Mis-alignment Headaches

Hi All, I have a continuing problem here with mis-alignment of parts on one of our Fuji CP-3 machines and I thought one of you esteemed engineering types may be able to give me a clue as to where the problem might lie. I have a Fuji trained engineer on staff here and he has been working on this machine for 6 months but between us, we can't eliminate the fault. The problem exists when the X-Y table moves in the X-axis. The first part placed after an X movenment is mis-aligned by approx 0.25mm, but all parts then placed with the same X co-ordinate, but different Y co-ordinates are OK if the table only moves in the Y-axis.

Slowing the machine speed right down helps, but doesn't eliminate the problem completely. We have replaced the high speed ball-screw support bearings and had the ball-screws checked and new balls fitted & pre-loaded by a bearing specialist. The linear bearings on the X-Y table are good. We have also:

Replaced the parts camera, vision processor card, X-axis motor & encoder, X-Y servo amplifier, servo cards, parts camera power supply, cpu card, nozzles & clutches. Calibrated the parts camera & fiducial camera. Checked & tensioned the timing belts. Checked, cleaned & greased the cams & followers. Checked vacuum. Made numerous adjustments to part data, proper data & programs. Removed the cooling fan filters & run the machine with the electrical cabinets open in case its an overheating problem. The only thing I can put it down to now is an irregularity in supply voltage. The 3-phase bus-duct which supplies the machine shows (depending on other loads during the day) 415-427 volts on two phases & 395 - 410 volts on the white phase (415 volts +/-10% is the actual supplied voltage). The servo amplifiers are showing input voltages of 207 volts on two phases & 200 volts on the other phase. Checking the outputs from the main transformer shows the same result. Could this be a possible cause of our problems? Any help will be much appreciated.

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