better view when placing a part.Idea being with a bent needle pickup, u could put the camera directly above the part or perhaps see well enough with the naked eye. A tradeoff, adding some extra work in picking up the parts, but aiding the placement and simplifying the PnP build.Quote