Weld controls

Weld controls

The PW Spot Welder Control range uses the latest Microprocessor technology to provide a cost effective solution to quality Spot Welding. Too often spot welding machines are let down by a poor quality control, which does not give accurate timing and on which it is difficult to set current consistently.

The PW Controls are all digital and offer exceptional accuracy with cost effectiveness. The Micro 8, available for both the Light and Heavy Duty ranges, is full 4-stage timer, with squeeze, Weld, Hold, and Off times. It offers dual programme facilities as standard along with Pulsation of the weld for zinc coated and heavier sheets.

A constant current version is also available, particularly useful on long electrode arms, where weld current can vary 20% or more between the edge of the component and the centre due to magnetic losses.

The Micro 8 monitors thermostats on the thyristors and the transformer, ensuring protection for both, should water flow fail or serious overuse occur.

WS2000 weld control from PW Resistance Welding Products LtdFor more sophisticated applications, where very close control is required, the WS2000 control is supplied. This is a state of the art unit, offering all of the facilities of the Micro 8 and in addition full monitoring, locally and remote with alarms when possible failures occur, heat stepping to compensate for tip wear, spot and batch counting, as well as comprehensive internal diagnostic facilities. Depending on the model offered, programming can be from a central computer, from a remote pendant or via an on board programming panel.

Both controls can be retro fitted to older spot welding machines, providing a cost effective upgrade to bring machines in line with modern quality requirements.

Variable frequency weld controls

Variable Frequency gives the same improved welding results using transformers which do not require expensive diodes for rectification of the secondary circuit. The diodes often represent a large capital and operational cost, so there are considerable cost reduction when compared to MF systems, both on purchase and operationally.

Compared to an AC welding control, the variable frequency welding control has higher heating efficiency and lower peak currents. This relates to shorter weld times with lower mains power requirements.

Main Features:

  • Welding frequency is programmable between 25Hz and 400Hz.
  • Transformers can be wound to suit required frequency or control programmed to match existing transformer.
  • 64 weld programmes
  • Three pulses in each weld
  • Heat stepping
  • Programmable weld force within sequence
  • Programmable outputs for (e.g.) robot interface
  • Weld count function
  • Spot and seam modes
  • Full monitoring of each weld pulse
  • Automatic re-weld facility (selectable)
  • Simple hand held pendant
  • Fully networkable

Weld controls - central monitoring

When larger numbers of spot welding timers are used in a factory, it is often very useful to be able to monitor these from a central control station. Programme changes can be made centrally and more importantly, monitoring information gathered centrally, allowing predictive fault analysis to be undertaken.

For example, if a shunt or weld cable is slowly failing, the constant current system may be compensating by increasing the firing angle to maintain the required spot welding current.. Monitoring the firing angle and asking the central computer to report on changes which are occurring would allow maintenance staff to predict failure of the shunt or cable and replace it prior to failure.

Central control of programme settings will ensure that local programme changes are visible and have to be justified in terms of weld quality gains.

The PW systems use a common but secure RS485 protocol for safety reasons.

WS98 software allows complete drill down into the production line. A weld failure alarm on a single robot cell will be highlighted and the user can immediately see the weld data for that single spot on a specific robot. The programme can then be adjusted remotely. When larger numbers are in use this facility is critical to overall weld failure rates and diagnostics.

Even for small users, the facility is cost effective, as faults are immediately highlighted in the production office and corrective action can be taken early. With computers now cheap and the software at a reasonable cost, this is the future of all production spot welding.