Inaccurate placement

[roberto_imai]

I just got my pcb in the mail today and started playing with component placement.
I have the machine calibrated, the tapes are setup and everything looks good.
The machine picks up the components from tape dead center, but when it goes to place it on the PCB, it just lands really far. Like 1 or 2 mm off.
If I use the camera and ask for measured location of the component, the camera zeros in to the component and shows me a correct position.
I already tried re-measure button, where it goes and finds the fiducials and calculates the positions, but that doesn't work.
Again, the camera does find the calculated position correctly and it does pick up the component from tape correctly.
It just lands it way off and the component is a 0603 capacitor... It's not even 0402 component.
What could be causing this? Do you think the machine is moving too fast? How can I make it more precise even at a cost of travel time???
My goal is to be able to place 0402 components reliably.

[mawa]

Have you adjusted the needle/nozzle to camera offset?

There are some methods described in this forum. The problem could be that the down camera does not exactly look vertically down (at least the one I have). You can see this by centering the camera center over a hole. If you only see one wall the camera is slightly tilted. Unfortunately the camera chip inside the tube is to blame. My chip even moves when I wiggle the USB cable.

Therefore the view vector is tilted and the point you assume to be the right position depends on the distance of the camera from the surface.

What can you do?

a) bring all areas where you intend to use the down camera from positioning to the same level +/- 1 mm. Tapes, PCB, visual homing mark etc.
b) fine tweak the X and Y nozzle to camera offset values by using a nozzle with a small diameter center the camera on a very small circle e.g. a fiducial and letting the nozzle probe down.
c) check your slew if a) and b) did not help.
d) finally check that the part is also picked up exactly in its center. The nozzle can suck a 0603 even if part of the nozzle is outside the parts case.

[JuKu]

This will be interesting to find out what is off. You say: "The machine picks up the components from tape dead center" which means that nozzle to cam and nozzle calibration are good. You also say that "If I use the camera and ask for measured location of the component, the camera zeros in to the component and shows me a correct position." which tells that the board measurement is also good. In other words, all the parts are working as they should, yet the results are way off.

Off hand, I have no idea. Things that might have something to do with this:
- Have you tried slower settings and slack compensation?
- Are your tapes and pcb roughly at same height (no standoffs or such)?
- Do check that the wheels are clean, nothing is loose, machine moves smoothly without strange noises and other mechanical issues
- There are buttons labeled "Probe down" and "Probe (n.c.)". These take the nozzle tot he spot shown in camera, with and without nozzle calibration correction applied. Do these work?

[roberto_imai]

Ok, I was finally able to get to this today.
Here is what I found out.
It was a combination of loose nozzle adapter and bad measurements of cam to nozzle distances.
Overall, I'm pretty happy with 0402 placements after fine adjustments.
I didn't have to move none after I dialed in the cam/nozzle distance.
The biggest problem I have now is for tape components that are not passive.
Because passive components have a very tight placement in the tape, the nozzle picks them up very accurately.
On the other hand, ICs on tapes are loose, so when the nozzle pick them up, there is a big play that can affect the placement, especially if the IC gets rotated.
I had to manually adjust almost all of them, which is very unproductive.
What is the best technique to get ICs on tape placed correctly?