Hello, I have a source for membrame pumps. These are used in professional printing press / publisher. These are very suitable for providing air to ....... (your paste dispencer ??) The problem would be how to turn the airflow off !? (A valve ???) And they work on 220 VAC. grtz Simon --- Roman Black wrote: > Alexandre Guimarces wrote: > > THANKS Alexandre for the excellent info you > provided, > and sorry I didn't reply sooner but I have been busy > in the workshop. :o) > > > > it has good power, high speed and 1/28th mm > > > resolution is fine for 0805 SMD stuff. > > > > How about the repeatability and backslash ? > Those are the problems I > > have seem on the printer mechanisms I used. The > printing head support was > > too loose without the belts being too tight. > > > It depends on the quality of the printer mechanism. > I have some 15" NEC Pinwriters from mid 80's that > are VERY rugged, full steel chassis and 2 large > steel > rails. Some of the smaller printers are not good at > all. One of my 15" printer chassis cost me $5 and > has a 25mm hardened rail with PB bearings! Don't > ignore good old printers. > > I just chose a chassis to make a CNC PAP (PNP?) > machine, > it's a 15" unit with steel cable drive from motor > to carriage, even less backlash than a belt. Even my > belt chassis get a lot less than 0.1mm backlash, the > cable driven unit will be good for 0.05mm > repeatability. > How accurate do you need for 0805 placement? I'm > sure > even 0.1mm will be ok. > > > Do you need just one machine ? I plan to have > a solution that can scale > > up with my production. That is another reason to > go for comercial new parts. > > Sure, but you are obviously doing the volumes to > need > good machinery. I'm still sticking parts on boards > with tweezers and a magnifying glass! The thing i'm > making will do 300mm x 120mm, perfect for pick and > place on small boards. > > > Loctite has some nice solutions in that area > and you can even use 454 > > gel cyanoacrilate !! It works great !! The only > problem is that you need a > > good dispenser for it. Dispensing paste is not > that critical, specially if > > you use water at the end of the system. Water does > not compress so it is > > easier to control the time and pressure as the > syringe goes down. You just > > have to control the time and pressure and it is > quite repeatable. > > OK, you've convinced me to drop the glue idea and > just dispense solder paste direct to the board. :o) > How do you mix the water with the paste, what sort > of applicator nozzle, pump etc are you using?? I > thought > of standard size rubber hose in a simple peristaltic > pump turned by a stepper motor. That should dispense > dots and also lines of paste quite well. > > > Wave solder is ok if you glue and have a very > controlled fluxing and > > cleaning of the board but I would never trust > dipping a critical board ! You > > will stress every component over their specs ! > > Not totally true, but i'm going to trust you and > stick to the paste and oven method for now as you > suggested. You helped me so much before with my > manual toaster oven system. :o) > > > > If the production is too big I would go for > the comercial machinery or > > let a factory do it for you. It may not be worth > the risc. My production > > levels do not allow sending them out and I cannot > handle it without some > > automation, that is the reason I went to the house > made solution. It is > > dependable and repeatable but not too fast or > energy efficient. > > My oven system is working well, thanks in part > to your temperature charts etc. I'm approaching > that point where it's a pain to tweezer tiny parts > by hand, and a machine that does the SMD placement > will be a big help. But I don't need high speeds > or quantities. > > > > > I have a suggestion here. Get the parts loose, > > > not on rolls. Sprinkle them on a white tray, > > > then use a cheap video camera into the PC and > > > just get the picker to identify the part > > > orientation and pick it up. You only need a > video > > > still capture board, > > > > Hey, that is a really cool idea ! The main > problem would be to correlate > > the real position of the components to the > distorted camera view and to > > solve the problem of refilling the trays and > making sure that you do not > > have one component over the other or on the back > side when using SOT23 > > transistors ! It is pretty hard to get the > components out of the rolls and > > not flip half of them on their back side. I am > really not sure what would be > > easier, a roll feeding system or the camera. > > You don't have to buy on the roll. In 1k > quantities you can often choose loose or rolled. > I see the only real work is pouring the parts > on a tray, making sure they are right side up. > Parallex error shouldn't be too much problem if > the camera is 40cm or so from the tray. I can live > with some manual parts fiddling, anything is much > better than placing with hand held tweezers. :o) > > > > Believe me on this one :-) It is easier with > the vaccum tweezer. You > > just turn the vaccum on and them rotate the > component to whatever position > > you need. With the mechanical tweezer you have to > get the right force and > > will have to rotate the head 2 times to get the > job done. The first time to > > grab the component and the second to put it at the > right orientation at the > > board. > > Ok, you've sold me on the vacuum tweezer. Are tips > commonly available? What type of vacuum pump are > you using? I have a vac solenoid from a bike fuel > injection system, a high speed one. Any suggestions > on how to set it up? Does it ever drop parts? > > > > Gluing is also safer for > > > double sided boards?? > > > > I also thought that way and got glue from > loctite for the components on > > the bottom of the board. I still have the glue on > the fridge and never used > > it after the first day ! The only components that > insist on falling once in > > a while are the AVX surge supressors. They are > pretty dense and fall once in > > a while. If you get the right solder paste the > surface tension is more than > > enough to hold the components on the bottom side. > > Good information, thank you again. > Any help you can provide on the CNC PNP stuff > will be very much appreciated. :o) > -Roman > > -- > http://www.piclist.com hint: The PICList is archived > three different > ways. See http://www.piclist.com/#archives for > details. > > > > __________________________________________________ Do You Yahoo!? Everything you'll ever need on one web page from News and Sport to Email and Music Charts http://uk.my.yahoo.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.