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Quad 4C origin unstable

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Quad 4C origin unstable | 19 July, 2013

We recently purchased some used Quad 4C machines. One of them does not seem to keep a stable origin reference point. I teach the nozzle and component pickup coordinates, then suddenly everything seems to be off by .030 to .040 inches in the X axis. I can no longer change nozzles or pick up or place components. If I tweak all my X coordinates by the amount of the error, it works again for a while. The origin point will suddenly shift even without power cycling the machine. It might be shifting when I hit the reset button, which I have to do altogether too often. It will also sometimes come up offset in the X axis when the power is cycled. It's not really useable as it is. Does anyone know how this machine determines its origin point?

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Quad 4C origin unstable | 22 July, 2013

You have 1 of 2 problems. 1. The encoder is losing steps so it has a problem or the glass scale that it reads has something wrong with it....dirt,cracked,etc..... 2. The downward camera is loose or has a problem. With power on move the head to a position over the front feeder base....then reach under the cover and tap on the camera. The lens assemble inside the camera was glued. I have seen machines where the lens becomes unglued and causes the crosshairs to change position when tapping on the camera.

Good luck

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Quad 4C origin unstable | 22 July, 2013

I don't think it is a loose camera lens. We are actually off on the position of the Z-rod. It's not just the camera position that is off. We really can't change nozzles because the z-rod misses the hole in the nozzle changer.

We have repeatedly cleaned the glass scale, and we can see no problem with it. I'm not sure what we could do if the encoder that reads the scale is bad. The optical encoder appears to be an incremental encoder. This means it can keep track of where the head is based on how far it moves, but it still needs to know where "zero" is when the machine is powered up or reset. The machine will power up, move the head around (I guess to find the "home" or "origin" point), and will sometimes be in calibration, and sometimes not. If it is in calibration it will sometimes stay good for hours. Then suddenly the X position jumps off by 30-40 mils. Power cycling or resetting does not seem to always fix the out-of-calibration situation. Sometimes it gets out of calibration and no amount of power cycling and/or resetting will make it right so I give up. The next day it might (or might not) power up back in calibration.

So my question is still- How does a machine with an incremental optical encoder find the absolute zero reference point at power up?

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Quad 4C origin unstable | 22 July, 2013

I dont have a machine to look at but its one of 2 ways.... 1. It finds a home sensor then counts out to a position. 2. It finds an etched mark on the glass scale then counts out to a position from there.

I know the Q-series machines does the second option. Check that the flag and sensor and encoder are all tight. I would even check the belt and make sure its tight and seems ok.

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Quad 4C origin unstable | 16 August, 2013


Sorry I don't have an answer for this but I have the same problem in the "Y" axis on one of my 4Cs after the machine has run for around 4 hours. The machine seems to partially correct for the pick-ups being off as the placements are fairly good but nozzle changes are a problem. I just re-teach the position and "Z" and carry on or press reset if there is no PCB in the machine.

I always assumed that the soft home at power up is how the machine finds it's origin using the near home flag sensor and some kind of motor current sensor. Good luck with it anyhow.


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