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Quad IVc Part rejection issue

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Quad IVc Part rejection issue | 15 August, 2012

Hello all. I'm having a bit of an issue with my IVc that's driving me insane. On occasion when placing a part, the machine will consistently reject the part 3 times before adjusting and then pick and place the part with no issues. I've done everything and anything I can think of. Extents are all ok. I get consistent function30 readings. Align data is consistent. It seems as though the machine is getting hung up on certain pickups even though a similar part, lets say a 0805, on a different pickup picks and places fine. If i set align date to 0, it will place the part, but it will also attempt to place it even if it miss picks, so that's not a viable solution. Any insight would be greatly appreciated!

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Quad IVc Part rejection issue | 16 August, 2012

Here are a couple of things to look at.

1. Watch the machine run....and if it misses a part....make sure it doesnt blow out the next part being presented. Sometimes the air pressure is too high and the vacuum verify will blow the part out of the pocket if it misses one. You can turn off the vacuum verify by doing shift/switch verify. 2. Open up your quad align tolerances. 3. Change the z-rod. It could be that the spring is worn out and it is contracting when the vacuum turns on and then scans under the part. 4. Make sure the nozzle is mounting correctly. Most times when it dumps 3 parts and then runs correctly it is after a nozzle change. If this is true....the nozzle is not mounting on the z-rod correctly. You need to reteach the nozzle positions and/or z co-ordinate for the changers.

Good Luck

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Quad IVc Part rejection issue | 16 August, 2012

Thank you for your reply Bob.

1. It appears the machine is picking the part up, hovering over the board and rejecting it. So it's not blowing the parts out of the pocket. Turning the vv off still results in the same issue.

2. All the tolerances are at maximum of 30

3. The z-rod on the machine did appear to be a bit tired, i swapped it for a new part, yet still seems to be rejecting parts.

4. the nozzles do appear to be seated fully. I thought that too as it seems to place after re-calibrating, but it's not always directly after a nozzle change. sometime it will be placing parts no problem then decide to have this hiccup.

I've noticed as well if i skip the pickup that is giving the issue, it will start happening on another pickup that was previously picking and placing fine. it's very strange and is driving me bonkers from all the waste of parts this is causing.

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Quad IVc Part rejection issue | 16 August, 2012

Sounds to me like a dirty quad-align. If you have cleaned the lens and have the same results then you may have dirt on the inside of the quad-align. The only fix is to replace it or blow it out with an air gun. Unfortunately it is not easy to tell if you have dirt inside the quad align. The newer machines (q-series) it is easy to see. I have taken the glass out of multiple quad-aligns and blown them out to resolve problems like you are seeing.

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Quad IVc Part rejection issue | 18 August, 2012

When I see this on my QSP2 it is always caused by the nozzle not seating ideally but I tend to set my tolerances really tight.

To test mount a nozzle and look at Z height. Now pick up the part (which in my case will suck the nozzle upward due to the vacuum). Dump the part and preform a new quad align calibration to see if the Z height of the nozzle just changed.

In my case after dumping the 3 parts - I see the machine recalibrate the head and it works perfectly till it reloads the same nozzle on the next board. But if you have a very loose nozzle you will see it happen again at a later time.

I have used a bit of thin super glue on inside of a few nozzles to good effect - this causes a thickness reduction of around 0.001". Also some nozzles have a very slight lip on the top. These parts really need to be lapped in manufacturing and air gaged.

I find matching some Z rods work better with all nozzles but I do not know why but I think it is in the mounting as opposed to the springs in my case.

This is by far the biggest issue I have with the machine.

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Quad IVc Part rejection issue | 20 August, 2012

To solve your should do the following: 1. Super Lube the o-rings on the z-rod bellows. 2. Make sure your head to camera calibration and head to head calibration is good. 3. Line up the nozzle changer pocket positions. 4. Make sure you are driving the z deep enough to pick up the nozzles.

If you really want to see if the nozzle is mounting good. Pick one up then go into machine/calibration/quadalign and look at nozzle height.....then park the head at home and push up on the nozzle by hand....then calibrate the nozzle height again. The nozzle height should not change more than a couple of mils if the nozzle changer is taught correctly.

Good luck.

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Quad IVc Part rejection issue | 9 September, 2012

More lube on the O-Rings caused lots of problems. Nozzles would drop downward at times.

So I pulled everything out and started from scratch.

Testing 3 new Z-Rods, 4 used Z-Rods in good shape (replaced the O-Rings) and around 20 nozzles - the process which worked well in the end for me was to 1) Remove the lip off any nozzles as required which is a common issue - a very sharp X-Axcto knife will do it. 2) I expanded the ID of the end O-Ring groove (at the bottom of the Z-rod). I want the end O-Ring to be a tighter fit than the top O-Ring. I view the goal of the 2 O-Rings as friction (end - lower) vs. alignment (upper). I did this mod by adding a bit of thin super glue into the O-Ring groove and after the film dried reinstalling an O-Ring. This fix could probably be done by using a slightly higher durometer O-Ring but I did not have this option. 3) I needed to lap the ID of 3 nozzles as they were rough. I did it with a slight undersized drill rod (not the bit end) and 9 um lapping film. It did not take too much time as I was only knocking off the high points so the ID does not look like a changed surface.

At this point all nozzles slide onto the Z-Rods and feel great. The run out is very low on all nozzles < 0.003" The nozzle height change with the hand seating is often under 0.001".

So far 3 resistors in the dump bins so I would say this process is working for me. YMMY.

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Quad IVc Part rejection issue | 11 September, 2012

I've been busy with a bunch of different projects lately, so I hadn't had a chance to tackle this further until recently. I ended up running through all your suggestions another time and low behold, it seems to have solved the issue. I'm currently not getting anymore skipping. Bob I really appreciate all the suggestions and help, as well as everyone else.

Now another question if I can be so bold. I haven't had to program a job with component fiducials in a very long time as the panel fiducials have been sufficient, even for very fine pitch parts. A customer has included a set of for a QFP,that I figured I'd use as they were there. The fiducials have been taught with the correct placement and feeder #(four digits) yet the machine isn't looking for the fiducials before placing the part. Am I missing a step? do I have to tell the machine in the sequence steps to look for the fiducial before placement? I'm at a loss and can't for the life of me remember.

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Quad IVc Part rejection issue | 12 September, 2012

Glad i could this is a little harder....been a long time since i have done comp. fids and i dont have a machine to test....but check these things...

1. In the teach menu.....there is teach component fiducials. Make sure you do this with entering the proper information (feeder number and placement number). 2.I cant remember but it is possible that you may have to go into sequence steps and find the placement with the local fids and tell it to use local fids. Once again....its been a LONG time so this is something i would check and i am not sure about.

Good luck

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