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CP4 of death

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#40960

CP4 of death | 13 April, 2006

Okay fellas...I posted awhile back regarding CP4 and CP6 placement issues. I think we may have figured it out. XO/YO and mark read positions were not correct. However, we have a new problem with the CP4-2. I was running the Fuji board, placing a strip of 0402's, and cycle stopped the machine after it placed a dozen or so parts. I brought the board to load position (didn't raise the lifter) and had a peek at the accuracy. The placement was perfect. I then continued to place parts, stopped, load position, and then inspected. This time, the remaining parts were shifted in -Y direction by about .2mm I repeated this and every time, the parts kept shifting another .2mm

To try and determine the problem, I placed a dial micrometer touching the side of the XY table, and got the servo counter value for the Y motor. (lets say 19000 pulses) I then brought the table to load position, manually entered the counter value of 19000 for the Y table, and found that to touch the dial guage, I had to jog to 19025. I did this again, and I was at 19058 pulses. In other words, 19000 pulses on the Y axis, is not the exact same position every time, and gets progressively worse. we think it may be a bad encoder, but I would sure appreciate everyones input on this one. Thanks!

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#40962

CP4 of death | 13 April, 2006

If I follow your description correctly (no fiducial correction occuring between load position and 19000 pulses) I agree that the encoder area is the problem. The encoder may be OK but the mechanical connection from the motor to lead screw may have come loose. This is the first place I would look. Also check the thrust bearing holder is tight.

Jerry

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#40970

CP4 of death | 13 April, 2006

Yes, you are correct, no fiducial correction. If I force a fiducial correction, then the placement is alright. I should also mention that the placement gets worse as the production continues. I checked the lead screws and bearing holder...looks okay. tightened em' up, and still no luck.

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#40972

CP4 of death | 13 April, 2006

Make sure the pulleys on the motor and lead screw have not come loose. Look for damaged encoder wires in the cable way. If all of this mechanical stuff checks out then you probably have a bad encoder. Jerry

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#40979

CP4 of death | 14 April, 2006

Have you checked the table itself. It seen it where either a PCB lifter or adjustble rail brake is operating properly.

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#40982

CP4 of death | 14 April, 2006

Dax, More than likely your moveable rail is slipping on the X-Y table. Make sure there is no oil where the breaks grab the table. Sometime the breaks wear out and need replaced. The contact surface on the break lever is only a couple of thou.. We have two CP4 machines that have the older mechanical clamping tables. The are a pain in the butt.

There are ways to fix this.

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oldtech

#40991

CP4 of death | 15 April, 2006

I once had a problem with the fid camera that caused this problem Try turning on the fid camera and align the cross hairs over the tooling pin or any stationary object. lightly tap the edge of the light housing with a alan wrench if you see the cross hair bounce all over the place, you have found the problem

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#40995

CP4 of death | 15 April, 2006

If I've been clear, the parts become offset as the XY table moves around, without fiducial correction. It's when it does a fiducial correction that the placement is alright. If the placement is excellent, and I just zip the table around...load position, and send the table to certain locations, and then resume production..the placement is off in the -y direction. I've tried loading the PCB, and tightening the conveyor really tight. Even with the board extremely secure, the errors still show up. Checking the PCB after shows no rail movement at all. Is anyone familar with the mec mode on the CP machines? I think it's possible to run a test on the motors and/or encoders, but cant remember how to use it.

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#40996

CP4 of death | 17 April, 2006

Get rid of the machine would be the best fix.

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#41170

CP4 of death | 25 April, 2006

Just thought I'd post and let you all know, SMT Research helped me identify the issue here. Turns out it's the outer moveable rail on the XY table. The clamp bracket brakes were in bad shape, and the outer rail was slipping.

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