Paste Dispensers setup

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kja...@gmail.com

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Mar 31, 2021, 6:33:21 AM3/31/21
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Hi,
I found that OpenPnP has solder paste dispensing functionality, which could be very helpful for me. The dispensing option is presented in multiple blog posts, for example in this video.  The functionality is also mentioned in the official documentation.  Where Machine setup tree shows "Paste Dispensers" setup item.


Unfortunately, I am not able to achieve this in my setup:

Is there something another which I missed to be able to set up the solder paste dispensing on my machine?  I am running the OpenPnP version 2021.03.28.21.10.35.edd1bb2 downloaded from OpenPnP downloads site.

Thanks

stone...@gmail.com

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Mar 31, 2021, 6:45:41 AM3/31/21
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Paste dispensing has been removed from OpenPnP v2.0. It would need somebody to actively maintain it.
In that video I'm using OpenPnP v1, and this is what I keep for my dispensing jobs.
I wish I would find time to spend time on maintaining/migrating it to OpenPnP v2.0.
So if there are any volunteers: please speak up. Jason does a lot of work and contributions, and I understand that he cannot do everything.

Martin Gyurkó

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Mar 31, 2021, 7:00:13 AM3/31/21
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Can be also like my Jetter Feature request.

David Griffiths

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May 16, 2021, 9:17:42 PM5/16/21
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Hi,

I have just built my PNP machine and I would definitely like to include paste dispensing functionality.  For a single board or an old design that you want to make a few more of, it is just not economical to buy a paste screen. Or you might not want to wait for a screen.

I am not a Java programmer so I can't offer to maintain the removed feature but I would be happy to get involved in any discussing of features or functionality, or help in any other way (doco?).

On a related question, how are people generating the paste file?  I can't see a direct way of generating a paste list in Altium Designer.

Cheers DG

Thorsten Wilmer

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May 17, 2021, 12:57:31 AM5/17/21
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Hi David

I like the idea of paste dispensing, too. Do you know if one could come away with a pure mechanical solution to portion the paste?

Is it feasible to move a "nozzle" into a suppply of paste and the "touch" the location where to apply the paste?

or would this "nozzle" have to suck for some time and then blow out the paste? With surveilance of the pressure the machine could detect the contact with the paste supply.

The advantage of this setup - it doesn't need any extra hardware, just a nozzle which is allowed to touch the paste.

The disadvantage - it would be much slower. The paste may dryout.


David, Would you try out this 'mess' and report back if it's feasible for you? Does your machine have a head which can suck, blow and do nothing? Or do you have a paste dispensing Head?

I see 3 steps to implement this idea:

Have a job import for paste locations as 'parts'. If this is there a kind of 'fake-paste' feeder could serve the paste.
A checkbox for 'pick part until pressure changed' could be usefull also in other situation where Z is not properly set. 

With the existing blow off one could define the amount of paste to put. 

The pick mode would have to be changed for this 'part' to not suck for too long (kind if switch off sucking immediatly, otherwise the paste rises too far into the tubes.

The paste must have feasible consistency.

An alternative would be a 'paste feeder' on the head, which oozes out a small portion. 

Jason, do you think such 'feeder'/pickup mode/parts would fit into your concept?


Any other warnings that this is not feasible? 

I would spend time in implementing it, if it's found feasible and David would be the one who tries the code without me to mess around. Obviously I have a day job, too - so it will take a long time to implement it.

David, are you okay if it'd take three+  years?

Kind Regards
 Thorsten 



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Michael Anton

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May 17, 2021, 1:55:58 AM5/17/21
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One of the series of commercial machines I've used has this feature.  They refer to it as paste stamping.  I think they just dip a special nozzle into the paste, and then touch the board with it.  See page 63 of this manual: http://wiki.ladyada.net/_media/mdcpickandplace/lunaexpmanuale.pdf.

bert shivaan

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May 17, 2021, 5:46:15 AM5/17/21
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Seems like doing it that way (paste pin dispenser) will work without modification to openPNP. And you will just need to build the "feeder".

It seems like a great idea really, I will follow this for sure :)

To view this discussion on the web visit https://groups.google.com/d/msgid/openpnp/9dfb43c6-b345-4bcc-a739-0f0d0055f2a4n%40googlegroups.com.

Harjit Singh

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May 17, 2021, 8:16:46 AM5/17/21
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I'm not following how the paste is kept, lifted and then applied using the paste stamp system.

To view this discussion on the web visit https://groups.google.com/d/msgid/openpnp/9dfb43c6-b345-4bcc-a739-0f0d0055f2a4n%40googlegroups.com.

Juan-Antonio Søren E. Pedersen

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May 17, 2021, 9:26:10 AM5/17/21
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To be honest, I can’t see the potential in this dipping approach. The reason for using stencils is to achieve a good solder connection on tricky parts without bridges. The time it takes to use a stencil manually will be way faster then having the machine work on each pad separately. I hope you take this criticism well. 

IMO a open stencil solder print setup has potential. 



bert shivaan

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May 17, 2021, 9:34:39 AM5/17/21
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Juan I agree, just stencil it. but tere are a few use cases for me at least where it would be nice to use something else. For instance I need to prototype a board. I can get the board made and shipped from China for <$20USD. I will have it in a week. Throw in a stencil for it and the price jumps to about $60USD. That is all from shipping. I have no issue paying for the stencil, and the shipping if I am ready to build. But there are times when I simply need to test something.

Harjit, it looks like a small container of paste is kept in something that has a rotating tray on it. I imagine the tray goes through the paste then there looks to be a squeegee to smooth the paste to a known layer thickness. The reverse of an oil skimmer in a coolant tank on machines. It would work quite well in fact as long as you can keep the paste from drying out.

To view this discussion on the web visit https://groups.google.com/d/msgid/openpnp/CA%2B7Q0cPLcrn7610Gz1-1TJ1LBfU4QiVw4EuGyYYCXXuLp--7EA%40mail.gmail.com.

Michael Anton

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May 17, 2021, 5:34:30 PM5/17/21
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A pin is just dipped in the paste.  There is nothing that attempts to hold it on, other than the paste being sticky.  When the pin is pressed onto the PCB, some of the paste transfers.

Here is a video of one of the machines showing the process: https://www.youtube.com/watch?v=lu_1iTU93kQ.  There is probably a patent on this somewhere, as they tended to patent these sorts of things.  Search for Tadao Isono, as he seems to be the primary inventor of the MDC ECM machines.

Harjit Singh

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May 17, 2021, 11:24:40 PM5/17/21
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Thank you. Great video.


I thought on one of the pictures on the document the 'paste head' looked like a surface mount LED profile but with a depression in the middle. I was speculating that this was made with a soft sponge like material that is pressed into the paste and it would pick up the paste and then you could press it on the pad and it would release/transfer the paste. This would give precise pick up and deposit of the paste.

I was imagining this was similar to how the apply a pattern to a bowl: https://youtu.be/8Ug-Bl2Z0tU

Michael Anton

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May 18, 2021, 3:28:01 AM5/18/21
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I think there were different stamps available that could apply paste to multiple pads at a time, the depression is the area between two pads that doesn't get paste.

Christian Kuhtz

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May 18, 2021, 5:40:31 PM5/18/21
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Except solder past has large solids and lots of them compared with ink pigment. The properties of an absorbing sponge may be undesirable.

David Griffiths

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May 19, 2021, 8:59:16 PM5/19/21
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Thanks for the comments everyone.  I hadn't heard of the dip method.
The ones I have seen are the air pressure operated syringe and the stepper motor actuated syringe methods. Plenty of examples on YouTube. I am leaning towards the stepper motor for simplicity (no air comp required) and accuracy.

As mentioned by me and others above, there are several use cases for using a paste dispenser over a paste screen. A screen is undoubtedly the best option when doing a production run, but for a single board or two the paste dispenser is more economical and available immediately (if you have the PCBs).

Jason, any comment please?

Juan-Antonio Søren E. Pedersen

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May 19, 2021, 9:08:25 PM5/19/21
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May I ask? If populating a single board, why not use a manual approach? How many pads are on the board?

David Griffiths

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May 19, 2021, 9:35:28 PM5/19/21
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It can vary - might be doing single boards with 10-100 components. I have been using the manual approach for years but reflow gives nicer results. Yes you could apply the solder paste manually too, using a dispenser of some sort, but I have a machine for that sort of work ;-)

bert shivaan

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May 19, 2021, 10:34:15 PM5/19/21
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The dip method seems like the best overall idea to me. No need to change openPNP and simple to implement

To view this discussion on the web visit https://groups.google.com/d/msgid/openpnp/d4af7318-cd9e-4982-99bc-8a63fc91109bn%40googlegroups.com.

tony...@att.net

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May 19, 2021, 10:48:51 PM5/19/21
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Just a crazy idea, has anyone thought about inverting the problem?  Instead of having a paste dispenser on the head that applies paste to the board, mount the past dispenser (like a stepper driven syringe dispensing up rather than down) at a fixed location on the table.  Then after picking a part and doing bottom vision alignment, the part is moved to the dispenser and paste gets applied to its leads just before it is placed.  That way you're not adding anything to the head plus you don't have to worry about the paste drying out before the parts are placed.  Like I said, just a crazy idea....

Harjit Singh

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May 19, 2021, 10:49:29 PM5/19/21
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In the past, I've tried dipping a pin into paste and then pressing it to a pad and didn't get any paste transfer. 

I think there is more to it.

To view this discussion on the web visit https://groups.google.com/d/msgid/openpnp/CA%2BKNHNxmwg-pjXXrR4ckHSWEN-1JDNDD5dBJYiiVJEXAQtCSHg%40mail.gmail.com.

Jason von Nieda

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May 20, 2021, 12:07:12 AM5/20/21
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It's not a high priority for me but if someone wants to revive the feature and bring it up to the current level of the app I'm okay with that.

Last time I tried to make it far too integrated with the PnP job running code and that is what really made it hard to maintain. A rewrite should just have it's own separate job tab, job processor interface, etc.

Jason


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stone...@gmail.com

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May 20, 2021, 12:59:48 AM5/20/21
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sorry for jumping in late here. A few thoughts and comments:
- I agree that a stencil is the way to go. But if you don't have one: applying solder with a hand dispenser is the way to go.
- OpenPnP solder dispenser is something I consider if you want to run a small batch and for which for some reason you don not have a stencil (what would be mistake imho because you get them these days for a few $): so the real use case is rather narrow
- but: having it is cool, and I see other use cases to dispense other kind of things like glue (but that's probably a different discussion)

It is kind of working, has some mechanical issues (so not perfect by far). Unfortunately we did not develop it further for multiple reasons. The conclusions are
- make the mechanics better :-)
- the hole head/dispensing needs to be easily detachable for cleaning or putting the solder into a fridge. Otherwise there are issues with clogging/etc.
- it is very usable as a 'semi-automated-paste-dispenser': OpenPnP moves to the pad and lowers the nozzle, then apply solder while pressing a button. This is very effective (fast move between pads) and 'user-visual-closed-loop-control': for this we attached a second camera to look at the pads from the side
- for good dispensing control you need an Auger pump: pure pressure pumps do not work reliable enough (air pressure, pressurizing paste): with the auger pump you get good results (we used one which is used for professional dispensing), but you need to factor in solder temperature and there are different mixtures available (more, less flux, etc)
- for an automatic dispensing we would need details about the pad (geometry): just having a single coordinate point is not good enough (can work for small pads where you just apply a single 'dot'). For larger pads or GND/heat pads you need to add multiple dots

I hope this helps,
Erich

ma...@makr.zone

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May 20, 2021, 2:47:08 AM5/20/21
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Or even like a collection of "permanently inverted stencils", with each of the used footprints present. Made like one of these rubber keyboards, out of silicone or such. The part would be pressed onto its footprint "key", which would be pressed into a bath of solder paste and the paste would well up onto the pads/pins. The "key" mold could even have some concave righting ridges, so the part would be aligned at the same time. You would need veery strong vacuum, so you can then lift the part off again... can anybody top this with an even crazier idea?

  :o)

_Mark

Mike Menci

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May 20, 2021, 2:47:40 AM5/20/21
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I agree here with Eric.
I have a hand- held dispenser - see details http://wordpress.mencinger.biz/
Long time ago I was testing a way with auger and with 2 bar duster spray pressure & 5V  stepper motor 
https://www.youtube.com/watch?v=w3fm-gYnoMY
It seams it would work with OpenPnP.....
Mike

stone...@gmail.com

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May 20, 2021, 3:28:46 AM5/20/21
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Frank Herrmann has a nice video about the same Auger pump I'm using:
So yes, this works with OpenPnP.

David Griffiths

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May 20, 2021, 7:36:01 PM5/20/21
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Is the doco of how it used to work still available somewhere?

Jason von Nieda

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May 20, 2021, 7:46:49 PM5/20/21
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One of the many problems with the previous implementation is that it was very poorly documented. My fault - but that's where we are :)

Jason


To view this discussion on the web visit https://groups.google.com/d/msgid/openpnp/1839aca2-c04d-40eb-8d50-45b6c212257fn%40googlegroups.com.

stone...@gmail.com

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May 21, 2021, 12:41:47 AM5/21/21
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The important pieces are on https://github.com/openpnp/openpnp/wiki/Paste-Dispensing . Not much, but gets you started. The rest is pretty clear if you are already familiar with OpenPnP.

David Griffiths

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May 22, 2021, 9:28:08 PM5/22/21
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Ah yes.  I had seen that page.  I was hoping for screenshots and such ;-)  I might have to install OpenPNP 1.0 to check it out.

Or better yet, if someone has Paste Dispense working on OpenPNP 1.0 could you post a video please?

Juan-Antonio Søren E. Pedersen

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May 25, 2021, 7:07:31 PM5/25/21
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