Sporadic contamination detected by the weld monitor without any indications of contamination on the can body.
Issue:
Sporadic contamination detected by the weld monitor without any indications of contamination on the can body. It shows anywhere on the seam a weld gap (not welded section) of 20mm
Cause:
• Loose connection on the voltage measurement.
• Short circuit of one of the voltage measuring wires to ground.
• Bad contact between voltage pickup and welding electrode (copper wire) – “jumping pickup”.
• Different wire thickness. The wire will influence the lower pickup.
Check list:
• Check all the wiring of the voltage measurement circuit for bad or loose connections.
• Check all the wiring of the current measurement circuit for bad or loose connections
• Check if the wire is turned around on the lower welding roll (the irregular tine mark could cause sporadic contamination)
• Insulate both voltage picks from the copper wire (X1 is still connected to +800 box). Check the resistance between one insulated voltage pickup to ground and the other pick up to ground.
| Nr | Resistance | Value | Remark |
| 1 | Unfiltered voltage black plug to machine ground | 212 Ohm | Pickups isolated |
| 2 | Unfiltered voltage red plug to machine ground | 212 Ohm | Pickups isolated |
| 3 | Unfiltered voltage black to red plug | 337 Ohm | Pickups isolated |
| 4 | Unfiltered voltage black to red plug Unfiltered voltage black plug to machine ground Unfiltered voltage red plug to machine ground | 1 Ohm | Pickups not isolated |
| Unfiltered voltage black to red plug 1 Ohm è measurement ok 203 Ohm è lower pickup ok; upper pickup open 337 Ohm è lower pickup open | Pickups not isolated |
Insulate both voltage picks from the copper wire. Disconnect X1from +800 box.
| Nr | Resistance | Value | Remark |
| 5 | X1:Pin1 to upper welding roll pickup | 1 Ohm | Pickups isolated |
| 6 | X1:Pin1 to lower welding roll pickup | Mega Ohm | Pickups isolated |
| 7 | X1:Pin2 to lower welding roll pickup | 1 Ohm | Pickups isolated |
| 8 | X1:Pin2 to upper welding roll pickup | Mega Ohm | Pickups isolated |
| 9 | X1:Pin2 to Z-bar | Mega Ohm | Pickups isolated |
• Check the resistance between one insulated voltage pickup to ground and the other pick up to ground.
• Check the ware of the voltage pickups on the upper and lower welding rolls
• Check the wire tension on the upper welding roll pickup. The wire should be slightly bent around the pickup.
Especially on all machines where the pickup is fixed with an elongated hole.
• Sometimes the lover welding roll pickup is bouncing because of some distortion or dirt on the wire.
A small piece of insulated tube, which just fits in the middle between Z-bar nose piece and pickup, could prevent this bouncing.
The wire should be slightly bent around the pickup.
A small piece of insulated tube, which just fits in the middle between Z-bar nose piece and pickup, could prevent the bouncing of the voltage pickup.