On Dec 27 2015 8:50 PM, Jon Elson wrote: > On 12/27/2015 02:35 PM, EBo wrote: >> On Dec 27 2015 10:47 AM, Jon Elson wrote: >> Hmm, that sounds really GOOD! I think my repeatability is >> probably closer to .005" or so. Just BARELY good enough for >> anything finer than SOIC lead pitch. >> I think you can probably get much, much better than that. > > Well, this is a 15 year old machine with some significant > production time on it. It is servo-controlled, but has > high-lead ballscrews, so the resolution of the encoder > counts isn't all that high. It is a 1700 Lb machine with > NSK double-row linear ball glides for the X and Y axes.
What is the stepcount on the encoders? If they are not wicked high, you might be able to replace them with one of the AMT capacitive encoders (which have a programmable resolution). That might get you up a bit, but the wear will have to be addressed by adjusting or rebuilding most likely. > <openPnP> > >> I am curious about what they got right and wrong in your opinions. >> I >> have heard of the project, but never had a need... > > Well, I don't think they have much error recovery in it. That seems > to be a REAL key feature. Detect (either by vision of vacuum > sensors) > that you don't have a good pickup of the part, dump it and try again. > After a couple mis-picks, call for help. The discussion of error recovery for LCNC (both how to detect, and how to restart) I think would be welcome. I talked to some one awhile back about setting up a stack pointer for the g-code (mostly for debugging, but would likely aid restart). Personally, I would love to see a vision system that was integrated into both machine calibration and part placement. >>>> The entire concept of using G-code for a PnP machine is not a good >>>> idea on >>>> any level. >>> Right. It is what is there, but not a proper fit to the task. >> So what do they use? > > The only system I know well is the Philips CSM (and Yamaha > CM) machines. (Yamaha made the early Philips machines, the > hardware is very close, the software is similar.) > They have a board file, that lists the feeder #, X and Y and > rotation coords to place the part, and which head to use. > (My machine has 3 heads which are mounted on the same X-Y > positioner. They have belts that make them all rotate > together, too. They have independent Z motion by air cylinder. > > Then, there is a component (or feeder) file, that has a lot > of data on each feeder position. It tells the tape width, > by which the machine can compute the centroid of the part in > a stock feeder, the proper head rotation to pick up the part > with (so the long side of the component will be aligned with > the long alignment jaws of the head) how many times to pump > the feeder advance lever, how much vacuum indicates a good > pick-up of the part, whther mechanical alignment is needed > on this part and other stuff. > if the part is in a tray, it needs to know the size of the > tray in number of pockets for X and Y, the pitch of the X > and Y pocket spacing, the current pick-up pocket in the > tray, and the coordinate of the first pocket in the tray. I > teach that with the teach camera. > > Since the machine can pick up 3 parts at a time, it > sometimes does that to optimize head motion. Picks up 2 or > 3 parts when over the feeders, then deposits the parts when > over the board. >> >> Do you have one you could test on? Or something you can set up as a >> test bench? I would be interested in following your progress, but I >> am >> unlikely to be free to contribute. I do know of someone that >> wants/needs a custom parts machining center. This type of logic >> process >> would likely be more amenable. >> >> > Well, I really do NOT want to tear apart this perfectly > running machine to try some experiments. > Without somebody to make a big head start, it seems like it > would take a LONG time to try to implement something like this. It would take someone who either has the will to retrofit a machine for funzies, or wants to build something like the BlackToe PnP machine I linked to before. I do not have a need for a PnP machine at the moment. Maybe someone else has one with a blown controller they do not mind having it played with... ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
