yet another manual (precision) stencil printer - Page 1
Forum section: electronics / general

author: khs
author_rank: Regular Contributor
timestamp: October 09, 2017, 04:52:57 pm
content: Here is a new manual stencil printer I made to print the solder paste on my boards.It is the result of the evolution over the last years.It started with a flake board with a taped stencil on it. It was more than nothing. It worked for 1206, sometimes for 0805 but not for much smaller parts.There was always a pain due the displacement between the stencil and the pc-board due to the elasticity of the tape, because there is always a force to the stencil from the squeegee.And there was always the need to mill the flake board for double sided boards.To shorten the story: It ended with a CNC machined massive aluminum structure.Here the video (https://www.youtube.com/embed/w_UzNvtd_6I).With a force far beyond the forces caused by the squeegee the xy deviation of the pads of the stencil is now in the range of some 0.001 mmThere are two main features providing this surprisingly accuracy:The first are the two massive pc board holders with a groove place its uper side and the upper side of the pc board at the same surface, so the stencil lays on both without any mechanical stress.The second feature is the massive gripper for the stencil, mounted together with the movable pc-board holder on a 3 mm aluminum plate.And the main trick of this stencil printer: It uses the fact the stencil is very rigid in x y direction but can be bended easily up in z-direction.Edit: code removed.

author: ebclr
author_rank: Super Contributor
timestamp: October 09, 2017, 05:52:19 pm
content: A hinge would be much better than forcing the stencil to remove the board

author: khs
author_rank: Regular Contributor
timestamp: October 09, 2017, 06:05:57 pm
content: Yes, this was my first idea too. But it's not necessary.Edit: Additional: To get the same accuracy with a hinge, the precision of the hinge should be better than 0.01 mm. This makes it more expensive and more difficult to mount.Regarding the handling, the stencil feels like a spring, so the stencilisthe hinge.This is the trick. As shown, this works with very small stencils too..Take a look at the video: (https://www.youtube.com/embed/w_UzNvtd_6I).(Unfortunately I don't know how to include it)Edit: Here a screen-shot of the video

author: KL27x
author_rank: Super Contributor
timestamp: October 09, 2017, 08:44:35 pm
content: Very cool, indeed.I always wondered WHY framed stencils. Is there a special fixture people use which holds it in place? I have never figured out how to make framed stencils work any better than non-framed, and they take up a lot of space. It looks like OP found a way to make non-framed stencils work very precisely.Now I know how to stencil for QFP/QFN/SSOP, thanks. I wonder what's the best way to de-frame a framed stencil.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: October 09, 2017, 08:53:58 pm
content: That's nice and all but 470€? Besides: isn't his some kind of advertisement if you're selling it?And maybe I'm wrong but my understanding is that the PCB thickness is fixed with this design. So what about non-standard PCB thickness?

author: khs
author_rank: Regular Contributor
timestamp: October 09, 2017, 10:28:48 pm
content: Quote from: 0xdeadbeef on October 09, 2017, 08:53:58 pmYes it is an advertisement, I remember some people here in the forum was searching for an not too expensive stencil printer. I hope I violated the rules of the forum not too much.Quote from: KL27x on October 09, 2017, 08:44:35 pmIt's an advertisement for the idea too. Everyone is free to make his own stencil printer at home.Quote from: 0xdeadbeef on October 09, 2017, 08:53:58 pmManufacturing the stencil printer is not as easy as it looks like. It's more than cutting slug material and drill some holes in it. Without a mill it will be quite difficult and without a CNC mill it's really a lot or work.I made this stencil printer to use the free stencils from my board manufacturer. It looks, you are from Germany too, so you can imagine the company. Most of my boards are quite small, so there is no way to put the small stencil into a stencil printer for frames. There are some stencil printers with extra frames for small stencils, but these printers are quite expensive.Maybe there are some people with the same problem. The stencil printer is designed to save time and the costs for the framed stencils.For hobbyists the flake board and a taped stencil or a similar self made stencil printer is the better solution.Quote from: 0xdeadbeef on October 09, 2017, 08:53:58 pmMy board manufactures offers boards with 1.0 mm and 1,6 mm thickness. If you take a look at the board holder, you can see two sides. One for with 1.0 mm boards and one for 1.6 mm boards. I think it's standard.Quote from: KL27x on October 09, 2017, 08:44:35 pmI think for bigger stencils and thin stencils it's better to use a frame to lift the stencil from the pc-board.

author: Yellofriend
author_rank: Regular Contributor
timestamp: October 11, 2017, 02:19:30 pm
content: I can clearly see themanual, but not theprecision.I think the working area is too small too. If you have one or three PCBs it's OK though.

author: khs
author_rank: Regular Contributor
timestamp: October 11, 2017, 06:45:43 pm
content: Quote from: Yellofriend on October 11, 2017, 02:19:30 pmMe too. I need it in my fingers. But you may take a look at the end of the video. Then you may get a feeling about it.Quote from: Yellofriend on October 11, 2017, 02:19:30 pmThis is a frameless stencil printer for low volume small prototypes.For bigger boards/stencils a framed stencil is better. No doubt.

author: cgroen
author_rank: Unknown
timestamp: October 31, 2017, 01:09:01 pm
content: Looking really good!I just ordered one from "khs", perfect to deal with!

author: cgroen
author_rank: Unknown
timestamp: November 08, 2017, 12:42:37 pm
content: Received my stencil printer today from khs.The build quality is superb, lots of attention to detail (even a nice manual!). Communication with the seller was also perfect, printer arrived well packed and in perfect condition!Looking forward to try it out "for real"A couple of pictures of the printer:

author: khs
author_rank: Regular Contributor
timestamp: November 10, 2018, 10:32:45 am
content: Meanwhile some stencil printers have been sold worldwide (the US is ahead), we looked for ways to simplify production (and lower prices).A big step forward was the change to a laser-cut stainless steel base plate.Fortunately a company around the corner has a huge Trump laser cutter. It amazing, the size of this machine is like a small house, but the laser head moves from one end of the machine to the other in less than a second.The guy of the company told me it only takes about one minute to cut a complete base plate. One hour of the machine may be quite expensive, but under the line the costs for machining are lower and the costs of anodizing are eliminated.Thus, this was a way to reduce the price for the stencil printer significantly.But there is one minor disadvantage:It's difficult to remove traces of fingerprints from the stainless steel surface. The (new) brushed surface looks a little bit better, but is difficult to clean too. On an anodized aluminum surface you cannot see anything. It always looks clean.The picture shows the evolution of the base plate.At the top left there is the original anodized aluminum plate.Upper right, the new stainless steel plate with end to end slots to reduce the need to move the board holder from one slot to another like shown in the video (https://www.youtube.com/embed/w_UzNvtd_6Iat 0:46).Bottom left, the new brushed base plate with protective film.Bottom right, the new brushed (and carefully cleaned) base plate without protective film.

author: cgroen
author_rank: Unknown
timestamp: November 10, 2018, 11:06:31 am
content: Very good idea with the end to end slots in one side! Makes it even easier to change PCB width

author: ar__systems
author_rank: Frequent Contributor
timestamp: November 10, 2018, 05:12:53 pm
content: Obviously it works, but then again, for such tiny boards pretty anything works.

author: 1276-2449-1-ND
author_rank: Regular Contributor
timestamp: November 30, 2018, 01:21:06 pm
content: That's very similar to the one I made, except it's made out of 3mm and 6mm MDF and PCB scraps. It was meant to be temporary but works so well that there's no need to replace it (other than it looks kinda funny).The MDF is laser cut, and the PCB parts are used to keep the stencil at the same height as the PCB being pasted. They were designed in Eagle and added to a PCB order.Hard to see in this picture, but the stencil is mylar that is cut with a cheap hobby vinyl cutter. This too was meant to be temporary but works well enough.Repeatability is excellent for everything down to 0603, and setup time is under a minute.

author: jc101
author_rank: Frequent Contributor
timestamp: December 01, 2018, 04:59:57 pm
content: You can get a pretty neat stencil alignment jig for €15 from Eurocircuits called ec-stencil-fix, just made from bits of PCB. If you use their alignment specs then it's pretty much plug and play (https://www.eurocircuits.com/ec-registration-system/).Works very well for prototypes and the like, especially if the boards and stencil are ordered from them, just tick a box when ordering and they sort it all out.

author: SMTech
author_rank: Frequent Contributor
timestamp: December 01, 2018, 06:13:29 pm
content: Quote from: jc101 on December 01, 2018, 04:59:57 pmI've never used it but yes, if everyone who made sh**y foil stencils introduced this very cheap solution to go alongside them they would be much better to use. Its also a great idea in general to keep hold ofrouted out tooling strip/panel borders that have right angles in, very handy for holding things in place.