AVR Freaks

+1

You should be aware that it's likely that you'll need vision. The components won't be sitting in their tapes in the exact same place, there's always a bit of wriggle room in the compartments, and even the components themselves aren't guaranteed to be the exact same size (take a look at a datasheet, there's almost always min and max values for dimensions - like anything manufactured today there's always tolerance). The small discrepancy in component size won't be so much of an issue (but it's certainly worth being aware of!) but the wriggle room in the tape will likely cause you a problem if you don't account for it.

For example if you simply use the same set of co-ordinates to pick the components from the tape, then when you come to place them, they could be slightly off in X, Y or θ (theta). This is where the vision comes in, either after you pick or before you place you're going to have to look at where the component is on the vacuum tip and adjust the head's position to align the component to where it should be. This is what professional pick-n-place systems will do. 

Now, depending on what type of components you're going to be placing with this thing, this may or may not be an issue, for example if you're talking not smaller than 0805s or even 0603s for discretes, and typically SOICs for ICs, then you can get away with it. Sure the components will look slightly shifted and the placement won't be perfect, but you should be okay. If you start talking about smaller compoents, and leadless packages such as QFN and BGA, then you will 100% need to do something about it, and it's likely to include vision. 

I'd suggest you take a look at Essemtec's Expert for inspiration as I'd imagine it's relatively close to what you want to do. 

As far as storage goes, I'd recommend doing what sparrow2 suggested and do a lot of the work on your laptop. Including storage - you can simply store stuff in text files if needs be, or a prefered option would be to use pick-n-place files as already suggested by Kartman :) (I know you said you don't have the 'appropriate software' - which does beg the question, how exactly are you designing the PCBs? Or are you not designing them and are actually planning on using this system to assemble boards for customers? In which case, ask them for the pick n place files! :D)

And finally, good luck with your project! 

The quickest and easiest thing I can think of is to use one of your micro's UARTs, along with a UART to USB converter IC such as an FTDI FT232RL and connect it straight to a USB port of your computer and access it as a serial port. Then if you use .NET to create your UI (I'm assuming you're going to be making some kind of PC based UI?) then the built in SerialPort class can help you achieve this. (Whatever technology you use for creating your UI, it's almost guaranteed to provide you with a means of accessing a serial port, the use of .NET is just an example I went with as it involves many different programming languages such as C# and VB for example.)

Ah yes, I'm familiar with ExpressPCB - never used them myself though. If they don't offer assembly services, then it might be worth contacting them to see if they can provide you with pick and place files for your designs. Of course if they do offer assembly services then the chances are that they'll fob you off and tell you that you'll have to get them to assemble your boards.

Also FYI, gerber files and pick n place files aren't actually the same thing - gerber data is specifically for the manufacture of the bare PCB itself, and while it can be used to assist in SMT processes, pick and place files (typically .PKP) provide information on where to place each component. In truth though you won't be able to use .pkp files on their own as they don't usually contain any information relating to where to pick the components from so you'd still need to get this information yourself, but you could maybe follow the format of .pkp. Typically pick-n-place machines establish where to pick the components from independently of the .pkp as the location of the component can be in any on of the feeder slots. 

So, it may well be easier to ignore pick-n-place files and implement your own way, but I'd certainly at least take a look at a .pkp for inspiration if nothing more! I can put together a quick and simple example of a .pkp if you like...

Lots of great info above.

Two additional thoughts:

I definitely like splitting the task into two parts, picking up and "centering" a component, and once that is done then placing the component.

I like the concept of feeding a table of components, and their PCB locations, via data, into the P7P machine, and not manually teaching the machine to lace each part.

That said, if you did want to have a manual "teach" mode, I'd consider using a joy-stick to move the head and position the given part, not moving the motors manually.

My old flight sim joy sticks hade multiple push buttons, coolie hats, and a couple of sliders, so easy to have some speed adjustment for rapidly moving the arm, and then having a fine adjustment speed.

Doing 50 PCB's, perhaps from different manufacturers, and perhaps having a second or third batch to do?

I suspect you will still need some sort of auto-alignment feature for both the X and the Y axis, as well as a rotational adjustment; all to compensate for how the board house trimmed the edges on the PCB.

Drawing two "X" marks on the PCB in essentially diagonal corners lets one both determine two known points, and also adjust for rotation.

You could manually move the arm there with a whisker pointer, or a fine beamed laser diode, or use a visual input from a camera, (significantly easier on the operator, but significantly hard to integrate into the software).

One of my PCB layout programs has a fancy bull's eye which, I think, is intended for this purpose.

Good luck with your project, please keep us updated!

JC